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bq40z60 together with battery pack BMS

oyvindne
Prodigy 40 points
Other Parts Discussed in Thread: BQ40Z60

I realize that I might have missed the main purpose of the bq40z60 slightly, that it is more a battery pack side IC, not system using a battery IC. But I have a few PCBs with the chip now, and I think it should be ok for my purpose as well.

However, my question is:

Would it be possible to use the bq40z60 together with battery packs that already have some simple protection circuitry. Either use 3 cells that each have their own protection electronics, or use a 3S pack that has its own 3S BMS (with or without balancing).

Im asking since I have a few such batteries and wondered if I could use them with bq40z60, or if it would be better/safer/necessary to remove the BMS PCB from them. 

  • 0
    TI__Guru 73830 points

    The device was not designed to be used as a host side gauge. You mentioned that the other BMS does not ell balance, so that will help. If the other BMS controls the FETs, then you will need to disable some of the safety features on the bq40z60 or your will get some false fails. e.g DFET and CFET.

  • 0 in reply to ThomasCosby
    Prodigy 40 points
    Thanks for quick answer
    I got separate FETs for the bq40q60, so it can still control those. The battery BMS probably has its own FETs.

    But I think that my original idea, to connect the bq40z60 to the output of the battery pack BMS, is flawed. If the battery pack BMS protection kick in, then the bq40z60 will no longer see the battery (no voltage), thus it will probably not allow to charge it in order to bring it back.

    Alternatively, I could connect the bq40z60 directly to the battery poles, in which case the battery pack BMS would be totally bypassed and I might as well remove it. The only thing it can do then is to cause problems.

    Regarding my application, it will have a battery permanently attached to the system PCB, thus I think the battery side and host side would effectively be the same.