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

Battery capacity is most commonly measured in ampere-hours (Ah), which indicates how many amps a battery can theoretically deliver over a one-hour period. To calculate how long your battery will last, you divide this total ampere-hour capacity by the average current (in amperes) that your equipment draws. For example, a 10 Ah battery powering a receiver that draws an average of 2 amps will last approximately 5 hours (10 Ah / 2 A = 5 hours). Distractors that suggest using peak current draw or peak power consumption are incorrect. Because amateur radio operation involves a mix of listening (low current draw) and transmitting (high current draw), you must use the average current draw to get an accurate estimate of real-world battery life.