It is a popular misconception that charging an EV takes longer than filling up a regular car at the gas station. It’s not irrational to assume this. After all, depending on a number of variables, charging an electric automobile can take anything from 30 minutes to a week. How on earth could someone fit in so much charge time? Although the time may be spread out over fewer, longer visits each year, many new EV users will spend less time waiting for their vehicle to charge than they are used to. Chargers, as opposed to petrol pumps, let owners schedule a session and leave. Even the sluggish charger overnight charging will result in an average U.S. motorist provide more than enough juice to get through the next day. As illustrated here, this all can be easily calculated based on the length of daily travel, vehicle efficiency, and charger operation. The obvious stuff.
Level 1 Charging
Level 1 charging involves plugging a car directly into a standard 120V power outlet. If one has electrical service, which according to the World Bank is available to 100% of Americans, all electric vehicles come equipped with the appropriate wiring, there are no additional upfront costs. The maximum power that can be pulled from an outlet is calculated by multiplying the voltage by the maximum electrical current, expressed in amps, that won’t trip the circuit breaker: Power is equal to I (current) * V (voltage).
The most frequent amperage allowed on a 120V circuit in the United States is 15 amps, which is equivalent to 1800 watts or 1.8 kW of power. Consumer electronics are often limited by manufacturers to 1500 watts (1.5 kW), which is a standard rating for any significant heating.
The math for how long a car takes to charge is simple at low rates like this. It’s the energy capacity of the EV’s battery in kWh divided by the power the charger delivers in kW. Assuming a capacity of 75 kWh, the time to charge from completely empty to totally full can be calculated as follows:
75 kWh / 1.5 kW = 50 hours = ~2 days
Two days is too long, but given the limited miles most people drive daily, access to overnight charging allows average drivers to keep their vehicles sufficiently charged using a Level 1 charger. “Most people” obviously aren’t all people. And Level 1 charging is best used by EV owners with consistent and predictable driving patterns within the parameters of the vehicle’s range and performance.
For example, assume a 40-mile round-trip daily commute, leaving the house at 8 a.m. and arriving home around 7 p.m. With a reasonably efficient car like a Tesla Model 3 or Lucid Air, expect to consume energy at a rate of around 250 Wh/mile. Plugging in after arriving back home would require about seven hours to charge fully.
Conclusion regarding Level 1 charging: A Level 1 charger may deliver up to approximately twice the energy needed to complete the typical American commute. However, not everyone will be able to rely on such a slow charger.
Level 2 Charging
Similar to Level 1, Level 2 charging involves connecting the EV to a 208-240V circuit, which may accommodate a higher current and provide more power, as opposed to a 120V circuit. The amount of power an EV can use changes after that. Every EV has an onboard charger, which converts the necessary AC to DC for L1 and L2 charging. The amount of power this charger can provide to the battery varies by car.
THE AMPERAGE OF 240V CIRCUITS
Homes are often wired to accommodate a few 240V appliances with more than 1.5 kW in power, such as water heaters, ovens, and laundry dryers. The amount of power that can be drawn from an outlet on a single 240V circuit relies on how many amps of current the circuit is designed to support since, once more, P(power) = I(current) * V(voltage). These circuits typically range from 20 to 100 amps. A wall-mounted L2 charger, which is actually just an extension cable dressed up, has a usual rating of 16 to 80 amps, plus a safety margin. This indicates that between 3.8 and 19.2 kW of power could be transferred from your socket to your EV.
THE ONBOARD CHARGER
Once the power level reaches that point, there is another choke-point besides the circuit breaker and charging wire, and it is located inside the automobile, thus the analysis for calculating charging speed is not complete at that time. The internal AC to DC conversion that takes place during L1 and L2 charging is what makes it possible to connect into a standard outlet. Every EV has an integrated charger with a limited amount of power it can supply to the battery, as was already mentioned.
In general, the onboard charger will be greater the bigger the car’s battery is. The GMC Hummer EV and Ford’s F150 Lightning have 19.2-kW chargers, while a Tesla Model 3 and a Hyundai Ioniq 5 have 11-kW chargers. Smaller EVs are there is no additional benefit to installing a 80-amp charger versus a 48-amp in a home, as the car will be limited by its onboard charger.
So, calculating how long it takes to charge fully using L2 charging is different from L1, depending on the onboard charger. First, calculate the power delivered by the circuit, which is 240V multiplied by the circuit’s amp rating minus a 20% safety margin (ie 30A becomes 24A).
240V * 24A = 5.8kW
The power delivered to the car is whatever is smaller between the circuit power and the power of the car’s onboard charger. Then, divide the battery capacity by the power delivered to the car. For an Ioniq 5 with a 77kWh battery and a 11kW onboard charger, the math for various charging options is as follows:
77 kWh / 5.8 kW (24A) = 13 hours
77 kWh / 7.7 kW (32A) = 10 hours
77 kWh / 9.6 kW (40A) = 8 hours
77 kWh / 11 kW (48A or 80A) = 7 hours
On the flip side, more powerful chargers may be necessary to charge a larger, more heavily used vehicle overnight fully. The Ford F150 Lightning has a 131-kWh battery and a 19.2-kW onboard charger that doesn’t max out on a 48A-amp charger, so the full charge times for it are as follows:
131 kWh / 5.8 kW (24A) = 23 hours
131 kWh / 7.7 kW (32A) = 17 hours
131 kWh / 9.6 kW (40A) = 14 hours
131 kWh / 11 kW (48A) = 12 hours
131 kWh / 19.2 kW (80A) = 6.8 hours
Finally, some new examples of extremely large EVs really push the limits of what L2 charging infrastructure can handle in a reasonable amount of time. The Cadillac Escalade IQ has a 200-kWh battery, the GMC Hummer EV boasts 212 kWh, and the upcoming Dodge Ram REV holds up to a staggering 229-kWh battery. Let’s do the same math for the Dodge.
The technological side of things becomes challenging when it comes to DC rapid charging, often known as Level 3 charging. Bypassing the vehicle’s onboard charger, L3 chargers feed DC directly into the battery using their own external inverters. The charger and cord in this case, the automobile battery itself, or both at various points during the charging session, could be the limiting factor.
The battery’s capacity is another consideration. The charge curves shown above stay true whether your battery is 60 kWh or 200 kWh, meaning the more energy you receive over a certain period of time, the bigger the battery. When a car offers two alternative battery sizes, the larger battery not only has a greater range but also charges more quickly. Both the Kia EV6 Light (normal range) and Wind (long range) can go from 10 to 80 percent in around 20 minutes, however the Light only adds 162 miles while the Wind adds 217, a noticeable difference.