Battery Runtime in Endurance Racing
In endurance racing, alternator failure must not immediately end the race. Teams calculate total system load, battery capacity, allowable depth of discharge, and minimum runtime required. See our race vehicle wiring systems for the full design guide.
Basic formula
Runtime (hours) = Capacity (Ah) / Load (A). Apply depth of discharge: usable Ah = capacity × DoD. Lead-acid: 50% DoD common for longevity. Lithium: 80–100% usable capacity.
Worked example
100Ah AGM battery, load 10A, usable capacity at 50% DoD = 50Ah. Estimated runtime: 50Ah / 10A = 5 hours. Use the battery runtime calculator.
Critical systems must survive
ECU, fuel pump, ignition, and data logging must run long enough to reach pit lane. Size conservatively for worst-case load and verify with the calculator.
Integration with other tools
Battery-to-bus wiring must be sized for charge and discharge currents. Check calculate voltage drop and wire gauge calculator. Fuse the battery output — use fuse sizing calculator.