The next few articles will deal with the battery test recipes that can be used to test secondary batteries.
One of the essential methods of testing a cell is cycling. Naturally charge and discharge recipes form the baseline of ModenJay Battery Laboratory.
(Figure 1) Recipe icons for Charge, Discharge and Charge&Discharge
Charge recipe represents the application of a positive current to charge a secondary cell. The user can customize the procedure by setting the measurement set property, end property and the safety property. As for the set property, the user can select the charging method (CC, CC/CV etc.) and its parameters (current and voltage values). Transient response measurement is also possible simultaneously. Details of TR will be discussed in a later issue.
Discharge recipe represents the application of a negative current to discharge a secondary cell. The settings for the measurements are identical to the charge recipe except for the absence of the CC/CV mode.
The user also has to set the end property to define when the test to stop. The end property may be a particular voltage value, current value during CV mode, the time length etc. The safety property can be set to protect the cell from damage by limiting the voltage, the current and the temperature ranges.
(Figure 2) Charge recipe measurement properties. Discharge recipe has identical properties except for the CC/CV mode
Metadata for Charge and Discharge recipes consist of a common part and a unique part. The common part records the experiment background information including the sample information and the test log, which were elaborated in the previous article “Test Recipe (3) Metadata”.
The unique part is where the raw result data for Charge and Discharge recipes are converted into metadata files. A group of chosen raw data are directly extracted to be a part of the ‘Extracted Data’ section of metadata. These include the voltage and the dV/dQ values at each SOC level. The ‘Characteristic Parameters’ aim to fully represent the result by recording the capacities during charging or discharging as well as some other parameters including the current decay constant while CV charging and highest power output during discharge.
(Figure 3) An example of the unique metadata section for the Charge recipe
(Figure 4) An example of the unique metadata section for the Discharge recipe
There are two EigenPlots for the Charge and Discharge recipes. One displays the voltage change with respect to the capacities charged and discharged. The other displays the voltage and current change with respect to time. These allow the users to understand the test process at a glance.
(Figure 5) Examples of the EigenPlots for the Charge and Discharge recipes
While Charge and Discharge recipes individually can be used to achieve partial charging and discharging, the Charge&Discharge recipe exists to achieve the analysis of a single full cycle of a cell. The motivation of this recipe is to measure the coulombic efficiency and record it as a part of the metadata which is unable to achieve by using Charge and Discharge recipes separately. Besides the measurement of the coulombic efficiency, Charge&Discharge recipe shares all other measurement set properties and metadata format with the Charge recipe and the Discharge recipe.
Thank you for reading this article and we will discuss some other battery test recipes in the next article.
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