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bq40z60 cell balancing

Brian Kuhnley
Prodigy 100 points
Other Parts Discussed in Thread: BQ40Z60

Does the Bq40z60 allow the use of external cell balancing fets? It appears the internal fets are probably only good for about 10-13mA (200 ohms RDSon + minimum external R of 100 ohms) and I believe I may need up to 40-50mA for proper balancing of my 4S2P battery pack.

Several other BQ chips specifically allow for this, but I think the only difference between internal and external balancing is that w/ external usually only one cell is 'bypassed' at a time, while with internal balancing multiple cells can be 'bypassed' simultaneously.

  • 0
    TI__Guru 73830 points

    Brian,

    You can add external cell balancing to the device. We recommend using a PFET for the bottom cell and NFETs for the other three cells. The series resistors will need to be increased from the typical 100 ohms to a higher value to provide enough voltage to turn the FETs on. We recommend trying to keep it in the 300 ohm range as higher resistances can affect cell voltage reading accuracy.


    You will also need to download the bq40z60 firmware update from the website. There were cell balancing issues with the original release.

    Tom