How to calculate my battery bank Ah ,kw and Kwh

StanW

Apr 4, 2022
3
I have (24) flooded/sealed lead 2vdc 165ah batteries connected in series/parallel to 48vdc.
thats 4 strings of 12vdc.
the answer I got from an online calculator was 640ah=32.2 kw= 720 kwh.
Is this correct?

kellys_eye

Jun 25, 2010
6,482
Ahr's add in parallel, voltage adds in series, watts = volts x amps.

Wattage remains the same no matter how you connect them (series or parallel).

Watt/hours is a simple measure of the total wattage available over a given time period (in this case one hour)

In your case you have (in series) 48V, 128Ahr, 7.92kW and therefore 7.92kWhr (or 1kW for 7.92 hours etc)

StanW

Apr 4, 2022
3
Thanks for your reply, However, not being argumentative...does not wiring the in a series-parallel config increase capacity?
4 strings at 165ah times 4=at 165ah ea = 640ah because of the parallel wiring?

Bluejets

Oct 5, 2014
6,859
As I see it from your explanation, there would be no parallel connection.
They would all be in series to obtain 48V (24 cells @ 2V a piece)
So Ah would be 165Ah.

On the other hand if you do indeed have 4 strings of 12v cells in parallel, then you still only have 12v all-be-it at 4 x 165 or 660Ah.
This would naturally be load dependant.

Last edited:

kellys_eye

Jun 25, 2010
6,482
does not wiring the in a series-parallel config increase capacity?
Yes, it does. But, as stated above, your's has no 'parallel' aspect to them.

Total 'power' is the product of their voltage and current and quantity - no matter how you connect them you will never get any more than 2 (volts) x 165 (Ahr) x 24 (qty) = 7920W

Series (to a maximum of 48V but only 165Ahr) or parallel (to a maximum of 3,960A but only 2V) the maximum will always be 7,920 watts.

May 7, 2021
834

kellys_eye

Jun 25, 2010
6,482
I believe that's Wh.
No necessarily - depends on what you are using as a reference, hours, minutes, days....... the total wattage is still the product of volts x amps - it doesn't include 'time' unless you reference it specifically.

StanW

Apr 4, 2022
3
Please see the attached photo. This is how I have my batteries wired in series and parallel.
Only difference is I have 4 strings of 12vdc to 48vdc and doubles the capacity.
as you say the KWh is dependant on the loads and time.
thanks

Attachments

• series and paralell combo connection.jpeg
44.5 KB · Views: 4

crutschow

May 7, 2021
834
No necessarily - depends on what you are using as a reference, hours, minutes, days...
In your calculation you had Ah as one of the factors, so that calculates to be Wh.

Bluejets

Oct 5, 2014
6,859
Only difference is I have 4 strings of 12vdc to 48vdc and doubles the capacity.

Afraid not.......

Which diagram are you referring to, there are 6 on the supplied sheet, all are 12v output.
4 strings of 12v in parallel is still 12v, not 48v.

kellys_eye

Jun 25, 2010
6,482

Confirm what?

We have calculated your total power availability and nothing you do in terms of rewiring in series or parallel connecting is going to increase the available power. It's 7920Whr. If you discharge the batteries in only 1/2 hour you can draw double (i.e. around 16,000W) or if you discharge it in ONE minute you can THEORETICALLY achieve 475,200W. Won't be happening btw!

You need to consider what it is you want from the batteries. If it's a case of powering a home you need to know both the average consumption and peak consumption.

Most houses can run at a very low average level (say 1kW - lighting, fridges, hot water circulation, entertainment stuff etc permanently on - it can be more, it can be less - that's for you to figure out) but need a peak that can cope with hot water production (up to 3kW) cooking etc.

With an 8kW backup (like yours), if you can reduce the average level to (say) 500W you can run the house for 16 hours BUT every time you boil the kettle or cook you reduce that time a little.

So, what is your ultimate goal????

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