Ascertain intra-module Cell-level thermal gradients and their effect on resistance heterogeneity

Ascertain whether intra-module thermal gradients exist at the Cell level in Audi e-tron 4P3S battery modules and determine how such gradients influence the observed differences in internal resistance among the three series-connected Cells by using direct Cell temperature measurements rather than only module-surface thermocouples.

Background

Resistance measurements show a consistent positional pattern: the central Cell exhibits lower resistance than the outer Cells across temperatures and states of charge. Surface thermocouple readings indicate small temperature differences on the module casing, but these may not reflect internal Cell temperatures due to thermal smoothing by the casing. Thus, the existence of Cell-level thermal gradients and their role in resistance heterogeneity remain unresolved.

The authors indicate that surface measurements are insufficient to infer or exclude internal gradients and point to the need for direct Cell temperature sensing to test and quantify this effect.