One of the questions we regularly get asked is, “What is an Amp-hour?”. A lot of people get confused about the difference between AH and volts.
An “AH” or “amp hour”, is an abbreviation of ampere hour.
An ampere is a unit of measure of the rate of electron flow or current in an electrical conductor. An Amp hour refers to the amount of energy charge in a battery that will allow one Amp of current to flow for one hour.
In order to define the AH rating of a lead acid battery, manufacturers will drain the battery down to 0% capacity, over a specific amount of time and the level of amperage it takes to get it to zero over that time is the AH rating.
The standard rating for a deep cycle battery is 20 hours, so if your battery has a rating of 100AH @ 20Hr rate, that means it was discharged over 20 hours with a 5 amp load.
Starting batteries, on the other hand, are normally rated at 10Hr due to the fact that they’re used faster.
The faster a battery is used, the more its Amp hour rating declines. Batteries that get drained more quickly have less overall available amperage, this is known as the Peukert effect.