Other Parts Discussed in Thread: BQSTUDIO
I would like some suggestions on how to improve the battery accuracy. I am currently getting a SOC error when compared to the calculated SOC.
I am calculating passed charge as the sum of the current x the elapsed time on a discharge of a fully charged battery. Also from the calculated passed charge, I match the capacity for 0, 3, and 7% to cell voltages to use as the fixed EDV points.
Full Charge capacity = 2437mAh
Calculated Passed Charge at terminate voltage = 2362mAh
Why is there a delta here and why does it not get updated after a qualified discharge?
I have read section 9.1.4 “Full Charge Capacity” in the technical reference manual, but I do not fully understand how FCC is calculated. Is the FCC updated from the capacity reading at the low battery level (7%)? Does the FCC capacity get set to “7%_capacity”/(.93)? What happens if the low battery cell voltage is incorrectly set?
The SOC is drifting from the calculated, as seen in the plot below. Also at 14-12% SOC I am hitting the EDV2 point and the remaining capacity is reduced to the 7% point. What other parameters need to be considered for improving the gauging accuracy?
My system is currently shutting off when the system software receives SOC = 0%. Is there any possible error that comes from the fact that the battery does not reach the full discharge? My thought is that the learned capacity would be reduced some and still report a linear 100 to 0% discharge. Am I not receiving a qualified discharge in this scenario, and thus not receiving an update on the capacity? How do I check for a qualified discharge?
Attached:
1. 20180718_bqstudio_log.csv
2. 20180718_bqstudio_log_edited.xlsx (includes calculated SOC)
3. 20180718_memorydump.gg.csv
Fixed EDV Settings:
Thanks,
John
