Dear TI-expert
I'm evaluating BQ27520-G4 device.
Our battery is UR18650ZY.
There are 3 Chemistry ID values (1146、2026、2678) for Panasonic UR18650ZY cell.
I have programmed ChemID=2678 into the gauge as shown below.
e2e.ti.com/.../bq27520-g4-chemistry-id-value-for-ur18650zy-cell
Attached is the result of running the learning cycle.
BQ27520-G4_Learning cycle failed_20230308_001.xlsx
During the first charge, VOK changed from 1 to 0 after FC = 1, but Qmax was not updated.
Qmax was not updated during the second charge as well.
I've checked the Initial Qmax Update Criteria for slua903, but I'm not sure what's causing it.
• Temperature — If Temperature is outside of the range 10°C to 40°C.
→no problem. Temp：20.9～26.5℃
• Delta Capacity — If the capacity change between suitable battery rest periods is less than 90% of the
full scale range of the OCV table during the initial QMax Update and 37% during field updates (2nd
and subsequent updates) of QMax.
→no problem. capacity change:2313mAh ＞ 2160mAh(Deseign Capacity2400mAh × 90%)
• Voltage — If Voltage() is inside the flat voltage region. This flat region is different for each ChemID.
The GaugingStatus[OCVFR] flag indicates if the cell voltage is inside this flat region.
→no problem. Voltage：4090mV ＞ Vqdis_min=3753mV、Vqdis_max=3789mV(ChemID2678)
• Offset Error — If offset error accumulated during time passed from previous OCV reading exceeds
1% of Design Capacity, update is disqualified. Offset error current is calculated as Coulomb Counter
Deadband/sense resistor value.
→unconfirmed(Please tell me how to confirm.)
What is the problem that the learning cycle fails?
Could you give me advice for this?
Best Regards,
Kazunori Morita
