How can you determine the length of time that equipment can be powered from a battery?

Answer: B. Divide the battery ampere-hour rating by the average current draw of the equipment

A battery's ampere-hour rating tells how much current it can supply over time. Divide the battery ampere-hour rating by the average current draw of the equipment to get the hours of run time. For example, a 20 Ah battery with a 2 A average draw lasts about 20 / 2 = 10 hours. Use average current, not peak, because the radio is not transmitting all the time.

Tip: Hours = amp-hours / average amps.