A unit of electric charge, with sub-units milliampere-hour (mAh) and milliampere second (mAs). Whether your RV is 20, 30, or 50 amp, a simple way to look at the power available is to think of these numbers in terms of thousands. For example, at 115v AC, 30 amps equals 3,450 watts. For comparison a common wattage for a microwave is 1000 watts. Volts x Amps = Watts. The AmpHour of a battery rating tells you how much amperage is available when discharged evenly over a 20 hour period.