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BQ4050: The SOC and FCC of BQ4050 are not accurate

Sunrain
Intellectual 615 points
Part Number: BQ4050
Other Parts Discussed in Thread: GPCCEDV, BQ40Z50

 Hello,

I have some more questions about the application of BQ4050. The battery is LiFePO4.

1、When I test, SOC and FCC are always inaccurate. When setting EDV_CMP=1, the SOC can be reduced from 100% to 0%, but the FCC lacks more than 100 mAH. When EDV_CMP=0, the FCC is normal, but the SOC can only be discharged to about 2%, not 0%. Turning on SMOOTH has no effect.

2、I have GPCCEDV, but I have not found a relationship between SOC and EDV0/1/2 or SOC and FD. It has not reached FDSETV/CUV/EDV0, and the SOC has reached 0%. How should I set the value of EDV0/1/2.

  • 0
    TI__Guru** 105590 points

    Hello,

    Can you share the data submitted to the GPCCEDV tool and the returned data?

    Also if you have any logs showing this behavior it will help us debug any issues quicker. One common mistake is the GAUGE_EN is not set during testing so the algorithm is not running.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Intellectual 615 points

    Hello, BQ40Z50 has GAUGE_EN setting. Which flag of BQ4050 means GAUGE_EN.
    The attachments are the GG file and log file with EDV_CMP=0 and EDV_CMP=1.EDV_CMP=0.logEDV_CMP=1.logCMP0.csvCMP1.gg.gg.csv

  • 0 in reply to Sunrain
    TI__Genius 10370 points

    Jingming,

    the GPC result file coefficients are used to tell the gauge where the 7% remaining capacity voltage point is. This threshold will shift based on temperature and discharge rate. Based on your GPC results the gauge willl have 7% capacity remaining when the voltage reaches 8400mV. This appears to be too low.

    I would recommend you recollect the GPC data following the data collection to a T to see if you can find some battery parameter. The result you have already has some high error which normally indicates a mismatch between all the data files collected. 

    It also looks like your FCC is too low. It updated in the log file by the max value it can change. 

    As is the device seems to be working functionally as expected. Meaning you are getting the correct update at the right time. 

    Thanks,

    Eric Vos

  • 0 in reply to Vos
    Intellectual 615 points

    Hello,

    how did you get the 8400mv value corresponding to 7%?

    GPCreport describes the deviation <5 or 3. I think the deviation is not very large?


    Another set of batteries I tested has the same SOC and FCC issues. The attachment is GPCReport. Please check if it is available.

    1781.GPCPackaged-report.zip

  • 0 in reply to Sunrain
    TI__Genius 10370 points

    JIngming,

    In your log file you will find a parameter called [CEDVTHr] which will let you know the next critical EDV voltage the gauge is looking for. In your log that value is 8400 which discharging. You can see SOC is held at 7% until voltage is below 8400 for a delay time. 

    Your error in the GPC is 4.8% at room temp high rate. this is beyond the 3% max error. This seems to be the root cause of your low EDV value. your high rate Dsg might be too high to create good match.  I suggest using 80% of your max system dsg rate to see if it produces a better result. 

    Thanks,

    Eric Vos