Other Parts Discussed in Thread: GPCCHEM
Tool/software:
Hi,
We are using a BQ28Z620 BMS with LiPo batteries in 2s configuration and are having some issues having a valid SOC value.
When searching for the procedure to execute a battery learning cycle, we had trouble finding all the information, but we were able to find pieces of procedures in multiple documents and forum.
Here is the latest procedure we executed on a brand new BMS evaluation kit (BQ28Z620EVM-071).
- Update the base image of the BQ28Z620 firmware from version 1.00 to version 1.01 using BQ Studio.
- Configure the minimal settings for the BMS to be functional with the batteries (2s config, enable FET).
- Perform a discharge (until 6V), relax, charge (until 8.3V), relax, discharge (until 6V), relax cycle while logging using BQ Studio.
- Rename the log file into `roomtemp_rel_dis_rel.csv`, remove the file header, zip the file with a config.txt.
- Upload the zip file to your Battery Chemistry Online Tool and check the chemical ID in the report (default 1210 is good in our case)
- Change the chemistry using BQ Studio and configure the following settings indicated in the learning procedure.
- Design Capacity: 2100mAh (also set the 1554cWh)
- Charge Termination Taper Current: Default 250mA
- Discharge Current Threshold: 20mA
- Charge Current Threshold: 50mA
- Quit Current: 10mA
- Termination Voltage: 6V
- Activate the GAUGE_EN setting and perform a discharge (until 6V), relax, charge (until 8.3V), relax, discharge (until 6V), relax cycle following the timing from the learning procedure.
- Once completed, the golden image was exported using BQ Studio.
After that, the SOC was tested by charging the battery to 100% capacity and discharching at a steady rate of 430mA (~C/5). The SOC, voltage and current was manually logged to observe the discharge.
We would expect the SOC to be mostly linear with a discharge rate that should match with the orange line for 2100mAh. However, the relative SOC procides invalid value and indicates 0% charge about 45 minutes before the real empty state.
Our application requires to have a good estimate of when the battery will be depleted, so we need to address this issue.
I also attached the golden image output files in case it can provide you more information.
20250123-BQ28Z620-LiPol Golden Rev2.0.zip
Thank you,
Sebastien