Heatmap showing detailed aging differences. A total of 86 batteries are partitioned into eight groups, arranged along both the horizontal and vertical axes from left to right and from top to bottom, respectively. Each square in the heatmap represents the aging difference between a pair of batteries, calculated only when both batteries belong to the same group. As a result, the heatmap contains eight blocks along the main diagonal, each indicating the within-group differences for one of the eight groups. The color in each square corresponds to the magnitude of the aging difference, with more intense colors denoting greater differences.
