I repeated the above and left them connected for 22 hours. Both settled at 7.93V at the time of disconnect, i.e., resting voltages for BOTH modules was 7.93V. 2013 module: 1161mAh (17.9% SoC) 2007 module: 2468mAh (38.0% SoC) The 2013 module was EMPTY - no usable capacity left - 0% SoC The 2007 module was charged to about 61.5% SoC - right where the Prius tends to keep them. After 22 hours there is still a 20% SoC different between those two modules. That is terrible. Given that there was essentially no change between 2 hours and 22 hours, it's hard to imagine that leaving these connected for even a week would do anything more. Now imagine paralleling an entire packs worth of modules with not 4000mAh of difference between them, but maybe 1000mAh or more or less. I expect LITTLE transfer would occur between modules. I'll try one more experiment to test that. I've charged 2013 with 1340mAh (20% SoC) and 2007 with as much as I can before it starts swelling (4250mAh). 2013: 8.13V, 2007:8.41V Strapped together and we'll see what happens in 22 hours or so. I'll admit I'm a little tickled by this. I've always told people this was a waste of time. Now I have the data to prove it.