Find the ah in my battery


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eli1729

New member
Joined
May 4, 2023
Messages
1
Hey, so I got some gel battery of Northstar and I don't understand how to convert the watt that wrote on it to ah.
i know that basically, I need to divide by the Volts but its not make any sense in this case.
Im added a photo of the battery. wish for some help
tnx!

 

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OffGridInTheCity

Active member
Joined
Dec 15, 2018
Messages
2,436
One form of the formula is 'ah * volts = watts'. For example, a 12v battery with 100ah is 12v * 100ah = 1200w if one were to go from 100% Charge to 0% charge.

When you only have 2 of the 3 pieces of information, you can use Algebra to rearrange the formula to solve for the missing piece of info. In this case there are 3 options.....
- ah * volts = watts
and
- watts / volts = ah
and
- watts / ah = volts

The pic says 649 watts / cell (15min to 1.67vpc at 25C). 1.67v * 6 = 10v. I take this to mean there are 659 watts of power from fully charged to recommended 0% charge at 10v.

The pic says Float Voltage of 2.27v at 75F. I take this to mean fully charged at 2.27v * 6 = 13.6v.

Not sure if you have 1 cell or 6 cells in this battery - but since it sounds like an 'overall' 12v nominal battery, I'd say you have 6 cells = a 12v battery.

Assuming a 6 cell, 12v nominal battery, I'd interpret the pic as saying that from fully charged (Float = 2.27v/cell) down to 1.67v discharge you'll get 659w.

So we have a voltage range of 2.27v - 1.67v = 0.6v.

And using the watts / voltage = ah version of the formula we get.....
649w / 0.06v = 108ah

Therefore, I interpret the pic as saying you have a nominal 12v battery with 100ah of capacity between fully charged at 13.6v and discharged down to 10.0v.

**Just my best guess - we'll see what others post - and better yet, maybe this will give you enough info to figure it out yourself.
Also, you can always to do a discharge test and see what it is in fact :)
 
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