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BQ27427: What can lead to a WDRESET? And 99% Issue

Johann
Prodigy 20 points
Part Number: BQ27427
Other Parts Discussed in Thread: BQSTUDIO,

Tool/software:

I am using BQStudio to create a profile and have connected the I2C lines to the test pins of our MCU. During the charging or discharging phases of the learning cycle, I encounter a WDRESET. What could be causing this? The MCU is not running and remains off.

One strange behavior I notice is that BQStudio reports a lost USB connection to my EVM2400. Afterward, I need to restart BQStudio. Since the connection is via I2C, could this be interfering with the watchdog timer? Any ideas?

Another topic is that I am not reaching 100% during the learning cycle. The state of charge stays at 99%.

The battery is from Jauch. Before starting the cycle, I set the chemistry ID to 0x1202 (4.2V) and then change it to a similar chemistry ID  afterward.

I only adjust the design capacity and energy; the rest of the parameters remain at their default values.

Any ideas? The taper rate and thresholds seem fine to me.

  • 0
    TI__Mastermind 24741 points

    Hello, 

    Firstly, I recommend you use the GPCCHEM tool to ensure that you are using the chemID that is the best match for the cells that you are using. 

    I also recommend you follow the Achieving the Successful Learning Cycle document for the minimum parameters you need to configure to complete the learning cycle. From what you are telling me, I believe you are not configuring the minimum parameters for the learning cycle. 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Prodigy 20 points

    Hello Jonny,

    I figured it out—it has something to do with the WDReset. If it does not occur, I can reach 100%; otherwise, the chip resets its value.

    When the WDReset is avoided, the learning cycle is successful. Could a WDReset be caused by disturbances on the I2C line? Also, can I upload the unmodified logfile from BQStudio for GPC?

    Another question: How can I ensure that when configuring a new fuel gauge for another MCU, I don’t need to perform the learning cycle again? For example, is it possible to make the fuel gauge show 100% directly after its first charge?

  • 0
    Prodigy 20 points

    Is it normal for bq27427 that it shows negative current when its charging? Because the DSG bit is set (DSG = Discharging detected. True when set.)

    Is this my problem? I am testing with  BQ27427EVM-037