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Original question:

BQ28Z610: Is it needed a new learning cycle after upload a golden .srec file?

BQ28Z610: After 1st charge/discharge cycle FCC is low and RemainingCapacity won't update ....

Maurizio Bonelli
Expert 1400 points
Part Number: BQ28Z610

Hello,

Following the opinion of Batt (who I thank once again) I have put in manufacturing the batteries using the procedure outlined in my original post:

  1. upload the board with golden file (gauge is disabled in the .srec). Board is supplied by a precision power supply.
  2. calibrate voltages
  3. test all the other circuit (different from battery gauge)
  4. enable gauge, shutdown the BQ28Z610, disconnect the power supply and store the boards for later assembly

when battery packs need to be assembled, then we do:

  1. connect the cells to the board
  2. insert in the housing
  3. activate the BQ28Z610
  4. discharge to 3.0 V (FD bit is set)
  5. charge to ValidChargeTermination (FC bit is set)
  6. check capacity -> if good, shutdown and store for shipment.

This procedure, done during design and small pre-series, has worked but now I do not know what could happen -> The manufactured batch has the most of the packs well below the rated capacity, also considering the tolerances of the process but the most strange is that when I attempt to discharge, the Remaining Capacity doesn't change for sometime (and RSoC is 100%), then suddenly it is updated to a value well lower i.e. RsOc goes 57%).

I have checked everything several time (FW, data and parameters and all is exactly like should be.

What hell has happened / is happening? I'm going crazy .....

Any help will be appreciated a lot.

Maurizio

 

  • 0
    TI__Genius 10830 points
    hi Maurizio,
    Most of our battery experts are out of the office today. We will look at your question on Monday.
  • 0 in reply to David Hien
    Expert 1400 points

    Thank you David.

    Meantime I am waiting the reply, I would like to take a look at the BQ28Z610 FW, but the SLUC653 document is not existing on the TI website.

    A last minute update to my previous post (arrived during weekend):

    the batteries with those strange behaviors was submitted to a 2nd cycle discharge-charge and at the end of charge the parameters are correct.

    This seems to close my fears about something seriously wrong, but I am still thinking at the remaining capacity that doesn't change during discharge: I would like to do not perform 2 discharge/charge cycles in factory, but I cannot put on market batteries whose performance are not 100% from the 1st use.

    Bye bye

    Maurizio

  • 0 in reply to Maurizio Bonelli
    TI__Mastermind 42535 points
    Hi Maurizio,

    Have you performed the chem ID matching for your batteries. Without that, no matter what you do, the learning cycle will not be accurate. The steps for the bq28z610 are available here, www.ti.com/lit/an/slua777/slua777.pdf. But you'll need to follow the steps in this document, www.ti.com/.../slva725 before you use the previous one. If you still have issues, please send me your battery DS and your srec.
  • 0 in reply to Batt
    Expert 1400 points

    Yes Batt,

    I have done. I followed everything possible after have read the slva725 and slua777.

    In the office trial tests, I closed several issues, like end charge voltage or termination current value, because not all chargers have the same end voltage....

    But the cycle done each time after to have installed the cell to the board was charge-discharge-charge and at least the minimum rated capacity of the cells was achieved.

    To short the manufacturing cycles, I asked to try just discharge-charge cycle and I was expecting a FCC less than the rated, but what I have not expected is the strange behavior when the Remaining Capacity did not decrease....

    In any case, doing charge-rest-discharge-rest-charge cycle, all the features are working fine.

    Thanks again, but I was a few panicked for manufacturing, you can guess. :)

    Maurizio