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bq40z50 - Battery Replacement

Karl Schwabe
Prodigy 90 points
Other Parts Discussed in Thread: BQ40Z50, BQSTUDIO

I have an experimental setup with which we are testing the bq40z50 for use in our product. Our system uses the PRES pin to wake the chip up and determine if a system is present, be that the charging source or the load.

If I wanted to replace the battery in the system, be that in the field or in the lab, e.g. if one of the cells died, what is the process that I need to follow to correctly replace the battery so that the chip doesn't become "confused" when the new battery is connected. Would I need to re-upload the "golden pack" parameters for the new battery, or do I just need to simply "reset" the chip.

On a side note: What does "resetting" the chip actually do? Does it reinitialise flash parameters to defaults or does it just update the RAM parameters?

  • 0
    TI__Expert 3385 points
    Hi Karl,

    One thing that I would like to note first is that it is not recommended to change one cell out of your pack because there will be a lot of mismatch in the resistance tables. Some of the cells may be aged a lot and one of them will be brand new. Usually, it is recommended to replace the pack.

    There might be some cases where you might be able to change the cell. For example, if the pack has not gone through any cycles and you discover there is a problem, swapping the cell may not have any negative consequences.

    Best,
    Justin
  • 0 in reply to Justin Erfan
    Prodigy 90 points
    Hi Justin

    I am not talking about swapping out an individual cell in the battery/pack. I am talking about swapping out the battery entirely. We are using a 3S1P LiPo battery that is charged and discharged. For all intents and purposes it is effectively an embedded battery in the device. I am trying to monitor and manage the battery using the bq40z50 chip. If the battery were to fail/become old, I would want to replace the entire battery. But this then leaves the bq40z50 still on our PCB. My question is, now when I put in the new battery what would I have to do the bq40z50 to reconfigure it or to tell it that this is a new battery? Would I just shut down the chip, swap out the battery and restart it, or would I have to reset the chip and re-upload the golden pack data?

    I am not expecting this to happen very often, I just want to be able to plan for it for when it does happen.
  • 0 in reply to Karl Schwabe
    TI__Expert 3385 points
    Hi Karl,

    When your battery is aged and you replace it, you should re-upload new golden data. Your gauge will have updated its resistance values to the aged battery, and you don't want to use the same values for a new battery.

    Best,
    Justin
  • 0 in reply to Justin Erfan
    Prodigy 90 points
    Great. Thanks!

    As a short follow up, I am a bit unclear as to what the "RESET" command from bqStudio does, namely the device reset command 0x0041. When if ever should I use this command. I haven't found much in the way of an answer in the Technical Reference Manual.
  • 0 in reply to Karl Schwabe
    TI__Expert 3385 points
    Hi Karl,

    The command x0041 Reset is a hardware reset that you can think of as a software POR. It is possible to think of it like a power reset on a computer.

    There are several cases where you might want to use it. For example, while running a learning cycle, you will want to send the IT Enable and Reset commands to initiate the process.

    Best,
    Justin