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Original question:

BQ27426: Questions about VatChgTerm registers

BQ27426: Question about manual value changes for VatChgTerm

Wang Dong
Intellectual 590 points
Part Number: BQ27426

Tool/software:

Hello，

Coming from another Case.

Our FS file manually modified VatChgTerm to 4252mV after gold learning.
It was verified that the FCC would drop over 150mAh at the start of charging.
After consulting at e2e, it was modified to 4400mV.

After modification, during actual verification, FCC will drop 7mAh when charging starts.

What is the reason for this?

The attached sheet[V4400_SOH100%] is the original log.

left:DOD final,AvgCurrent

Right:Qmax,FCC,DODatEOC

从另一个Case过来的。

我们的电池充电截止电压是4400mV。在应用中，修改VatChgTermTerm=4400mV，

实际验证过程中，发现修改为4400mV后，充电开始时，FCC会下降7mAh，请问原因是什么？

附件中sheet[V4400_SOH100%]是原始日志。4252Vs4400.zip

  • 0
    TI__Guru 55826 points

    The gauge will calculate depth of discharge for a full charge (DOD at EOC) at start of charge (and during charging under certain circumstances), hence you will see a change in FCC at this point. DOD at EOC decreases, which usually leads to an increase in FCC. However, other factors play a role as well (temperature, load, delta voltage) so it's not as easy as saying lower DOD at EOC = higher FCC.

  • 0 in reply to Dominik Hartl11
    Intellectual 590 points

    Hello Dominik，

    What happens to us is that after modifying VatChgTerm=4400mV, the FCC rises slightly when charging starts.

    1, What does delta Voltage mean?

    2, Can different charging currents also cause DODatEOC to simulate different results?

    3, How to define the current is high or low? Compare with 0.2C?

    4, Excluding other influencing factors, the higher the charging current, will DODatEOC simulate larger values?

    5, charging current is the same as 0.2C at Golden Learning, DODatEOC will not change due to different current?

    我们发生的现象是，修改VatChgTerm=4400mV后，充电开始时，FCC会小幅度上升。

    1、delta Voltage是什么意思？

    2、不同的充电电流也会导致DODatEOC仿真出不一样的结果吗？

    3、充电电流大还是小，是与Golden Learning时的0.2C相比吗？

    4、排除其他影响因素，充电电流越大，DODatEOC会仿真出较大的值吗？

    5、充电电流与Golden Learning时的0.2C一致，DODatEOC就不会因为电流不同而发生变化了？

  • 0 in reply to Wang Dong
    TI__Guru 55826 points

    #1: The gauge measures abrupt changes to voltage and stores this in a parameter called "Delta Voltage". It adds the value of this parameter to Terminate Voltage for prediction purposes (not as a threshold for measured cell voltage during discharge). This will reduce RM and FCC if there were sudden load spikes that resulted in a sudden voltage drop during discharge.

    #2: Not directly but indirectly if they cause different cell temperature.

    #3: A current is high if it has a significant effect on temperature and measured cell voltage.

    #4: No. DODatEOC is a function of voltage at charge termination, taper current and temperature. It is not a direct function of charging current.

    #5: Correct.