Charging
EV Charging Time Calculator
Estimate charging time from the energy to add and the effective charging power — the lower of the charger's output and what the vehicle accepts.
Results are mathematical estimates from the values you enter — not measurements and not data about a specific product or vehicle.
How does the EV Charging Time Calculator work?
Charging time ≈ energy to add ÷ (effective power × efficiency). Effective power is the smaller of the charger rating and the vehicle's maximum acceptance (on-board charger for AC, peak DC rate for DC). The estimate is linear; real DC sessions slow down at high state of charge.
Formula
E = C × (SoC(to) − SoC(from))
P(eff) = min(P(charger), P(vehicle)) × η
t = E ÷ P(eff)Worked example
60 kWh from 20% to 80% on a 7.4 kW wallbox (car accepts 11 kW), η 90% → 36 kWh ÷ 6.66 kW ≈ 5.41 h.
Limitations and warnings
- DC fast-charging power is not constant: most vehicles reduce it as the battery fills (typically above roughly 80%) and when the pack is cold or hot. This linear estimate is optimistic for those sessions.
- AC charging also depends on the supply (single/three-phase, breaker rating).
Four values that are often confused
- Nominal capacity (Ah)
- Charge a battery delivers under rated conditions, usually over 20 hours (C20) at 25 °C.
- Usable capacity
- The part of the nominal capacity you can use without damaging the battery — about 50% for lead-acid, 80–90% for LiFePO4.
- Cranking current (CCA)
- Current deliverable for a short time in the cold to start an engine. It measures power, not stored charge, and cannot be converted to Ah.
- Stored energy (Wh)
- Ah × voltage. The right unit to compare batteries of different voltages.