HEV Multi-Cell Battery Pack Design and Considerations

Block diagram (SBD) of a HEV multicell battery pack using TI digital power controllers and multicell battery devices.


Design Considerations

Plug-in hybrid electric vehicles (PHEVs) and battery electric vehicles (BEVs) are two rapidly emerging technologies that use powerful electric motors as a source of power. To power these motors, large battery packs consisting of hundreds of cells totaling 300-400V are installed in the vehicle. Due to the limited capacity of the batteries, PHEVs and BEVs must be recharged periodically, which is usually done by connecting to the power grid.

The charging system for these vehicles contains an AC/DC rectifier that generates a DC voltage from the AC line and a DC/DC converter that generates the DC voltage required by the battery pack. In addition, advanced charging systems may also use a PLC modem to communicate with the grid to regulate charging based on grid conditions. The battery pack must also be carefully monitored during operation and charging to maximize energy usage and extend battery life. High-performance analog parts also provide important system functions and features such as sensor feedback, isolation, chip power , and communication transceivers. The bq7xPLxxx device family is designed for multi-cell battery packs. They can handle voltages and currents in higher power applications such as power tools and electromobility . The more cells connected in series in a battery pack , the greater the differences in charge state, impedance, and capacitance that affect the condition of the battery pack and the energy supply. The bq7xPLxxx devices include circuitry to return the cells to a balanced state . This extends the life of the battery pack and helps to deliver as much energy as possible to the application. Each bq7xPLxxx device protects the battery against overcharge, overdischarge, overtemperature, and high-voltage conditions, keeping the battery pack and system safe.

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