New energy vehicle battery pack

　　The new energy vehicle battery pack is composed of multiple batteries stacked in series. A typical battery pack has approximately 96 batteries, which can generate a total voltage of over 400V when charged to 4.2V lithium-ion batteries. Although the automotive power system considers the battery pack as a single high-voltage battery, charging and discharging the entire battery pack each time, the battery control system must independently consider the situation of each battery. If the capacity of one battery in a battery pack is slightly lower than that of other batteries, then after multiple charging/discharging cycles, its charging state will gradually deviate from other batteries. If the charging state of this battery is not periodically balanced with other batteries, it will eventually enter a deep discharge state, leading to damage and ultimately forming a battery pack failure. To prevent this from happening, the voltage of each battery must be monitored to determine its charging state. In addition, there must be a device to charge or discharge the batteries separately to balance the charging state of these batteries.

　　An important consideration for the battery pack monitoring system is the communication interface. In terms of communication within PC boards, commonly used options include Serial Peripheral Interface (SPI) bus and I2C bus, each with low communication overhead and suitable for low interference environments. Another option is the Controller Area Network (CAN) bus, which is widely used in automotive applications. The CAN bus is very robust, with error detection and fault tolerance characteristics, but it has high communication overhead and material costs. Although the connection from the battery system to the car's main CAN bus is desirable, using SPI or I2C communication within the battery pack has advantages.

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