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BQ40Z50: BQ40Z50 Golden Image Learning Adjustments for Same Model Batteries at Different SOH's

Parker Schless
Prodigy 90 points
Part Number: BQ40Z50

I have successfully completed the ChemID and learning cycle for one of my 4S batteries, and plan to make 7 more of my battery management boards for 7 other battery pods for our ROV. However, our batteries (all same model) are all at different states of health. Four of them are brand new and have not been used yet, while the other four are at varying states of health after having been used for at least a couple months. I completed the learning cycle using one of our older batteries, and the SOH reported by the BQ chip is 82%. My question is when I export the golden image and flash it onto the other BMB's, what steps do I have to take to make sure the gauge re-adjusts its remaining/full charge capacity and other statistics for each individual battery? Thank you in advance!

  • 0
    TI__Mastermind 35471 points

    Hey Parker,

    Full Charge Capacity and Remaining Capacity are values that are calculated by the gauge. Ideally, the learning cycle should be completed on a brand new battery, and  the golden image should be flashed onto gauges that are going to use a brand new battery. The learning cycle that was completed on the older battery would most likely be suitable for the 4 old batteries, but I would not advise using that golden image on the 4 new batteries. The learning cycle should be completed again using a brand new battery.

    Regards,
    Nick Richards

  • 0 in reply to Adrian
    Prodigy 90 points

    Hi Nick,

    What’s the best way to erase the current learning cycle parameters to start a new one?

  • 0 in reply to Parker Schless
    TI__Mastermind 35471 points

    Hey Parker,

    The easiest way to restart is to flash a brand new srec file and start from scratch. www.ti.com/.../BQ40Z50-DEVICE-FW

    Regards,
    Nick Richards

  • 0 in reply to Adrian
    Prodigy 90 points

    That makes sense, thanks!

    In addition, I am planning on making some changes on my next iteration of the board, and would like to reference the SMBus circuits to battery ground instead of pack ground to be compatible with a microcontroller I have on my board. Will this cause any issues? I also want to use 2 FETs each instead of 1 FET each for the charge and discharge FETs - do I need to add any additional circuitry or can I just simply connect them in parallel?

  • 0 in reply to Parker Schless
    TI__Mastermind 35471 points

    It is recommend that SMBus lines are referenced to the pack ground. This will ensure stable communication. To learn more about connecting FETs in parallel, please read this document. www.ti.com/.../slpa020.pdf

    Regards,
    Nick Richards

  • 0 in reply to Adrian
    Prodigy 90 points

    Would it then be an issue to power the microcontroller with BAT+/Vin referenced to PACK-? I don’t want the microcontroller to turn off if PACK+ turns off.

  • 0 in reply to Parker Schless
    TI__Mastermind 35471 points

    I don't believe that would cause an issue.

    Regards,
    Nick Richards

  • 0 in reply to Adrian
    Prodigy 90 points

    Hi Nick,

    Thanks so much for your help thus far! Going back to the parallel FETs, I was previously using the single FETs in the configuration shown here:

    If I want to duplicate Q2 and Q3, should I also duplicate R7 and R2 (for the Q2 duplicate) and R10 and R3 (for the Q3 duplicate) with the same values as shown? In addition, would I also need to duplicate Q4 and its related circuitry?

  • 0 in reply to Parker Schless
    TI__Mastermind 35471 points

    Hello Parker,

    You will need to duplicate R7, R2, R10, and R3 if you duplicate Q2 and Q3. You will not need to duplicate Q4.

    Regards,
    Nick Richards

  • 0 in reply to Adrian
    Prodigy 90 points

    Thanks so much, Nick! I appreciate you taking the time to answer my questions! Looking forward to this new version of the board!