BU-401: How do Battery Chargers Work?

Discover which charger is best for your application

A good battery charger provides the base for batteries that are durable and perform well. In a price-sensitive market, chargers often receive low priority and get the “after-thought” status. Battery and charger must go together like a horse and carriage. Prudent planning gives the power source top priority by placing it at the beginning of the project rather than after the hardware is completed, as is a common practice. Engineers are often unaware of the complexity involving the power source, especially when charging under adverse conditions.

Horse and Carriage Figure 1:  Battery and charger must go together like horse and carriage.
One does not deliver without the other.

Chargers are commonly identified by their charging speed. Consumer products come with a low-cost personal charger that performs well when used as directed. The industrial charger is often made by a third party and includes special features, such as charging at adverse temperatures. Although batteries operate below freezing, not all chemistries can be charged when cold and most Li-ions fall into this category. Lead- and nickel-based batteries accept charge when cold but at a lower rate. (See BU-410: Charging at High and Low Temperature)

Some Li-ion chargers (Cadex) include a wake-up feature, or “boost,” to allow recharging if a Li-ion battery has fallen asleep due to over-discharge. A sleep condition can occur when storing the battery in a discharged state in which self-discharge brings the voltage to the cut-off point. A regular charger treats such a battery as unserviceable and the pack is often discarded. Boost applies a small charge current to raise the voltage to between 2.2V/cell and 2.9V/cell to activate the protection circuit, at which point a normal charge commences. Caution is required if a Li-ion has dwelled below 1.5V/cell for a week or longer. Dendrites may have developed that could compromise safety. (See BU-802b: What does Elevated Self-discharge Do?  in which Figures 5 examines the elevated self-discharge after a Li-ion cell had been exposed to deep discharge. See also BU-808a: How to Awaken Sleeping Li-ion.)

Lead- and lithium-based chargers operate on constant current constant voltage (CC/CV). The charge current is constant and the voltage is capped when it reaches a set limit. Reaching the voltage limit, the battery saturates; the current drops until the battery can no longer accept further charge and the fast charge terminates. Each battery has its own low-current threshold.

Nickel-based batteries charge with constant current and the voltage is allowed to rise freely. This can be compared to lifting a weight with a rubber band where the hand advances higher than the load. Full charge detection occurs when observing a slight voltage drop after a steady rise. To safeguard against anomalies, such as shorted or mismatched cells, the charger should include a plateau timer to assure a safe charge termination if no voltage delta is detected. Temperature sensing should also be added that measures temperature rise over time. Such a method is known as delta temperature over delta time, or dT/dt, and works well with rapid and fast charge.

A temperature rise is normal with nickel-based batteries, especially when reaching the 70 percent charge level. A decrease in charge efficiency causes this, and the charge current should be lowered to limit stress. When “ready,” the charger switches to trickle charge and the battery must cool down. If the temperature stays above ambient, then the charger is not performing correctly and the battery should be removed because the trickle charge could be too high.

NiCd and NiMH should not be left in the charger unattended for weeks and months. Until required, store the batteries in a cool place and apply a charge before use.

Lithium-based batteries should always stay cool on charge. Discontinue the use of a battery or charger if the temperature rises more than 10ºC (18ºF) above ambient under a normal charge. Li ion cannot absorb over-charge and does not receive trickle charge when full. It is not necessary to remove Li-ion from the charger; however, if not used for a week or more, it is best to place the pack in a cool place and recharge before use.

Types of Chargers

The most basic charger was the overnight charger, also known as a slow charger. This goes back to the old nickel-cadmium days where a simple charger applied a fixed charge of about 0.1C (one-tenth of the rated capacity) as long as the battery was connected. Slow chargers have no full-charge detection; the charge stays engaged and a full charge of an empty battery takes 14–16 hours. When fully charged, the slow charger keeps NiCd lukewarm to the touch. Because of its reduced ability to absorb over-charge, NiMH should not be charged on a slow charger. Low-cost consumer chargers charging AAA, AA and C cells often deploy this charge method, so do some children’s toys. Remove the batteries when warm.

The rapid charger falls between the slow and fast charger and is used in consumer products. The charge time of an empty pack is 3–6 hours. When full, the charger switches to “ready.” Most rapid chargers include temperature sensing to safely charge a faulty battery.

The fast charger offers several advantages and the obvious one is shorter charge times. This demands tighter communication between the charger and battery. At a charge rate of 1C, (see BU-402:What is C-rate?) which a fast charger typically uses, an empty NiCd and NiMH charges in a little more than an hour. As the battery approaches full charge, some nickel-based chargers reduce the current to adjust to the lower charge acceptance. The fully charged battery switches the charger to trickle charge, also known as maintenance charge. Most of today’s nickel-based chargers have a reduced trickle charge to also accommodate NiMH.

Li-ion has minimal losses during charge and the coulombic efficiency is better than 99 percent. At 1C, the battery charges to 70 percent state-of-charge (SoC) in less than an hour; the extra time is devoted to the saturation charge. Li-ion does not require the saturation charge as lead acid does; in fact it is better not to fully charge Li-ion — the batteries will last longer but the runtime will be a little less. Of all chargers, Li-ion is the simplest. No trickery applies that promises to improve battery performance as is often claimed by makers of chargers for lead- and nickel-based batteries. Only the rudimentary CC/CV method works.

Lead acid cannot be fast charged and the term “fast-charge” is a misnomer. Most lead acid chargers charge the battery in 14–16 hours; anything slower is a compromise. Lead acid can be charged to 70 percent in about 8 hours; the all-important saturation charge takes up the remaining time. A partial charge is fine provided the lead acid occasionally receives a fully saturated charge to prevent sulfation.

The standby current on a charger should be low to save energy. Energy Star assigns five stars to mobile phone chargers and other small chargers drawing 30mW or less on standby. Four stars go to chargers with 30–150mW, three stars to 150–250mW and two stars to 250–350mW. The average consumption is 300mW and these units get one star. Energy Star aims to reduce current consumption of personal chargers that are mostly left plugged in when not in use. There are over one billion such chargers connected to the gird globally at any given time.


Simple Guidelines when Buying a Charger


Last Updated 2016-05-04


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Comments (81)

On April 15, 2011 at 12:00am
desda wrote:

I need ni-cd charger chema.

On May 16, 2011 at 6:28pm
che wrote:

Do we need to do the long hour charge for a brand new Li-Polymer battery, I mean the first charge, peoples say its up to 10 hours (some say 8 hrs, others insist it’s not applicable nor not necessary for Li-po anymore), which one is correct? what is the reason behind this?

Another things, I had another Li-ion battery as a a backup, if I’m not using it, what make a better choice for the sake of battery life, to store it on a full charged or half one since the battery will discharges itself anyway.

On July 5, 2011 at 5:44pm
Stu wrote:

After reading several of your great articles, it became clear that consumer chargers specs do not give the information required to make an informed buying decision.

Now I know more, and I’m scared more but I’m better educated. What a situation!

Thanks for the education, anyway.

On July 18, 2011 at 3:49pm
James L. McCann wrote:

can you use nicad in a nimh charger

On September 8, 2011 at 8:26pm
Tony wrote:

If a NIMH battery charger’s maximum cutoff voltage is 1.6V/cell, i don’t think it can chage NICD battery well.

On September 9, 2011 at 1:46am
Tony wrote:

Here are some schematic drawings for battery charger:

On January 13, 2012 at 10:10pm
Jimmy wrote:

I want to use a charger with the same voltage (5V) and an output of .7 A. The original charger output is 5 V and 1 A will this affect the charger, the battery or the phone ?

On February 3, 2012 at 9:51am
Bryan wrote:

I know a lead acid battery left discharged will soon be U/S, on my motorhome I have left a trickle charger connected to both engine and house batteries a total capacity of 370ah. Today I looked at the state of charge, the current was charging at 0.1amps and the voltage was 15volts across all batteries, is this high voltage at 0.1amps a problem for my batteries?

On April 30, 2012 at 8:03pm
Glenn wrote:

I have charger that will only charge up to a 5000 MaH, I have a 5800 maH pack. Will my charger hurt the battery pack ?

Sent from my iPad

On June 9, 2012 at 2:35am
Rik wrote:

I have a Nicd and Nimh charger but the battery says it takes 7 hours to charge at 40 mA but the chargers says it charges at 11 mA. How long will it take to charge the battery?

On June 25, 2012 at 7:09am
Pancy wrote:

I have a Sealed Lead Acid Battery (6V; 4.5 A ) , I want to charge it by using 5 V adaptor,what will happen?I think it is possible but , battery will charge up to 5 V ,and discharging will take longer time .Am I right ?

On June 29, 2012 at 2:22am
Pratik Halvadiya wrote:


I would like to develop a BATTERY CHARGER that charges 12 v battery form 17-18 v which i got from SOLAR PV Panel. This battery charger system with auto cut off system..

If anyone have a idea about is please share with me..!!

On July 31, 2012 at 9:20am
Ben Watson wrote:

Could anyone give more detail on the problems/dangers of using a charger that claims to charge both Li-Ion chemistries and Nickel chemistries

On September 17, 2012 at 4:05am
DAN GREEN wrote:

Does saturating a phone battery work

On October 9, 2012 at 2:16am
Sharad wrote:

Hello sir,
i want to know the rating of a charger for charging Li-ion batteries which are now a days being commonly used in mobile devices. what should be the Volt and Amp rating of the charger for say 3.7v 800mAh(3.7Wh)Li-ion battery? also if i have another battery 3.6v 6200mAh (2.3Wh) Li-ion, what would be the best common charger for charging both batteries? What all parameters should be keep in mind while calculating charger rating? what these figures (v,mAH,Wh) tell about the battery?
Also on my charger i see
INPUT : 150-300VAC 50-60Hz 0.15A
OUTPUT: 4.75V 0.55A
What these figures (0.15A) and (0.55A) in I/P and O/P are?
can u please give me some brief knowledge on it.
Best Regards

On October 9, 2012 at 2:48am
Ben Watson wrote:

for a lithium charger you need to match the voltage so you want a 1 cell 3.7V li ion charger. 

the current or charge current of your charger is important to the lifetime of your battery.  I recommend charging at 0.5C which is half the capacity of your battery, in this case 400mA. In this case your battery will charge in about 2 hours.  But your larger capacity battery will take more than 15 hrs to charge with the same charger.  You could use a higher capacity charger for instance a 1A charger then your larger capacity battery will charge in 6 hrs and your smaller capacity battery would charge in less than one hour.  But your small battery would become damaged over time.  Lithium batteries have maximum charge current limits, it would depend on the spec of your battery.

Basically there is no single charger with a fixed charge current that will charge both batteries either safely or within a reasonable amount of time.  There are universal lithium chargers available but these only charge at 800mA max. http://uk.rs-online.com/web/c/?searchTerm=vario+lithium&sra=oss

the more i read your post the more i think you mis-typed 6200mAh, im guessing you meant 620mAh as the Watt-Hours dont add up for that battery.  So a universal li-ion charger like the one in the link would be ideal for both these batteries.

with regards to your charger I/P 0.15A means your charger uses/draws 1500mA of current from the mains supply.  the O/P 0.55A means it chargers at 550mA of current.

in conclusion matching the voltage is very important and charge current should be roughly half the capacity of your battery.  So a 1Ah battery would charge with 500mA

On November 1, 2012 at 6:44am
richard wrote:


Is a charger rated at 100mAh suitable for a battery that specifies 150mAh charge rate? Same voltage of course. I’m guessing that it would take somewhat longer to charge but wouldn’t hurt the battery in the long run.


On November 4, 2012 at 4:10am
chito wrote:

is it ok to use a 40watts laptap charger to 30watts spec?
same volts only the output watts differ

On December 17, 2012 at 10:31am
Ataullah wrote:

I am looking charger i can charge my laptop battries at least 4 at a time?its avilable in market ?if not any body help me ?for design

On December 17, 2012 at 10:38am
Ataullah wrote:

Hi,How we can used Solar power for charger ?for my laptop ,

On December 26, 2012 at 2:08pm
sheryl wrote:

I have a Sharp AC adaptor battery charger for a Sharp 8Viewcam video camera. They both have some age but have continued to work well. The charger’s red Power light blinks constantly while the battery is inserted. The Charge and Refresh lights do not come on. Two new batteries I’ve tried charging are not working in my camcorder. One site suggested trying to charge again for an hour, then remove the battery and reinsert to see if it will charge.  I’ll try…appreciate any help.

On February 10, 2013 at 4:45pm
haider wrote:

hi can charge a single 12v 200ah battery on 220vac ups and 300w solar panel it same time to charge quickly thanks

On March 25, 2013 at 5:52pm
Ramamurthy magal wrote:

How to know the battery is charged

On June 27, 2013 at 11:23am
Abhishek Thapliyal wrote:

Can anyone suggest me the circuit of 1A mobile charger

On July 16, 2013 at 12:08pm
A. DasGupta wrote:

The charger that came with my Toshiba Satellite Laptop which is rated at 19V and 3.95A is not charging the battery.  I used another charger which is for a HCL laptop.  This is rated at 19V and 3.42A.  When i used this charger it seemed to be charging my laptop but the charger got extremely hot. Is it to be expected.  If so, why does it get so hot?  Is it normal? Or is it due to the fact that ithas a lower amperage than the original charger?

On August 18, 2013 at 7:23am
HelloWorld wrote:

My Original laptop charger had the following specs:
100-240v 1.5A
50/60 Hz
Output:19v 4.47A

If I use a charger with the below specs will it do harm?
100-240v 1.5A
50/60 Hz
Output:19v 3.95A

On September 27, 2013 at 2:35pm
Ian wrote:

I have a lithium battery for a single seat golf buggy and it can be connected at the golf club. The battery will, therefore, be under charge for more than 36 hours, and I am told that should the charging continue after that time there is a danger that the charger could overheat.  Someone suggested I connect the charger to a timer, set it to X hours and all should be well.  But then someone says no, because a trickle of electricity is always there and will eventually overheat the battery.
So am I safe to leave the battery on charge for more than 36 hours, or should I take the battery home to charge where I have control over time?

On October 17, 2013 at 1:08pm
Yuvaraj wrote:

Can it cause problems leaving the phone attached to the charger for hours after its fully charged?

On October 31, 2013 at 11:29pm
Stan wrote:

I purchased a EGO CE4 electronic cigarette in Thailand. It came with a charger that has a USB connection

Trying to recharge in Australia but no result

Does anyone have any hints to it it charged ??


On October 31, 2013 at 11:31pm
Stan wrote:

I purchased a EGO CE4 electronic cigarette in Thailand. It came with a charger that has a USB connection

Trying to recharge in Australia but no result

Does anyone have any hints for charging   ??


On November 17, 2013 at 5:49pm
Wei Yan wrote:

I looked for a 40 watts laptop charger but according to the manufacturer, it was already phase out and they only have 30 watts. Is it ok to use a 30 watts charger even the specs must be 40 watts? They have the same volts only the output watts differs.

On November 23, 2013 at 2:58pm
robert ray wrote:

I want to use 4 AGM batteries 12V 35AH wired in series to produce 48 volts. They will be installed in a 48 volt golf cart. What charger do I need to recharge these batteries. I don’t need specs bla bla bla. Just tell me what brand charger, and who sells it. A part number for the charger may be needed so I can make sure I get the right one.

On November 27, 2013 at 11:56am
Gerry Schreiber wrote:

So I see lots of questions on here but not one answer….is there somewhere else I should b looking?

On December 7, 2013 at 12:57am
anirudh wrote:

sir i am working on a project of electric car i need help in deciding what type of battery and how to recharge it effectively

On January 21, 2014 at 8:34am
RAJA wrote:

i want a charger to charge my lead acid batteries(12V-26Ah) within 6hours.
any options for do this, pls reply

On January 27, 2014 at 11:58am
jerson wrote:

Hi can I use my old rice cookers plug and socket to use on my ebike battery pack instead of using the anderson plug its an SLA battery. . So I can charge my ebike battery pack .

On February 10, 2014 at 10:25am
David Nelson wrote:

I’m a high school teacher working on an engineering problem for a student competition.  We allowed to put solar panels under a halogen lamp for up to 10 minutes.  We have to store the accumulated energy,and use it to power a vehicle, with a 2V electric motor (hobby size).  All we need 10-20J of usable energy.  NOTE: I’m doing this with 9th grade students who haven’t had a full physics course yet.  We’re supposed to build our system from scratch.  My local electronics store suggested AA NiCd batteries.  We connected solar panels delivering 4V and 0.3A for 10 min to three AA batteries in series.  We only got 1.1V out of the batteries at the end 10 min of chaging, barely powering the electric motor.  Any suggestions- should we try Li-ion batteries?

On June 21, 2014 at 4:20pm
melissa wrote:

Hi I have a 48 watt charger that I use on my ebike can what would happen if I use a 60 watt charger can someone please let me know thanks.

On July 8, 2014 at 11:46pm
Aniket wrote:

What will happen if I charge 6V 1600mA battery with 4.6 V 160 mA charger?

On August 6, 2014 at 10:31am

can it is possible to charge 2 set of different capacity (70 Ah 24V Ni-cad, 200 Ah 24V Led-acid)  battery’s with a single charger ( Capacity 2.5A 24V), If any Problam? Pls help me.

On August 21, 2014 at 10:57am
Ray wrote:

“A lithium-based battery should not get warm in a charger and if this happens, the battery or charger might be faulty. Discontinue using the battery and/or charger.”

Uh, unless you have 100% conversion of energy, which is not the case, you have waste heat. If your battery does NOT get warm, then your charger is dead or its not plugged in.

On October 18, 2014 at 7:04pm
maureen wrote:

what happens to your phone if it charges more than 36 hours

On October 24, 2014 at 6:34pm
David Zurick wrote:

Just got 4 10000 mAh D cell batteries 1.2 volt with a 150 mA charger. The charger does not shut off when batteries are charged. There is a calculation in the manual:  1.2V X mAh divided into charging currant mA. Doing the math this is 80 hours of charge time. Is that possible? I don’t know what the charge time would be for one battery or four. Please help if you can. Thank you very much- Dave Z

On January 9, 2015 at 3:52am
Dom wrote:

Hello. I have a question:

‘‘If four 5W lights are left switched on, how long will a 30 Amp-hr battery last before becoming discharged?’’ On a car, light vehicle.

Waiting for your reply, thank you.

On February 13, 2015 at 6:08am
David Devine wrote:

Dear Sir,

I am wondering if either of these two chargers are better then the other. It seems to me that they both offer a bit different profile amd want to know which would be better for my situation. Charging wet 12 volt 232 ah batteries used as a back up power supply.

On February 13, 2015 at 5:11pm
Mark wrote:

Can I use a Lithium ion battery charger to charge a Nickel cadium battery.

On February 16, 2015 at 9:25am
Mark wrote:

If I use a Lithium Ion charger to charge a Nickel cadium battery, will it damage or shorten the life of my battery?

On March 16, 2015 at 11:58pm
tesfish kiyyaa wrote:

what are the key parameters THAT I have follow while i will go on to make charge a cyclon lead battery (12v 8AH)

On March 29, 2015 at 8:11pm
Hanson Tan wrote:

Dear Expert

Your video is very educational!

I have a question about my lithium charger.
The output voltage rating as shown on my charger brick for my hub motor shows its providing sum of of all the lithium cells in series where each cell is 3.3v.
I measured with voltmeter and indeed thats the output voltage or open voltage.

What puzzles me is that the lithium battery pack when fully charged, is at the sum of all the batteries in series where each cell is at 4.2v, the max voltage rating of each cell.

So, I am not sure why the charger is providing a lower voltage than the voltage when the battery pack is fully charged. Its logical to say the controller circuit has somehow stepped up the voltage either by PWM or other means.

I am seeking advise why the charger is designed like this and is this a standard for lithium chargers for electric motor lithium packs.

Thanks very much.

On July 15, 2015 at 2:56pm
Tery Haymond wrote:

Does a battery charger draw current from the battery if it unplugged from AC but with the battery clips still connected.

On August 5, 2015 at 9:25am
mistry virenbhai m wrote:

why lead acid battery can not charge using ultra fast charging method?
please tell me in detail.

On September 12, 2015 at 3:59pm
Reinhardt Schmidt wrote:

I own a M-243 Rail-gun. It runs off a battery pack, but I can’t figure what to recharge it with.
I really love this rifle. I took it to a cow pasture one night.
One shot from 100 yds literally SHREDDED a bull

On September 14, 2015 at 6:46pm
Kelly wrote:

I’ve purchased new rechargable batteries and a Charger. i have a few questions
Do the bateries need to be charged before first use?
how long should you chage these for?.
Also have i got the right charger?

UltraFire ICR123A 800mAh 3.0V rechargable batteries.
Charger is 16340/123A
input AC 110-220V 50/60Hz
Ouput DC 3.8V 300 +/- 50mA

On October 2, 2015 at 11:43pm
Alexander wrote:

What would happen if I double the amperage on a battery charger for a ni-cd battery that should take 11V 400mA

On October 6, 2015 at 10:10pm
abd halim ibrahim wrote:

two chargers got same input and output voltage
also got same output ampere
the difference is input.
one is 0.2 A and another on is 0.3 A
Are they interchangeable?

On March 7, 2016 at 4:22pm
Tomt wrote:

I am trying to find out if a power pack with an output of 20 volts/3.0 amps will work safely and efficiently on a laptop that takes an input of 19.5 volts/3.3 amps

On April 7, 2016 at 5:33am
Willam Benitah wrote:

Is my charger 24v 2am classe 2 for led battery is ok, I loaded the charger with a resistor of 25 ohm and the voltage went to 0v?? No load voltag bak to 27.4v..

On May 15, 2016 at 6:03am
Nikola Raskovich wrote:

Hello.  I want to see if I can charge faster.  I charge now at about 15/16 amps or 15/16 ah per hour with a straighforward on board charger for my small EV.  I am in Europe and want to know how/if I can charge at a faster pace - I see 32A chargers and even higher ones.  I am in the process of swapping out the SLA batteries for Lithium ones so if there are any considerations related to charging, please comment.  The current setup is 150ah SLA and I am going to 480ah Lithium.  The voltage of the battery will also change from 48 to 72volts. 

Is it correct to assume that a 3000W rated charger can charge a 72volt battery at a current of 41 amps (amp hours per hour)?  And can this charger be used with regular house current or does the charging current go down to the 16A electric service?

Thank you in advance.

On May 19, 2016 at 8:52pm
mic tay wrote:

My cellphone (Samsung Galaxy Note 2 ) battery printed as 3.7v 3100mah. While the wall charger printed as 5v. So i wonder is it safe to use? The charger i mentioned here came with the cellphone i bought as a USED PHONE in same box, but i am wondering if the shop put in the wrong charger in the box.

On July 29, 2016 at 1:18pm
Roy wrote:

So, what I’m wondering is how the charger actually puts power into the battery. DC applied with negative to the negative and positive to the positive? What happens if the battery is reverse charged? If I manually charge the battery but get it backwards… what happens?
Is it possible for a higher-charged battery to charge a lower-charged battery? Is it possible for the higher-charged battery to reverse charge the lower-charged battery?

On August 15, 2016 at 7:39am
samuel wrote:

I have a 15amp 12v battery fast charger its perfect but I use it to charge my two 75amps batteries. It takes time. I want to buy a 15amps 24v charger will it reduce the total charge time? I can’t use a higher amp charger because I am using a small generator to charge the batteries.

On August 26, 2016 at 12:20pm
sir gold wrote:

pls list the whole laptop chargers volts and their amperes.

On September 19, 2016 at 6:04pm
danny gonzalez wrote:

I’m wondering if you, or someone, can tell me whether using a commercial quality charger is a requirement, a good idea or not necessary? I have a 12v/40ah battery of commercial quality (Full BMS, A123 brand 22650 cells) and it is set up to charge with a DPI Accusense 15a charger. I’ve been using a consumer grade three stage 25a charger and, as far as I know, it’s been working just fine (I have no BMS monitoring set and it’s very expensive to buy from the OEM).
I read in the user manual that the charger needs to have very little ripple current and be voltage stable in all situations to be accepatable for use by the manufacturer.

Do I need to buy the recommended charger or am I fine as I’m going?

On October 28, 2016 at 4:52am
Adney wrote:

i am wondering if you can help me.
i have a CD 550 with 12v / 24V. What is the time line for charge with the 12 v also for the 24 v respectively.
Also is the difference between 24V and 12V the number of batteries charged at a time?

On November 7, 2016 at 11:48pm
SAQIB ALI wrote:

my modam chargar is a damage and damage charager voltage 09 volt out put
and new extra charger 9 volt aualibal i m exchange this charger but voltage diffrince .this charger is correctly working yes ya no

On November 30, 2016 at 2:57am
JamesAbr wrote:

Hello to everyone here! Can som to advice to whic one of the solar charger i need to buy to charge my devices when i camping (important condition) http://www.gadgets-reviews.com/review/185-5-best-portable-solar-chargers.html - one of them!
Btw - i have my iphone and MackBook! Thanks!

On December 23, 2016 at 12:07am
Nidhi Raj wrote:

Could anybody pls healp me to make a charger that having configuration of input voltage 240V AC out put of 29.4 V DC/16.8VDC ani it have a Rated Amp of 2. 75 Amps

On December 29, 2016 at 9:54am
Guillermo wrote:

Hello I need help . Can I convert a battery charger input voltage rated only 240v to 480v ? How ? Nameplate says input voltage 240v and I have panel 480v only. Thank you in advance

On January 18, 2017 at 10:45pm
venus wrote:

hello…want to ask..i have battery charger from US 110V..i wonder if i can use rechargeable batteries from here in Philippines? my rechargeable batteries i have from US also are too old n not working anymore n plan to buy rechargeable batteries here in Philippines….Thank you for reply

On March 31, 2017 at 11:12am
Stephen miles wrote:

I have a mean well power system and i am trying to charge a set of 12 volt batteries but when i hook up the power system to the batteries the power system goes to sleep and on ly register s battery voltage why is this different from a charger and what if anything can i do to change this situation help

On July 14, 2017 at 10:54am
Will wrote:

I’ve got a bit of an unusual question. I bought a phone with a 2800MAH battery(one of those phone slash powerbank devices). Instead of using the supplied charger, I used my 2.1amp third party charger. My phone got significantly warm but cooled down towards the end of the charge cycle. I checked the originally supplied charger and its specs says 0.15amp. Did I just mess up my phone’s battery by using the 2.1amp charger?

On July 27, 2017 at 12:56pm
Mike wrote:

My alarm system has a 12V 7Ah battery as standard.  So if I connect a 12V 100Ah battery to the system am I going to stuff up the battery or the charger since the charger is obviously designed for 12V 7Ah?
I ask since the standard batteries are typically overpriced for what they are and laymen such as myself just buy the batteries at the store since that is what the alarm system was installed with.  There has to be a better way…
Thanks for the help!

On November 10, 2017 at 12:58pm
Denise wrote:

1) How can I view the responses to other submitters questions?
2)  When using a double outlet USB port cell phone recharger,, say 4.8A, how much charge is traveling to each cable when both outlets are being used?  When only one cable is plugged in and charging?
Thank you.

On December 19, 2017 at 1:54am
Amperis wrote:

“Battery and charger must go together like a horse and carriage”
This simile is great, especially in the High Frequency Battery Charger and High efficiency battery charger.

Great article.

On December 28, 2017 at 1:47am
Kamil Orhan wrote:

What is difference between Float charge and trickle charge?

Thank you for your answer,

Kamil Orhan

On February 16, 2018 at 12:53am
Carlos wrote:

Very comprehensive post, thank you!

A quick question regarding NiMH batteries: is it safe to charge 1.5V AA/AAA batteries using a charge with a nominal output of 1.2V? Or will this difference prevent the battery from reaching full capacity or wearing more quickly?



On March 2, 2018 at 7:49am

Where can I learn to build a battery charge and battery pack. for NiMh. I need books and tutorials. Thanks.

On March 27, 2018 at 4:17am
Franklin wrote:


Please I need a multiple usb charger with auto detect when the device battery is full and stop charging.

Can you advice me something?

Thank you in advanced.


On March 27, 2018 at 4:38pm

To Franklin, no one responded to my request, this place is a ghost town, you should go to quora. Stack exchange was also a no go, they are all question snobs, if you do not ask a question in a way that they think you should they prefer to waste more time criticising the question than it takes to answer it. Sorry I can not answer your question, I am a learner too.


On July 17, 2018 at 10:16pm
RC wrote:

Can you elaborate a little on Magnesium Crystal batteries?
How do you charge a Crystal battery?
What will happen if you connect a charger that can only provide fluctuating power? Not PWM but a variation in voltage and current?

On February 4, 2019 at 9:36am
Thomas WHATTON wrote:

My battery charger needle goes to green indicating the battery is fully charged with 12 volts. The fully charged battery turns the engine but will not start it. Apparently its the amperes that are needed to actually fire the engine. Is this a fact? the battery is a 72 amp/hour what does this mean?