## Easy Charging Time and Charging Current Formula for Batteries. ( with Example of 120Ah Battery).

How to Calculate the time for battery Charging?
Easy Charging Time Formula for Batteries. ( with Example of 120Ah Battery).

Here is the formula of Charging Time of a Lead acid battery.
Charging Time of battery = Battery Ah / Charging Current
T = Ah / A

Example,
Suppose for 120 Ah battery,
First of all, we will calculate charging current for 120 Ah battery. As we know that charging current should be 10% of the Ah rating of battery.
so charging current for120Ah Battery = 120 x (10/100) = 12 Amperes.
but due to losses, we can take 12-14Amperes for charging purpose.
suppose we took 13 Amp for charging purpose,
then charging time for 120Ah battery = 120 / 13 = 9.23 Hrs.
but this was an ideal case...
practically, this is noted that  40% of losses ( in case of battery charging)
then 120 x (40 / 100) = 48 .....(120Ah x 40% of losses)
therefore,  120 + 48 = 168 Ah ( 120 Ah + Losses)
Now Charging Time of battery = Ah/Charging Current
168 / 13 = 12.92 or 13 Hrs ( in real case)

Therefore, an 120Ah battery would take 13 Hrs for completely charging ( with 13A charging current).

By: Wasim Khan
http://www.electricaltechnology.org

1. there is some error in calculation for 120 ah and 13 amps it would be 9.23 bt u have type as 150 instead of 120 so change it

1. Dear Sudharsan M,U@
Thank you so much for taking a valuable review.

2. Most battery manufacturers recommend sizing the charger at about 25% of the battery capacity (ah = amp hour capacity). Thus, a 100 ah battery would take about a 25 amp charger (or less). Larger chargers may be used to decrease charge time, but may decrease battery life. Smaller chargers are fine for long term floating, e.g. a 1 or 2 amp "smart charger" can be used for battery maintenance between higher amp cycle use. Some batteries specify 10% of capacity (.1 X C) as the charge rate, and while this doesn't hurt anything, a good microprocessor charger of the appropriate charge profile should be fine up to the 25% rate. You talk to different engineers, even at the same company, you get different answers.

3. Anonymous19:39

i have battery in my home with ups
NS-175 of Osaka company
how i find its voltage nd ampere-hour rating...???
plz tell me

1. The rating of Osaka NS-175 battery is ( 12V, 175Ah)

4. Anonymous06:10

thanks
but can u telll how u find it??so that next time i also find it
plz

1. Just check the battery Code like NS-200, NS-175, NS- 120.
So these are it Ah rating for instant, NS-200 = 200Ah, 12V.,,and we also know that these battery comes in 12V DC.

2. Anonymous12:22

thanks.dear

3. Welcome Dear

5. Anonymous12:31

could u please tell me how to increase the battery power..what are the specifications to be considered while bying a new ups...?

6. If i have a battery bank as follows:

25 batteries(12v) x 120 Ah = 3000 A

So in this case I need 300A rating for charging?
In this case I need charge controller for 300A?

Please can you help if this is correct?

1. Saravana18:35

practically is it possible??

7. sir i want to ask you that There is no difference in the 12v 120Ah and 220v 120Ah

1. Dear,,,, 12V batteries comes in DC, while 220V is AC..... and we cant not store AC in batteries.
Also the question is irrelevant, but refer to basic calculation
12V x 120Ah = 1440Wh
and for 220V
220V x 120Ah = 26400Wh

8. Anonymous00:32

Hi friends, I bought electrical scooter (Its name is Volta VS4 3000W, made in Turkey) . It has 60V,20A gel accumulator and charging valuse are 60v and 3A. How long does it take caharging time? User guide explains charging time is nearly between 6-8 hours. How can I find these charging durations?
Thanks

1. The accumulator [Battery] rating should be 60V, 20Ah.
Thus charging current for 20Ah would be 10%. of it rating [20Ah].
Therefore, [20Ah x 10]/100 = 2A.
Ideally, the charging current for this battery would be 2A.
but due to losses, we can take 2-3A for charging propose.
Now charging Time = Battery rating / charging current
= 20Ah / 3A = 6.6Hrs. ideal case.
Due to 30 to 40% losses. This 60V, 20Ah battery would take 6-8 Hrs charging on 3A.
Thanks

9. Hi sir ur blog is superb..
i hav a general question that what will be the discharging time, and load capacity of a battery, how we can calculate that..

1. Dear Reddy Marala.
http://www.electricaltechnology.org/2013/05/a-complete-note-on-solar-panel.html

10. Anonymous04:32

Hi, my solar energy system comprises a 200watt-solar panel, a 10A(12/24volt-charge controller), 2 120Ah batteries and a 1000watt-invertor(24volts). How should I efficiently charge my batteries: in series or in parallel. Also, is it possible to watch TV while charging in parallel?

1. if your solar panel is 24v (36v open circuit ) means you connect your batteries in series and connect your inverter definitely you can watch your TV (depend on your TV watts )

11. hi sir... what can i do to improve the efficiency of the cahrging time? means to make the charging time is less

1. Increase the Charging current for less time..

12. dear ser weare charging 300 ah batery 10 hr with 10 amp then howmony unit corrent is taking from electricity

13. Wrong Q dear..

14. Anonymous23:25

dear sir how can I find out that what ampere current my 12 volt
charger produce

15. SIR I WANT KNOW ALL ABOUT BATTREYS PLZ SEND ANY LINK ABOUT THAT TOPIC ITS VERY USE FULL TO ME PLZ SIR

16. Sir can I run 1 Ton AC on 1000watt solar panel.

1. http://www.electricaltechnology.org/2014/02/why-AC-rated-in-Tons-Not-in-kW-or-kVA.html

17. Anonymous09:31

Dear Sir,
i understood your explanation but was confused a little. Is the fixed rate 10% for charging current and can be same the rate charging with Charger, Inverter and Solar? let me known clearly, Sir?

18. sir , my battery is (33ah/20h) so what will be the charging current n time of that battery?

19. sir my dry cell battery of indus company is(33ah/20h) so what will be the charging current n time of the battery?(plz tell me wid formulae)

20. sir,
130ah /12 vdc 8nos batteries in series so what is the correct charging current for this tubular batteries ...i am some what confusion pls clear

21. Sir,
I want to buy an inverter & battery. My wattage usage are approx 300 - 350 . I want to run inverter around 10 hour/day. Plz suggest : 1) inverter VA & respective battery AH for above requirement.

22. Sir,
I wanr to buy an inverter & battery. My wattage load is around 300 to 350 watt. Plz suggest Inverter VA & corresponding barrery AH to fulfil above requirement.

23. Hi .. Good day

I have a question

I have two banks of batteries and two battery chargers in parallel 48cvd

and a total current of 35 amp, i thought that was going to of dividing the current in half

but charger was left with 10 and one with 25 amps ...

because that would happen?

24. Hi .. Good day

I have a question

I have two banks of batteries and two battery chargers in parallel 48cvd

and a total current of 35 amp, i thought that was going to of dividing the current in half

but charger was left with 10 and one with 25 amps ...

because that would happen?