BU-001: Sharing Battery Knowledge

BU-001: Compartir conocimiento sobre baterías (Español)

Battery research is advancing at a rapid pace, which is a clear indication that the Super Battery has not yet been found, but might be just around the corner. While today’s batteries satisfy most portable applications, improvements are needed if this power source is to become a serious contender for the electric vehicle.

With so much hype about batteries, people want unbiased information and Battery University promises to provide this. The website went live in 2003 and quickly gained popularity. Besides being a teaching tool, it has become a social media network to exchange valued information about your battery experience. Users' input, in my opinion, is as important as reams of laboratory test data. The critical mass speaks louder than promises made by device manufacturers that cannot always be met. 

The website is continuously being upgraded and much of the information comes from the best-seller Batteries in a Portable World: A Handbook on Rechargeable Batteries for Non-engineers. The book will soon be in its fourth edition. 

The first edition of Batteries in a Portable World went into print in 1997 and the handy little book sold out quickly. The larger second edition was published in 2001 and served public safety, healthcare and defense industries, as well as the esteemed hobbyists and everyday battery users. The expanded third edition was released in 2011 before low stock prompted me to write the up-and-coming new edition. 

There are no black and whites in the battery world, only shades of gray. The battery is a black box with a mind of its own; mystical and unexplainable. For some, the battery causes no problems whatsoever; for others it’s nothing but a headache.

Much effort is devoted to battery care, and it appears as if battery diagnostics are stuck in medieval times. Let’s not blame our scientists for this; the technology is complex. Also good care alone does not always show the expected results. The often asked question, “How many cycles can I get out of my battery if I do this?” has no quantitative answer. The reasons for the eventual demise are multifold and have similarities with our own human frailty. We suffer health issues even if we try to keep fit and eat our vegetables.

Battery University is for the professional needing a basic understanding of how a battery behaves, a student completing an essay, and a user wanting to get the most out of a battery. The information comes from my battle-tested experience working with batteries in the Cadex laboratories, as well as other research organizations and the input from battery users. I appreciate these contributions and I add citations where appropriate.

There is no perfect battery and each pack is tailored for a given use. Batteries in consumer products are optimized for long runtime, small size and low cost; longevity is less important. Industrial batteries may have high load capabilities and improved reliability, but the pack gets bulkier. A third variety offers long service life and these packs are expensive.

All batteries have one thing in common: they run for a while, need recharging and require an eventual replacement as the capacity fades. Battery replacement comes often before retiring the host. The idea of an uninterrupted energy source is still a pipedream.

Last updated 2016-08-04

*** Please Read Regarding Comments ***

Comments are intended for "commenting," an open discussion amongst site visitors. Battery University monitors the comments and understands the importance of expressing perspectives and opinions in a shared forum. However, all communication must be done with the use of appropriate language and the avoidance of spam and discrimination.

If you have a suggestion or would like to report an error, please use the "contact us" form or email us at: BatteryU@cadex.com.  We like to hear from you but we cannot answer all inquiries. We recommend posting your question in the comment sections for the Battery University Group (BUG) to share.

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Comments (261)

On November 29, 2010 at 3:25pm
sawyer clayton wrote:

what is the name of the person who made sharing knowledge of the battery article my science project is due tommorow and i need the name of the author

On December 1, 2010 at 2:45am
Battery Wizzard wrote:

Just look up the author of the book he mentions which he wrote.  Hah, duh.

On December 13, 2010 at 10:59am
muhammad javeed wrote:

i want to ask u in lead acid battery (+v plate) what is the that matereial with the help of this   plate make oxaid

On December 20, 2010 at 3:12am
inbasekaran wrote:

For mohammed javeed, for testing the material, give the material to a material testing laboratory for a complete report.

On January 13, 2011 at 3:08am
Tony wrote:

My Laptop current rating is 1.5 ampere at 240 Volts AC ,how many laptops can I charge simultaneously with a power points rated 240 volts AC,13 amperes?

On January 23, 2011 at 6:17pm
Ramon wrote:

i have a battery pack of 18 volts ni-cad and 18 volts lithium batteries, my battery charger is for ni-cad battery pack, can i use my ni-cad charger for my lithium battery pack?

On March 24, 2011 at 1:08pm
Paul wrote:

No you cannot.  Li-Ion batteries require specialized chargers to avoid damaging the battery.

On April 15, 2011 at 9:43am
Jimy wrote:

Nice concerning as better as clarifying position.Gives Thanks for providing for us.I show your article with my delight.

On April 15, 2011 at 9:44am
Simith wrote:

thanks a lot for sharing the helpful information.

On April 15, 2011 at 2:50pm
julie wrote:

can you use a lithium-ion with a regular power tool that used older batteries? I have dewalt power tools..

On May 2, 2011 at 1:00am
kamal hossain wrote:

For kamal, for testing the material, give the material to a material testing laboratory for a complete report.

On May 2, 2011 at 1:10am
kamal hossain wrote:

I want to procedure manuals for Battery production

On May 2, 2011 at 6:07am
Paul wrote:

For Julie, the answer to your question is usually no, because Li-Ion requires a specialized charger,  If you can make a Li-Ion pack fit a Ni-Cad tool, then it is possible, but again you cannot use the NI-cad charger.

On May 19, 2011 at 12:25pm
Adrian Hall wrote:

What might be the cause of a VRLA battery swellin g and bursting its case? We have two of them in a 24v battery back up system. Float volatge is maintained at 27volts by a specially designed battery supply so i do not think that it is overcharging.

On May 19, 2011 at 1:37pm
PAUL J. wrote:

Sounds like the valve failed.  When pressure rises, the “Valve Regulated Lead Acid” battery is supposed to vent that pressure. 
If it can’t vent through the valve designed for that purpose, it will vent another way.

On July 8, 2011 at 10:06am
mr rajinder kumar aggrawal wrote:

very nice imformation…about battery technology as a manifacturer of batteries in india.. its very good to read all about batteries…..appricated…

On July 14, 2011 at 7:45pm
Cameron Malek wrote:


‘filed’ should be ‘field’.

On July 17, 2011 at 7:41pm
Ramon wrote:

thanks Paul for the info.

On August 1, 2011 at 3:49am
Anthony wrote:

spelling….. “field”

“This interface with the user gives me an advantage in learning how the battery behaves in the filed.”

On August 2, 2011 at 9:57am
Cadex Electronics Inc. wrote:

Thanks Anthony, we have made the correction.

On September 14, 2011 at 9:52am
David Marlow wrote:

I have observed many problems with voltage depresion in NiMH batteries usen in defibrilators. This is usualy corrected with cycling. Recently the impedence has also become a important value to look at on these batteries as well as the ones with higher impedence are not performing adquately even though the total capacity of the battery is still over 100%

On September 29, 2011 at 2:50am
Abhijit wrote:

I want to produce UPS batteries.
Can anyne help me?

On September 29, 2011 at 4:16am
David Marlow wrote:

Vietnam seems to be the new place to start producing UPS batteries.

On September 30, 2011 at 1:23pm
ayie wrote:

i want to ask,,,,can a rice cooker be power by using battery power,,,,,if can,,,,what the best battery for it.small battery to make portuble rice cooker

On October 17, 2011 at 4:59am
David Marlow wrote:

While electrical energy is efficent for powering moters and electricial circuits, there are a lot of better ways to generate heat.  Battery powered heaters are not a good idea.

On November 14, 2011 at 6:15pm
Christopher John wrote:

I’m looking for the most basic first principle explanation of how a battery works. Why do differnet metals like copper and zinc have different potentials and can they be calculated from their atomic structure.

On December 30, 2011 at 11:59pm
fanaa wrote:

i really want to know what is the difference between old batteries and new batteries?,please help me =) btw thanks for the answer

On January 5, 2012 at 1:18pm
David Marlow wrote:

Batteries are parishiable items, while they do not go bas as fast fruit, whould you want old fruit or fresh fruit?  Refrigiration helps extend the shelf life of batteries as well as fruit.

Just as different fruits go bad at different rates. different battery types go bad on the shelf at different rates as well. NiMH batteries seem to go bad in a few years, SLA batteries should last 5 or more years, as long as charge them at least once a year. Primary lithum batteries may last 10 or more years, rechargeable lithiums should last 5 or more years with about 1/2 a charge maintained (most are the smart type and that smart logic draws power so it helps to charge them some every three to six months..  Nicad batteries will sit just fine discharged, for 10 or more years, but will require a long trickle charge to wake them up after sleaping more than 3 months.

On January 22, 2012 at 1:33am
Zvi wrote:

The problem: a small drive, do not rich to 43V.We want to get your help on Battery 36V 10Ah,and in general to understand the operation of the battery.Here are the following story:
We got a battery that travel distance, less than 20 k’m.We opened the battery and we find the following cell data in Vallts:3.368\3.71\3.46\3.71\3.296\3.75 - 3.349\3.36\3.35\3.35\3.69\3.45
We took the battery and emptied it, and we measured again and found that one cell was 2.5 volts.We replaced the cell.Then we charge the battery to “full” , we measured the battery and it show 40.6V.the following cell date:3.328\3.334\3.314\3.482\3.326\ -  3.321\3.335\3.317\3.319\3.339\3.332All cells look OK , but the battrey to not rich to 43V. Why the battrey does not rich to 43V? why the charge stop at 40.6V?Is it the BMS?Can we get instructions for testing ,so we can see if BMS or one of the cell is not work?

On March 16, 2012 at 1:23am
May wrote:

I finally find this perfect website about batteries.
I’m doing some test about LiFePO4 batteries, e.g. self-discharge rate test.
I usually charge and discharge the cells completely. Then charge the cells to some capacity. After that, put them in 60°C for 7 days. Then discharge them to test the capacity.
I’m wondering if there is a standards for me to do the test or it’s just everyone has his way.
Thanks for sharing.smile

On March 16, 2012 at 5:56am
David Marlow wrote:

I do not know of a standard for this type of test, however what ever info you could shair from your tests would be of interest.

I usualy compair the loss in 24 hours after a full charge to the loss after a week or so, to try to deturman how much is loss of over charge vs normal self discharge.

sense you are not fully charging, there should be no over charge.

On March 16, 2012 at 8:35pm
May wrote:

I was told that the high temp. aging test is the most common used way to test self-discharge rate in China. I used to compare the charged capacity read from the battery tester to the discharged capacity after 7 days in high temp. tank. But recently, my data is totally different from what the supplier gives us, even though our methods are totally the same. And the engineer said that they use the real capacity of the cell to compare with the discharged capacity. I don’t think it makes sense since the cell is not fully charged. So I began to search what is the right way to test the self-discharge rate of a cell. I’m confused about which data should I use to do the calculation.

On March 23, 2012 at 10:57pm
jasbir wrote:

please tell me about battr

On March 31, 2012 at 2:58am
vipul wrote:

hello. i m battery manufacture in india. made rv battery.(automotive battery)i plan makeing marein battery. if u know how work marein batt. plat size thiknes. plat size standerd. deep cycle?sugess me. thanks for read msg

On April 5, 2012 at 5:47pm
neil bochow / ta cool-cats boat builder wrote:

Hi David, just found your site wow thanks,  Question   what damage if any will a li-ion polymer charger do to a li-ion phosphate cell.

On April 15, 2012 at 4:41am
Nayan wrote:

I want know that “how make the active material"pleas help me.

On April 29, 2012 at 2:06pm
Syed Muhammad Tahir Hussain wrote:

Dear May,

I am Tahir from Karachi , Pakistan and i am working in lead acid battery company.
i had been tested many batteries, self discharge test (another name Retention of charge test )  in our lab. Self discharge means the loss of useful capacity of a battery on storage due to internal chemical action its called local action.

(1) Battery shell be fully charge.
(2) Check battery capacity (5hrs or 20 hrs) its called—-C1
(3) The battery shall be store for a period of 28 days
(4) Check battery capacity in same condition, its called—-C2

Self discharge test (%) = Loss of capacity (C1-C2) / C1 x 100

Note : Percent shell be not more than 20%
(It is PSI Standard)

Best wishes,

On May 14, 2012 at 2:11am
Abdul Jabbar wrote:


I have a question that I have assumbled a battery in which I used 5 positive plates (new) and 6 negatives plates(used) per cell. I tried to test my battery but the problem is that each cell gives me 2.3v and total of 6 cell provide me around 13.8v and I tried my inverter and tried to start a fan and 2 savers and checked the voltage which was 13.4v but my fan and saver just fluctuate and don’t work at all. Can you guys please let me know what could be the probelm.

I have checked there’s no problem with terminals.  I am still using my inverter on another battery and inverter works fine there.

Thanks in advanced.

Abdul Jabbar

On May 17, 2012 at 9:54am
David Marlow wrote:

Hello Abdul,

From the Voltages you have given I will assume that you have a lead acid battery and these voltages are no load voltages.

If your connections are good, then your battery has too little capacity and or too high of impedeance (check for a poor conection between the cells).


On May 25, 2012 at 9:48am
alan wrote:

Hi, We are ceating a miniature social alarm using a Quad Band mobile (cell phone)
module.  Can anyone advise where we can go to get a 450MaH lithium ion polymer analysed to see what its peak surge current is over 20 micro seconds.

On May 25, 2012 at 11:55am
David Marlow wrote:

Any good electronic tech with access to a good scope should be able to measure this for you.

The other info you may need is from the battery MFR on what the particular battery in question should be able to do and under the conditions that you are concerned with.

On June 8, 2012 at 4:46am
maulana wrote:

how do you choose the best solar charge controller

On June 22, 2012 at 3:19am
Badrinath wrote:

Can you please provide info on how to maintain a battery..(charging & discharging)


On November 12, 2012 at 7:47pm
Michael Wei wrote:

This website is usefull for me,battery is a complicated keypart for most electrical products.
i hope more and more new technology will be here for us to share.

On January 23, 2013 at 10:59am
Venkat wrote:

Is partial charging of Lead-acid batteries a good practice?What is the optimal way of handling a lead-acid battery system?Does it require a BMS?
Also, what power outputs can be achieved from the different lead-acid batteries available?

On January 23, 2013 at 1:06pm
David Marlow wrote:

Lead acid batteries do best if kept near a full charge, definetly above 2.1 volts per cell, but not over 2.3 volts per cell long term. 2.35 to 2.4 volts per cell is OK for a current limited fast charge (about 4 hours or less at this voltage).

Allowing lead acid batteries to set for days or loanger at less then 2.1 volts per cell will result in sulfation. A badly sulfated battery may not take a charge at all. Trickle charging may partialy recover a sulfated lead acid battery.

A battery managment system is not normaly needed for lead acid batteries as constant voltage charging at 2.3 volts per cell with a current limit (see mfr specs.) will usualy maintain them, unless a cell shorts, then that one shorted cell will cause over charging of the other cells. 

A short (less than 12 hour discharge) deep cycle about once every 6 months (for a deep cycle type Lead acid battery) will help manage Voltage depression problems and let you know that the capacity is still adquite.

Once they fall below 80% of rated capaicy the usefull life falls off quickly and it should be replaced.

On January 29, 2013 at 1:54pm
Josiah Gana wrote:

Pls I’m new to this site and relatively new to the world of battries. My project is to find sutable batteris for storing solar enery. Is there a particul type of battery for this purpose?

On January 30, 2013 at 9:50am
David Marlow wrote:

Josiah, any rechargeable battery can be charged by solar. The battery choice is much more dependent on how often it needs to be discharged and how fast, do you have space or weight restrictions?, how important is cost?

The electrical Grid can be best storage method, with a Time of Day rate you can actualy get more back from the grid at night than you put in during the day and still break even.

On February 1, 2013 at 7:53am
sreenivasulu wrote:

Hai im working in automotive company. Related battery section. I want to know the battery plate design? How to calculate the plate size related to capacity? Ps elaborate the details.
2nd thing is liion battery after life how can i dispose to waste management centers pls give me u r valuable suggestion.

On February 1, 2013 at 1:45pm
Josiah wrote:

Thanks alot David. lets say I’m considering cost, space and a good discharge time, which would you recomment. Thanks.

On February 2, 2013 at 9:10pm
David Marlow wrote:

Hi Josiah,
Most systems use lead acid batteries as they are the least costly per Watt hour, are easy to manage and great for standby or occosinal power.  However they take up the most space, weigh the most and have the lowest cycle life. get the deep cycle type and don’t let them set discharged.

LIthium Ion batteries have several types and can be the opposit of lead acid batteries, just dont fully charge or discharge them regulary and dont let them get over 100 degrees F. if you want to get the most life out of them.

Ni:Cad have the Highest cycle life so the woul be the best for daily full charge and discharge cycles.

I would not recomend Ni:MH batteries for solar power applications.

On February 5, 2013 at 4:14pm
Josiah wrote:

Thanks alot David. I do appreciate your help.

On March 10, 2013 at 2:59pm
Paiboon Onpattanasin wrote:

I would like to know the trend of battery using of lead acid, Li-Ion, Ni-MH batteries.
Will the lead acid battery be replaced by Li-ion battery or others?

On March 12, 2013 at 7:28am
David Marlow wrote:

Lead acid batteries will be around for a long time, as they are the least expensive and most recyclable batteries available.

They are great for standby applications such as in Uninteruptable Power Supplies (UPS) systems, situations where they are usualy being charged and not usualy siginificently discharged.

Li-ion Batteries are and will be used where size and weight are more important than cost.

On March 21, 2013 at 8:16pm
Jay wrote:

I have a question about calculating a theoretical run time for a battery and power inverter combo…  I understand that there are inefficiencies in batteries and after a certain amount of power is used up, the battery no longer performs to spec, so to speak, but forgetting all of that for a second, I wondered if the following calculation would be theoretically correct…

If I had a 12 Volt, 10 Amp battery:
could a 12 Volt, 1 Amp load could run (again, theoretically) on that battery for 10 hours? - I believe this line of thinking is correct, no?

If that logic is correct, I am trying to figure out if:
that battery were connected to a 12v - 120v Power Inverter (assuming a theoretical 100% efficiency) and a 120 Volt, 1 Amp load were running on the inverter, could that load run for 1 hour?  (voltage multiplied by 10… amperage divided by 10)

I have a couple of those inverters that I would like to use for an event to power some equipment (in lieu of a generator) and I am trying calculate what size battery I would need to keep things running for the amount of time I need.  I hope my rudimentary “logically based” math is correct, will give me a base number and then I will account for inefficiencies and whatnot.

Thanks very much everyone!


On March 22, 2013 at 5:03am
David Marlow wrote:

If an ideal battery is assumed with an ideal inverter that would be true, unfournatly the ideal battery dosent exist.

I will assume that you are talking about a typicla SLA batery that is used in UPS systems.

Those batteries are rated at a 20 hour discharge rate, if they are discharged in 10 hours they will only deliver about 90% of their rating, if discharged in one hour they may only delever 50%.

Also the heaver the load the lower the cut off Voltage will have to be to achieve a full discharge.

You can usualy find this information on the battery MFRs web site,

On March 26, 2013 at 7:37pm
Jay wrote:

Hi David, how are you?

Thanks for your reply.  I was thinking to use either SLA batteries or maybe even Motorcycle Batteries or Smallish Marine Batteries.  I would like to setup some IP cameras and networking equipment for a couple of hours during an event I have coming up and I was looking for a “simple,” power solution.  I could go with small generators, but I already own some 1000mw inverters and figured that with a large-enough batter, I’d be good to go for what I am trying to do.

Unfortunately, I am aware that batteries have their inefficiencies and their “strange” discharge curves not to mention the losses of the inverter (though I could not seem to get those specs from the company when I emailed them).  I suppose I am trying to estimate a “base-line” (the smallest battery that would theoretically work for me) and go up from there.

(Another thought of mine is that if by some chance all of the equipment I have can run off 12 wall-wart adapters, maybe I can just wire them directly to the battery and forego the inverter.)

Thanks, again.

On March 27, 2013 at 12:17pm
David Marlow wrote:

Hi jay,

I am well.

The batteries that you mentioned are all Lead acid batteries, the SLA and Marine batteries are deep cycle type and are best for applicatons where you are using more than 1/2 of the batteries capacity and have a cycle life of about 200 deep cycles.  The motor cycle battery may have a cycle life of much less than that.

You did not mention how frequently you intend to deep cycle these batteries.

NiCad batteries are rated with a cycle live of 1000 or more cycles

NiMH batteries are rated with a cycle life of around 400 cycles, (usulay they last less than 4 years regardless of cycle count)

Li-Ion batteries vari greatly depending on the exact type and how they are used. And as their temp is allowed to go over 100 degrees F. their life decreases dramaticly.

The Li Ion batteries in my Chevy Volt are rated to last at least 8 years or 100K miles (equate that to over 2,000 cycles), 10 years or 150K miles in California (3000 cycles)
They are tempature controled as well as voltage, current and % charge and % discharge controled (never fully charged or fully discharged).

On April 18, 2013 at 3:07am
Josiah wrote:

pls what can be substituted for lead in a lead acid battery

On April 18, 2013 at 5:14am
David Marlow wrote:

There are no othere materials that would be nearly as cost effective or they would have been used long ago, some others will work but at reduced voltages and increased cost.

So if cost is not a problem go to a Li-Ion type of battery, or a Li-Iron

On April 20, 2013 at 5:43am
Rob Davidowitz wrote:

Referring to charging and monitoring LiPo batteries.

I am currently using a 2200Mah, 40-50C 11.1V batteries to fly my 450 helicopter and foam trainer
I use the I Charger 208b to recharge these batteries
I have flown 30 flights on a battery
I have been doing an individual 1C balance charge on each of my batteries after every flight and I try very hard to never fly any of the cells down below 90% of the voltage capacity.
I use 11.34V as my “fly to lower limit”
There have been a few, but very few, times that I have taken 1 or 2 batteries down to ±11.2V but no lower than that.
So I think I am being quite conservative and careful with these batteries. “I think” I might be wrong.

My questions:
1: I believe that it is not a good idea to charge after every flight but rather leave the batteries at ± 3.5 -3.7V per cell and rather charge fully just before flying again. Is this correct?

2: Is it a good idea to store these semi charged batteries in a fridge until just before use.

3: I have been monitoring the IR. of each cell after each flight and then again after each charge. I have been told that there is no benefit in measuring IR after a flight and should only measure after a charge at which point the individual IR readings of each cell should be close to the same. Is this correct and if so, how close to each other should these readings be and at what value of IR should I be suspecting a failing battery?

4: Is 90% being too conservative or should I be flying down to 80%?

Thank you in advance.

On April 21, 2013 at 5:11am
David Marlow wrote:

Hi Rob,

While I am no an expert on LiPo batteries I think tha you are well on your war to finding your own answers,

The only concern I have is that wile keeping the batterire cool in storage is good,  charging or discharging them while cool may not be, especialy at rates around 1C or above..

On April 22, 2013 at 11:35am
Rob Davidowitz wrote:

Thanks David,

This is most kind of you to comment.

I will certainly heed your advice regarding fridge storage and time frame of charging.

Would I be better off posting these questions on another page on this site to get more a more detailed answer with the parameters I am looking for or are you the moderator for all the different battery pages?

Regards and thanks

On April 22, 2013 at 12:00pm
David Marlow wrote:

Your welcome Rob.

This page is the one I am watching.

I guess I have been acting as a moderator for this page for a while sense I have not recently seen others trying to help with the questions. 

While the manufactures are the bet source for specific inormation on a particular battery, there are not too many good sources for general information, some vendors are helpfull, some are not.

On May 9, 2013 at 5:01pm
Josiah wrote:

pls is it possible to have a deep cycle, dry cell battery? and which materials would you recommend for use if i were to build up one.

On May 10, 2013 at 5:00am
David Marlow wrote:

The batteries that I remember being called dry cells were not recomended as recharageable, all though they could be recharged to a small amount of capacity a few times.

SLA batteries do not have liquid acid loose in the cells, it is eather gelled or the plates are like a sponge to hold it in place.

I am not a battery builder and do not have the knoledge that you are seaking to invent a new type of battery cell.

On May 30, 2013 at 2:27pm
Josiah wrote:

pls I need responce. Will lead (Pb) and iron (Fe) make a good combination for a battery if used as electrodes with alkalin as the medium. Thanks

On June 2, 2013 at 1:23am
Eric wrote:

When charging two identical batteris connected in series tthe voltage is different on both of them (approx. 12.5V vs. 13V). Why is it different?

On June 3, 2013 at 4:25am
David Marlow wrote:

The Batteries in Series aperently are not Identical, sense you have provided no specific information as to the type of battery or state of charge or age of the batteries, or if they are under any load when the Voltage is measured, it is difficuld to speculate why these two batteries that should be reading the same voltage are not.

On June 13, 2013 at 8:50pm
Andrew Macgrgeor wrote:

Thanks for all the useful info on this site.
I have 4 by Lead Calcium 12v 102Ahr batteries that I use with a 220V/48V 4KVA pure sine wave grid connected inverter to power my home when the utility is down. The system has seldom been used over the past 5 years but will be more regularly in the future as our utility load-sheds. The system is set to a max charging rate of 5 amps. Cut off DC voltage was 42V.  Approx every two months I would switch the system on and charge the batteries until the charging current had dropped to about zero +/- 1 amp. Every 6 months or so I would balance the batteries if the system didn’t do it automatically.
On switching on the system one of the batteries exploded. They were all 2nd hand batteries that were part of a 24 V truck set. When one battery failed during warranty it was scrapped and the other was ‘re-rejuvenated” and sold as 2nd hand.
My question is should I replace all 4 batteries or just the failed one with a new 102 Ah battery?
I am about to check their voltages after standing for 2 months after being “fully” charged.

On June 14, 2013 at 6:21am
David Marlow wrote:

I would not mix old and new batteries in series.

Your batteries being five years old are nearing end of life (expect 5 to 7 years of normal stand by use with out being left a day or more with out recharging (every day left discharged will equal about 5 cycles of use for this type of battery)  or 200 cycles

Checking individual voltages as you mentioned after standing is good, that will tell you if one is self discharging faster than the others.
Also you should check the voltages wile under load to see if the internal resistance of each of the batteries is similar, the voltages should be similar.

On June 22, 2013 at 5:17pm
Josh wrote:

Hi Everyone,

Great site as I only just stumbled upon it. Does anyone know the role “Sea Air” plays in diminishing the power of a car battery?

As I live about a kilometer from the beach and have gone through 2 Car Batteries in the past year, as the terminals remain quite healthy and from corrosion. I’m just so bemused and not very well versed in Mechanics.



On June 23, 2013 at 12:08pm
Jay wrote:

As I understand it, any time you have batteries in moist humid air (like that near the ocean) current can actually trickle from one terminal to the other through the moist air (salty, moist air makes for a relatively good conductor) and drain the battery. That is also the reason (so I’ve been told) that you should not store batteries on the floor… Cool, moist air can drain the battery.


On June 23, 2013 at 4:53pm
Josh wrote:

Thanks for your feedback Jay. So does that mean the moist air can make it Arc?

On June 23, 2013 at 5:21pm
Jay wrote:

No.  12volts is not nearly enough to arc through the air… further, while humid air might allow a tiny amount of current to flow causing a slow drain over time, it is not THAT good of a conductor to permit a spark (especially over the distance between the terminals on the battery at 12volts… if it were tens of thousands of volts, I imagine a spark would be possible.

On another note, has your mechanic checked your cars alternator?  Humid air could drain your battery, but if you’re driving the car regularly, it should be recharging the battery faster than the air could drain it… (even on a repetitive basis).  Lead Acid batteries don’t like to be drained all the way or they don’t recharge too well (see other posts on this site for a ton lf good info)... if your alternator is not working well, it may not be recharging your battery well-enough.  This will definitely kill a battery over a few weeks or months regardless of the moisture in the air.  I used to have a car that went through 2 alternators and 3 batteries in a year.


On July 8, 2013 at 1:44am
S.A.Brahmaraju wrote:

What is the life cycle of inverter lead acid batteries

On July 8, 2013 at 4:13am
David Marlow wrote:

Generaly deep cycle SLA batteries have a cycle life of about 200, 1/2 to full discharges, other factors are tempature, how long they are left discharged, how they are charged and time.  With the cycle limit in mind, you should expect 1 to 5 years of use. Also do not mix old and new batteries in series.

On July 10, 2013 at 3:11pm
ben hutchinson wrote:

When you place one hand on a copper plate and one on aluminum foil, then the connect the two metals to a multimeter you create an “hand battery” since a voltage of 700 mV can be seen on the multimeter.

My question is, are there any aluminum ions created on the foil or your hand in the process?

On August 22, 2013 at 11:00am
Jaspal Singh wrote:

What do you think about Super capacitor. I know super capacitor hold less energy density and high power density. can we use super capacitor instead of batteries because the charging time is less and life time is way better than batteries. Some people says the next hot market will be super capacitors to store energy because of longer life span.

On August 22, 2013 at 11:05am
David Marlow wrote:

They have now move on to Ultra capacators but they are still a long way away from storing as much energy in the same size pacakage as even a NiCad battery

On August 22, 2013 at 11:07am
David Marlow wrote:

for some applications that require little energy they have replaced coin sized batteries.

On September 21, 2013 at 1:56am
prashant vispute wrote:

plz,help me,  my idea is, i want share charging via blutooth can ths posible.?????????

On November 10, 2013 at 5:13pm
jorge wrote:

Does anyone know, on a 12 volt 100 Ah SLA battery, when you use it on a bank with three other batteries, if one fails, what will that do to the battery bank other than having a voltage drop across the terminals? will the life of the other batteries be compromised?  how much time do you have to replace the failed battery before the others fail as well?  I know that as a general rule, old and new batteries should not be mixed but in this case one battery has failed after one month and replacing all doesn’t seem to be justified.  Any insights?

On November 11, 2013 at 5:17am
David Marlow wrote:

It depends on how the battery failed (open shorted or low capacity, and weather the bank of batteries is connected in seris or paraell.

If the battery failed with a shorted cell and the batteries are connected in series then the charger may see that as low voltage and then over charge the other batteries.

if the batterie failed open or low capacity then the other batteries may not get enough charge add the system would act like all the batteries are bad.

On November 11, 2013 at 9:36am
jorge wrote:

Thanks David.  The 12 V batteries are in series to supply 24 v.  One more question.  A Nortstar Battery has a rated capacity of 100 AH.  The useful energy of the battery is constrained by the low voltage disconnect, right?  If there is no constrain on the voltage the battery can be drained of its entire capacity.  At what voltage as a percent of nominal capacity will the battery end when you drain the 100 AH?  If i am using 10 AH the battery will last for 10 hours?  Is this the way manufacturers calculate the capacity or do they take into consideration that there is a minimum voltage where you do not want the battery to continue draining?

On December 20, 2013 at 3:36pm
Moe Sabourin wrote:

Just curious about the technology of automotive batteries in newer vehicles… many manufacturers now mount the battery in the trunk, but there’s no mention of harmful gases being discharged.

Is there new technology in automotive batteries that they do not discharge gases when being charged by the alternator?

It would seem that if auto manufacturers are mounting batteries in trunks now, they must have either went to a new battery technology or they’re not concerned about the level of discharge… there must be some safety considerations for passengers in these vehicles…

On December 21, 2013 at 5:04am
David Marlow wrote:

Yes, they have been using the newer newer technology of the
sealed lead acid batteries for many years now, along with better charging control circuits.

But your concern is still valid, while normally the system is now set up so the battery does’ not vent, under some conditions they may.

My car has the battery in the back and I the noticed that cabin ventilation system vents out of the car near the battery, so your concern was addressed in that way.

On December 23, 2013 at 7:45am
Moe Sabourin wrote:

Thanks David,

I’m the director of a major car audio competition organization and we’re reviewing our rules for competition for the 2014 season, and this question has been posed by many of our members.

My assumption is that the auto manufacturers would have to meet certain global safety standards regarding passenger safety and if there is a potential of gases being emitted while charging, how can we confirm that the auto manufacturers and battery companies are meeting this requirement?

Our organization’s first concern is for the safety of our members; in our rule set, we are very specific that any battery mounted in a passenger area, or an area that vents to the passenger compartment, must be encased and vented to the outside.

However, if battery technology has reached a point where auto and battery manufacturers are secure that gases are not being emitted when charging, we would naturally have to look at amending our rule.

That’s why I ask. Any insight into the battery type they are using in today’s newer vehicles, that could help us to properly amend the rule to take this new technology into account would be appreciated.

Thanks again,


On December 23, 2013 at 8:15am
David Marlow wrote:

I am not in the automotive industry, and do not know the specifics that you are seeking.

Normaly over charging would be the condition when current SLA batteries would vent, however over charging can occure if a cell in a battery fails with a short.  The batteries must be able to vent or gas pressure could build up until they may explode.

I would also assume that all major car manufactures comply with the standards, but your members should be concerned when modifing a vehical in such a way that my compromise the ventilation of the battery area or when adding additional batteries that may vent. Non rechargable batteries normaly do not vent unless over heated.

On December 23, 2013 at 10:51am
Moe Sabourin wrote:

Thanks again David,

I understand that you’re not in the automotive industry, I was just hoping you may have info on where I could go to find out. smile

Our rules are very clear that for any battery mounted in an area where gases could escape to the passenger compartment, it has to be in its own case sealed off and it must vent to the exterior.

The question that has been posed to us is that with newer battery technology and auto manufacturers now installing batteries in the trunk, why do we need the rule? This question is what led me to your website in search of an answer.

Thanks again for your assistance and Happy Holidays,


On February 1, 2014 at 5:58pm
Batteries Plus 274 Mesquite TX wrote:

This is a fantastic site with a variety of really useful information, especially graphs etc. I just wanted to let everyone know that if you need any batteries recycled, any Batteries Plus will be glad to help!!!!
- All rechargeable batteries are recycled Free of Charge wink including SLA(automotive/power-sport) NI-CD NI-MH LI-ION Etc.
- Fluorescent lighting, small electronics, and alkaline batteries are also recycled properly, fees vary by location! 
Remember to keep the Earth clean and recylce!

On February 7, 2014 at 3:53pm
99guspuppet wrote:

If an SLA battery is slow charged to 13.5 and then disconnected , how long will it take for the battery ( at 25 degrees C ) to decay to 12.5 volts ?  Does the time correspond with it’s Ah or cold cranking capability ?    #SLAcapacityTest

On February 7, 2014 at 5:39pm
David Marlow wrote:

a good battery should hold its voltage for 6 months to a year.
Spec. capacity doesn’t make much difference, but some batteries are better than others.

On February 7, 2014 at 6:26pm
99guspuppet wrote:

I did not ask my question very well.  6 cell SLA batteries assume a voltage of about 12.5V after they have been allowed to *rest*.  This means they have not been charged or loaded for 4-8 hours.  I am wondering if the amount of time required for the battery to slump from the 13.5V the charger brought it to .... to the *rest* voltage is indicative of anything about the battery’s capacity..

On February 8, 2014 at 1:46am
jj wrote:

back in 2003 i bought an e-charger model plane that contained a LiPo cell that could charge in 10 sec and fly the plane for a minute or so allowing good heights and distances. I want to learn more about this 10 sec recharge battery but cannot find anything on it. Please comment if anyone knows.

On February 8, 2014 at 10:02am
David Marlow wrote:

to 99guspupprt:

the volage at that point will not tell you much about the capacity, as a SLA battery with very low capacity can have good Voltage when charged and then hold it for a short time under load, then suddenly drop dramatically.

On a good SLA battery, voltage under a given load from a full charge to almost depleted drops fairly evenly and has been used to indicate the amount of charge remaining

to jj:

I am no sure about that specific battery, however 50 years ago I had a toy car with a NiCad battery that could be charged for ten seconds and then go very fast, of course the temptation was to charge for longer times go farther, which did work, but the battery would get hot which caused it to fail much faster.

Remember heat accelerates the demise of all batteries.

On February 28, 2014 at 10:51am
Josiah wrote:

Hello everyone.
I’m producing a 7.2V battery. Is it possible to test for the current without connecting a load to it? If no what load do guys suggest I use that’s going to be in safe range.

On February 28, 2014 at 11:05am
Josiah wrote:

Also, is Peukert law the only way of calculating a battery’s efficiency? or is there another way?

On February 28, 2014 at 11:06am
David Marlow wrote:

I need more information about the battery to suggest possiple maximum load. If you could at least tell me what type of cells, how many cells and give physical demintions of the cells. I could make a good guess.

On February 28, 2014 at 11:26am
David Marlow wrote:

Peukert’s law applies to Lead Acid batteries very well, I am not sure if or how to appliy it to other battery types.

On March 1, 2014 at 12:28pm
Josiah wrote:

Thanks a lot David.
Its a 6 cell battery, deep cycle battery meant for backup in the event of power outage. With Pb and Fe as its active plates.

On March 2, 2014 at 1:32am
Josiah wrote:

I know 7.2V is prity small to serve as backup for power failure. But what I’m working on at the moment is experimental. Also anyone knows of a software I could use to simulate it?

On March 3, 2014 at 6:05am
David marlow wrote:

Josiah, I am not fimilair with a Lead Fe battery and sense the size is still not specified, I will assume that this is similar to the 7.2 AH, 12 volt SLA battery.  With a discharge. of 350 to 450 mA to a Voltage of about 10.4 volts it would last about 20 hours.
With a discharge of 700 to 900 mA you will get about 9 hours to about 10 volts
with a discharge of 7 to 9 A you will get about 20 to 25 minuts to about 9.6 volts.

If you are running an inverter to drive a 120VAC load from this battery you must also concider the losses in the inverter, a 1 A, 120VAC load, will require 12 A or more current from the battery, which should give you about 10 or 15 minutes of run time on a good battery.with a 2A 120VAC load you may get 5 minutes.

If you are just trying to figuer out a cpacity rating for your battery, find a load that it will drive for 20 hours to about 80% of its fully charged, open circuit Voltage.

I hope that this info will help.


On May 27, 2014 at 2:20am

What will be the ideal frequency for SMPS charger?
Does the charging efficiency depends on frequency?

On May 27, 2014 at 6:32am
David marlow wrote:

Do you mean a Smart Buss Power Supply?

On June 20, 2014 at 10:30am
Jeffrey Deutsch wrote:

I am useing after market 3.6V NiMH Versapak batteries for some old B&D devices. I junked the the trickle charger for a smart charger that can handle the 3.6V to 7.2V range at 0.9A. Is there any benefit to charging each 3.6V battery separately or will two 3.6V packs do just as well charged in series? Thank you.

On June 20, 2014 at 11:30am
David Marlow wrote:

if the cells are all mached in capacity charging in series should be fine, however if you have used batteries of possible different remaining capacities it may present problems.
NiMh batteries usualy only last 2 to 4 years and as they age their capacities are reduced, all NiMh cells do not age the same.  The cells with the least capacity will get to full charge faster when charged in series with other cells. When a cell reaches a full charge and charging current is still flowing through it, it will heat up to get rid of the extra energy flowing into it.

Heat distroyes all batteries, it just depends on how much heat for how long for each typoe of battery.

On June 21, 2014 at 1:00am

David I mean switch mode power supply

On July 3, 2014 at 12:06pm
David marlow wrote:


I did respond earler but it did not seem to make it here so,

The only issue that I can think of with a switched mode power supply (other that possible noise interficerence with other devices) is if it is not filtered adquatetly the AC content may cause the batteries to get warm and it may also shorten cycle life, both factors could siginificently shorten battery life.

On July 7, 2014 at 11:49am
James B wrote:

Great site. very helpful!

On July 29, 2014 at 12:26am
Edward wrote:

I am a battery engineer , I woulld like to help people to solve the battery problem

Edward   zzrm316@163.com

On August 7, 2014 at 5:29am
Bryan P wrote:

Hi, I’m looking at using an FPC lithium ceramic battery (FLCB)...what can you tell me about this newer battery tech? Anyone have experience testing TX/RX and discharge rates for FLCB?

On August 7, 2014 at 6:39am
David marlow wrote:

I have not tested this typ of LIthium battery.
and can not answer you questions.

I did find some info on the web, it appears to be a very safe form any hazardus responce to damage

On August 7, 2014 at 5:29pm
Edward wrote:

it is very new and advanced battery, We have no much information about the battery

On August 8, 2014 at 3:59am
David marlow wrote:

One of the reasons it may be so safe, is that it may have a high internal resistance, limiting its charge and discharge currents.  A high internal resistance would not let a short in one part of a cell cause a catistrostrific failure.

On August 8, 2014 at 6:16am
Bryan P wrote:

Thanks for the responses regarding FLCB. I’ve begun working with Prologium to spec their FLCB for a new wearable device. I will update the board with what I learn.

On October 6, 2014 at 2:28am
Jamshed F. Mehta wrote:

I think I’ll read your site.
But what I liked is your statement - “there are no perfect spouses”. I am an old man married for over 40years but I wouldn’t hazard telling my spouse that.
I am starting this assignment as I want to start a small retail business for my son in “batteries”.
Keep in touch,
Jamshed , Mumbai, India.

On October 6, 2014 at 4:00am
David marlow wrote:

Concerning SLA battery swelling,  I recently noted a baddly swellon set of batteries in a UPS. However the batteiries were still functional, I measured their capadity at around 60% and there were no shorted cells. The swelling was caused by the UPS overheating from haveing its air intke plugged up with dust and being located in a poorly ventelated space.  Cleaned off the dust and tested the ups on my bench with nearly a full load and it worked even with the swellon batteries, I did however have to disassemble teh case of the UPS to replace the betteries as the 60% batteries could not be expected to work much longer.

So when SLA batteries swell it is a symtom not the orrigional problem, the problem is over heating caused by overheating that could be due to poor venetaltion, overcharging (due to a shorted cell?), high internal resistance in the batteries (due to the batteries getting old?), or just ambiant heat.

On October 7, 2014 at 1:26am
varun wrote:

The majority of large motive power battery users operating hundreds of batteries, even thousands per site, in the USA, Australia and South Africa, use tap water. A minority use purified water. The situation in Europe is exactly opposite.

The majority of Europeans are happy to pay the full going rate for deionized, reverse osmosis water. It is a question of perception and of economics.
RGPV,UIT-RGPV, RGTU bhopal is going to declare the result of main-back examination 2014 2015 soon. the result will be declared at RGPV RGTU Results Sem B.E. B.Pharma MCA BHMCT MBA 2014 main-back reval 2015 updated regularly by exam results update.

On October 8, 2014 at 6:23pm
Edward wrote:

Jamshed F. Mehta, if you want to start a small retail business in “batteries”. please email to me zzrm316@163.com     Edward, there are many battery factory for your choose.

On January 30, 2015 at 11:50pm
Mohiaa wrote:

Dear sir..how are i have a qustion about acid battery12 v100 a..for charging ...which better the charging with12 v 35 a or charging by 24v20a…thanks at all

On February 3, 2015 at 3:19pm
David wrote:

A 12V, 100 AH lead acid battery can be charged in about 4 hours with a power supply limited to 14.5Volts and 35 Amps.

On February 4, 2015 at 3:07am
Gaurav Sharma wrote:

Hi.. Can anybody tell how a battery helps in damping out the fluctuations in system voltage??

On February 15, 2015 at 10:09pm
Durga Mishra wrote:

Hi, am interested in Li battery discharge curve @ temperatures (-10°C, 0°C, 25°C, 40°C) w.r.t 0.5C, 1C & 2C rate

On April 11, 2015 at 4:48pm
Mike Danaher wrote:

Excellent writing—you provide the clearest explanations I’ve come across in the battery world. Thanks!

On April 13, 2015 at 5:11am
David marlow wrote:

To Gaurav,
If the battery is tied directly across the voltage supply you are concerned about a battery can absorbe some voltage surges or spikes and can help support a heavy load,.However a battery is not designed to be capacitor, each time it absorbes a surge or supports a sag, that is a partial sysle of the battery, fast cycling or over charging will cause heat which will eventulay cause most batteries to fail, If a lead acid battery is kept below its rated voltage for days or weeks, that will cause it to sulfate and that will render it useless.

To Durga,
Check various battery MFR web sites there is a lot of info available..

To: Mike,
Thank you,

On May 15, 2015 at 4:09am
john meehan wrote:

I have a question i have 12 individual cells on a 24VDC battery 11 cells are reading 2.2Volts and 1 is reading 4.4volts and i am getting voltage going from 13 VDC up to 30 when i talked to manufacturer he said i had an open cell so do i just replace this cell or all 12.
Regards john

On May 15, 2015 at 4:20am
Durga Madhab Mishra wrote:

Yes Mr. John, you need to replace that particular cell from the Pack. If am not wrong, you are working with LI Battery pack.you need to measure temperature always during charging & discharging process.

On May 15, 2015 at 5:55am
David marlow wrote:

While replacing that one cell may temporaly fix the problem, I never recmend mixing new cells with old. when just reeeplacing one cell use another good used cell, and this may get you by for a while, but if you want it to be dependable, use all new cells.

On June 10, 2015 at 10:14am
Richard Cox wrote:

I have never read anywhere about charging efficiency on LiPo or Li-Ion.
Meaning what percentage capacity is expected compared to mAH input.
For Lead Acid, I have read somewhere around 80%.

On June 11, 2015 at 4:51am
David marlow wrote:

I have not seen that spec eather, butI now on the Chevy Volt the charging efficency is about 75% but that includes losses in the charging circuits as it takes 12.5 to 13 KW from Edison (depending on charging rate) to put about 10KW of charge in its batteries. So assuming the charging circuits have a about a 5 to10% loss, that would put the Li-ion battery it self at around 80 to 85%, charging efficency.

On June 11, 2015 at 8:03am
Richard Cox wrote:

After some further research yesterday, I saw articles that indicated the charging efficienty is 100%.  That can’t be correct.  The internal resistance of a cell when discharging is on the order of a few tens of milliohms.  Assuming that is the only loss, that would put the efficiency very high, but there are probably other factors in the chemistry.  Since I have never experienced any temperature rise during charging which would indicate losses, I would expect the efficiency to be very high, over 90%.

On June 11, 2015 at 9:52am
David marlow wrote:

You may be correct as I said I ws estimating the charging circuit losses in the Volt.

I remember doing some testing on some SLA batteries and with each cycle I was getting more energy out than I was putting in, Then I realized that I was doing the cycles rather quickley and the battery was increasing in temp and that Lead acid batteries preform better at higher temps,. but wont last as long. I think that this is some what true for Li-Ion batteries, only that the higher temps are much more detretramental to the Li-Ion cells.

On July 29, 2015 at 9:11am
chuck wrote:

I was told by a manufacturer’s rep that charging a 12V >50Ah battery (SLA) with only 2A would cause degradation of capacity over time. I understand it would take a long time to charge, but will it cause degradation of capacity?

Thanks for your response. I appreciate your very informative site.

On July 30, 2015 at 4:04am
David marlow wrote:

I do not know that particular battery, but if the charging was constant (even after the battery had reached a full charge), that would shorten the battery life.  The other possibibilty is if the load on the battery was equal or greater than a 2A average.

On July 30, 2015 at 7:32am
chuck wrote:

Thanks for the reply.
I’m talking about charging a battery disconnected from everything but the charger.
The rep was speaking generally about charging a “large” battery with a 2A current. I had asked about a specific “smart” charger they sell recommended for charging batteries up to 35Ah. (“Smart charger” automatically switches to “maintain” mode when battery reaches a specified voltage.) I asked him about using it for charging larger batteries, e.g., a 66Ah battery. He said they recommend a charger with 3A or 4A output for that size battery. When I asked if the 2A charger would charge the large battery (albeit with a more lengthy charge time) he told me that repeated chargings with low current like that would result in decreased capacity over time. I can find nothing to support his statement.
I am very much interested in your thoughts on this matter.
Thanks again.

On July 30, 2015 at 8:22am
David marlow wrote:

The only problem with slow charging would be on a battery that was discharged frequently and not being fully charged before being discharged again.

Some Lead acid batteries start getting higher self discharge rates as they get older and with use, so if your 50 AH battery were to require even 1/2 an AMP or more of constantant charging to maintain its charge, it would be time replace it.  The maintaince voltage for a 5 amp SLA battery and 50 AMP SLA battery would be the same (some SLA battery types do require slightly lower maintaince charge voltages, most are 2.3 V/cell, for your 12 V battery that would be 13.8 Volts. Maintaining at a higher Voltage would decrese the life of the battery. Fast rechargeing can be done at up to 2.45V/cell.

On July 30, 2015 at 8:58am
chuck wrote:

So would the following be true for the SLA battery:
A 50Ah battery drained to 40%-50% of capacity can be safely recharged with a 2A charger at 13.8V (or 14.6V for fast charging) until battery is fully charged (requiring ~15-20 hours at 2A)  with the 13.8V left on indefinitely to maintain full charge.
And multiple recharges using this method would not cause “premature” loss of battery capacity over time.
This is all about us finding an inexpensive charger that we can sell for batteries that we sell. I don’t want to pay $60-$100 for a 3A/4A charger if I can charge it, albeit slower, with a $25 charger. But…. I’m just trying to make sure I’m right about it.

And.. thanks again.

On July 30, 2015 at 10:08am
David marlow wrote:

OK, lets assume that the battery is discharged for about 4 hours a day to 50% capacity and then placed on charge with the 2A charger for 20 hours and then used again like this 5 days a week, the battery should last about 1 year or so.

On August 5, 2015 at 9:57pm
Shu Ting wrote:

Thank you so much for taking the time and effort putting this knowledge base together! I just started researching materials on batteries, and stumbled upon this site. It really put things in perspective for me, and fun to read too!

I often admire very knowledgeable experts who could put things in a layman terms. That shows that they really know. A LOT! smile

Thanks again for having this great site!

On August 26, 2015 at 8:00pm
Azahar wrote:

I have problem with traction batteries, which is dry out during operation, it not due to high consumption of water, it is because overlooked on the battery water maintenance. After the performance decrease from time to time than only found that the battery water is already dried. Unfortunately the truck operator accidentally pour or filling up the battery cells with the other acid or maybe some other liquid such as detergent. because after filling that the battery drastically in bad performance less than 20%.almost dead. (seems like dry sponge immerse to unknown chemical cause sponge to be destroyed)
My question is
-What was the active material react to the unknown chemicals or acid?
-Can be dead active material cause bad performance?
-Can we refurbish the cells to get back the performances?

Thank you

On August 27, 2015 at 4:00am
David marlow wrote:

The only thing that should be added to the batteries is distilled water,

If you werre to try to flush out contiminenates you could use distilled water to flush the cells clean and then refilling with fresh acid might help.

If the battery is sulfated from sitting discharged a trickle charge over a few dayt might help (if it will take current at all).

On December 24, 2015 at 8:17am
Sherri wrote:

Why does it happen that some batteries explode while in a mod (mini). A person walked in a vape shop to show his mod and battery, he saved his mod mini, but the battery was burnt. He said at the time it happen he was laying down with his mod on his chest when he heard a hissing noise and saw smoke, he quickly took his battery out before it damaged his mod.  The rep in the store could not explain told him to call the manufacture company of his mod.  I believe it had to do with the battery not the mod. What be the best advice for the next person if this was to happen.

On March 20, 2016 at 7:12am
Malik Javaid wrote:

I am from Sargodha Pakistan. Here we have power shortage problem and almost every home have inverter or UPS. I have 1500 watt 24 volts inverter with squarewave.The charging kit has some variable for amp, low battery, fix volts, and main supply control. I have attached 2 new lead acid batteries of 110 Ah each in parallel. I have to run 3 ceiling fans 6 energy savers bulb of 25w each during load shedding hours. It is about 4 hours in a day and not longer than an hour.I have very little knowledge about electronics but after spoiling lot of money due to overcharging of batteries I am now little bit concious and just purchased a multimeter to checkthe charging amperes and cut off volts of the batteries. Would you please guide me that what should be the maximum charging anperes for the aforesaid batteries.The charging kit installed with leds displaying and amperes gradually decreases in three phasis. Presently it start charging from 15 amp and ends at 6 amperes. Is it ideal chagung setting?
Thanks in advance.

On March 21, 2016 at 4:24am
Durga Madhab Mishra wrote:

First of all, check H2SO4 (acid) level in batteries. It should be in between MIN-MAX mark.
Two lead acid battery connected in parallel is not acceptable for charging & discharging. For mentioned configuration, You can minimize charging current to 8-10 Amp to make battery life healthy.

On March 21, 2016 at 5:45am
David Marlow wrote:

Hi Malik,

I need to make sure that we have the correct information, are the batteries two 12V, 110AH batteries connected in series or two 24V, 110AH in parallel?

I do not believe that connecting two lead batteries in parallel while charging or discharging is a problem unless one of the batteries is bad, only while sitting long term unused, could parallel connection possibly cause a problem. 

Assuming that your 3 fans use about 100 watts each and that the efficiency of your inverter is about 80%, that would be about a 500 watt load and at 24 volts the inverter should be using about 20 to 21 amps from the batteries.  So if 12 volt batteries in series that would still be 21 amps, if 24 volt batteries in parallel that would only be about 10.5 amps each.

Sense 12 volt batteries are much more common, I will assume that is what you have.
so a one hour discharge would be a about a 25% discharge (the 110 AH rating may be for a 10 hour discharge or 11 amps at a 21 amp discharge rate the battery should be de-rated to about 90 AH).  Discharging this way four times a day would mean that I would expect these batteries to last about 200 days before needing to be replaced.
in the case of 24V batteries in parallel that life time might be 500 days, if the fans are using more that 100 watts each, the lifetime would be less

How much life time are you experiencing?.

On March 21, 2016 at 5:50am
David Marlow wrote:

my previous comment is assuming that you are using deep discharge type batteries, if using automotive type batteries the expected lifetime could be less than 100 days.

On March 21, 2016 at 6:05am
David Marlow wrote:

One more thought, if the load is greater that I think, your charger may not be fully recharging the batteries between uses, and this could cause the batteries to fail faster.

On March 29, 2016 at 2:36am
Vedran Bobanac wrote:

Dear readers,

As a part of the research project Electric Vehicle Battery Swapping Station - EV BASS http://evbass.fer.hr/en/evbass we have prepared a short online questionnaire on EVs, hoping we will learn more about the habits of the existing EV owners and expectations of the future ones. The survey will take up to ten minutes; we are grateful to everyone who will take this time, contribute to our project and help us better understand the needs and habits of the prospective EV owners.
The questionnaire is available at:


If possible, please also share the questionnaire to as many of your contacts.
Also, every help and suggestion on how to increase the visibility of the survey and the number of people who will take the survey is more than welcome.

Thank you for your time and for your help.

Best regards,
Vedran Bobanac

On March 29, 2016 at 10:01pm
Gaurav Sharma wrote:

Helo again asking the same question as i was not able to understand.. can anybody please explain
how a battery helps in damping out the fluctuations in system voltage??

On March 30, 2016 at 2:40am
david marlow wrote:

Within its limits, it will charge from voltages higher than it is currently at and discharge to support voltages that try to go lower than its voltage.


On March 30, 2016 at 2:44am
Gaurav Sharma wrote:

ok thanks. but if spikes arises in the vehicle , how will battery protects the complete system from spikes.

On May 15, 2016 at 4:28pm
Dave Kay wrote:

I am in the process of balancing ( discharging / charging ) my 2005 Prius battery made of nimh cells. I am discharging 0.8 mah down to 6V, 5 min. cool down, charging at 5V to a max of 7300 mah x 3 cycles. What do you think about these settings?

On May 16, 2016 at 4:27am
David Marlow wrote:

I do not know much about the Prius Battery packs, but the gain after the first Cycle will be minimal, How old is you battery? NiMH batteries do not work well after about 4 years, your batteries are probably approaching their end of life if you are trying this to revive them. Properly managed Li-Ion batteries will potentially last twice or more as long as NiMH batteries.

On May 16, 2016 at 8:02pm
Dave Kay wrote:

The car is a 2005 Prius. The battery capacity has increased after discharge/charges. There is no way to use Lithium batteries.

On May 17, 2016 at 5:03am
David Marlow wrote:

If this is the original battery, I am surprised that it still has sufficient capacity and current to be of use as the NiMH batteries I am familiar with are not of much use after 5 years.

Has it been upgraded to a Plug in with the extra battery? 

What do you estimate the current capacity is as compared to when it was new?

I have a 2011 Volt with 65K miles on it (about 55K running on just the Lithium battery), I estimate that the capacity is down about 5%.from when it was new.

On May 18, 2016 at 5:27pm
Steve Gee wrote:

My cars battery has been flat once before does that change the capacity of it as well because I’ve noticed that my battery hasn’t produced the same amount of amps in it so i was just wondering what the go is. thanks in advance if any one knows.

On May 18, 2016 at 7:50pm
Kaleb Choyce wrote:

Hey, I have a Suzuki Swift but im noticing that within a few days im having issues with it starting due to low battery, the battery is new and I always check it but now its preforming poorly Help?

On May 18, 2016 at 9:08pm
Not telling you wrote:

what kind of battery would last longer for a hilux ive got a water deep cycle but its the same issue as Kaleb Choyce has

On May 18, 2016 at 9:29pm
not telling anyone wrote:

l0l ye battery that’s funny any1 can save battery’s by not turning it on

On May 19, 2016 at 4:48am
David Marlow wrote:

Regular Lead Acid car batteries do not tolerate very well being run down and left that way for very long, they can recover some what, but if they have been discharged for a total of about 1 month they will fail.  A deep cycle type Lead Acid battery has better tolerance (like a Marine or Aircraft battery).

On May 23, 2016 at 1:54am
devi wrote:

Can u please explain how is DOD related to cycle life?

On June 24, 2016 at 6:43pm
nate wrote:

Apologize if my question was asked/answered and I missed it.
What is your recommendation for a 12V battery for a back up sump pump application?
The backup battery is only activated if the main AC power goes out and it is raining and water is flowing into the sump pit.
This occurs from 0 times to maybe 2 times a year.
But perhaps once every 5 years Niagara Falls is flowing into the pit with no AC power. Then, the profound importance of the backup system is hard to overstate.
It appears most back up sump units are sold with maintenance free deep cycle 100 or 75 AH AGM batteries. Do these seem like the best choice to you given my rare usage pattern (yet critical when needed)?
Also, most back up units are sold with controllers that trickle charge the batteries periodically. I assume this is essential to maximize battery life? Any advice here?

On July 6, 2016 at 6:25pm
Danny wrote:

Hi, can someone tell me if valve regulated lead acid batteries are safe to use in a motorhome situation, I have 2 x190amphr batteries that are ex telecom,the info I have read from www.enersys.com say they are safe and suitable for all sorts of uses but not expressly says motorhome or caravan, I do realize that I will need to ventilate them as they will be stored under the bed along with the smart charger any advice in simple terms please as have little understanding of batteries and 12 v as I’m converting a bus to a motorhome and now at the stage of installing the battery management system and got these 2 batteries ex telecom with plenty of life still left if treated correctly and want to learn as much as I can so I can do as much as I can myself thanks danny

On July 8, 2016 at 3:55am
David Marlow wrote:

It sounds like you have a good understanding of the issues, the only question I would have is if these batteries are intended for only stationary applications, as the vibrations might be an issue.

On July 9, 2016 at 1:04am
Danny wrote:

Thanks david, the batteries will be secured to the floor, info I have from battery university is that the batteries used for my purpose will be OK as long as they are vented to the outside, thanks again danny

On July 19, 2016 at 11:05pm
Edward Chee wrote:

I am Edward, student from University Malaysia Science are now doing research on battery. may i ask about some question?

Why does western country mostly using 6V to 12V lead acid battery for car/truck while asia or eastern country mostly use 12V to 24V battery? is it because of the weather or the temperature of the country? this is because i mostly found that the battery tester that produced by western country only limit to 6V and 12V.

On July 20, 2016 at 12:09am
Edward Chee wrote:

Hi, i would like to ask why western country use 6V to 12V lead acid batter only for their car while for Asia they use 12V to 24V??

On July 20, 2016 at 9:22pm
david marlow wrote:

My guess is that the larger manufactures have a greater investment in the 12 volt system standard. There are reasons to go to a 24 volt system such as lower cost of wiring and less weight. However all of the electrical devices in the car need to work with that 24 volt system.  DC to DC converters have come down a lot in price so a car with few electrical accessories could be economical to produce. But western Customers expect a lot of electrical features in their cars.

On July 21, 2016 at 9:00pm
Edward Chee wrote:

Hi David,
thanks for the reply, may i ask some more question?

if a trucks state that they have 24V battery, do there mean they have two 12V battery combine? or only one 24V battery that install in it? if there is only one 24V battery instead of two 12V battery, how do i test it with 6v to 12V battery tester?

On July 22, 2016 at 10:32am
David Marlow wrote:

I am not a Truck expert, I would think that it may vary and some would be 2 12 volt batteries and some might have a 24 volt battery. You will have to check to see what your exact situation is..

On July 23, 2016 at 7:18am
rand kemslety wrote:


I’m a first time visitor.

Can someone tell me if it’s practical to run power from a 80 Ahr car battery, to a (I don’t know) Ahr deep cell marine battery, to a 2000w power inverter?

And if so, how long before they are 50% discharged with a continuous 5 amp draw?

On July 25, 2016 at 12:30am
Edward Chee wrote:

thanks for the information, and may i ask about the starting and charging system? if both system is 12V, does it mean the car battery is 12V? what if the system is 24V, does it mean they have 2 12V battery in car???

On July 26, 2016 at 4:13am
David Marlow wrote:

I do not know about cars with 24v systems, some vehicles usually RVs, have two 12 volt batteries but use one to power other lights, fans, TVs, etc. but are still 12 volt systems. The only way to have a car with a 12 volt charging and starting system to have other systems at 24 volts would be to have a 12 volt to 24 volt dc to dc converter, then you could have one or more 12 volt batteries on the 12 volt system.

On July 26, 2016 at 6:13pm
Edward Chee wrote:

Hi David,
Thanks for your reply, it do help me a lot. thanks again!

On July 31, 2016 at 9:18pm
edward wrote:

i would like to ask that why trucks that run with 24V use two 12V battery instead of using just one 24V battery?


On August 3, 2016 at 4:48am
David wrote:

I would guess that 12V batteries are more common and more economical to purchase, also for servicing it would be easier to handle two smaller batteries that one larger one, and for placement more options.

On August 3, 2016 at 8:47pm
edward wrote:

oh, thank you for the answer!! thanks

On August 3, 2016 at 10:15pm
Danny wrote:

Can anyone tell me if valve regulated lead acid batteries can be treated the same as regular lead acid for charging as my new smart charger only says regular lead acid batteries, I rang the supplier of this charger and so far haven’t been able to tell me??????regards danny

On August 5, 2016 at 4:31am
David Marlow wrote:

Interesting, I wonder what they consider “regular” as most lead acid batteries now in production would be valve regulated
If it is a smart charger, what is so smart about it?  Some smart chargers are only for charging smart batteries, that is batteries, that can tell the charger how to charge them.

Lead acid batteries that are not valve regulated can have distilled water added to them to compensate for the losses from over charging of the weaker cells or constant current charging, which a smart charger should not be doing to lead acid batteries.

So I to have more questions than answers about this smart charger. more information would help a lot.

On August 8, 2016 at 11:24pm
edward wrote:

hi again, i have some questions to ask, its about jump starter.i found out that the battery capacity in jump starter will decide the peak current that will produce during jump start a battery. if this concept is true, may i ask how many battery capacity and C rate will be needed to produce 1000 A peak current??

On August 11, 2016 at 4:50am
David Marlow wrote:

The C rate is not directly related to output current, usually the higher the C rate the greater the current, However it is actually the internal resistance of the cells that limits the output current and that is usually a result of the design of the particular cells.
Manufactures can make several different cells that appear the same on the out side and have the same Capacity but have different output current specs.

On August 14, 2016 at 8:54pm
edward wrote:

hi David,

thanks for the reply, i wonder if the resistance is the same, why it will cause some jump starter can jump start the boat battery while some other cannot??

thank you

On August 15, 2016 at 11:29am
Vishal Sharma wrote:

I am Vishal From Pulstron Battery India
We wants to know the Chemical Composition and best Manufacturing process Of Lead Acid tubular Battery Plates So That we can get Full Battery Backup.

On August 15, 2016 at 8:05pm
guillaume gerondal wrote:

Dear Sir
Could you please tell me the best way to discharge a li-ion battery 18650 ?
What is the minimum voltage and current to be able to recharge ?
why do we have to discharge those BAT before we can charge them again ?
What is the best way to charge them in Parallel or in Series ?
Same time when I charge them they get very hot can NOT touch them and they get around 4.2 Volts is that O.K ?
And my last question how can I find out the Currents of those Batteries ?
Thank you
Best Regards
Guillaume Gerondal

On August 15, 2016 at 8:16pm
guillaume gerondal wrote:

Dear Sir
Sorry I forget to tell you I have around 260 of Batteries 18659 ! maybe is important for you to know !

On August 18, 2016 at 8:11pm
david marlow wrote:

Very hot is very bad for LI-ion batteries, Heat over 37 degrees C to Li-ion cell should be avoided to prevent them from catching fire, but mostly to prolong their life,  The heat comes from the cell getting rid of more energy getting put into it than it can absorb, Also when a Li-ion cell is discharged when it gets hot you are either discharging it to fast or to deeply or both.

So If a li-ion cell is getting hot, you are doing something wrong, charging or discharging too fast or too long.

Li-ion cells do not need to be cycled like other battery types do.

They are best stored with a 20% to 80% charge.

On August 30, 2016 at 7:41pm
Juan Rodrigues wrote:

Hello, I have been working with 96 VDC Batteries to feed automated equipment.
Its voltage is read by PLC through a DC voltage converter 96VDC to 10VDC (to be read and displayed). the equipment changes its battery by itself when a logic compares the battery voltage with a set value.

I have been getting too many batteries request and when I have got connection with the PLC I realised that the voltage being read is fluctuating from 96VDC to 40VDC (not always the same values) in few seconds and coming back to the previous value.

I am wondering what might be causing this issue. I will appreciate any information.

On September 1, 2016 at 4:49am
David Marlow wrote:

My first guess would be a poor connection some where in your system.
It might also be an intermittent cell
Try using a separate volt meter and compare readings.

On September 21, 2016 at 12:27am
Bob wrote:

Please what is the acyual meaning of these things:
Current (A)
DateOfYear: hh:mm:ss
Test_Time 2


On September 22, 2016 at 4:51am
David Marlow wrote:

Are you trying to fill out a form for some particular purpose?.
What you are looking for is an electrical engineering college course, or graduate to help you with your situation.

On November 8, 2016 at 3:15am
Georges wrote:

Hi David
If a UPS battery exploded for a reason, it will create a voltage surge on the batteries charger line. Can this surge cause damages to the UPS thyristors? Thanks

On November 8, 2016 at 11:53am
David Marlow wrote:

The only reason I can think of for any lead acid battery to explode is to have a solid short across its terminals, and this would not create a voltage surge but a current surge, assuming this is what happened, and that the surge did not pass through the thyristors, I would think that the UPS should be designed to handle a short with maybe only a fuse blowing. If the current did pass through the thyristors then they very well could be damaged.

I am not an expert on all UPS units and you have given me very little info to work with.

On November 19, 2016 at 12:23am
Electronics wrote:

Thank you so much for taking the time and effort putting this knowledge base together! I just started researching materials on batteries, and stumbled upon this site. It really put things in perspective for me, and fun to read too!
I often admire very knowledgeable experts who could put things in a layman terms. That shows that they really know.

On November 28, 2016 at 4:32pm
Kalim wrote:

Dear sir…
I am from Odisha and I request you to help me out to bay a inverter with a perfect battery..
In my home we have
8 celling fan
2 table fan
8clf bulb
2 _ 100 wt bulb
1 colour tv
I want artist 8 to 10 hr backup
So please tell me which inverter and which battery should I buy….
My email____ kalimkhan2007@yahoo.com

On November 29, 2016 at 5:33am
David Marlow wrote:


Sorry there are no perfect batteries, all will fail some time.

The lowest cost Per Watt hour would most likely be 12 volt lead acid batteries, but you must get the deep cycle type for the best life time in this application and if you cycle them most days you would have to replace them every year (for your usage that would get quite expensive, a generator would be a lower cost option.

However, I will estimate that you will require an inverter (or generator) rated for at least 1500 watts.
Then you will need batteries totaling 20,000 or more Watt Hours (no inverter is 100% efficient and for longer battery life times you do not want to fully deplete them each cycle),  A 12 volt lead acid battery rated at 50 amp hours would be 600 watt hours, so you would need at least 34 of them, Assuming about $100 ea. for the deep cycle type

On December 8, 2016 at 3:39am
hey_gluppy wrote:

Thank you very much for enlightening me about the battery world! My project is about designing 20KW Battery Charging System. I hope I can learn from you and other experts here.


On December 9, 2016 at 7:51am
david marlow wrote:

The information that you will need is the charging specifications for the batteries that you will be using and your local electrical codes.

On December 14, 2016 at 10:33am
manmohan wrote:

please tell me my computer ups is double battery . and capacity is per battery 12 volt and 7.2 Ah. so i want to use 5 watt led tube light
please tell me ups back up time

On December 15, 2016 at 7:47am
david marlow wrote:

If you are asking me how long a UPS with 2 12 volt 7.2 AH batteries run a 5 Watt light?

Two variables that I do not know are, they are the condition of the batteries and the efficiency of the UPS at that low load.

So a test you can do is to see how long the UPS will run it self (no load), then you will know that the run tine with the load will be less than that.

On December 18, 2016 at 6:39am
manmohan wrote:

i have a computer ups. 24 volt transformer in ups.
so i want to charge 26Ah battery.
my question is any problem in transformer.
if charge is battery how long time will charge from main current.

On December 19, 2016 at 4:55am
manmohan wrote:

my computer ups transformer is 24volt.
7.2Ah battery total 4 battery.
i using 4 battery for charging from my ups.
any problem my ups

On December 19, 2016 at 5:20pm
david marlow wrote:

Most UPS units are not designed to recharge their batteries quickly, so attaching more or larger batteries to them will result in a longer time to recharge the batteries. The increase of battery capacity added to the UPS to increase the run time will proportionally increase the recharge time.

On January 3, 2017 at 4:47am
manmohan wrote:

i have 12v 26Ah battery.
so how much should be transformer Amp for battery charging

On January 3, 2017 at 11:07am
david marlow wrote:

A normal fast charge for a SLA battery would be 4 hours with about 90% of the charge in the first 3 hours. So to charge this battery in 4 hours the charging transformer would need to be rated for at least 9 amps.  If you are trying to figure out a transformer in a UPS then this would not apply as It is not that simple.

On January 3, 2017 at 6:25pm
manmohan wrote:

thank you sir for this information

On January 17, 2017 at 11:16am
Alejandro wrote:

Hi Everyone,

I see a lot information about the diference between Li-ion batteries and Li-polymer, but still don’t find anything about what its more security to about the catching fire risk.

Would like to ask if anyone have futher information about this point?

Thanks in advance.

On January 19, 2017 at 6:08pm
david marlow wrote:

The causes of Lithium battery fires that I have head of fall into one of three categories.

Most seem to be from battery manufacturing defects (beware of new or cheep products).

Some have been due to design problems with, or lack of a battery management system.

A few have been from physical damage to the cell or cells.

On February 15, 2017 at 8:17am
david wrote:

Is it safe to use a 12 volt wet cell batter if the fluid has leaked out of one compartment but it still holds a charge?

On February 16, 2017 at 5:59am
david marlow wrote:

There are a lot of things to consider when thinking about safety.
The acid leak it self could be a serious safety hazard.
The loss of fluid from one cell will reduce the capacity of the battery at rated voltage, that in some situations could be considered a hazard.

Without knowing the exact situation of how or why it leaked and I cant comment on what is safe, but in general to be safe replace the battery.

On March 1, 2017 at 1:57pm
ss wrote:


I am a member of RC Groups and there are frequent discussions on damaged LiPo cells. More specifically, when they have “puffed” up.

Does this condition render the battery useless even though it still works and maintains a charge?

Is the battery now in a dangerous state and must be disposed of?

Everyone on RC Groups has an opinion on this, but I’m hoping that BUG can provide a definitive answer.


On March 8, 2017 at 5:24am
Aini wrote:

My problem is my battery of smartphone always fast finished and low when I use it. Every second lost one of 100%. and when I charging with the desktop charger, it is not untill full (not 100%, usially only 70%. It hold out approximately 1 hour.  My phone ever get water, and I try to drying. How do I should??

On March 8, 2017 at 4:50pm
david marlow wrote:

Puffed up battery indicates a problem with the battery, it may still be working OK for now, but a more serious problem may follow.  Is it worth chancing a possible fire by continuing to use it?

If I understand your problem correctly, your cell phone got wet and now battery charging and run time is not what it should be?  It may take several days for your phone to completely dry out and return to normal operation.

On March 9, 2017 at 12:39pm
ss wrote:

Thanks David,

So it is a fact, that a puffed LiPo battery is either structurally or chemically unstable and could spontaneously combust.

Is there more information in BUG about LiPo batteries?

On March 9, 2017 at 4:44pm
david marlow wrote:

I am not an expert on LiPo batteries, however swelling of any batteries indicates a problem
these problems could be caused buy defects in the cells, or by some type of abuse electrical, or mechanical.

On March 13, 2017 at 9:24pm
ss wrote:

But either way, if they are puffed, then that is the end of them.

OK, thanks.

On March 16, 2017 at 9:23am
Enrique wrote:

My current laptop’s battery has the Li-ion “stamp” on it. I am on the market for a new one, and I have seen several offered with the plain Li-ion stamp, but others with a “Li-ion 20” stamp on it. Both are genuine, but do not know the advantage of one versus the other.

Is there any significant difference between them if both have the same voltage and Whr?

Thank you

On March 17, 2017 at 12:44am
david marlow wrote:

While this is the first I have heard of this, as it is part of the recycle info label/ stamp. it has to do with the recycling of the battery.

As there are now many sub types of Li-ion batteries, there may be differences in how they should be recycled, or sorted for recycling.

It would not have to do with the voltage or rating of the battery, as that is listed separately.

On March 20, 2017 at 9:33pm
Miyie wrote:

hai.. i just wondering about drain of battery,
if we use non rechargeable battery, the battery will be drain the capacity, but the voltage drain or amp drain? if voltage drain mean they have cut off voltage which if voltage cut off 4.5v from 5v so the battery cannot use.

On March 22, 2017 at 4:20pm
david marlow wrote:

The shape of the Voltage discharge curve is different for different types of batteries.  The current depends on how the load responds to changes in voltage.

A simple resistive load will draw less current as the voltage decreases.

The current that a switching power supply (that is in most modern electronics) will draw will increase as the battery voltage decreases until a limit is reached.

On March 24, 2017 at 2:06pm
Christopher D. Johnson wrote:

Is there someone I could talk with regarding notice requirements on 18650 batteries?  I continue to see these listed on Ebay and Amazon, claiming outrageous capacity and duration.  Many have few or no mark9ng about size, or composition.

On March 24, 2017 at 6:41pm
david marlow wrote:

Li-ion batteries are changing fast and can be optimized for heat sensitivity, cycle life, years of life, capacity. 
The size should be close to the 18 mm diameter and the 650mm length.

The chemistry of the electrolyte, and exact plate construction could be considered a trade secret.

The recycling label mentioned in a previous post has to do with labeling for recycling. Checking on those requirements may help you.

On April 9, 2017 at 8:15am
Edward wrote:

I have a 1150 CCA AGM Marine/Auto battery I use for camping in my van.  I have a solenoid that automatically charges this auxiliary battery when the vehicle is running.  I have dual 850 CCA batteries that start my van.
When the van is running and charging my auxiliary AGM battery does it fully charge since the auto batteries are 850 CCA auto batteries?
Basically I am wondering if ALL batteries need to have the same CCA specs and if it matters that two of them are auto batteries and the other is an auto/marine combination AGM.

I also have roof top solar panels I use through a controller for the aux battery.  I have noticed that the aux battery will not hold a charge greater than 12.7v anymore but when I bought the AGM battery it tested at over 15v.  Is my alternator or solar controller somehow lowering the potential of my $400 AGM aux battery?

On April 9, 2017 at 5:24pm
david marlow wrote:

As long as all of the batteries are 12 volt lead acid types and the batteries are connected in parallel while charging,,  the differences in battery capacity ratings should not matter much, unless one of the batteries has a bad cell, as may be the case for your battery that will not charge to 13.5 volts.

All batteries will eventually fail.  When they will fail depends on many factors, such as type of battery, quality, cycle life, years of use, abuse.

On April 24, 2017 at 12:39am
Priyo wrote:

Can we recharge battery with voltage below the battery specification, ex. i have 72 Volt battery, i recharge with 60 volt charger,

On April 24, 2017 at 1:23pm
david marlow wrote:

the short answer in no,  However depending on how the charger works and the type of battery you have it might charge it partially

On May 7, 2017 at 2:34am
mohit wrote:

What is the problem with my phone battery when I charge it heated up very much

On May 9, 2017 at 7:16am
david marlow wrote:

I could be a charger problem, but a shorted cell in the battery is the usual cause.

On May 31, 2017 at 8:54am
Adedeji Daniel wrote:

please I need sum DAT can assist me,I’m a novice but I need to know all dis

On July 24, 2017 at 5:34pm
Chris Shortt wrote:

Does anyone know where i can get a fairly complete list of all the batteries in existence with their specifications like size and operating features like voltage, amperage, approx number of rechargeable cycles etc.?

On July 25, 2017 at 7:32pm
david marlow wrote:

such a list is not possible to be current as battery improvements are coming so fast that the list would not be current as soon as it was published.  It would be better to evaluate what features are most important for your application.  And then start focusing on the battery types that have those features.

On August 13, 2017 at 3:02am
Jim Welsh wrote:

i am interested in receiving updates please.

On August 13, 2017 at 1:03pm
Jerzy wrote:

Does anyone know when a NiCad battery on an old computer motherboard leaks (due to age, not mechanical abuse—the computer is a TRS 80 Model 4), is it just the electrolyte that is released, or do I have to worry about cadmium residue also being present in the white powder that results? Many thanks for any info you can provide.

On August 14, 2017 at 5:45pm
David Marlow wrote:

Any NiCad battery should be considered toxic waist and should be disposed of properly.  So far, I have not suffered from contact with small amounts of contact with NiCad battery leakage/ corrosion (white powder).  I have a “D” cell NiCad battery that is over 30 years old and has a small amount of white power at the seam end. It still has over 100% capacity, but the internal resistance is a bit high. The way to long life for a NiCad battery is to keep it discharged when not in use and do not ever over charge it.

On August 16, 2017 at 2:05pm
Jeffrey Rice wrote:

I have several 18650 li-ion batteries that I am attempting to resurrect.  I am using a Thunder AC6 Balance charger (used by hobbyists for RC toys).  When I connect the charger using the Li-ion configuration (3.7 V .3A) the voltage slowly goes up to about 3.6.  I remove it from the charger (I realize this is under charged) and use my VOM and find a voltage of over 5 V!!!  Is this normal or some kind of surface charge?  The battery was never warm to the touch at all.  It has me doubting my charger.

On August 16, 2017 at 6:34pm
David Marlow wrote:

A 5 volt charge may be possible, but it will cause the battery to degrade quickly, possibly catch fire!. Normally a 4.2 volt charge is what you would want. If you need a little more the 4.3 volts could be used as a limit, as long as temp is controlled below 90 degrees F.
It sounds like there is a problem with the voltage cut off in your charger, or something is wrong with you meter.

On August 17, 2017 at 4:57pm
Robert Applegate wrote:

When Wahl introduced NiCd powered cordless soldering circa 1970’s or so, I bought one quickly. I soon noticed that it was warm when sitting in the charge stand so I built a simple constant current stage into the charge base designed for ~5 mA.

I used it heavily for many years building numerious electronic project kits, etc. I always kept it in the charge stand and it never ran down, no matter how much i used it.

Sadly, it stopped working last year (2016).  By my estimation, that NiCd cell charged non-stop for 40 - 45 years at ~5 mA.

It is still sitting there, and I can’t bring myself to throw it away! lol

On August 21, 2017 at 1:06pm
David Marlow wrote:

Good to know! The sub ““C” cells used then were rated at about 1 AH and the cell MFRs recommended a 14 hour charge at 1/10C or 100 mA that would result in the sells getting warm when fully charged.  If left charging at this rat when already fully charges the cells would only last one to four years, before needing to be replaced, 

On August 22, 2017 at 11:39am
Robert Applegate wrote:

I concur completely with your assessment.  What continues to amaze me was the longevity of that battery when it was trickle charged for all of those decades.  I hope that there is an opportunity for you to pay this forward.

FYI….I’m just about to turn 70 in a few weeks and I have been using and caring for rechargeable batteries since they were invented.  It is really interesting to explore the capabilities of these newer families of devices.  While I have been using 18650 cells for a while, I just came across a few that are rated 9800 mAh.  Shortly thereafter, I discovered that they are not Li ion but rather Li-Iron-Phosphate (LiPos) which are a great deal more dangerous.

My day job continues to be the design and construction of factory automation systems in a facility that handles the recycling of Titanium, which is a very complex material to handle in some of its many forms.  As an example, the local fire department has been trained to do traffic control when we have a fire because that is all that can be done.  From what I have seen, these LiPo cells have pretty much the same kind of dangers.

In conclusion, I would advocate that these dangers publicized so that the use of these cells is done with appropriate care.

On October 23, 2017 at 1:02pm
Edmond wrote:

pls kindly explain to me the chemical reaction that takes place in the battery for vehicles

On October 28, 2017 at 9:53am
Jim Win wrote:

Having a 100+ amp source which I can only access for a short time, how can I use it to fast-charge a super capacitor bank then slow-charge a 20Ah Li ion battery from the super capacitor? 

On October 28, 2017 at 10:40am
Jim Wilson wrote:

Having a 100+ amp source which I can only access for a short time, how can I use it to fast-charge a super capacitor bank then slow-charge a 20Ah Li Ion battery from the super capacitor?

On October 30, 2017 at 9:30am
David Marlow wrote:

While you could charge your super capacitor bank quickly (assuming you do not exceed the voltage rating of the bank),  to fully charge the battery would require a capacitor bank that would hold more energy than the battery (a very large bank at least 1000x the size of the battery) and a battery charging circuit that could work with the decreasing voltage output of the bank.  The voltage output of capacitors decrease as the energy in them decreases.  So some type of step up DC converter to a voltage higher than the battery and then a battery charging circuit approiate for the battery.


On October 30, 2017 at 9:45am
David Marlow wrote:

Even though you have supercapacitor bank, you will need to be sure that its energy storage capacity exceeds that of your battery, to provide a full charge the battery, also make sure you do not charge the bank beyond its voltage rating (it may explode).  Then remember that a capacitors output voltage decreases as its energy decreases, so you will need a DC voltage converter to regulate the output to what your battery charger requires.

On December 13, 2017 at 6:21am
Rob Lowe wrote:

need help ,will a 48volt charger harm 24 volt batteries ?

On December 13, 2017 at 4:35pm
David Marlow wrote:

If two 24 volt batteries are reasonably matched and connected in series (48 volts) it should work fine, but charging one at a time will cause problems. 


On February 24, 2018 at 9:12am
Eddie Birch wrote:

I am new to this forum and I am learning a lot just by browsing this site. Please keep up the good work and I may eventually understand batteries.

On June 6, 2018 at 1:11am
Juliana wrote:

Some articles say, the charging frequency does not affect the battery lifespan, but some others say it does. Which one is right? Say I have two separate batteries supplying two identical loads and each battery is at 100% SOC.  One battery i always recharge it back to 100% after it discharges to 80% SOC and the other battery I always recharge it back to 100% after it discharges to 30%. which of these two batteries will last longer?

On June 6, 2018 at 10:58am
David Marlow wrote:

If the batteries are a lead acid type, then the battery only discharged to 80% should last longer (discharging most of the way once or twice a year could be helpful).
If they are Li-ion or NiMh then the batteries discharged to 30% should last longer.
If they are NiCad they would last longer if you would discharge them all of the way and not fully charge them.

On September 4, 2018 at 2:45pm
greg wrote:

anybody know the evaporation rate of water in a l

On September 30, 2018 at 6:26am
Alan B wrote:

30kWh EV battery requiring five hours to charge from ‘empty’ to ‘full’. (Nissan LEAF or similar).
What is the maximum current during the ‘constant current’ phase and how long does that phase last?

On October 1, 2018 at 2:34pm
David Marlow wrote:

you will need at least a 40 amp, 240 vac circuit to do this,

On October 2, 2018 at 11:22am
Alan B wrote:

Thankyou for the information.
How long does the ‘constant current’ phase last for the above 30kWh battery?

On October 3, 2018 at 10:47am
David Marlow wrote:

My Vollt charges at 15 amps 240 vac drawing 3.3 KW The KW drops for about 10 min before charge is complete.  I do not know about the Leaf. It may taper the charge for a longer time.

On October 6, 2018 at 11:42am
Akki wrote:

Sir can i use lithium ion battery for inverter and automate??

On October 9, 2018 at 9:55am
David Marlow wrote:

While you can run an inverter from a lithium ion battery. You will need an automated system to manage the battery,  or a battery management system.  there are systems that include the inverter that can do this.  To maximize the lifetime of a lithium ion battery several factors must be controlled:
Most important is the battery temperature.
Current in and out.
Minimum and maximum Voltage.
It would be best not to leave the battery in a fully charged or fully discharged for more than a week at a time, good systems will prevent this.
It is also good to have an indicator of actual charge level and capacity as compared to original specification.

On February 5, 2019 at 10:30am
Stephen Price wrote:


I am trying to configure a 240 volt power supply for a narrowboat in the UK. I have dozens of questions but in deference to you being a busy person, I shall go steady and restrict myself to three.
I am trying to understand what are the basic components that are essential for a very
simple system.
I would like to incorporate into my system a 12v wind generator, 2 or 3 Monocrystal
solar panels, the boat’s engine alternator and a small petrol generator that charges at 8 volts, as well as a plug-in mains charger.
I see from the internet, that a Victron Inverter can come with an integral charger.
First question is could an MPPT charge controller supervise all of these components
adequately? Is a Victron battery monitor kit an essential component?
My second question is, to see if I can get my head around Amp/hour battery ratings and their in use performance.
What is the significance of either of the following, two possible systems.
Given that I can install 2 x 6 v batteries in series to produce 220 Amp hours into
a 3000W 12V low frequency pure sine wave off-grid power inverter 220V-240V AC with peak power up to 9000W, how long could a 3 Kw electric fire last.
My second option would be, 6 x 2 volt batteries (rated at 595 Amp hour each cell) to produce 3570 Amp hours, how long would my 3 Kw electric fire keep working?
Apologies for the detail of my questions but my knowledge is rudimentary to say the least and I do need considerable hand holding to produce a successful result.

Your sincerely

Stephen Bennett Price

On February 5, 2019 at 1:42pm
David Marlow wrote:

Complicated questions, lets start with the batteries. 6 x 2V 595 AH batteries = 1, 12V 595 AH battery battery or 1, 2V 3570 ah battery the difference is weather they are connected in series for 12 volts or parallel for 2 volts. You did not mention what type of batteries you were talking about, I will assume deep cycle type lead acid batteries, typical boat batteries. Your 3000 Watt inverter could require up to 300 amps to power it.
so your 595 AH batteries could be drained in as little as two hours.  Less than full load will last longer.

It happens that I rented a narrow boat in the UK last fall for a week, and it had two banks of 12 volt batteries, one for the cabin power and one for engine. The engine alternator charged both banks through diodes separating the banks.  I did see several narrow boats with solar panels.  It did not seem to me that wind power would work out well in most situations with a narrow boat.  I think there may be problems with connecting different types of power sources at the same time to a single MPPT controller, while it may work with one at a time..

The monitor would be most help full for the cabin battery bank,.as that is the power that you have the most control of.

On February 5, 2019 at 2:11pm
David Marlow wrote:

I will start with the batteries, assuming you are talking about Deep cycle type lead acid boat batteries.  The Amp Hour rating is how many amps the batteries can produce for one hour, on one charge, at their rated voltage. Connecting 6, 2 Volt batteries with a 595 Amp hour rating each in series will produce a 12 volt battery with a 595 amp hour rating.  So that battery could power your 3000 watt 12 volt inverter for about 2 hours or more..

Concerning the MPPT, I would not recommend connecting more than one type of power source at a time. 

I did, just this last fall, rent a narrow boat in the UK for a week.  It had two banks of batteries one for the cabin items the other for powering the necessary for the boat & engine..There could be different ways of powering your boat.  I noticed several narrow boats with solar panels.  Wind power may be usable in some moored situations.

On February 7, 2019 at 6:09am
Maciej Jarkowiec wrote:

What is better for battery life:

1. To keep the laptop plugged (I have an Asus Zen, a version that does not give option to charge it maximum up to 80% and does not support apps that do that. What it does it charges to 100% and then it says it is “discharging”)?

2. Manually keep plugging and unplugging it to run it on battery between 70-80 %?

Thank you in advance for your answer.
Warm regards,

On March 15, 2019 at 8:13am
Phillip wrote:

Question is a lithium ion battery percentile broken if it is dropped in a toilet (don’t ask why) if not how do you fix it?