Battery Management: High Cell Count for HEV

Design Considerations

Plug-in Hybrid Electric Vehicles (PHEV) and Battery Electric Vehicles (BEV) are two quickly emerging technologies which use powerful electric motors as the propulsion source. In order to power these electric motors, large battery packs made up of hundreds of cells totaling 300-400 volts are installed in the vehicle. Since batteries have a finite energy capacity, PHEV and BEV must be recharged on a periodic basis, typically by connecting to the power grid.

The charging system for these vehicles consists of a an AC/DC rectifier to generate a DC voltage from the AC line followed by a DC/DC converter to generate the DC voltage required by the battery pack. Additionally, advanced charging systems might also communicate with the power grid using PLC modems to adjust charging based on power grid conditions. The battery pack must also be carefully monitored during operation and the charging process in order to maximize energy usage and prolong battery life.

High-performance analog parts are also available to provide critical system functions and features such as sensor feedback, isolation, chip power supplies, and communication transceivers.

The bq7xPLxxx device families are designed for high cell count battery packs. They can handle the voltages and currents found in higher power applications like power tools and electronic mobility. The more cells a pack has in series, the greater the difference in state of charge, impedance and capacitance affect the health and energy deliver of the pack. The bq7xPLxxx devices include circuitry for bringing the cells back into balance. This increases lifetime of the pack and can help deliver as much energy to the application as possible. Each bq7xPLxxx device protects from over charge, over discharge, over temperature and high current events for pack and system safety.

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