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Original question:

BQ27426: Loss of first byte when data is read (occasional)

BQ27426: Increased reserve capacity, high and low temperature with SOC jumping problems

Wang Dong
Intellectual 600 points
Part Number: BQ27426
Other Parts Discussed in Thread: TEST2, BQSTUDIO

Hello there！

Fs file using Ecmm, containing the chem id and calibration data

During our test, we found that there are still jumps in high and low temperature even if the reserve capacity is set, please help to check the phenomenon of SOC Jump occurred.

1. Jump from 20% to 1% (we prepared 225mAh reserve capacity) 996mA@0℃ , 225mA reserve capacity (For details, see: CH7-COM41-225mA-0-996mA-DONGTAI.xlsx)

2. Jump from 10% to 1% (we prepared 225mAh reserve capacity) 1160mA@75℃ , 225mA reserve capacity (see: CH1-COM26-225mA-75-1.16A-DONGTAI.xlsx)

Attachment CH7: reserve capacity 225mAH, temperature 0°, discharge current 996mA, continuous discharge

Attachment CH6: reserve capacity 225mAh, temperature 75°, discharge current 1.16A, continuous discharge

CH7-COM41-225mA-0-996mA-DONGTAI.xlsxCH1-COM26-225mA-75-1.16A-DONGTAI.xlsx

  • 0
    TI__Guru 61076 points

    Please attach the configuration files that you program to the gauge before this test.

  • 0 in reply to Wang Dong
    TI__Guru 61076 points

    I tuned the high and low temperature adjustment tables based on the provided log files.

    Please use this configuration: https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/196/ECMM_5F00_with_5F00_Cal_5F00_230403_5F00_Rc225_5F00_Trise_5F00_Rb0411.gm.fs

  • 0 in reply to Dominik Hartl11
    Intellectual 600 points

    Thanks for you reply。

    After comparing the original Ecmm file, I have the following questions, please help me to confirm

    1、What is the reason for the change of these registers?

    2、Does it affect the prediction of room temperature?

    3. Are there any other effects?

    4. In Figure 1 below, Enables Fast SOC Convergence is changed to disable, what is the reason? What is the impact?
    5、In Figure 3 below, CC CAL has changed, what is the reason for the change? Does it need to be recalibrated on our device?

    Figure 1

    Figure 2

    Figure 3

  • 0 in reply to Wang Dong
    TI__Guru 61076 points

    #1: The changes affect how the gauge adjusts cell resistance at 80deg.C and at 0deg.C

    #2: No.

    #3: I disabled fast resistance scaling because this may not work well if temperature is extreme (80deg.C). This will have an impact on how the gauge calculates SOC close to end of discharge in all use cases, not just 80deg.C.

    #4: See #3

    #5: This is the CC CAL from my setup. You don't need to re-calibrate, just replace it with your CC CAL. Note that CC Offset will always change (also on your gauge) because the gauge will auto-calibrate its offset.

  • 0 in reply to Dominik Hartl11
    Intellectual 300 points

    We conducted a test in a 0°C environment using the optimised FS file to confirm that the SOC jump problem still exists, refer to the attachment and the chart below for the test results.

    CH2-COM14-3v-225mAh-0414fs-0-996mA-DONGTAI.xlsx

    Test 1 ，Test2 

    Please help us to solve this problem.

    and some questions for the FS change before.

    1. What is the rootcause for these SOC JUMP issue for the 0℃ testing?

    2. As mentioned earlier, fast resistance scaling has been disabled, what we would like to know about this Fast resistance scaling is at what cycle the gauge performs the fast convert and how it performs the fast convert?

    3. Are there any new changes to improve this issue? Will the new changes have any other ripple effects?

  • 0 in reply to chengxiaobin
    TI__Guru 61076 points

    #1: Is the only difference in your configuration Reserve Capacity? In both cases, if you use the configuration that I attached previously, the gauge should estimate around 510mAh FCC (for Test 1) or 735mAh (for Test 2).

    Test 1 FCC:

    Test 2 FCC:

    In your log file, FCC for Test 1 is 974mAh while FCC for Test 2 is 1231mAh. So that's the problem. Something in the way that you configure the gauge leads to FCC that's too high.

    Note that TEMPS[1:0] is 10 in your configuration which means that your host must write temperature to the gauge. Is the temperature column from your log file what you actually read from the gauge? The gauge will not measure temperature with your configuration. So if you write temperature incorrectly, you will not get correct gauging results.

    Even if I set temperature to around 30deg.C will the actual gauge not estimate 1232mAh for Test 2:

    --> Please verify that you program the gauge correctly. I suggest using bqStudio to test the configuration before moving to your own platform.

    #2: Fast Resistance Scaling is a method to calculate cell resistance at high level of discharge and scale the whole resistance table with the scaling factor of measured resistance / stored resistance. This works will in many cases where we know that the configuration is basically correct. But it's not useful during development of configuration because it masks errors in resistance due to incorrect configuration, hence I disabled it.