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BQ40Z60: Can't complete a learning cycle.

Michael Korolyov
Prodigy 180 points
Part Number: BQ40Z60
Other Parts Discussed in Thread: BQSTUDIO, BQ40Z50, BQ28Z610, GPCCHEM

Hello everyone,

My setup is bq40z60 custom board with 3s Panasonic NCR18650B cells, Charging and discharging works flawlessly.  Then, I try to complete the automatic learning cycle, and things go weird.

I had followed slua777.pdf cycle order:

4.2.1 Discharge Battery to Empty

4.2.2 Relax for 5 Hours

4.2.3 Charge Battery to Full

4.2.4 Relax for 2 Hours

4.2.5 Discharge Battery to Empty

However, I am stuck at different steps
1) If I start the learning cycle, it clears QEN bit. It is never set afterwards. So, after step 4.2.2, it cancel the cycle with a corresponding message. Relax time is also less than 5 hours (varies on different attempts, but I guess it's okay because RDIS is cleared).
2) If I try to bypass the issue with QEN bit and send GAUGE_EN command after having the cycle started, here's what I get. Step 4.2.2 is skipped (relax time is 00:00:00, the cycle goes right next to charging). Charging is done properly (FC bit is set), and relax time (4.2.2) ends with an error "VOK is not cleared". Looking in the log, it really never clears while relaxing.

What shall I do to make this cycle work? It is unclear what causes such failures.

I've attached the log file and gg.csv files:bq40z60_learning_cycle_fail.rar

Will be endlessly thankful for any help!

Best regards,

Michael.

  • 0
    TI__Guru* 76230 points
    Hi Michael
    if you send the IT command (0x21) if QEN was already set, that will disable QEN and you will have to send the 0x21 command again to set the flag before starting learning. Pls carefully reread the app note you referenced. These points are captured there

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 180 points

    Thanks for your reply, Onyx.

    But I made sure QEN bit was set before the learning had started. After I hit "Start" in BQStudio, it was cleared automatically.

    slua777 reads:

    Before beginning the discharge, turn on the charge and discharge fets by sending command 0x22,

    then send IT (Gauge) enable command (0x21) to set the GAUGE_EN in manufacturing status register

    and QEN flags in IT Status register. Then send the reset command (0x41) to set the RDIS flag and
    disable resistance updates during this initial discharge cycle.


    which is exactly what I did. 

    Shall I re-enable QEN after the cycle starts (I can't proceed otherwise)? Shall I disable GAUGE_EN before the start, maybe?

    These questions may sound silly, but I'm really stuck at this point, and these learning cycles are awfully long to experiment with.
    Can you please describe the right sequence to make the cycle work?

  • 0 in reply to Michael Korolyov
    TI__Guru* 76230 points
    Hi Michael,
    The app note is describing the learning cycle process with you doing stuff manually and not with using the automated features of bqstudio. The automated feature carries out the process described in the app note. You shouldn't combine both.


    The right sequence is to follow what is described in the app note. Do not use the learning cycle feature of bqstudio.

    Thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 180 points
    Thanks a lot, Onyx. I'll try the manual cycle.
    One last little question - is automatic learning feature unapplicable for bq40z60 chip? It's a pity then...
  • 0 in reply to Michael Korolyov
    TI__Guru* 76230 points
    It might be applicable.. if using it, you will do so independent of the app note. Reason being that the app note has you manually sending commands. The automatic learning sends those commands for you. so if you are trying to follow the app note, eg sending IT enable command, and then clicking the automatic cycle, it is likely that sends the IT enable command again effectively disabling Impedance track. On our newer multicell devices like this one, the bq40z50 and the bq28z610, if you send 0x21 twice, the first command will turn off IT if it was on and vice versa while the second will turn it on if it was on and vice versa.

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 180 points

    Thanks again! Now I understood.
    The only unresolved issue is why VOK isn't cleared... but I guess I might need to correct my ChemID using gpcchem.

  • 0 in reply to Onyx Ahiakwo
    Prodigy 180 points
    Sorry, but it seems something's not right in bqStudio learning cycle (be it automatic or manual). If GAUGE_EN is enabled before the cycle starts, it disables it, thus the cycle cannot proceed past the charging stage. If GAUGE_EN is disabled, RDIS bit is not set, thus the cycle cannot start and reports a corresponding error.
    So, the only option is to use the app note sequence. Am I right?
  • 0 in reply to Michael Korolyov
    TI__Guru* 76230 points

    Hi Michael,

    The app note sequence at this point will be the preferable choice.

    thanks

    Onyx