BQ27Z561-R2: During the charging and discharging process, the FCC value suddenly jumps to 0，HELP！！！

Hello Yiyang,

Yes, the first 2 grid points in the Ra table are abnormally high. Whenever you first completed the learning cycle, did you save the gg file then? If so can you send it to compare what the Ra table now and when the learning cycle was completed. What type of load are you applying for your test?

Regards,

Adrian

Hi Adrian，

This is the first GG file writed
The coulometer is used in lithium-ion polymer, which is used as a cell phone battery。

thanks，

the flist cycle.gg.csv

Update charge and discharge log data

chg&dcg-0927.xls

Hello Yiyang,

If you program the original gg file onto the gauge does this resolve the issue. It is weird that the Ra table updated to those values. This is not expected behavior.

Regards,

Adrian

If the GG file is reburned, the Ra tab can be updated to normal levels, but batteries that have this problem cannot be updated by reset and standing learning.
Is it possible to theoretically explain why the value of Ra tab is so large? Why does FCC report 0 after updating a larger value

Hello Yiyang,

The issue is probably the large discharge that is being used for this application. The gauge is not expecting a large discharge and that why is drops the FCC value. However, it is weird that FCC value is reported low as 353. What is the nominal capacity of the battery you are using.

I would recommend trying to change the load select to 6. and change User Rate  -mA to -4900. This could possible offer better gauging.

Regards,

Adrian

HI Adrian

The nominal capacity of the battery is 5000mAh, and the minimum capacity is 4900mAh

From the ra tab, it is observed that ra0 and ra1 show a huge difference, that is, there is a problem of excessive impedance compensation in the 100%SOC to 88.9%SOC segment, resulting in FFC 0.
So what is the logic of ra value calculation? How to calculate the relationship between ra value and FCC value?

Hello Yiyang,

To learn more about Ra calculations and FCC calculations, please read this document: https://www.ti.com/lit/an/slua364b/slua364b.pdf?ts=1728513160058

Regards,

Adrian

thank you
The possible cause is still unclear. According to your analysis, are there other possible causes for this case?

Hello Yiyang,

I am not aware of any other causing for this behavior. Testing different load mode and load select can help mitigate this issue.

Regards,

Adrian