Battery calculators · FREE TOOL

Battery Charging Time Calculator

Estimate an ideal constant-output charging time between two states of charge, with an explicit storage-efficiency assumption.

1

Your inputs

Edit the example
Core inputs
Ah
V

Use the nominal rating on the battery, not its charging voltage.

%
%
A
Planning assumptions
%

Retained charge or energy at the battery. Input is already battery-side; do not apply AC charger efficiency again.

Example estimate · editable inputs

Loss-adjusted constant-output time

3 hours

Ideal baseline
3 h
Energy to store
720 Wh
Charge to store
60 Ah

Charging taper can take longer. This is not an upper bound and does not determine a safe charge current.

BEHIND THE RESULT

How the calculation works

Added Wh = nominal Wh × (target SOC − starting SOC). Ideal h = added Wh ÷ battery-side charger W; charger W ≈ A × nominal V for current mode. Loss-adjusted h = ideal h ÷ storage efficiency.

The loss-adjusted result is a constant-output scenario, not an upper bound. Charging often slows near the target state of charge.

A worked example

A 100 Ah battery moving from 20% to 80% needs 60 Ah. At a constant battery-side 20 A and 100% storage efficiency, the ideal baseline is 3 hours. At 90% storage efficiency it is about 3.33 hours, before taper.

What this estimate can’t tell you

Taper, chemistry, nominal-voltage approximation, temperature, BMS and charger control may materially change the time. This tool never determines a safe charging current.

Sources & methodology

Formulas are derived from the units shown. Read our methodology or report a correction. Sources reviewed 2026-11-01.