AUTO
Battery runtime calculator
Estimate how long a battery can power a device at the specified load.
How is battery runtime calculated?
If capacity is given in amp-hours, nominal energy is calculated as Ah × V = Wh. The calculator then applies the selected usable-capacity percentage and, when an inverter is used, its efficiency. Estimated runtime is usable energy in Wh divided by load power in W.
Important for lead-acid and AGM batteries
Conventional automotive starter lead-acid and AGM batteries are not intended for regular deep discharge. The calculator uses 50% of nominal capacity as a conservative default. Repeated deep discharge can significantly shorten battery life.
AGM describes a battery construction technology, and dedicated deep-cycle AGM batteries also exist. The discharge limits from the specific battery manufacturer always take priority over the calculator default.
Why can real runtime differ?
The result is an estimate. Battery age, temperature, actual load, cable losses, inverter efficiency and low-voltage cut-off all affect runtime. With lead-acid batteries, high discharge rates can also reduce available capacity because of the Peukert effect.
This calculator is not intended to assess cranking current, CCA or whether a battery is suitable for starting an engine.