Amp hours, also known as Ah, are units of measurement that tell you how much charge is in a battery. To calculate the amp hours of a battery, you need to know the voltage and capacity of the battery. The formula for calculating Ah is:
Ah = (V x C) / 1000
Where V is the voltage of the battery and C is the capacity in mAh. For example, if you have a 12 volt battery with a capacity of 100 Ah, your calculation would be:
Ah = (12 x 100) / 1000
Which equals 1.2 amp hours.