Difference between AC and DC Energy Consumption in electric vehicles

　・In Japanese

■What is Energy Consumption

The Energy Consumption of an electric vehicle is the driving distance per unit of electricity, and is expressed by the following formula.

■What is AC and DC energy consumption

The difference between AC energy consumption and DC energy consumption is how the energy consumption is calculated using the formula above.

The amount of power consumed in AC energy consumption refers to the amount of electricity charged from the charging equipment to the battery. Therefore, like the full tank method for gasoline vehicles, you can first fully charge the battery, then fully charge it again after driving a certain distance, and calculate the AC energy consumption from the distance traveled and the amount of charging electricity at that time. Since the charging equipment uses AC (alternating current), it is called AC charging. If you charge using a quick charging equipment, it will be DC (direct current), but it is still called AC energy consumption. The energy consumption listed in the catalog is AC energy consumption.

On the other hand, the power consumption in DC energy consumption is the amount of power consumed by the battery. Since automobiles use an internal computer to monitor the current flowing in and out of the battery, DC energy consumption can be calculated from the amount of power consumed by the battery when traveling a certain distance. Since the current flowing in and out of the battery is direct current, it is called DC energy consumption. The fuel consumption displayed in real time on meters and the mileage listed in catalogs are calculated from DC energy consumption.

■Why are there concepts of AC and DC energy consumption?

The difference between the calculation methods for AC and DC energy consumption is as described above, but the values ​​for AC and DC energy consumption are different. The reason is that in the case of AC charging, the power supplied from the charging equipment is used not only for charging the battery but also for operating electrical equipment (such as warming the battery while charging), and the charging efficiency of the equipment is also taken into account when calculating AC energy consumption. Therefore, when trying to estimate the driving distance using AC energy consumption, there will be a discrepancy with the actual driving distance, but DC energy consumption (the driving distance in the catalog calculated from it) is closer to the actual driving distance. On the other hand, AC energy consumption represents the actual environmental impact of the car.

Even if you calculate the driving distance from the battery capacity and electricity consumption (regardless of AC or DC energy consumption) listed in the catalog, there will be a discrepancy with the actual driving distance. The reason is that you cannot drive until the battery capacity is completely 0%.

■How to accurately estimate AC energy consumption and driving range (DC energy consumption)

The AC energy consumption and driving range (DC energy consumption) listed in the catalog are calculated by conducting certification tests as shown here. When calculating the DC energy consumption, the battery current/voltage values ​​are not measured by the computer inside the vehicle, but are measured using an external measuring device (such as a clamp meter). This means that the current values ​​output by the computer operated by the manufacturer cannot be trusted.

■Summary of the differences between AC and DC energy consumption

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