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BQ2083-V1P3: SAFE output activated after flashing and calibrating

Jeffrey Chase
Intellectual 510 points
Part Number: BQ2083-V1P3
Other Parts Discussed in Thread: BQ2083, BQ29311, BQ2085

We are using the bq20830V1P3 with the bq29311 in one of our legacy product lines. We have an issue in which the SAFE output on the bq2083 is activated right after we program the GG file, reset the gas gauge, perform V/I/T calibration, and seal the gas gauge. This has been an issue for quite some time, and we have not been able to resolve the issue. There are no faults set while the SAFE output is low, and the only way we can reset the SAFE output is by removing and reapplying power to the gas gauge. 

We use a trace wire in the safety circuit that is driven by the SAFE line that is set up similarly to the reference design that we install when we have completed building and cycle testing the battery. The biggest difference between the design and the reference is that we do not use the extra cell voltage monitoring IC in the circuit. This issue requires us to remove the protection board from the battery case, disconnect the cells from the board, solder the trace wire to the board, reconnect the cells, and finally reinstall the board. There is a fairly high risk of damaging the boards while performing this process due to the battery and board design. 

Do you have any suggestions on why the SAFE output would be low when we finish processing the gas gauge? We are using the bq2085 GUI for this. 

  • 0
    Intellectual 510 points

    After sending this, I looked at the process step by step. It appears that when the flash settings are programmed, the gas gauge sets SOV and SUV, setting the SAFE output low. I would expect, however, that when the gas gauge is reset and the faults are cleared, the SAFE output would go high. It does not appear to be happening on this chipset. 

  • 0 in reply to Jeffrey Chase
    TI__Mastermind 27321 points

    Hi Jeffrey,

    I have assigned this thread to an expert.

    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    TI__Guru** 105740 points

    Hello Jeffrey,

    Unfortunately once the SAFE pin is activated the only way to reset it is to POR the device. I would ensure there are no transients on the cell voltage input pins during cell attach and make sure you attach them from low to high to prevent any unintended safety triggers.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Intellectual 510 points

    It is not going low when the cells are attached. It is high just before programming the gg file, then goes low once the gg file is programmed. Cells are already attached at this point. This has nothing to do with attaching the cells.

    I did notice that the gas gauge is set up for a 3S battery when received with TI's flash settings, and we are reprogramming for a 4S battery. 

  • 0 in reply to Jeffrey Chase
    TI__Guru** 105740 points

    Hello Jeffrey,

    I don't believe the 3S to 4S application would make a difference. What is the occurrence rate for this issue? Is it 100% of all battery packs?

    This is a very old product so we only have limited support capabilities due to the age, I have not seen this type of issue before on this device.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Intellectual 510 points

    It seems to happen on almost 100% of product. I ran five batteries myself monitoring SAFE throughout the process, and it occurred on four of the five. There was no difference in processing between any of the batteries. 

  • 0 in reply to Jeffrey Chase
    TI__Guru** 105740 points

    Hello Jeffrey,

    The only thing I could think of is something with the upload process itself, or the voltages are not stable. Can you provide the details of how you extract the .gg file and how you upload it to the gauge?

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Intellectual 510 points

    We are using bq2083 Evaluation Software version 2.5.0. We are plugging the cell strings into the board using a 5-pin Molex connector, then waking the battery by applying 9V across the positive and negative terminals of the battery. At this point, SAFE is high. We then plug the battery into a fixture and use the battery's +, -, SCL and SDA pins to communicate with and measure current and voltage of the battery. Once the battery is plugged into the flash fixture, we go to the Data Flash tab on the left, open the gg file using the File>Open Gas Gauge Flash Constants menu path. Once loaded, we click on Write All button at the bottom of the flash screen. This is when SAFE is pulled low. In SBS, SOV and SUV are set, which is why I am guessing SAFE is low. We then enter the current date in MfrDate field and the battery serial number in Serial Number field.

    After that, we go to SBS and click on Options>Special Options>Reset Device. This clears the SOV and SUV bits, but SAFE is still low, which, as you stated, will stay that way until power is cycled on the board. 

    We then go to Calibration and perform offset, voltage and temperature calibration, then current calibration and finally seal the battery. That completes the flash process. 

  • 0 in reply to Jeffrey Chase
    TI__Guru** 105740 points

    Hello Jeffrey,

    If you program the protections first then the rest of the parameters, or do one value at a time (just the ones changed from default) do you still see the issue?

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Intellectual 510 points

    I will try these options for informational purposes, but I may not be able to complete it before 13 Oct, 2023.