Enter the total batter reserve capacity into the calculator to determine the total amp hours left in the battery. This calculator can also perform the reverse operation.

Battery Reserve Capacity to Amp Hours Formula

The following formula is used to convert a battery reserve capacity to amp hours. 

AH = BR *60 *25 / 3,600
  • Where Ah is the amp hours
  • BR is the battery reserve capacity (minutes)

To calculate amp hours from battery reserve capacity, multiply the capacity in minutes by .41666.

Battery Reserve Capacity Definition

What is a battery reserve capacity?

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.

Example Problem

How to calculate amp hours from battery reserve capacity?

The following example problem illustrates the steps and required information needed to calculate amp hours from reserve capacity.

First, determine the reserve capacity. As mentioned above, this is a unit of time the battery can run at 25 amps without dropping below 10.5 volts. For this example problem, the battery has a reserve of 45 minutes of capacity.

Next, multiply the time in minutes by 60 to get the result in seconds:

45* 60 = 2700 seconds

Next, multiply the seconds by the 25 amps above:

2700 * 25 = 67,500

Finally, divide the result above by 3,600 to get the number of amp-hours:

67,500 / 3,600 = 18.75 amp hours