"Full factorial design of experiments dataset for parallel-connected lithium-ion cells imbalanced performance investigation"

Abstract

This paper shares an experimental dataset of lithium-ion battery parallel-connected modules. The campaign, conducted at the Stanford Energy Control Laboratory, employs a comprehensive full factorial Design of Experiment methodology on ladder-configured parallel strings. A total of 54 test conditions were investigated under various operating temperatures, cell-to-cell interconnection resistance, cell chemistry, and aging levels. The module-level testing procedure involved Constant Current Constant Voltage (CC-CV) charging and Constant Current (CC) discharge. Beyond monitoring total module current and voltage, Hall sensors and thermocouples were employed to measure the signals from each individual cell to quantify both current and temperature distribution within each tested module configuration. Additionally, the dataset contains cell characterization data for every cell (i.e. NCA Samsung INR21700-50E and NMC LG-Chem INR21700-M50T) used in the module-level experiments. This dataset provides valuable resources for developing battery physics-based, empirical, and data-driven models at single cell and module level. Ultimately, it contributes to advance our understanding of how cell-to-cell heterogeneity propagates within the module and how that affects the overall system performance.

Keywords: Cell characterisation; Cell-to-cell parameters variation; Current and temperature imbalance; Design of experiments; Lithium-ion battery; Parallel-connected cells.

Graphical abstract

Fig. 1

A visual flowchart of the implemented experimental procedures, selected steps, and design of experiments. Single-cell characterization (top) is performed before module-level testing (bottom) and consists of four phases: pre-inspection, namely visual investigation, weighting and sample labelling, identification of discharge capacity via the pseudo-OCV procedure, derivation of impedance via HPPC and MultiSine protocols, and conditioning for long-term storage. Module-level testing is grounded in the selected Full-Factorial DoE and consists of four phases: cells' selection and grouping, module assembly, test delivery, and data processing. Between the two campaigns, Hall-type current sensors are calibrated, and derived voltage-current maps are then leveraged to translate raw data into processed data.

Fig. 2

Cycling module-level testing protocol. (a) Terminal voltage (grey line) and total current (orange line) profiles across the 8 steps of the testing protocol listed in Table 3. (b and c) Distribution of the supplied current across the four parallel connected cells (red-scale lines) and module terminal voltage (grey line) during the constant-current discharge (Step ⑤) and CCCV charging (Steps⑦-⑧) phases. (d,e) Distribution of the individual cells’ surface temperatures during the constant-current discharge (Step ⑤) and CCCV charging (Steps ⑦-⑧) phases.

Fig. 3

a) Hall sensors supplied-current ramp (grey line) to response voltage profile (red dashed line). b) Example of a resulting linear regression line (continuous grey) used to map the gathered voltage-current data (red crosses).

Fig. 4

Dataset files structure.

Fig. 5

Comparison between module-level raw and processed data, where the signal names are highlighted.

Fig. 6

Equipment available at the Stanford Energy Control Lab [8].