Steven,
indeed, somehow I misinterpreted this concept differently, and missed the point completely.
I was not aware of the importance of matching internal resistances of parallel packs, but your graph shows it clearly. And even when matched at the beginning, a divergence over lifetime could lead to some instable behaviour.
I am unsure whether higher temps lead to higher resistances or lower (I hope higher, so PTC), and whether deterioration due to temperature loads leads to higher or lower resistances.
Looking a that graph, I am a bit bothered by the fact that one cell more or less influences a whole sting. In the picture all cells of the middle string have now 9 A more than the cells of the left and right string.
What if in the next "layer", the unbalance would be in the left or right string, then this difference would be smaller, isn't it?
I am having troubles grasping the deeper concept after this idea, that's the reason I ask these questions, that are most likely simple to see for you.
Thanks a lot for doing this analysis,
Huub