BQ76940: how to achieve cell balancing and get the healthy information of battery?

Hi User,
The BQ76940 is a battery monitor and as such does not perform analysis on a battery pack or include a balancing algorithm. It does provide measurement systems for voltage, current and temperature, as well as some protection thresholds, a balance mechanism, and protection FET outputs. The MCU used with the BQ76940 as part of the battery management system must provide the balancing algorithm, additional protection limits or controls, and determine state of health.
Balancing can be done by voltage. The best measurement of voltage will be obtained when no current is flowing, during current flow the voltage can be influenced by the resistance of the cell and interconnect. Since balancing is achieved by dissipating power, many controllers will balance only during the end of charge while the battery is still gaining energy but current is low and any resistance contribution to the voltage should be small. Other systems which might charge less frequently may balance at rest. The MCU used with the bq76940 will give flexibility to determine the best balancing algorithm for the system. The bq76940 duty cycles balancing and measurement, but the MCU must select which cells to balance and when to stop.
State of health might be determined in many ways depending on the needs of the system. Some may measure time, cycles or usage and compare to the manufacturers recommendations. Temperature history might be used in the determination. Unexpected voltage changes might be monitored or prolonged balancing of a particular cell. Other algorithms may determine if the voltage change for a current or an amount of passed charge is within a suitable range. A system which can be discharged completely on a maintenance schedule could measure the pack capacity and compare to an accepted limit. The designer must implement something suitable for the specific system.