In recent years, an increasing number of electric vehicles have been equipped with 800V high-voltage charging platforms, doubling the voltage of the previously mainstream 400V system.
However, if you expect this to double charging speeds, you may need to adjust your expectations.
High school physics teaches us that electrical power equals voltage multiplied by current (P=U*I). For similar battery capacities, increasing either voltage or current can increase charging power and shorten charging time.
The problem, however, is that increasing current leads to increased resistance heating, which not only increases energy loss but also poses safety risks.
By contrast, increasing voltage is a more feasible technical approach. Furthermore, high-current charging requires thicker cables, which increases costs. However, for the same power, increasing the voltage from 400V to 800V reduces current, allowing for thinner wiring harnesses. This not only saves material but also reduces vehicle weight, ultimately improving range.
Research shows that upgrading from a 400V to an 800V platform can reduce current from 375A to 125A, and copper usage per meter of wiring harness can be reduced by approximately 63%.
Another report indicates that a vehicle equipped with a 100kWh battery can be approximately 25kg lighter using an 800V high-voltage platform compared to a 400V platform. In other words, the 800V system theoretically offers the advantages of "faster charging and lighter vehicle body."
So why isn't the actual experience as pronounced as imagined? For example, when choosing a car, one user compared two models of the same brand with similar battery capacity and range: the 400V model took 26 minutes to charge from 30% to 80%, while the 800V model took 20 minutes from 10% to 80%.
While the 800V model is indeed faster, the advantage is only a few minutes in the commonly used fast-charging range. Furthermore, these data are mostly from ideal laboratory conditions and require matching supercharging stations to achieve results.
The reality is that the so-called "800V" refers to a voltage range, typically between 550V and 930V. Many models do not consistently charge at 800V during actual charging.
For example, a new car's rated maximum charging power is 440kW. Even running at full 800V, it requires nearly 600A.
The current output current of common 120kW public chargers is typically only 300A, which is insufficient to meet the peak demand of this vehicle. Therefore, in actual use, the charging power of 800V models is often lower than the theoretical value, naturally narrowing the gap with 400V models.
Furthermore, when the battery charge exceeds 80%, the vehicle automatically switches to trickle charging mode to protect battery life, significantly reducing the power, further diminishing the advantage of 800V.
If using a home AC slow charger, the power is already low, and the impact of voltage on charging speed is even more minimal.
Overall, the 800V high-voltage platform represents an important technological advancement for automakers seeking a balance between range and charging efficiency, and it represents a significant advancement in technology. However, consumers should consider the increased charging speed rationally and make choices based on their individual vehicle usage scenarios.