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BQ34Z100 Learning Cycle, FC not registering, single stage charger

Other Parts Discussed in Thread: BQ34Z100

Hi


We are using the BQ34Z100 with 2 series Li-Ion cells (2900mAh).

The charger we are using (I don't think it can be changed) is a single stage charger that cuts off the charge at 8.4V and does not do the second stage saturation charging down to 50mA.

I am currently tying to "teach" the pack prior to production. The problem is the FC bit doesn't get set when charging.

I've set the taper current to 300mA (the chargers seem to stop around 200-250mA), cell taper voltage to 200mV, taper window to 20s and FC Set to -1.

The pack passes the taper current and taper voltage, but the FC bit is never set.

The datasheet says

"The bq34z100 detects charge termination when (1) during two consecutive periods of Current Taper Window, the
AverageCurrent() is < Taper Current and (2) during the same periods, the accumulated change in capacity >
0.25 mAh /Taper Current Window and (3) Voltage() > Charging Voltage - Charging Taper Voltage."


I don't understand how I can read the second requirment, do I need to adjust Min Taper Capacity? Its set to 25mAh

Is it the case that FC will never be set due to single stage charging?

Can I optimise the settings without FC being set, I thought it was required to update an internal parameter, but perhaps I misunderstood this?

Thanks

Morgan

  • The 0.25mAh/Taper Current Window is looking for at least 0.25mAh of charge to be stored into the pack during each of the Taper Charge Windows after the Taper Current has been reached. Do you have a log file that you can send to me for review?
  • Hi Tom

    I think these logs show what I mean, I'm just making another charging logs, I'll send it this evening.

    Thanks

    Morgan

  • Morgan, 

    I checked you log data and ran the same scenarios on the bench and the FC bit did set. Can you export a .senc file, so that I can check your setup?

    Tom

  • Hi Tom

    I charged 3 pack and only one set FC, I think my chargers may be a bit flakey, please ignore the many errors in the log file, this is because my micro clashed on I2C with logging program, I think I've sorted this now.

    Please see attached log from yesterday as well as senc file. I had to rename it zip so it would attach, but its just a senc file.

    Cheers

    Morgan

  • Hi Tom

    I followed the instructions on pack learning and it didn't set the Update Status to 06, its still 05.

    Did I do something wrong.

    Please see attached the discharge log and gg files. (the log is in accross 2 files.


    Thanks


    Morgan

  • Morgan,

    Was this the discharge log for the Qmax update or for the Ra table update? It looks like the gauge was reset near the beginning of the discharge and this would abort the update. The charge / discharge process for an optimization needs to be very clean without any resets or load or charging interruptions.

    Tom

  • Hi Tom

    I managed to get 3 packs to complete learning, i.e. set 06.
    I will hopefully have a 4th tomorrow.
    The Ra values between tham are all different, should I average them when making my golden image?
    Are there any other values I should average together when making my golden image?

    Thanks

    Morgan
  • Morgan,
    It is hard enough to get someone to run one optimization cycle and you have done three or four. How close are the Ra table resistances? There will be some variation, but they should be fairly close. Qmax will also differ, but it should be close as well. I would not average them, because the pack that you loaded to will be different as well. The only parameters that some people choose to average are the calibration parameters. Some people do not want to calibrate every pack in production and they will use the averaging method for current and temperature. This is discussed in our Going to Production document that is available on the product website.

    Tom
  • Hi Tom

    I had misread the going to production doc and though it was 20 units averaged.

    I now see its only one optimised unit and an average of 20 current and temperature calibration readings.

    We will probably calibrate temperature during production.

    Of the 3 I've optimised the cal values all look about the same, only 0.01 difference in CC offset.

    As I said the R_a tables are quite different, especially the R_a 14 values.

    I've attached all 3 .gg files, pack4 and pack5 are new cells (only cycled a few times trying to get it to optimise) and pack 7 has older cells from an older batch used about the same number of times.

    In slua334b section 3 it says I need to read out the gg file, which I have done, see attached.

    It then tells me to edit Update status to 02, at this point sould i also reset cycle count, LT Flash Cnt and the various Lifetime Max Mins?

    Also one pack has cell delta voltage at 7 and the others 1.

    Can you advise wich gg file looks "the best"? If thats imposible to tell well just ignore that question.

    In step 5 it says to write the .senc file for my chemistry to the pack, is this the senc file you have put on the forum before? bq34z100_R0_V0_06_BLD_0006.senc?

    I think I'm happy with the rest.

    I take it that if my optimised values are way off, it will just effect how long it takes for production cells to become accurate?

    Thanks


    Morgan

    BatteryCalFiles.zip

  • Morgan, 

    It looks like a current pulse mat have occurred in the Bat7 run. I would use Bat4 gg file for the golden file. You will need to change the Update Status and Cycle Counts. You can also reset the Lifetime parameters in the file. You should leave the DeltaV at 1. bq34z100_R0_V0_06_BLD_0006.senc is the latest firmware for the bq34z100 device.

    Tom