The formula to convert battery reserve capacity to amp hours is:
AH=BR×60×253600
where AH is the amp hours, and BR is the battery reserve capacity (minutes).
To simplify, you can multiply the capacity in minutes by 0.41666.
The battery reserve capacity is a measure of the total amount of time a battery can run at 25 amps of current without the voltage dropping below a set value of 10.5 volts.
Let's assume we have the following value:
Step 1: Multiply the reserve capacity by 0.41666:
AH=120×0.41666=50
Therefore, the Amp Hours (Ah) is AH=50 Ah.