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BQ28Z610-R1: BQ28Z610-R1 capacity questions

Kevin Chuang
Prodigy 155 points
Part Number: BQ28Z610-R1

Hi,

Our Battery pack is 2 series 3 parallel and battery is using 18650.

Gauging IC BQ28Z610-R1 "Charge Term Taper Current" was set to 350mA. 

In the special status, the charger may charge <350mA current to battery pack, the Relative State Of Charge will jump to 100% from e.x any the Relative State Of Charge.

The phenomenon is abnormal.

The voltage and full charge capacity of battery pack is not normal value.

What should I do to avoid this phenomenon?

Thanks!

  • 0
    TI__Guru** 102415 points

    Hello Kevin,

    Can you share a log and .gg file from before and after the test? I will need to look at your settings and log file to get a better idea of what is going on with your test.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 155 points

    Hi Wyatt,

    I used a new battery pack for this test.

    Attached is log and .gg file from before and after the test.KevinChuang_Test_20211018.rar

    1. gg file：before first charge using low current

    2. log file：First charging (SOC jump to 100%)

    3. gg file：After first charge using low current

    4. log file：Second charging (SOC  no jump to 100%)

    5. gg file：After second charge using low current

    What should I do to avoid this phenomenon?

    Thanks!

    Kevin

  • 0 in reply to Kevin Chuang
    TI__Guru** 102415 points

    Hello Kevin,

    You can try disabling the CSYNC bit, this will prevent the gauge from forcing FCC to equal RemCap when a valid charge termination is detected. If you decreased the charge taper current in the system it may help reduce the issue, but that leads to longer charge times.\

    You can see in the logs the the FCC value gets forced to RemCap when the charge completes.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 155 points

    Hi Wyatt,

    I want to know why this phenomenon only happened for the first time.

    The second charge did not happen.

    Is it related to the gauge setting or gg.file?

    Thanks!

    Kevin

  • 0 in reply to Kevin Chuang
    TI__Guru** 102415 points

    Hello Kevin,

    The impedance track algorithm learns the battery over time, each cycle it should be better at calculating RemCap and FCC. So it may be that with each cycle the jump would lessen as the gauge learns the battery better with the specific application.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 155 points

    Hi Wyatt,

    I don’t want this phenomenon to occur when customers use the product.

    So what can I do to avoid this phenomenon.

    Attached is 2_FirstCharge.xlsx mentioned ERROR : Please check D:\20211018.log.err.20211018.log.rar

    I can't read the file, please help check if there is any information mentioned in the document.

    Thanks!

    Kevin

  • 0 in reply to Kevin Chuang
    TI__Guru** 102415 points

    Hello Kevin,

    The bit I mentioned in the previous post should stop the jump from happening (CYSYNC).

    The error log is only for communication transaction errors, the logged data is what we look at for debug.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 155 points

    Hi Wyatt,

    I used a new battery pack for this test.

    Attached is log and .gg file from before and after the test.KevinChuang_Test_20211027.rar

    1. gg file：CSYNC default set：High

    2. gg file：CSYNC set：Low

    3. log file：Using low current to charge

    Phenomenon：We can see SOC can become 100% but voltage is still at 8.1V. When SOC become 100%, the Charge MOS no turn off. I think the phenomenon is abnormal.

    4. gg file：After charge using low current

    Is there any other way besides disable CSYNC?

    Thanks!

    Kevin

  • 0 in reply to Kevin Chuang
    TI__Guru** 102415 points

    Hello Kevin,

    It looks like the RSOC didn't jump near full charge in the log. You can change what triggers the FC to set, either VCT, RSOC or voltage.

    The gauge should learn the DOD at EOC (End Of Charge) to correspond 100% SOC when the FC is detected. It looks like the voltage is around 8160mV when RSOC 100% is reached. You can see in your log the DODEOC went from 0 (full range of chem ID) to 2000 (missing capacity) You should change when the valid charge completion is set to charge to a higher voltage.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 155 points

    Hi Wyatt,


    Can you explain carefully the item 3 & 4 means?

    All of the following conditions must occur for two consecutive 40-s periods:

    1. Charging (that is, BatteryStatus[DSG] = 0)

    2. AverageCurrent() < Charge Term Taper Current

    3. Max (CellVoltage2...1) + Charge Term Voltage ≥ ChargingVoltage()/number of cells in series

    4. The accumulated change in capacity > 0.25 mAh

    Thanks!

    Kevin

  • 0 in reply to Kevin Chuang
    TI__Guru** 102415 points

    Hello Kevin,

    3: basically states that the cells must be in CV charging, if the max cell voltage + the charge term voltage is greater than the specified ChargingVoltage() per cell, then it will meet the criteria.

    4: This just means that there needs to be some charge current, if it's just a trickle charge we shouldn't consider it a valid charge termination. This one is usually the easiest to meet.

    Sincerely,

    Wyatt Keller