Preface

With the news of various electric vehicle manufacturers introducing high-voltage charging platforms, such as 600V and 800V, these charging voltages have continuously captured people’s attention. The most notable advantage of these high-voltage platforms is faster charging speed and higher power, or in other words, achieving a higher nominal power level for the charging station.

But why do different vehicles have varying charging speeds on the same EV charger in practice? This article will explore this question from the perspective of Power achievement rate.

Specific Analysis

What factors affect charging speed?

The different charging speeds with the same EV charger are primarily due to variations in the vehicles themselves. However, every link in the charging chain, including the charging station, vehicle interface, and battery, can impact the charging speed. As the starting point of this chain, a charging station’s influence extends beyond what is superficially displayed on charging apps as power.

The nameplate of EV chargers generally indicates three attributes: voltage, current, and power. These three attributes greatly influence the speed of charging.

Case

Rated power: 120kW
Output voltage: 200V~500V
Output current: 0~250A

If the vehicle requires 800V (greater than 500V), then this charging station cannot directly charge the vehicle and would require voltage boosting through means such as DCDC.

If the vehicle requires 400V (less than 500V), it meets the charging conditions, but the maximum power can only reach up to 400V*250A=100kW, falling short of the rated capacity of this charging station at 120kW.

For this particular station, when the demand voltage increases to 480V, the current can reach its peak value.

In summary, only within a narrow range of 480V-500V can this charging station achieve a power output of 120kW. This brings about an issue – it is difficult to improve the power achievement rate for this charging station.

As we know, battery voltage increases with higher state-of-charge, just like how water pressure in a dam increases with more accumulation.

Assuming a vehicle is equipped with a 450V rated battery pack, which consists of individual lithium-ion cells rated at 3.75V and has a charging/discharging cut-off voltage ranging from 3.2V to 4.2V, the voltage when the battery level displays as 0% (very low charge) is approximately around 384V, resulting in slower charging; whereas when fully charged (high charge level), the voltage reaches up to 510V, requiring an even higher charging voltage.

With a voltage of 510V, this exceeds the rated capacity of the 500V charging station, so it will not be able to fully charge this vehicle. It may automatically stop at around 90% charge. Additionally, when the charging voltage requirement exceeds 480V, the vehicle’s state of charge (SOC) is already around 70-80%, and in such cases, it is the battery’s high state of charge that limits the charging current.

Therefore, even with a power output of 120kW, it will not be sufficient. Unless the vehicle has a higher rated voltage and a relatively lower SOC corresponding to 480V, there might be a possibility to utilize the full power output of this charging station.

It can be said that vehicles capable of utilizing this station’s power output cannot fully charge on this particular station while those that can fully charge on this station are unable to reach maximum power.

The above examples fully illustrate that the charging station cannot be solely judged based on its power. Voltage, current, and power must be considered together in order to determine whether your vehicle can charge quickly or not. It’s similar to how the water storage capacity of a barrel often depends on its shortest plank.

Unfortunately, current charging apps only indicate the power of the charging station without specifying voltage and current. Some stations may appear to have high power, but they may not meet the requirements of your vehicle model, resulting in a subpar charging experience.

Advantages of high voltage charging

The maximum output voltage of EV chargers in the earlier years was generally only 500V. However, in recent years, newly built chargers are usually planned at levels ranging from 750V to 1000V.

The power varies depending on the electricity grid conditions of the construction site. Nevertheless, the output current is generally limited to 250A or below. These EV chargers’ current and power are restricted by the electricity grid of the construction site, with varying levels.

The current can range from as low as 50A to as high as 250A, and there is also a variety of output powers such as 40kW, 60kW, 120kW, and180 kW.Vehicles using high-voltage platforms demonstrate advantages when utilizing these EV chargers.

The actual output power can reach up to either 120kW or 180kW but is constrained by a maximum current of 250A. On these chargers, vehicles with a platform voltage around 400V can achieve a maximum power slightly over 100kW; whereas vehicles with an 800V platform are more likely to fully utilize the charger’s power capacity and have higher power achievement rates in terms of power.