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BQ28Z610-R1: SOC drop issue when low temp

Statham Su
Genius 4990 points
Part Number: BQ28Z610-R1
Other Parts Discussed in Thread: GPCRB

Hello Sir:

We have RSOC drop issue when low temperature. (-10 degree)

Please refer attached files, which include gg, log and golden log.

Would you please help to check anything we can improve? 

Please help to provide your recommendations.

Thanks a lot.

20220328.rar

  • 0
    TI__Genius 11770 points

    Hello,

    Have you used the GPCRB tool? It will help you set parameters to increase the accuracy of the gauge in low-temp situations. Basically, the gauge is occasionally simulating the discharge to predict capacity. When the temperature drops, the internal impedance can increase drastically, especially at lower temperatures. This means the simulated voltage drop will shoot up and the gauge will predict the battery to be empty sooner.

    You can improve the performance of the gauge by using this tool, but to a certain extent, li-ion batteries will struggle with low temperatures no matter what. Please let me know if you have already used the tool and are still seeing drastic changes.

    thanks,

    Alex M.

  • 0 in reply to Alexander Mazany
    Genius 4990 points

    Hi Alexander:

    Yes, we used GPCRB.

    Would you please help to what's the problem let SOC drop?

    We need to fix this, please help to provide your recommendations for us.

    Thanks a lot.

  • 0 in reply to Statham Su
    TI__Genius 11770 points

    Hello Statham,

    I agree that those drops are pretty extreme, especially if you already used the tool. Would it be possible for you to share the logs you sent to the tool and the tool's report you used? I'd like to reference those to see if they look okay; I really wouldn't expect this even after using the tool. 

    Looking again at the logs, the FCC doesn't adjust properly at the start of discharge. IT seems to overestimate the FCC in cold and it hits a wall near the end because of that, leading to the SOC drop. Since you are using present average discharge, I would expect the FCC to recalculate once the discharge starts to reflect this, but it doesn't seem to change.

    Please send the report form the tool, I think it will help explain this issue.

    thanks,

    Alex M.

  • 0 in reply to Alexander Mazany
    Genius 4990 points

    Hi Alex:

    Sorry, we had a vocation, updated lately.

    Please refer attached files, any recommendations please let us know.

    Thanks a lot. 

    LUNA3_1S1P_RBTABLE-report (1).zip

    5383.lowtemp.csv

    4544.roomtemp.csv  

  • 0 in reply to Statham Su
    TI__Guru** 105770 points

    Hello Statham,

    We will review the data and get back to you by tomorrow.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    TI__Guru** 105770 points

    Hello Statham,

    After reviewing the data submitted to GPCRB we noticed the current for the Room Temp log was 4000mA, which is a very high discharge rate for the battery tested. This is leading to a large increase in temperature during discharge which can impact the tools ability to accurately calculate the resistance information it needs at room temperature (temperature increases by approximately 22degC over 25degC)

    The GPCRB tool then uses the incorrect Ra information calculated from the room temperature discharge to calculate the Rb low temperature coefficients, which will lead to errors in the Rb values as the errors cascade upon themselves.

    Please try decreasing the discharge rate of the room temperature log to 1500mA so the battery does not heat up to the high levels it did with the 4000mA discharge.

    Sincerely,

    Wyatt Keller