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BQ40Z50-R2: BQ40Z50-R2 got measurement battery capacity not same base on different test condition

Jimmy WANG
Genius 4025 points
Part Number: BQ40Z50-R2

Hi team,

My customer uses BQ40Z50-R2 than test condition as below.  the GG file and test log data also as attached. 

Have any suggestions can improve the CP test result?

1. Use constant power 40W and 86W and TC 25C. The FSOC test result is quite volatile.

The X-axis is test cycle, Y-axis is mAh. (orange line is current-time integral).

2. another test condition used 0.2C and seems the result is stable. 

The X-axis is test cycle, Y-axis is mAh. (orange line is current-time integral). GEON- 4SP001_20200908 gg.csv

 

測試數據.zip

3. Could you provide max supply current? 


Drastically

  • 0
    TI__Guru** 105590 points

    Hello Jimmy,

    Can you explain the graphs and what is being compared? The x-axis is the number of cycles or the time passed?

    The max current during sleep mode is not defined because it is dynamic depending on what tasks the gauge is performing. From what I have seen in other test results it can be around 250uA when taking measurements, but I would recommend you test it for your system.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Genius 4025 points

    Hi Wyatt,


    The graphs mean when use constant power discharge cycle test. When test cycle=4 times get 6650mah. but test over cycle 4 times or more.

    The FCC test result will get a big result such as 7000mah. As the number of test cycle increases, the test results down to min value as 6500mah

    so my customer wants to improve the test result.(it is means reduce the gap) if can through IC setting.

    By the way, another test condition(0.2C CC) seems stable than constant power.

  • 0 in reply to Jimmy WANG
    TI__Guru** 105590 points

    Hello Jimmy,

    FCC will update when there is a temperature change and is dependent on the previous max avg I value, you can edit the load mode and load select to match better with your expected load to get a more accurate FCC value.

    It is normal for FCC to reduce with age and fluctuate as the battery is under different conditions.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Genius 4025 points

    Hi Wyatt,


    Base on the test result. We observed FCC has a different capacity report in constant power discharge test.

    So, does any register can improve FCC variation? Let FCC change to smooth.

    Thanks!

  • 0 in reply to Jimmy WANG
    TI__Guru** 105590 points

    Hello Jimmy,

    Yes it will yield different values because the gauge uses different parameters to run it's simulations for each mode.

    You can also set the SMOOTH function which will help eliminate jumps in the FCC.

    Sincerely,

    Wyatt Keller 

  • 0 in reply to Wyatt Keller
    Genius 4025 points

    Hi  Wyatt,

    Could you help me check GG file setting ? Which register could be modified ?

    If want to keep FCC smoothly. Thanks!

    GG file 7115.GEON- 4SP001_20200908 gg.csv

  • 0 in reply to Jimmy WANG
    TI__Mastermind 24870 points

    Hello Jimmy,

    There's no way to keep FCC constant. You can enable the smooth bit and during discharge, we will hold FCC filtered. Refer to the TRM for this bit.

    However, the gauge during discharge should have some modification in FCC if the load dynamics are different. Wyatt mentioned this previously.

    Thanks!

  • 0 in reply to Kang Kang
    Genius 4990 points

    Hello Kang Kang and Keller:

    Thanks a lot your recommendations.

    But...the design capacity is 6700mAh.

    Yes we know that FCC update in every cycle is a normal operation, but at cycle 4 the FCC is about 6635mAh, cycle 7 the FCC is about 6983mAh and the cycle 32 is about 6532mAh. (In constant power mode)

    End customer is asking why the FCC tolerance is over 4%?

    Please kindly provide the recommendations for us.

    Thanks a lot.

  • 0 in reply to Statham Su
    TI__Guru** 105590 points

    Hello Statham,

    This is fairly normal for FCC to change depending on the discharge or charge condition, and other parameters. If the battery is very cold for example the FCC could drop by 50% of design capacity. If the battery is hot it could increase as well. The FCC value will also decrease as the battery ages.

    Sincerely,

    Wyatt Keller