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Inhibit charging when one cell is zero volt condition in 10-cell Li-polymer pack configuration using bq77910

Eungsoo Kim
Prodigy 20 points
Other Parts Discussed in Thread: BQ76PL536, BQ76925, BQ78PL116

I am reviewing the bq77910's functionality to design a protection circuit module for 10-cell Li-polymer battery of 20AH with 5A LiPo standard charger (CC/CV).

I found there is no protection feature preventing charging if there is a cell with zero volt in multi-cell pack configuration.

Is there any solution to inhibit charging when one cell is under low volt (almost  zero volt) condition in multi-cell r pack configuration while charger detection feature of bq77910 is still available.

At the moment, the CHG FET is enabled immediately if charger is detected under UVP condition.

Thanks in advance!

Eungsoo Kim

  • 0
    TI__Guru 54715 points

    You are correct. The bq77910 is a relatively simple protector device. For voltage it will prevent charge above OV or discharge below UV.  It does not have a zero-volt charge mode or the sophistication to provide a pre-charge current or disable the pack if the cells become too severely imbalanced. For this type of monitoring you may want to consider a gauge product like the bq78PL116, or building a system using the bq76925 or bq76PL536 and a micro-controller. With an AFE or monitor and micro-controller you can search for abnormal cell voltages, detect trends and implement limits of your choice.

    It may be possible to build a pre-charge circuit around the bq77910 by enabling a reduced current path when the CHG is on but DSG is off. That circuit is beyond the basic implementation of the device.