What is the difference between the 400V high-voltage system and the 800V high-voltage system of electric vehicles?

Slow charging and difficult charging have always been problems faced by electric vehicles, and high-voltage platform technology is one of the more promising solutions at present. At present, in addition to the 400V high-voltage system, an 800V high-voltage system has been launched on the market. So, what is the difference between the two systems?

400V high voltage system: high current low voltage (400V) charging

Usually includes: battery, motor, electronic control, charger (OBC), high and low voltage converter (DC/DC), high voltage control box (PDU), connector and wiring harness, motor/battery thermal management related components.

From the perspective of core component functions:

1. The battery is the power supply unit of all electrical appliances, and the PDU protects the battery and circuit;

2. The drive motor and controller are the power source, converting electrical energy into mechanical energy;

3. DC/DC converts high and low voltage to meet the electricity demand of low-voltage devices in the car;

4. The OBC converts the alternating current of the charging pile into direct current and then charges the battery through the junction box.

According to the power (P), voltage (U), current relationship (I) formula P=U*I, other conditions remain unchanged, the charging efficiency can be improved by either increasing the charging voltage or current.

Tesla and Extreme Krypton are the representative brands of high-current fast charging. Among them, Tesla V3 supercharger can reach 250kW of power under the condition of 400V voltage, and the peak charging power can replenish Model 3 about 250 in 15 minutes. The amount of power required for the mileage.

800V high voltage system: high voltage (800V) low current charging

The specifications of the high-voltage wiring harness are reduced, the consumption is reduced, the cost is reduced, and the weight is reduced. Under the condition that the voltage is doubled and the charging power increase is not doubled, the series connection is increased, and the current of the high-voltage wiring harness becomes smaller.

The SiC inverter increases the frequency of the power supply, the speed of the motor increases, the torque decreases under the same power, and the volume decreases. The motor voltage is doubled, and the current is halved under the same power, so the copper wire is thin (but the number of turns is increased, so the amount of copper used is not reduced), the current density is small, and the torque is small. To increase the power, the rated current only needs to be increased from half of the rated current of the 400V motor.

The 800V architecture makes the whole vehicle more efficient. After the launch of the 800V voltage platform, compared with the 400V platform, the operating current is smaller, which saves the volume of the wiring harness, reduces the internal resistance loss of the circuit, and improves the power density and energy efficiency in disguise.

Under the premise of the same power, it is expected that the launch of the 800V platform will increase the cruising range by 10% and the charging speed will more than double. Of course, the popularization of actual fast charging technology requires the simultaneous matching of charging pile power and battery charging rate.

 

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