Determining amp hour rating

[mitchbooth]

Hello,

I have a group 27 lead acid battery and I’m trying to determine the amp hour rating. Here is a photo of the battery. Thanks in advance.

Mitch

 

[Mattb4]

This might help. https://www.batteryequivalents.com/how-to-convert-cold-cranking-amps-cca-to-amp-hours-ah.html

 

[mitchbooth]

so with a 25 amp average at 175 minutes I did the following:
175 minutes X 60 seconds X 25 amps = 262,500 / 3600 coulombs in an amp hour = 72.91 would be my amp/hour rating

 

[sunshine_eggo]

Hello,

I have a group 27 lead acid battery and I’m trying to determine the amp hour rating. Here is a photo of the battery. Thanks in advance.

Mitch

They give reserve capacity, RC. RC is the number of minutes the battery can deliver 25A and stay above 10.5V.

175 minutes (let's round up to 180 for 3 hours).

So, your battery can deliver 25A for 3 hours or 75Ah. That's a very high rate of discharge. Standard capacity is based on a 20 hour discharge or C20 rate. You have a C3 rate.

Here's a datasheet for a Trojan T-1275, 150Ah 12V battery:

https://www.trojanbattery.com/pdf/datasheets/T1275_Trojan_Data_Sheets.pdf

It has a reserve capacity of 280 minutes or 280/175 = 1.6X more than your battery, thus its C20 rating should be about 1.6X yours.

It's C20 is 150Ah, so yours is closer to, 150Ah/1.6 = 94Ah.