(Edited by Yujingsuifeng from China)

As a manufacturer, we often need to explain to our B2B/B2C/retailer clients how charging speed is calculated for different EV chargers.

First, let's explain the calculation method for charging speed:

1. Power (unit: Watts W) = Voltage (unit: Volts V) * Current (unit: Amps A)

Commercial fast charging commonly uses 400V DC voltage, with peak current easily exceeding 100A. Based on this value, the power is calculated to be 40 kilowatts (40kW). In reality, many car models can achieve a charging current of 80A, resulting in a power of 80kW.(PS: For home charging stations using 220V AC power, the voltage is calculated as 220V, and the calculation method is the same as for DC power.)

2. Charging Time (unit: Hours H) = Charging Amount (unit: kWh, 1 kWh = 1 kilowatt-hour) ÷ Power (unit: Kilowatts KW).

3. Actual Charging Amount = Battery Capacity * Charging Percentage.

For example, if your car battery has a total capacity of 60 kWh, and you charge it from 20% to 80%, then you've added 60 * 80% = 48 kWh. This doesn't consider charging losses, which are minimal when the car is off.

After explaining the calculation method, let's look at some common charging stations. Substituting these into the formula above, you can easily calculate the desired figures.

Many single-gun power outputs can reach 120 kW. However, in actual use, it's usually one station with two guns, charging two cars simultaneously, one at half capacity, meaning each can only reach 60 kW (when both cars are the same type of pure electric vehicle; for different models, it depends on which one can compete for power).

During charging, you can see the real-time voltage and current on the station, making it easy to calculate the real-time power; you can also infer the current from the power displayed on the car's screen. Well, since you're bored anyway, why not do some calculations for fun?

Common power is 7KW, obviously much slower than the first type, especially at parking fee collection points, requiring more time and incurring higher parking fees.

Since it's for home use, it certainly won't reach the power of commercial fast charging, but we won't call it "slow charging" here, mainly because the fourth type is even slower.

Common voltage is 220V AC, and the common power is 3.5KW (peak). According to the formula, the peak current is approximately 16A. For household electricity, this current is not low, which is why it requires a dedicated line for installation; you can't just run a random extension cord to install this thing.

At this power, charging 60 kWh would take approximately 17 hours. Since it's at home, you can charge whenever you want, without wasting time, and the electricity cost is cheaper.

Unlike the three kinds of EV chargers mentioned above, which are connected to fixed charging stations, car chargers have a slow charging gun on one end and a 220V plug on the other, which can be plugged directly into a household socket (a special reminder: the socket must have sufficient current capacity; never use a power strip and connect it to a bunch of appliances like air conditioners or electric heaters!!!).

A typical portable EV charger has a power output of about 1.5KW, or about 8A of current. This is not a small current, which is why we mentioned above the importance of paying attention to current capacity and safety, avoiding sparks and flashes along the way; especially for those who illegally use extension cords—we're talking to you!

When using a portable EV charger, it's best to use a dedicated circuit, calculate the current capacity, and carefully monitor the wire temperature; excessive heat is dangerous.

Based on charging 60 kWh, it would take approximately 34 hours. Doesn't that seem incredibly slow?

(PS: Using extension cords is highly dangerous and explicitly prohibited by law.)

Of course, the charging speed calculations above mainly apply to pure electric vehicles. For plug-in hybrid vehicles (PHEVs), fast charging speed primarily depends on their designed charging speed, not the theoretical speed of the charging station.

For example, the top-of-the-line BYD Song dmi has a maximum fast charging power of 18kW, so its maximum commercial fast charging power is also 18kW.

Compared with pure electric vehicles, PHEVs' fast-charging speed is indeed less impressive. It's just that due to their smaller batteries, the actual time to fully charge isn't too long.

Furthermore, not all PHEVs have fast charging ports, but all do have slow charging ports.

Finally, let's briefly discuss charging prices.

For home use, the keyword is "cheap."

There's an interesting phenomenon with commercial charging stations: fast charging is often cheaper than slow charging. Fast charging often comes with integrated apps, and with VIP memberships and various coupons, it can often be as low as 1 yuan per kilowatt-hour, or even lower. There are also additional discounts for commercial vehicles, making 70 cents per kilowatt-hour not uncommon, almost equivalent to the daytime price of household electricity.

In China, many commercial slow-chargers, perhaps due to their early construction, lack integrated apps and therefore offer little to no discounts, typically charging 1.8 to 2.0 yuan per kilowatt-hour.

For plug-in hybrid vehicles without fast-charging ports, if you don't have home charging facilities, it's better to use gasoline (going through the trouble of commercial slow charging is simply not cost-effective).