ChargeEstimateKit

Battery Charging Time Calculator

Estimate charging time for general batteries, power banks, portable power stations, and small devices from Wh, Ah, or mAh.

Last reviewed: 2026-06-14

Learn how this estimate is calculated

Estimate

V
%

Estimated result

Battery energy Enter values

Wall energy Enter values

Estimated time Enter values

Charging prices and charging speeds vary. Use this as a planning estimate.

Formula

Wh = volts x Ah
Wh = volts x mAh / 1000
charging hours = battery Wh / (charger W x efficiency)

Example

A 500 Wh battery charged by a 100 W charger at 85% efficiency takes about 5 hours and 53 minutes.

Assumptions and limits

  • Battery chemistry, charge controllers, temperature, and manufacturer limits affect real charging time.
  • Do not use this calculator to design, repair, modify, or revive damaged batteries, DIY lithium packs, swollen batteries, or unsafe chargers.
  • Follow manufacturer instructions and stop using equipment that overheats, smells, swells, sparks, or behaves abnormally.

FAQ

Why does mAh need voltage?

mAh is a charge capacity, not energy by itself. Voltage is needed to convert mAh into Wh.