Hello,
I am using BQ28400 battery gas gauge in my design, which is based on 2S1P Li Poly battery pack rated for 5000mAh. The part is placed on the internally designed battery board to which two battery cells are attached. An independent switch mode charger is located on the system board and is configured for the fast charge current of 2.5A. The issue that I see is that when the charger cuts off at ~10% of fast charge current, BQ28400 indicates SOC of less than 100%, which varies slightly depending on the full charge capacity calculated at the end of the previous discharge cycle. The interesting thing is that at the beginning of the new charge cycle SOC stays at 0% for a long time before it begins incrementing. Conversely, during a discharge cycle SOC reaches 0% at pack voltage of about 6.8V and remains at 0% until CUV protection is triggered at 2.7V. So there seems to be a region where SOC remains at 0% for a significant amount of time during both charge and discharge cycles. I have already configured the learning cycle to be optimized for an independent charger (SC bit in the CEDV config register is set). I am also using fixed EDV values (CEDV bit in CEDV config register is cleared). I also went through all of the calibration steps. So is there anything I can do by either changing Data Flash parameters or cycling the battery in a certain way to get rid of this 0% SOC region? I attached the ".gg" file I used to initially configure BQ28400.
Thank you very much,
Peter Levinshteyn
