battery charging time calculator

Battery Charging Time Calculator

Estimate AC, vehicle, or custom charging time from battery capacity, state-of-charge gap, known accepted input watts, conversion loss, and late-stage taper.

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Battery capacity (Wh)Starting charge (%)Target charge (%)Accepted charging power (W)Enter a known accepted charging power above 0 W.Enter the station's documented AC charging input, not its AC output rating.Conversion efficiency (%)Average taper / derate (%)

Input origin

User-entered value

No model preset is applied. WattRunTime does not infer AC or vehicle charging power from solar limits or fast-charge wording.

Estimated charging time

Enter known charging power

Enter a known accepted charging power above 0 W.

Visible assumptions: Conversion efficiency and taper are separate editable factors. The estimate excludes charging while loads are running. Energy to add = capacity × state-of-charge gap. Time = energy to add ÷ (accepted watts × efficiency × taper factor).

AC charger: Use the charger or station input specification for your region. Do not use inverter output watts.

This is a planning estimate, not a guaranteed charge time. Temperature, battery management, cell balancing, loads, and late-stage taper can extend charging.

Plan solar charging separately

Enter a known accepted charging power above 0 W.

Estimated charging timeEnter known charging power

Battery charging time plan

Battery charging time plan
Charging path: AC charger
Input origin: User-entered value
Battery capacity (Wh): 1,024 Wh
Starting charge (%): 20%
Target charge (%): 80%
Accepted charging power (W): Enter known charging power
Conversion efficiency (%): 90%
Average taper / derate (%): 90%
Estimated charging time: Enter known charging power
No model preset is applied. WattRunTime does not infer AC or vehicle charging power from solar limits or fast-charge wording.
This is a planning estimate, not a guaranteed charge time. Temperature, battery management, cell balancing, loads, and late-stage taper can extend charging.

Use the charger or station input specification for your region. Do not use inverter output watts.

This is a planning estimate, not a guaranteed charge time. Temperature, battery management, cell balancing, loads, and late-stage taper can extend charging.

How the charging-time estimate works

This calculator separates the energy gap, accepted charging power, conversion loss, and late-stage taper. All four remain visible and editable instead of being hidden inside a brand-specific promise.

Use input watts, not output watts

A station's inverter output rating does not describe how quickly its battery can recharge. Enter the accepted charging input documented for the exact charger, station, region, and connection.

State of charge defines the energy gap

A 20% to 80% charge on a 1,024 Wh battery adds 60% of nominal capacity, or 614.4 Wh, before charging losses and taper are applied.

Solar remains a separate path

Solar input varies with panel power, station limits, sun hours, and weather. Use the solar charge time calculator rather than treating a solar limit as an AC or vehicle charging specification.