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BQ27220: Apply

Muyan Lin
Prodigy 50 points
Part Number: BQ27220
Other Parts Discussed in Thread: BQ40Z50

1. BQ27220 can monitor the fuel gauge of a single lithium battery. If there are 2 same batteries, the first battery is powered at the beginning, and BQ27220 starts testing. Then switch the second battery power supply and BQ27220 starts testing. My question: Can BQ27220 be used in this way?

2. Do you have any suggestions to monitor the fuel gauge of each battery?

  • 0
    TI__Guru** 105960 points

    Hello Muyan,

    1:

    If they are both very close in aging and the same battery ID, then you may be able to do this. I would recommend using the same gauge for the same battery, so use one gauge per battery.

    2:

    I'm not sure what you mean by this, are you talking about the communication interface?

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 50 points

    Thanks for your reply and support.

    １．Battery ID is the same and close to aging，but first power on and battery voltage is different. Use one gauge to manage one of the two batteries through toggle. Is there a problem with gauge? Can we do that in SW?

    ２．Gauge IIC Addr is fixed. So use one gauge per battery, need to add 2GPIO. MCU has no GPIOs. Based on this, can you recommend other gauge that IIC Addr is unfixed?

  • 0 in reply to Muyan Lin
    TI__Guru** 105960 points

    Hello Muyan,

    I would not recommend doing this approach, the gauge needs to learn the Qmax and Ra table for each battery which can deviate with age. If you are constantly toggling I would not expect good gauging results.

    You would need to use an communication MUX or switcher in order to use 2 devices. Only the newer devices like the BQ40Z50 have ability to change the address.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 50 points

    Hi Keller,

    When battery A switches to battery B, MCU first reads and saves all the register of gauge on Battery A. When battery B switches to battery A, MCU first reads and saves all the register of gauge on Battery B, then writes all the register of gauge to battery A. Does the gauge support this operation? What are the consequences?

  • 0 in reply to Muyan Lin
    TI__Guru** 105960 points

    Hello Muyan,

    When you transfer the data you would need to reset the gauge after the transfer, this will force the gauge to correlate the OCV (voltage) to the SOC. So the battery must be relaxed.

    We also recommend that the gauge is sealed once it goes to the field so the data cannot be modified or tampered with. If you don't seal, or send the unseal keys over the communication lines, someone could potentially hack the device. If this is not a concern for you, then it could be a possible solution.

    Sincerely,

    Wyatt Keller