BU-415: How to Charge and When to Charge?

Batteries have unique needs and Table 1 explains how to satisfy these desires based of common batteries. Because of similarities within the battery family, we only list lead, nickel and lithium systems. Although each chemistry has its own requirements, there are common denominators that affect the life of all batteries. These are:

Batteries for the electric powertrain have changed the philosophy of battery manufacturers from designing packs for maximum energy density, as demanded by the consumer market, to focusing on optimal safety and longevity. Batteries on the road are exposed to extreme environmental hazards; they must perform at maximum duty under severe heat, cold, shock and vibration. Storing energy of several kilowatts, batteries for the electric powertrain can be dangerous if stressed beyond normal conditions. Furthermore, vehicular batteries are expensive and must last for the life of the car.

Pampering a battery to achieve an extended service life, as is sometimes possible with a laptop or cell phone pack, is more difficult with a large battery in a vehicle that must deliver high load currents on command and is exposed to freezing temperatures in the winter and blistering summer conditions. The user has limited control as to the care and attention of the battery. This task is passed over to an intelligent battery management system (BMS), which takes over the command and does the supervising. The BMS assumes the duty of a lead commander who must make sure that the troops in a large army are well organized and that all soldiers are marching in the same direction.

While a battery in a portable device can have its own personality and occasionally slack off, this liberty does not exist in a large battery system where all members must be of equal strength. Managing fading and failing cells as the battery ages is a complex issue that the BMS must address effectively. Monitoring and eventual replacing the cells or battery groups is far more complex than getting a new pack for a portable device when the old one becomes a nuisance.

asked question

Lead acid
(Sealed, flooded)

(NiCd and NiMH)

(Li-ion, polymer)

How should I prepare a new battery?

Battery comes fully charged. Apply topping charge

Charge 14–16h. Priming may be needed

Apply a topping before use. No priming needed

Can I damage
a battery with incorrect use?

Yes, do not store partially charged, keep fully charged

Battery is robust and the performance will improve with use

Keep some charge. Low charge can turn off protection circuit

Do I need to apply a full charge?

Yes, partial charge causes sulfation,

Partial charge is fine

Partial charge better than a full charge

Can I disrupt a charge cycle?

Yes, partial charge causes no harm

Interruptions can cause heat buildup

Partial charge
causes no harm

Should I use up
all battery energy before charging?

No, deep discharge wears battery down. Charge more often

Apply scheduled discharges only to prevent memory

Deep discharge wears the battery down

Do I have to worry about “memory”?

No, there is no memory

Discharge NiCd every 1–3 months

No memory

How do I calibrate a “smart” battery?

Not applicable

Apply discharge/charge when the fuel gauge gets inaccurate. Repeat every 1–3 months

Can I charge with the device on?

Some UPS systems simultaneous charge and deliver current.

It's best to turn the device off during charge; parasitic load can alter full-charge detection and overcharge battery or cause mini-cycles

Must I remove the battery when full?

Depends on charger; needs correct float V

Remove after a few days in charger

Not necessary; charger turns off

How do I store
my battery?

Keep cells above 2.10V, charge
every 6 months

Store in cool place;
a total discharge causes no harm

Store in cool place partially charged, do not fully drain

Is the battery allowed to heat up during charge?

Battery may get lukewarm towards the end of charge

Battery gets warm but must cool down on ready

Battery may get lukewarm towards the end of charge

How do I charge when cold?

Slow charge (0.1): 0–45°C  (32–113°F)
Fast charge (0.5–1C): 5–45°C (41–113°F)

Do not charge
below freezing

Can I charge at hot temperatures?

Above 25°C, lower threshold by 3mV/°C

Battery will not fully charge when hot

Do not charge
above 50°C (122°F)

What should I know about chargers?

Charger should float at 2.25–2.30V/cell when ready

Battery should not get too hot; should include temp sensor

Battery must stay cool; no trickle charge when ready

Table 1: Best charging methods. Strenuous demands cannot always be prevented.

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On January 6, 2011 at 11:52pm
antonyananth wrote:

tnx sir

On January 15, 2011 at 3:36am
arpit wrote:

gr8 article

On January 15, 2011 at 3:36am
arpit wrote:


On January 19, 2011 at 2:31pm
Glyn wrote:

Very useful and informative - keep up the good work

On February 8, 2011 at 7:39pm
john wrote:

Is there a problem if 5 batteries in different stages of remaining capacity are charged together with one charger?

On March 25, 2011 at 7:04pm
Francisco Bolivar wrote:

I have an elerctric bike with a 600w - 36v motor.
It uses a li-Ion battery.
Usually each time I use the bike its charge drops about 20% of the total battery charge.
1 - CHARGE THE BATTERY EACH TIME I USE THE BYKE (battery with 80% of charge)

On April 18, 2011 at 1:23am
Sameer Wagh wrote:

Good articles , but I have one question…..

If we add batterties in Parallel to increase capacity , how much capacity chargers are required. i.e. do we need to add the Ahr. capacity of all batteries to determine the capacity of charger?

If we add batteries in series to increase voltage requirements , do we need to increase the capacity of charger.


On June 8, 2011 at 1:42am
Lazaros wrote:

My original charger is at 700 mAh. Could I use another at 1500 mAh or it would deteriorate my phone battery?

On July 4, 2011 at 10:37pm
Jerome Girard wrote:

Simple, precise, thanks a lot!

On July 18, 2011 at 3:39pm
rich chapman wrote:

I’ve got one- Why do instructions for many battery cell chargers say to first put the battery in the bay and then to plug the unit in?  Does it not charge correctly if you put a battery in the bay when its already plugged in?

On August 26, 2011 at 5:49pm
fastman wrote:

Thanks ...this article is very useful ..I am going to buy a new laptop tomorrow with lithium battery and I will not fully cahrge it the first time as i thought

On October 5, 2011 at 2:35pm
Ramakanth Viswanatha wrote:

can i use a dynamo ( for example a dynamo in a cycle to lighten the head light ) in a byke rear wheel . So, that while running the byke the dynamo works and through wiring the dynamo is connected to a rechargeable battery and so the battery is charged and there is no issue of charging drop rate….This was my assumption .

On October 13, 2011 at 10:59pm
jacob wrote:

What is the recommended charging time for the first charge of a lithium ion battery for a new cell phone? I should charge it before I turn my phone on, correct? Its a 1500halloween mah, 3.7v. Any help would be appreciated. Good articles here.

On November 22, 2011 at 7:09am
zachary wrote:

how long do you charge a 12v Lead acid
(Sealed, flooded) battery?

On December 1, 2011 at 8:07am
mahesh wrote:

sir i have a huiandai tubler bettary for my invertor it is 60% damage but company can not change it. in what type i can dead fully damage my bettary

On January 9, 2012 at 10:04pm
Himani wrote:

Informative article !

On January 22, 2012 at 12:01pm
Junedul wrote:

my batteries alithium ion

i bought it new as a replacement and have been charging it for 3 day

i turned it on and it was at 75% and said critical

i turned the adapter off and the laptop lasted a minute, have i damaged the new battery
and why is it stuck on 75%

On January 23, 2012 at 5:31am
Mercy Ejindu wrote:

my phone battery is charging on it own with the power what should i do

On February 25, 2012 at 11:48am
Craig wrote:

Lithium Ion batteries, can I check voltage to determine if they are fully charged?  They are for portable radios at 7.4 volts.

Thanks in advance for your help.

Warm regards,


On March 16, 2012 at 1:14pm
Tina wrote:

what does topping mean?

On March 26, 2012 at 3:31am
Ali wrote:

tnx for your gr8 article
I had a question about li-on batteries
Is it right that some people say
charge your battery only when it is on 40% or 60% of charge
and cut off the battery from charger when it reached the 80%?
plz answer me!

On June 20, 2012 at 7:26am
James Japp wrote:

“Discharge NiCd every 1-3 months”

Does this mean that I should be discharging even those batteries that I don’t use very often. In some torches it would take me half a year, if not more, to fully discharge battery by normal use. Should I intentionally drain those batteries every 3 months?

On September 24, 2012 at 7:16am
omar wrote:

when the battery is completly charged is there any damage on it when i keep the charge on and is it disconnect when it fully charged ??

On October 12, 2012 at 12:51am
Jose wrote:

I just bought a tablet and i just like to know if it is okay to leave it plugged in while it is docked after it has charged to full while using it…

On November 19, 2012 at 10:03am
Mário wrote:

This topic it has been very helpful to me, I’ve 4 12v 100 amp batteries, in a 12 volts battery bank. I want to charge them as quickly as is possible without damaging them from 220v a/c source, Whats the technical specifications that i should look for in a charger. A model would be a great help but as I live in Africa it can be difficult to find.

On November 24, 2012 at 9:22am
Davey Dee wrote:

Strange that the author here does not reply, for those needing help.

On November 28, 2012 at 7:11am
Jaka wrote:

You are the best! It is really helpful instruction.

On January 9, 2013 at 8:33am
SOUISSI wrote:

Des cours tres instructis un grand merci a tous .l’echange du savoir humain merite notre reconnaissance car un jour l’humanite en y puisera son salut.

On January 12, 2013 at 6:42am
jayasuriya nandhagopal wrote:

its a owesome site which i have seen. i like tis one .i got useful informations in tis site

On September 9, 2013 at 7:33am
Solomon wrote:

a useful message

On November 23, 2013 at 6:37am
Megha wrote:

not fare enough…

On December 11, 2013 at 10:51pm

All batteries when not in use self discharge. The type determines the rate of discharge. In the case of lead-acid batteries not being used for any period of time should be put on a charge maintainer. Keep in mind that weak or discharged lead acid batteries can freeze if left in prolonged freezing temperatures, which can render them useless. Ni Cads discharge fairly rapidly. Keeping them in a cold location will slow down the self discharging. Lithium batteries have a very long shelf life at normal room temperature.

On December 22, 2013 at 11:58pm
muhammad Bilal wrote:

what are the principles work behind the cahrging of a battery?? can anybody help me

On March 21, 2014 at 6:55am
Nigel Ndlovu wrote:

My battery has not been charged for two weeks and it seems to have a problem cause i put the charger on and its still 0% full . What can I do

On June 17, 2014 at 6:14pm
Angelo wrote:

Half the battery pros say plug in the charger first then plug the charger into your battery. Other so called battery pros say plug into your battery first then plug into the charger then plug the charger in. Which is it?

On June 19, 2014 at 6:11am
Azlan Aziz wrote:

Informative article & very helpful..
Thank you.

On June 23, 2014 at 10:40pm
volker wrote:

there’s following setup given:
cheep model helicopter with a single LiPo cell (3,7V, 1000mAh)
and a simple “charger” Vout= 4V, 500mAh.
charger seems not to have any charging-electronic.

Possible to coverload the battery with this “charger”?

On June 24, 2014 at 1:00am
Volker wrote:

this seems to depend on the charger. I know that e.g. for all Jun-si iChargers (chargers for rc model) first method is the correct method (First plug the charger to powersupply , then plug battery to charger)
and 2nd method can damage the charger.

For other chargers may be you can choose either method.

On June 27, 2014 at 3:44am
Narcais wrote:

I have a problem with my phone:
In normal charging the phone battery is not charging more than 51%. I tried several types of chargers and is the same problem (battery charger is not the problem).
On an external charger battery charging normal 100%....
Which is the problem?

On August 6, 2014 at 9:50am
sumit wrote:

I just bought a moto G How do I first charge it to increase battery life. pleeaase help

On August 13, 2014 at 6:53am
V.H.SHAJI wrote:

I have one touchmate MID 790 tablet which is new and one year old,not working so far,
Now I charged with power,the charge not existing at all.What is the reason,and remedy also.Please advice me to my email.

On October 23, 2014 at 6:40am
Aruna wrote:

does the amount of input voltage equals to each of the output voltage

On October 25, 2014 at 2:59pm
Angelo wrote:

Volker thanks for your response. Your right. I researched firther and it all depends on the charger.

On November 18, 2014 at 10:51am
Filippo wrote:

I have a samsung galaxy s3 or anyway smartphones in general

could you tell me which range of charge is better for the life of a lithium ion battery?

something between 20 and 85%  ? I guess

On January 15, 2015 at 8:16pm
Vidya wrote:

can i use the sony rechargeable batteries in kodak charger?

On January 31, 2015 at 7:42pm
Daniel Rawinsky wrote:

I would like to know more about locomotive batteries. We have a 1943 Alco RS1 which runs on 8ea 8v batteries. We have been trying to keep the batteries charged but since the alternator for keeping the batteries charged (as compared to the alternator to power the traction motors) is not working. We have found some dead cells and these batteries are expensive and very heavy. What kind of battery would be suitable to replace the dead batteries?
Thank you
Daniel Rawinsky