What does the battery term AH or "Amp - Hour" rating mean?

The amp-hour rating of a battery (also known as "AH") is a measure of how many amps a battery can supply for a period of time. It is calculated using the formula Amps X Hours. For instance, in the ideal world, this rating would mean that if you have a 33AH 12 Volt battery, you should be able to supply 33 Amps (~412 Watts) out of it for 1 hour, or 16.5 Amps (~206 Watts) for 2 hours, or 8.25 Amps (~100 Watts) for 4 hours, etc. Unfortunately we don't live in the ideal world, so the values above are not spot on. It turns out that your battery has more Amp Hour capacity when you use it at lower Wattage and Amperage levels. So the values above are just very rough guidelines. Each manufacturer may calculate Amp hours differently which is to say they may manipulate the test to get themselves a very high Amp Hour rating which can mislead people like you and me. One common Amp Hour rating is based on using 20 hour time period where at the beginning of the test the battery is 100% charged ... more