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BQ35100EVM-795: Step-by-step instructions to measure SOH using BQ35100EVM and bqStudio

YgorPBrand
Prodigy 20 points
Part Number: BQ35100EVM-795
Other Parts Discussed in Thread: BQSTUDIO

Tool/software:

Hi everyone,

I'm working with the BQ35100EVM-795 evaluation board, a CR123A primary battery, and a 23.5Ω resistive load to measure the State of Health (SOH) using bqStudio.

I've already:

  • Calibrated the gauge

  • Selected the correct battery chemistry (Duracell CR123A from the chemistry list)

I’m currently using the following procedure to initiate SOH measurement in SOH mode:

  1. GE High (turn on the gauge)

  2. Send GAUGE_START command

  3. Wait for the [GA] bit to set

  4. Apply the load

  5. Send GAUGE_STOP command

  6. GE Low (turn off the gauge)

However, I have a few questions and issues:

Questions:

  1. GE pin control: To set GE high/low, should I physically remove/place the GE jumper on the EVM board? Or is there a recommended way to toggle GE from software (or externally)?

  2. SOH measurement failure: Despite following the steps, I keep reading SOH = 100% in bqStudio. What could be the reason for this? Am I missing any prerequisites? 

  3. Why does the SOH value show 0% after the second time I initiate the SOH measurement using the procedure I described?

  4. Impedance & R values: The measured Z and Scaled R values always show up as 0. What conditions must be met for these to be correctly updated?

What I’m looking for:

  • A clear, step-by-step guide using bqStudio and BQ35100EVM to correctly perform an SOH measurement for a primary battery.

  • Optionally, a firmware script or instruction sequence that can be loaded in bqStudio (like from the Data Memory or Command panel) to automate or verify the process. In other words, a code that I can use to correctly trigger GE with a relaxation time.

Any advice, documentation references, or example setups would be greatly appreciated. Thanks!

  • 0
    TI__Mastermind 27095 points

    Hello Ygor,

    1- with a EVM setup you would have to mainly remove/place the GE jumper on the EVM board and there is no way of using the software. However you can add that functionally with your own made PCB.

    2-Most likely you programmed the wrong ChemID and would need to redo this step.

    3 & 4- As mentioned above it is most likely your chemID, not doing calibration or having the data flash parameters setup wrong as well

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Prodigy 20 points

    As shown in the first image, I selected the CR123A battery from Duracell, which is exactly the one I'm currently using. I'm cycling the GE pin by manually removing and reinserting the GE jumper on the BQ35100EVM. However, as seen in the second image, the SOH value remains unchanged—whether the relaxation period is short or long. I’m discharging the battery with a constant 30 mA load.

    I’m unsure what the minimum required relaxation time is for this discharge current, and I’d also like to confirm the maximum allowed current draw during the relaxation period.

    Additionally, as shown in the third image, the values for measured Z and scaled R are always 0, and the SOH stays at 100%. However, I do observe a sudden drop in SOH when I reset the IC.

  • 0 in reply to YgorPBrand
    TI__Guru 62076 points

    The CR123A from Duracell is Mno2. Please use the SOH mode (not the EOS mode) for this chemistry. See TRM, 5.2.

    The gauge uses relaxed voltages only for this type of chemistry. It won't use Z and R. Make sure that the load is not on (or minimal, like C/25 or less) when you assert the GE pin.

  • 0 in reply to Dominik Hartl11
    Prodigy 20 points

    Thank you for the answer. I am using SOH, not EOS. What do you mean by C/25? Do you mean 1/25 of the load? 

  • 0 in reply to YgorPBrand
    TI__Mastermind 26605 points

    Hi, 

    The C in C/25 refers to the capacity of the battery pack. Please discharge at 1/25 the battery pack capacity.

    Regards,

    Diego