The required test consists of the following steps for 25°C and your target lower temperature:

1. The charging is performed at room temperature. Optional: If the cell was at a different temperature before, let it relax for 2 hr at room temperature prior to the test.
2. Charge using CC/CV charging to full using taper current as in your actual charger, for example C/20. Use nominal CC charge rate and CV voltage. If another charging method is specified by the cell maker, this other method can be used. If you are charging in a device, using the device charger is the best.
3. Let the battery relax for 2 hrs to reach full equilibrium open circuit voltage (OCV). If in a device, shut down the device during this period to avoid low current discharge.
4. Set discharge test temperature (first 25°C, than 0°C or other low temperature of your choice).
5. Wait for 1 hr until pack reaches thermal equilibrium and cell temperature will stop changing. If temperature did not stabilize (can happen for larger systems) use more time.
6. Discharge the battery at system typical high rate until the minimal voltage, as specified by the cell manufacturer, is reached. If you are discharging in a device, discharging to device minimum voltage is acceptable. This can either be a constant current or constant power load.

   1. For best RbL values: Discharge the battery at the following rates, depending on temperature, until the minimal voltage, as specified by the cell

      manufacturer, is reached.:

      C/5 for T >= 0°C

      C/7 for T < 0°C and >= -10°C

      C/10 for T < -10°C and >= -20°C

      C/15 for T < -20°C

   2. For best thermal model parameters: Discharge the battery with a typical high rate for your device until the minimum voltage for your device. The goal is that the battery heats up as it would in your device.

   3. If you want to combine RbL and thermal model parameter calculations in one test setup: Use the test setup for thermal model parameters (3.2.1 step 6.b) and discharge the battery with a medium load so that there is self-heating between 5°C and 10°C. This rate needs to be above a C/10 rate and the temperature cannot exceed 20degC.

   Note:

   For the best gauging results, please complete at least two tests, one following the instructions detailed in 6.a and another following 6.b. This will allow for the gauge to have the ideal RbL and thermal model parameters.

   If 6.a and 6.b are completed, there is no need to complete 6.c. Only use 6.c if only one test can be completed for the GPCRB input.

7. Verify that temperature during low temperature discharge does not exceed 20°C. If it does, rerun the test at a reduced rate to reduce self-heating.

8. Let the battery relax for 5 hrs to reach full equilibrium OCV. If in a device, shut down the device during this period to avoid low current discharge. Go to step 1, and repeat all steps with temperature set to 0°C in step 4).

The resulting room temperature log is exemplified in Figure 2-1. Low temperature log should have similar shape of the curves, but discharge would start at a lower temperature. :

Figure 3-2 Voltage Current and Temperature Profiles of the Room Temperature Test Required for Golden GG Creation

Data logging should store data into a file containing the following columns, in a coma-separated (CSV), tab separated, or space separated format:

• Time (in seconds elapsed)
• Voltage (in millivolts)
• Current (in milliamps where discharge current is negative)
• Cell temperature (measured by a thermistor attached to the surface of the cell, in degrees Celsius). One decimal place is acceptable.

If the original data format is not one of the supported formats (for example Microsoft®Excel®), the data file must be saved as .csv. Any text that is not part of data-columns, such as the log file header generated by bqStudio or EV Software, as well as empty lines should be removed from the file prior to submission. One row of column names can remain, (the tool will skip it), as long as it has just one name per column. An easy recording method utilizes TI's bqStudio software utility called GPC Packager that reads data directly from a TI fuel-gauge.

Values of current in ampere and voltage in volts are acceptable, the tool will auto detect it and use the correct scale factor.

The columns can be in any order since the column positions are defined in the config.txt file.

However, both room temperature and low temperature logs should have the same column positions for t,V,I,T values. The log file can have some other data columns that are not used in this tool (no need to remove them), as long as the size of the zip file prepared for submission does not exceed 2MB. Note that since it is a compressed file, you can sometime squeeze it some more by utilizing different compression settings in your archiver program.

The sampling interval can be from 5 to 100 seconds.

The initial charging portion needed for Ra0_charge calculation. Relaxation data is required both before and after the discharge.

Precision of the measurements is important. In particular, current measurement should be better than 0.1% of range accuracy, and for voltage measurement 1 mV at room temperature. 16-bit ADC is recommended.

The room data log should be renamed as: roomtemp.csv, and low temperature log as lowtemp.csv prior to submission of the package, regardless of actual text format.