What does AH(Amp Hour) mean?

An amp hour (AH) is a rating usually found on deep cycle batteries. If a battery is rated at 100AH it should deliver 5 amps per hour for 20 hours.
Peukert’s Law expresses the fact that the capacity available from a battery varies according to how rapidly it is discharged. A battery discharged at high rate will give fewer amperes than one discharged more slowly.