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bq20z90EVM-001 Cell Balancing and Pulse charging

Edward Alvarado65953
Prodigy 205 points

Hello ,

I am using the evaluation module with 2 cell lithium batteries connected in series.

After a few charge/discharge cycles the 2 cells have become imbalanced, one sell reads 4177mV OCV and the other cell reads 3970 OCV.

The first cell is very close to being over voltage. The evaluation board seems to be initiating Pulse Charging which is allowing the batteries

to get more charged without allowing the first cell to become over charged but the problem I am having is with the cell balancing.


I am not sure if the cell balancing is properly configured. Min Cell Deviation has been set to 1700. During normal operating pulse charging is not desired, my main question is how do I go about setting up for proper cell balancing.  I have read SLUA340C but still seem to be having balancing issues.

  • 0
    TI__Genius 10235 points

    The Min Cell Deviation parameter should not be changed if you are using the TI recommended schematic.  It should be kept at 1750. 

    This value depends on the internal cell balancing resistors and on the external 100 Ohm (recommended) resistors connected in series with the VCx inputs.

    Also, pulse charging can be disabled by setting the Turn OFF, Turn On, and Max OFF voltages to high values (5000mV each).

  • 0 in reply to Chase7071949597
    Prodigy 205 points

    Is the TI recommended schematic the same as the one in the EVM user guide SLUU234 ?

     

    edit : found the schematic in the slua404.pdf in section 17.6

    thanks