BQ27Z558: GPC report show abnormally low Qmax

Hello Yichong, 

This doesn't seem unreasonable especially with lower temperature, I would verified with your cell vendor to see what capacity you should expect at lower temperature and you can run a SOC verification test with the two links below. Another option to get higher accuracy/usable energy is to run a GPCRB tool to get lower temperature optimization. But on a aerospace application note as well, they experience the same issues with battery cells being in extreme temperatures that they would often have a heating element in there packs to get there cells in the most optimal range. 

GPCRB:
https://www.ti.com/tool/GPCRB

Accuracy and Verification Methodologies for Advanced Fuel Gauge:
Verification and Accuracy Test Methods of Gas Gauges

Thank you,
Alan

Hi Alan,'

thanks for your reply, actually the real capacity with low temperature can still keep 320mAh, and have run the GPCRB for twice,  but every time the report show the  Qmax is 99mAh, while the gg file shows a Qmax of 490mAh after learning. Here is the GG  file and log data for the low temperature learning, please help to explain why the GPCRB report show the Qmax is 99mAh and if any risk ?

T0009_After_LT_CycleLearning_NEW_CELL.gg.csvBanshee_NewCell_cycleLearig_LT_ReTest_0224.xlsx

Hello Yichong,

I can't review "Banshee_NewCell_cycleLearig_LT_ReTest_0224.xlsx" since it says that the file has been corrupted, however I would reach out to the cell manufacture and confirm the capacity you should expect a the temperatures you are testing at. Your parameters seem fine but you can validate the result that you are seeing by looking at section 7.1 as well. However especially if you are testing a extreme temps seeing that temperature drop isn't unexpected.