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BQ28Z620: OCVFR Flag

David Godden
Prodigy 20 points
Part Number: BQ28Z620
Other Parts Discussed in Thread: GPCCHEM

Tool/software:

Hi,

I'm using a BQ28Z620 in my design, and running into an issue for a golden image. I can discharge correctly to 0, get FD & TD, and REST flag as usual.

However, when charging to full, I get FC & TC flags set, but OCVFR is always set, so I don't get a QMAX update.

I've completed the CHEMID and received two possible CHEMIDs, 4195 & 0457, both with 12% deviation. 

  1. Can OCVFR be disabled?
  2. Does OCVFR mean a QMAX update cannot happen, or does it happen after 48 hours?
  3. Does anyone know the flat voltage region of 4195?
  4. Is 12% deviation too high?

Thanks,

  • 0
    TI__Mastermind 26395 points

    Hello David,

    A chemI2 deviation of 12% is far too high and a acceptable range is 3% and below. The only options you have is to rerun the GPCCHEM calculator to validate that this is indeede your best chemID or send your cells to get a custom chemID.

    ChemID:
    www.ti.com/.../GPCCHEM

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Prodigy 20 points

    Hi Alan,

    Thanks for the response - I'm struggling to get a valid chemID, with multiple sent, and no deviation below 10%. The setup I have is 2s5p - would completing the GPCCHEM with 5 cells in parallel cause these issues?

    Or, although the end use case is 2s5p, should I complete the GPCCHEM with a single cell, or in it's eventual end use?

    How do I go about sending these cells in to get a custom chemID? 

    Thanks,

  • 0 in reply to David Godden
    TI__Mastermind 26395 points

    Hello David,

    Having multiple cells in parallel would not cause an issue but what would cause an issue is using different aged cells or having cells with poor quality control. However if after multiple attempts and calibration and you still can't get a chemID for your pack than you can contact your local Texas instruments FAE to get you cells characterized for a custom chemID.

    Thank you,
    Alan