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BQ27441-G1: What do I need to do to get QMAX and RA table to get updated?

Scott Harsany
Prodigy 130 points
Part Number: BQ27441-G1
Other Parts Discussed in Thread: BQ27411-G1, GPCCHEM, BQSTUDIO, EV2400

I have a device that I am trying to get the QMAX and RA table to be maximized and so I follow the steps below but after 20+ hours I can't get the QMAX or RA table to show any new learned numbers.

1. Bring up the BQ27441-G1 from my device and program only 4 numbers to it  (Design Capacity, Design Energy, Terminate Voltage, and Taper Rate)

2. I then re-read them from the BQ27441-G1 and they match the values I wrote (Design Capacity = 470, Design Energy = 1739, Terminate voltage = 3100, and Taper Rate = 50)

3. For now I have turned SLEEP off in the OpConfig register, since I was worried it might have been the problem.

4. I then go into a loop to simulate the work the my device will be doing ... Do work for for 15 seconds, then sleep for 10 seconds and then start over and do the work again, etc...

5. Since this is a LoRa based device, I transmit the state of QMAX_UP and RES_UP, and read the value of QMAX, and the complete RA table ... and transmit to a device where I can read the values

6. After 13 hours the battery is almost drained (8% left from 100% starting point)  During this time NEVER received a QMAX_UP or RES_UP flags set and the values have stayed to the default values.

7. I then plugged the device into a charger and in about 2 hours it was back at 100% charged.

8.  Still never received QMAX_UP or RES_UP flag set or any of the values changing to anything other than the defaults.

9 . Control Register is constant at 0x008E

I am sure I am missing something else I need to do as I have reread the specs and it seems like the BQ27411-G1 will just take you starting point variables and continue to tune itself.

Thanks for any pointers.

Scott

  • 0
    TI__Guru 52115 points
    I would suggest you follow the app note below to perform a learning cycle.
    Andy
  • 0 in reply to Andy Liu (BMS)
    Prodigy 130 points

    Thanks Andy!   I read the document you passed on and it is great!   The document seems focused on using the TI reference board and tools.  I am working on a custom IOT board and the tools won't work.    I can follow most of the manual and do it from the host cpu with i2c commands, except for one main section in the manual ... it states the following:

    "Send IT (Gauge) enable command (0x21), or use the GAUGE_EN command to set the GAUGE_EN in
    manufacturing status register and QEN flags in IT Status register. Then send the reset command
    (0x41), or select RESET, to set the RDIS flag and disable resistance updates during this initial
    discharge cycle"


    The problem I am having is that the "Gauge enable command (0x21) is not documented anywhere in the TRG.   Neither is the Manufacturing status register.   Do these translate to commands and registers in the TRG I can use?

    Thanks,

    Scott

  • 0 in reply to Scott Harsany
    TI__Guru 52115 points
    Hi Scott,
    The BQ27441-G1 doesn't have this IT enable command or GAUGE_EN command.
    Just send a RESET command, which is available in the Commands Window.
    Andy
  • 0 in reply to Andy Liu (BMS)
    Prodigy 130 points

    Andy,

      Thanks for the update on sending the RESET command.   I have done this and then set all of the parmeters that need to be set (Design Capacity, etc...) and still no luck getting any changes.   So My sequence in code is ....:

    1. establish i2c connection with BQ27441.

    2. Wait for the device to initialize.

    3. Send RESET

    4. set all parameters (Design Capacity, terminate voltage, etc...)

    5. Send the host device (CPU) into loop doing some work and then sleep, and then repeat.

    6.  All the time watching the QMAX and RA registers to see it they change at all. so far no luck with seeing any change after 8 hours.   Also the Update Status register is 0, and the Control status is 0x008E

    Since I can't use the tools as I have built the BQ27441 device into my custom board it there a flow chart, or code snippet to help me send the command sequence to the part?

    Thanks,

    Scott

  • 0 in reply to Scott Harsany
    TI__Guru 52115 points
    Unfortunately, I don't have that kind of code snippet or flow chart.
    In order to make the QMax update or resistance update occur, you need to do a charge-relax-discharge-relax cycle as we mentioned in the app note.  Did you ever do that? Also,  did you ever use the GPCCHEM tool to check the chemistry id?
    Andy
  • 0 in reply to Andy Liu (BMS)
    Prodigy 130 points

    Andy, TI team,

      I am 20 more days into the debug and still can't get the device to go into calibration mode.    Surely there has to be a sequence of commands that send the device into calibration mode?   I sometimes get luck without calibration and the when charged the device returns 100% ... other times it will return 97% or 96% and never reach 100%, then I will unplug and replug charging source and it will read 100%, so I think calibration is going to be required.   Is there a newer part that will allow calibration to be activated, assuming this part can't be put into calibration mode?

    Thanks,

    Scott

  • 0 in reply to Scott Harsany
    TI__Guru 52115 points
    I would suggest you get an EV2400 and then you can use bqStudio to do the calibration pretty easily.
    Did you check the accuracy of current, voltage, and temperature measurements without any calibration?  If the accuracy is acceptable, your issue should not due to the calibration.
    Andy