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Original question:

BQ27426: The change of RM between new battery and aged battery

BQ27426: The reason of the change of DODfinal

chengxiaobin
Intellectual 300 points
Part Number: BQ27426
Other Parts Discussed in Thread: BQSTUDIO

Tool/software:

    我们使用了一块SOH约55%的电池，使用TI的Demo板进行了充电实验
    动作如下：
    1. 将电池接入到demo板。
    2. 使用100mA电流，放电100mAh电量（从700mAh到600mAh）
    在这个过程中，发现DODfinal有变化（大概在日志的第510采样点位置）。
    
    请帮忙确认下此时DODfinal是因为什么而产生了变化？
We used a battery with about 55% SOH and conducted charging experiments using TI's demo board
The action is as follows:
1. Connect the battery to the demo board.
2. Use 100mA current to discharge 100mAh power (from 700mAh to 600mAh)
During this process, it was found that there was a change in the DODfinal (probably at the 510th sampling point of the log).

Please help confirm why DODfinal has changed at this time?
  • 0
    TI__Mastermind 18951 points

    Hello, 

    In this test, did you use a default configuration, or is this a learned configuration that was tracked with the battery? If you plug in a severely cycled battery into a gauge that expects a new battery, you will have to wait a couple of cycles for the gauge to relearn the critical gauging parameters that correspond to the deeply cycled battery. 

    Regards, 

    Robert. 

  • 0 in reply to Robert
    Intellectual 300 points

    Yes, we use the default configuration from golden learnning, do not relearn the cycled battery.

    what we want to know is that why DOD final changed at this situation? could you please answer this question?

    Thanks.

  • 0 in reply to chengxiaobin
    TI__Mastermind 18951 points

    Hello, 

    You will not get good accuracy right away if you connect a deeply cycled battery to a gauge that has a default configuration. This is because from the gauge's perspective, it will be expecting a brand new battery with a larger Qmax, where in reality the battery is deeply cycled so the maximum chemical capacity of the battery is less. This will cause an inaccuracy in the gauging. I recommend referring to this document for more details on the patented Impedance Track Algorithm. 

    Regards, 

    Robert.