Battery capacity refers to the amount of electric charge a battery can hold.
Amp hours
Battery capacity is measured in amp hours. Each battery is given an amp hour rating which is written as a number followed by the letters ‘AH’.
This number tells you how many amps of electrical charge the battery can deliver for the duration of 1 hour. For cordless drill drivers, battery capacity ranges from 1.1 AH to 4.0 AH.
The higher the battery’s amp hour rating, the longer you can use the tool before its battery runs out and needs to be recharged.
You can work out how many amps are being used by looking at the tool’s battery voltage and capacity.
For example:
A cordless drill driver with an 18v battery and an amp hour rating of 2.0 AH will be able to deliver an electrical charge of 2 amps for the duration of 1 hour, or 4 amps for 30 minutes, or 8 amps for 15 minutes and so on…
If the tool runs at full power for 15 minutes before the battery runs out, then we know that at full power, it’s using 8 amps.