Discuss the design issues of electric vehicle fast charging

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Nowadays, for electric vehicles, increasing the cruising range to make long-range electric vehicles is the main development path. When the cost of batteries drops and the combined range reaches 500-600 kilometers, the main contradiction of electric vehicles changes from range anxiety to charging anxiety. Improving the charging power of electric vehicles mainly includes several core elements. The following is the way to analyze the reasons:

First: increase the current. If we keep the other components the same and choose the path to increase the current, the main limitation is the heat loss due to the high current, which can make a big difference in the overall design. High currents in a circuit create high heat losses, as the resistance of all components (connectors, cables, electrical connections to batteries, bus bars, etc.) inevitably heats up. If the battery overheats during charging, these heat losses need to be taken into account when designing and sizing conductive elements to avoid problems such as overloading, overheating, or controlled derating of the charging current.

Second: increase the voltage. Since the increase of the above current is limited, the current limiting current is generally defined as 500A, and the achievable power is around 200kW (Tesla designed more than 600A at 400V as an attempt), increasing the voltage to switch the 400V system to 800V becomes an option. This is a systematic improvement of all electrical components. The core switchgear and other parts have changed. At current costs, these modules developed to the 800V specification are relatively expensive. Taking the main inverter as an example, the cost of the core SiC module is about 4 times that of the original IGBT module.

Let's take a closer look at some of the issues that need to be considered in a path that can be reached either way. Since several methods have the same requirements for the cell, we list the cell problem at the end, focusing on the electrical connection and thermal management inside.

Thank you for watching！