Definition
Battery capacity, or ampere-hour, determines the amount of current a battery can deliver per hour. Besides the battery's pure capacity, the discharge curve is also important. This curve determines the battery's behavior during discharge, with an ideal situation where the battery consistently delivers the same amount of energy. This ideal battery doesn't yet exist. The influence of temperature, the number of discharges, and the conditions in which the battery is charged and stored determine the battery capacity over the course of its life.
Conversely, the charger's Ah rating indicates the capacity delivered to the battery. The higher the capacity, the faster the battery will charge.
Calculation example
18V 3.0Ah (3000mAh) and a screwdriver that consumes 600mAh per hour. If you use the tool continuously at full load, the battery will be drained by 600mAh per hour, or:
3000mAh/600mAh = 5 hours.
If you upgrade your battery to an 18V 6.0Ah version and your screwdriver still consumes 600mAh per hour at full load, the battery life will double:
6000mAh / 600mAh = 10 hours.
