When selecting a meter setting for a battery-powered system, you should reference the battery's which rating?

• A. Voltage rating
• B. Ah rating
• C. Capacity in mAh
• D. Battery type

Answer: (B)

Understanding how long a battery-powered system will run relies on the energy stored in the battery, described by the ampere-hour rating. This Ah rating tells you how much charge the battery can deliver over time for a given current. To estimate runtime, divide the battery’s Ah by the continuous current draw of the system (in amperes). For example, a 40 Ah battery powering a 2 A load would run for about 20 hours. The voltage rating is about the electrical potential and compatibility, not how long the battery lasts. The capacity in milliamp-hours is the same concept scaled down and is less practical for larger systems, though it means the same idea at a smaller unit. Battery type describes the chemistry and construction, not the amount of usable capacity by itself. So, reference the Ah rating when assessing how long the system will run or when sizing the battery for a desired runtime.