This estimator calculates the time needed to charge an EV battery from a starting state of charge to a target state of charge. It combines usable battery capacity, the desired percentage increase, charger power, and charging efficiency.
Drivers can use the estimate to plan home or public charging sessions and compare charger options. The result assumes average power remains constant, so high-state-of-charge tapering may make real sessions longer.
1. Enter usable battery capacity
Use usable rather than gross pack capacity when available.
2. Set starting and target charge
The target must be higher than the starting percentage.
3. Enter sustained charger power
Use the lower of charger capability, vehicle acceptance rate, and site limit.
4. Set charging efficiency
Account for conversion and thermal losses.
5. Review the estimated duration
Allow additional time for tapering, preconditioning, or charger setup.
The result is the idealized time needed at the entered average power.
DC fast charging often tapers substantially near a high target state of charge.
Given: 75 kWh battery, charging from 20% to 80%, 11 kW power, and 90% efficiency.
Calculation: Battery energy = 75 × 60% = 45 kWh. Grid energy = 45 ÷ 0.90 = 50 kWh. Time = 50 ÷ 11 = 4.55 hours.
Result: Estimated charging time is about 4.55 hours.
Use usable capacity because state of charge normally refers to the energy available within the protected operating window.
Use the sustained power limited by the weakest part of the system: charger, vehicle, cable, or site connection.
Real charging power can taper as the battery fills and may be reduced by temperature or charger sharing.
Yes, but the constant-power assumption is least accurate near full charge.
It can. Energy used for battery conditioning or cabin climate may increase grid energy and session time.