Battery capacity refers to the amount of electrical charge a battery can hold. The larger the battery’s capacity, the longer it can run before needing to be recharged.
Battery capacity is measured in amp hours and each battery is given an amp hour rating which is presented 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 example, a battery with an amp hour rating of 2.0 AH can 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. Typically, for cordless impact drivers, battery capacity ranges from 1.0 AH to 4.0 AH.
You can work out how many amps are being used by looking at the tool’s battery voltage and capacity. For example, if you have a cordless impact driver with an 18 volt battery and an amp hour rating of 4.0 AH, it should be able to deliver 4.0 amps of electrical current for the duration of 60 minutes, or 8.0 amps for 30 minutes or 16 amps for 15 minutes. If the tool runs for 15 minutes at full power before the battery runs out, then you know that at full power, it’s using 16 amps.