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Original question:

BQ27426: Golden Learning，Relax Fail

BQ27426: SELF-LEARNING, Conditional Confirmation of FCC Correct Updates

Wang Dong
Intellectual 600 points
Part Number: BQ27426

Tool/software:

hello,

A summary of the conditions that enable Fuelgauge to correctly update the FCC, based on previous enquiries.
Please help confirm if there are any errors or omissions? And please help to correct them.

parameter Update Steps Conditions for correct updating
Qmax step1：Relax before charging or discharging Battery voltage not in flat area
Battery temperature between 10 and 40°C
Battery OCV voltage 4uV/s or Relax over 5 hours
All of the above conditions must be met
step2：Charging or discharging Charging or discharging more than 37% of Qmax* at one time.
step3：Relax after charging or discharging Battery voltage not in flat area
Battery temperature between 10 and 40°C
Battery OCV voltage 4uV/s or Relax over 5 hours
All of the above conditions must be met
DODfinal step1：Relax before discharging Battery OCV voltage 4uV/s or Relax over 5 hours
step2：Discharging Discharge starts (Dsg Current Threshold and Quit Relax Time：discharge current >-15mA for more than 1 second).
Ra Table is correctly updated.
All of the above conditions must be met
DODatEOC step1：Relax before charging Battery OCV voltage 4uV/s or Relax over 5 hours
step2：Charging Charging starts (Chg Current Threshold and Quit Relax Time：charging current > 60mA for more than 1 second).
Ra Table is correctly updated.
All of the above conditions must be met
RATable step1：Relax before discharging Battery OCV voltage 4uV/s or Relax over 5 hours
step2：Discharging After 500 seconds of discharge, the discharge current is > C/10 in 60 seconds and crosses 1 grid point.
Qmax is correctly updated.
All of the above conditions must be met
  • 0
    TI__Guru 61366 points

    In addition, if your charge into the flat zone, the gauge will apply a 48 hour relax requirement before it starts monitoring for stable voltage (OCV).

  • 0 in reply to Dominik Hartl11
    Intellectual 600 points

    Hello Dominik，

    1, Are there any errors or omissions in the conditions in the table above?

    2, Battery voltage reaches flat zone during Relax and OCV measurement timeout is extended from 5 hours to 48 hours?
    3, Based on Q2, if the battery is discharged to the flat zone during the Qmax update, and Relax exceeds 48 hours, OCV will also be measured and Qmax will be updated?

    Dominik Hartl11 said:
    In addition, if your charge into the flat zone, the gauge will apply a 48 hour relax requirement before it starts monitoring for stable voltage (OCV).

    1、上表的条件是否有错误或遗漏？

    2、电池电压在Relax期间达到平坦区，OCV测量超时时间将从5小时延长到48小时？

    3、基于Q2，如果在Qmax更新过程中，放电到电池平坦区，Relax超过48小时，也会测量OCV，会更新Qmax？

  • 0 in reply to Wang Dong
    TI__Guru 61366 points

    #1: It's a good summary. There are a few additional rules that I can't share on E2E but they are about outlier boundary checks.

    #2: The 48 hours timeout applies if charging stops in the flat zone. If charging stops outside the flat zone and then the cell relaxes into the flat zone, the 48 hours do not apply.

    #3: No, Qmax won't be updated if OCV is taken in the flat zone. Cell state (DOD0) will be updated with an OCV measurement (even in the flat zone) but the Qmax update will be rejected.

  • 0 in reply to Dominik Hartl11
    Intellectual 600 points

    hello Dominik，

    A few questions about the conditions of summary：

    1、Ra Table update, is the condition ‘Battery OCV voltage 4uV/s or Relax over 5 hours’ required before the discharge starts? What is the reason?

    2. Qmax update, is the ‘Battery temperature between 10 and 40°C’ during Relax before charging or discharging necessary? What is the reason?

    3. Qmax update, is ‘Battery voltage not in flat area’ during Relax before charging or discharging necessary? What is the reason?

    1、Ra Table更新前，"Battery OCV voltage 4uV/s or Relax over 5 hours"的条件是必须的吗？原因是什么？

    2、Qmax更新，充电或放电之前Relax期间的"Battery temperature between 10 and 40°C"是必须的吗？原因是什么？

    3、Qmax更新，充电或放电之前Relax期间的"Battery voltage not in flat area"是必须的吗？原因是什么？

  • 0 in reply to Wang Dong
    TI__Guru 61366 points

    #1: No. Ra updates can also happen if voltage is not stable in relax (e.g. short relax). The main criteria for Ra updates are: Qmax must be updated at least once (in the past) and load must exceed C/10. The gauge will disable Ra updates if OCV < loaded voltage (e.g. grossly incorrect cell state DOD or incorrect Qmax).

    #2: The temperature limits only apply to relax and the moment that gauge takes the OCV measurement.

    #3: Yes, OCV needs to be outside the flat zone. The reason is that Qmax = passed charge / DOD0 difference. And DOD0 = function of OCV and temperature, hence if OCV is in the flat zone or if temperature is outside the limits, DOD0 may not be accurate enough for good Qmax updates.