Most EV owners who charge at home want a simple answer: how many hours will it take? The honest answer depends on three things: the size of the battery, how much charge is already in it, and how much power both the charger and the car can accept. This article shows how to estimate the time using round numbers.
The basic estimate
A useful rule of thumb is that charging time in hours is roughly the energy needed in kWh divided by the charger's power in kW. Charging is not perfectly efficient, so real time is usually somewhat longer than the simple result.
Worked examples
Assume a battery of 75 kWh. The table below shows rough times to charge it from empty to full at several power levels, before losses.
| Charger setup | Power | Approximate time, empty to full |
|---|---|---|
| 120 volts, 12 amps (Level 1) | 1.4 kW | about 52 hours |
| 240 volts, 30 amps | 7.2 kW | about 10 hours |
| 240 volts, 40 amps | 9.6 kW | about 8 hours |
| 240 volts, 48 amps | 11.5 kW | about 6.5 hours |
Many drivers do not need a full charge every night. Charging from 20 percent to 80 percent of the same 75 kWh battery requires 45 kWh. At 9.6 kW, that takes about 4.7 hours, which is often less than a typical overnight stay at home.
Why the car matters
The car's onboard charger converts incoming AC power into DC for the battery, and it has a maximum rate. If a car accepts only 7.2 kW of AC power, a 9.6 kW charger will still deliver about 7.2 kW to that car. The slower of the two limits sets the session speed, so the time in the table is only an estimate until you know the car's limit.
Factors that change the time
- Starting charge level. Charging from 10 percent takes longer than topping up from 70 percent.
- Battery temperature. A cold battery may accept less power until it warms up.
- Charging losses. Some energy is lost as heat during conversion, so a session takes longer than the simple calculation.
- Tapering. Most cars slow charging as the battery approaches full.
Planning an overnight charge
For drivers who use only part of the battery each day, a Level 2 charger usually refills the car during an overnight stay. Plugging in whenever the car is parked gives you the most flexibility, because even short sessions add useful range.
How this applies to EVIQO chargers
EVIQO chargers run on 240 volts at 9.6 kW (40 amps) or 11.5 kW (48 amps). Using the 75 kWh example, a 9.6 kW charger takes roughly 8 hours from empty, and an 11.5 kW charger takes roughly 6.5 hours, before losses and before the car's own limits. The 48-amp option must be hardwired and needs a 60-amp circuit. The 40-amp option is available as a NEMA 14-50 plug-in and needs a 50-amp circuit. Each charger includes a 25 ft cable and a 3-year warranty.