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Mihsaba›Battery Runtime Calculator

Battery Runtime Calculator

Estimate battery energy and runtime from voltage, capacity in Ah and load watts, with optional efficiency and usable-capacity factors.

Results are idealized or estimated; component behavior, temperature, losses and battery discharge curves can change real-world values.

How to use

This battery-runtime calculator estimates nominal energy from V×Ah, applies system efficiency and the usable-capacity fraction, then divides available energy by load power.

  1. Enter battery voltage and Ah.
  2. Enter load watts.
  3. Enter system efficiency and usable-capacity percentage.
  4. Review nominal/usable Wh and runtime.

How it is calculated

Nominal Wh=V×Ah; usable Wh=Wh×efficiency×usable fraction; runtime=usable Wh/W

Example

Example: 12 V and 100 Ah is 1200 Wh nominal. At 90% efficiency and 80% usable capacity, 864 Wh is available; a 120 W load gives about 7.2 hours.

Important notes

This is a simplified energy estimate. Actual Ah varies with discharge rate, temperature, age, chemistry, cutoff voltage and inverter efficiency; runtime is not guaranteed.

Frequently asked questions

Is Ah the same as Wh?

No. Wh≈V×Ah when using a nominal voltage.

Why include efficiency?

To approximate inverter/wiring/system losses.

Why not always use 100% capacity?

Many systems stop before the full nominal capacity is practically available.