Another way the current through a battery could be measured is the rate of discharge. This is the ability of a battery to deliver power continuously over a given period of time known as the discharge time. The discharge time of most car batteries is 20 hours. The rate of discharge is measured in amperes per hours. Batteries can also be rated in terms of useful capacity.
Useful capacity is measured in ampere-hours.
A 80 amp-hour battery will provide any combination of current and hours whose product is 80. The useful capacity of a battery changes depending on the discharge rate.