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Battery Runtime Calculator

Estimate how long a battery or power station will run a device, from capacity (Ah or Wh), voltage, load watts, usable depth of discharge and inverter efficiency.

Capacity (Ah (set 0 if you enter Wh))

Battery voltage (V)

Or capacity in Wh

Usable depth of discharge (% (LiFePO4 ~90, lead-acid ~50))

Inverter efficiency (%)

Load (W)

How to use it

Enter capacity in amp-hours with voltage, or directly in watt-hours.
Lithium (LiFePO4) batteries can use ~80-100% of capacity; lead-acid about 50% for long life.
Use inverter efficiency for AC loads (85-95%).

How it works

Runtime (h) = Wh × DoD × efficiency ÷ load watts. A 12 V 100 Ah battery holds 1,200 Wh; at 90% DoD and 90% efficiency it runs a 150 W load for about 6.5 hours.

FAQ

How long will a 100Ah battery last?

At 12 V, about 1,200 Wh; a 100 W load runs roughly 9-10 hours on lithium, about 5 hours on lead-acid (50% DoD).

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