Battery Runtime Calculator
Convert battery volts and amp-hours into usable energy and ideal load runtime.
What would you like to do next?
Translate battery capacity into load runtime
Enter nominal voltage, amp-hour capacity, usable-capacity percentage, average load watts and conversion efficiency. The calculator converts volts times amp-hours into nominal watt-hours, applies both allowances and divides usable output energy by load power. It also shows ideal current at nominal voltage for a quick scale check.
Respect chemistry, discharge and electrical limits
Rated amp-hours depend on test conditions, and usable capacity changes with chemistry, discharge rate, temperature, age and voltage cutoffs. Inverters and converters also draw idle power. Check manufacturer documentation, cable sizing, fusing, ventilation, charging requirements and protection before building or operating a battery system.
Frequently asked questions
Why multiply volts by amp-hours?
The product provides nominal watt-hours for this planning calculation.
What should usable capacity represent?
It is the share of nominal energy available before the chosen discharge cutoff.
Is inverter idle draw included?
Only if it is added to the average load or reflected in the efficiency allowance.