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BQ34Z100-G1: Calibration for High Cell Count

Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: BQSTUDIO, , GPCCHEM

Dear Sir,

My Battery Pack is 17S10P NMC 62.9V,26Ah

I'm trying to calibrate the voltage but bqstudio shows that parameter value beyond limit.(right now battery voltage is 58.7V)

How to calibrate the voltage for high cell count? Actual no. of cells in series is set to 17. Then I should calibrate the gauge as single cell or 17S?

Hardware is designed as per "bq34z100-G1 High Cell Count and High Capacity Applications".

Configuration Page parameters should be set as single cell or scaled capacity?

Qmax Cell 0 is scaled set by scaling down the capacity by 2. because maximum discharge current in the application above -32A.

for chemistry programming, I'm using BAK 18650 2600mAh NMC cells. which is more suitable chemistry 2404 or 2447?

In future I'm planning to use gauge for 23S,30S,60S etc. Will it support? how should I calibrate it?

Regards,

Samruddhi

  • Hello Samruddhi,

    I would follow the guide to increase the voltage range of the gauge, it is described in the app note "bq34z100-G1 High Cell Count and High Capacity Applications". 1 High-Voltage Batteries ( > 65.535 V).

    I believe your voltage is too close to the max and so it is capped by the software in order to prevent overflow.

    If you are not sure which chemistry ID to use I would use the GPCCHEM tool in order to find the proper match.

    Sincerely,

    Wyatt Keller

  • Dear Sir,

    What should I do now?

    Scale down the voltage by 2, but application note says not to do it.

    What value to enter so that gauge voltage will be calibrated?

  • Hello Samruddhi,

    The application note indicates you can scale the voltage as well, the first section covers how to do this with the voltage divider.

    Sincerely,

    Wyatt Keller

  • Dear Sir,

    I have followed the application note for the hardware design. My voltage divider is 1.62Mohm & 16.5Kohm.

    But my query is when calibrating the voltage in bqstudio what value should be entered?

    Calibrate the gauge as a single cell?

    Number of cells in series is 17 so can't divide the voltage by 2 as result is 8.5.

    Please help. What should be done in case of odd no. Of cells in series?

    Regards,

    Samruddhi

  • Hello Samruddhi,

    The scaling factor does not need to be an integer. It just needs to be selected so that the stored number of cells value is an integer. For an even number of cells, it is best to use an even scaling factor. But, you could use a scaling factor of, say, 1.7 and enter the # of cells as 10. Then the calibration would have to be scaled 1.7 to accommodate. 

    Thanks,

    Alex M.

  • Dear Sir,

    okay, Thank you.

    But then why application note says, "As an example, if the actual number of series cells
    was 17, then the number of series cells must be set to 17 and the voltage will be reported as
    a single cell."

    can you please explain the meaning of this?

    Regards,

    Samruddhi

  • Hello Samruddhi,

    I believe the application note is mentioning that the total cell count could be scaled down to one cell. So essentially you would calibrate with a scale factor equal to the number of cells, so 17, then everything would be reported by the gauge in a single cell voltage range.

    What Alex mentioned will also work, you will be using a non-integer scaling factor is the only difference.

    Sincerely,

    Wyatt Keller