Question T4A09
From subelement T4 - T4A
How can you determine the length of time that equipment can be powered from a battery?
Why is this correct?
Battery operating time is calculated by dividing the battery's ampere-hour (Ah) rating by the equipment's average current draw. This gives you hours of operation. For example, a 12Ah battery powering equipment drawing 2A average current will last 6 hours (12÷2=6). Option A uses peak power instead of average current and watts instead of amperes. Options C and D use incorrect mathematical operations that don't yield meaningful time calculations.
Memory tip
Always use average current draw, not peak consumption, since equipment rarely operates at maximum power continuously. The ampere-hour rating directly corresponds to sustained current delivery over time, making this division the most practical calculation for real-world operating scenarios.
Learn more
Understanding battery capacity in amateur radio operation helps plan field operations, emergency communications, and portable activations. Battery performance varies with temperature, age, and discharge rate. Lead-acid batteries shouldn't be discharged below 50% capacity for longevity, while LiFePO4 batteries can handle deeper discharge cycles. Consider that transmitting typically draws 10-15 times more current than receiving, so actual operating time depends heavily on your transmit duty cycle during contacts.
Think about it
Why do you think the calculation uses average current draw rather than peak power consumption, and how would your operating habits affect the actual battery life compared to this theoretical calculation?