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BQ34Z100-G1: Cell Terminate Voltage/Qmax Cell 0 values

James McDaniel
Prodigy 70 points
Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: GPCCHEM

Seeking clarification for the expected value in the Cell Terminate Voltage and Qmax Cell 0 registers.

We are using a battery pack design with 3 Li-ion cells in series.  Should the values for these two registers be calculated on a per-cell basis, or for the pack in total?

For example, the voltage at which the pack is expected to fail is 9.6V - should the Cell Terminate Voltage register be set to 3200mV (9.6V / 3)?

The expected capacity of the battery pack is 4800mAh - should the Qmax Cell 0 register be set to 1600mAh (4800mAh / 3)?

Are there any other registers that expect a per-cell value, rather than a total pack value?

  • 0
    TI__Mastermind 25955 points

    Hi James,

    For Cell Terminate Voltage:

    Set this value to the per cell terminate voltage - the minimum voltage for end of discharge where the remaining chemical capacity is assumed to be zero.  This value will be in the datasheet.

    For your example, 9.6 V / 3 = 3200 mV.  The default value is 3000 mV.  If the cell datasheet shows that the cells go lower, please use that value for:

    1) Logging for GPCCHEM tool to find chemID

    2) Learning cycle for cells

    After the learning cycle has been successfully performed, the gauge may be configured to a higher value.

    This learning cycle may be performed on the EVM instead of the in system board.

    For Qmax Cell 0:

    Initially set this value to the battery cell data-sheet capacity.  This value will be updated automatically by the gauge after the learning cycle is complete.

    For your example of a 4800 mAh pack, this value would be 4800 mAh because the pack is 3S1P and additional capacity comes from adding cells in parallel.

    Sincerely,
    Bryan Kahler

    Find out more about the BQ34Z100-G1 including technical documents and tools/software/firmware and frequently asked questions.  Refer to the quickstart guide to get up and started. Also, learn how to find your chemID and perform voltage and current calibration.

  • 0 in reply to Bryan Kahler
    Prodigy 70 points

    Thank you for the answer and description, Bryan.  I'll give that a go.

  • 0 in reply to James McDaniel
    TI__Mastermind 25955 points
    Hi James,

    If this answer helped resolve your issue, please hit the 'resolved' button to improve search-ability so that other customers that may have the same question can find this answer.

    Thanks!

    Sincerely,
    Bryan Kahler