Charging Speed and Time Calculator
Calculate EV or device charging time, charging speed (power), and energy delivered based on battery capacity, charger power, and efficiency.
Formulas
Charging Time:
Energy Needed = Battery Capacity × (SoCend − SoCstart) / 100
Energy from Charger = Energy Needed / Efficiency
Charging Time (hrs) = Energy from Charger (kWh) / Charger Power (kW)
Required Charging Power:
Required Power (kW) = [Battery Capacity × ΔSoC / 100] / [Efficiency × Desired Time]
Energy Delivered:
Energy Drawn = Charger Power (kW) × Duration (hrs)
Energy Delivered (kWh) = Energy Drawn × Efficiency
Assumptions & References
- Charging efficiency accounts for AC-to-DC conversion losses, heat dissipation, and onboard charger losses (typically 85–95% for EVs).
- Default efficiency of 90% is a commonly cited average for Level 2 AC EV charging (SAE J1772).
- Battery capacity refers to the usable (gross) capacity of the battery pack in kWh.
- State of Charge (SoC) is expressed as a percentage of total battery capacity.
- Charger power is the rated output power of the EVSE (Electric Vehicle Supply Equipment) or charger adapter.
- DC fast charging (DCFC / CCS / CHAdeMO) typically has higher efficiency (92–95%) than AC Level 2 charging.
- Real-world charging times may vary due to battery thermal management, tapering at high SoC (>80%), and grid voltage fluctuations.
- References: SAE J1772, IEC 62196, U.S. DOE Alternative Fuels Data Center (afdc.energy.gov).