What is BDU?
BDU is an abbreviation for Battery Disconnect Unit or Battery Distribution Unit.
PDU (Power Distribution Unit): Responsible for the distribution, management, and safety protection of the vehicle’s high-voltage electrical energy. It distributes the high-voltage DC power from the high-voltage battery to key components such as the motor controller, on-board charger (OBC), air conditioning compressor, PTC heater, and DC/DC controller.
From another perspective, a BDU placed outside the battery pack can be called a PDU, while one placed inside the discharging battery pack can be called a BDU; their overall functions are similar, both distributing circuits and ensuring the switching on and off functions.
Therefore, its main functions can be divided into three aspects: switching on/off, pre-charging, and status monitoring. Its main electrical components can be summarized into the following categories:
Circuit on/off control: Through internal main positive relays, main negative relays, etc., the connection between the battery pack and the vehicle’s high-voltage system (such as motor, air conditioner, charger, etc.) is safely connected or disconnected.
Pre-charge function: When the vehicle is powered on, the pre-charge relay and pre-charge resistor limit the current to prevent the capacitive load in the high-voltage circuit from generating an instantaneous excessive current, thus protecting the main relay and circuit.
Safety protection: Integrated fuses (including conventional fuses or the more advanced “explosive fuse” Pyrofuse) can quickly cut off the circuit when a fault such as a severe overcurrent or short circuit is detected, ensuring the safety of the battery and the vehicle.
Condition monitoring: Some BDUs also integrate current sensors (such as shunts) to monitor the charging and discharging current of the battery pack, providing key data for the battery management system to estimate the power capacity.
And necessary connectors, mainly copper busbars and aluminum busbars and wiring harnesses: high voltage is used to connect the high voltage main circuit and connect electrical components to ensure the circuit.
