Which units are used in the runtime formula for a 12V battery?

• A. Battery Capacity In Amp-Hours And Voltage.
• B. Battery Capacity In Amp-Hours And Load Current In Amperes.
• C. Battery Capacity In Volt-Amperes And Current In Amperes.
• D. Battery Capacity In Watts And Current In Amperes.

Answer: (B)

Runtime is determined by how much charge the battery can deliver and how fast that charge is drawn. The stored charge is measured in amp-hours (Ah), and the current drawn by the load is measured in amperes (A). The time the battery can run is t = Q / I, so runtime in hours equals the capacity in Ah divided by the load current in A. The 12V rating doesn’t enter this simple calculation, it just defines the system voltage; it affects power, not the basic time-to-depletion relation.

For example, a 100 Ah battery feeding a load at 8 A lasts about 12.5 hours (100 Ah / 8 A). The other options mix in volt-amperes or watts, which are units of power or energy, not stored charge, so they don’t fit the straightforward runtime formula without additional conversions.