Quote:
Originally Posted by chrismechanic
one more fact i just thought of while i was just repairing a bouncy castle blower...DC voltage allways flows in one direction...this would explain why the packs are swollen at one end only..now i cant remember if its + to - or - to +.
durr....  the old grey matter is not as good as it used to be 
chris |
Most explanations of electric theory kinda assumes the flow goes from + to -, which is technically "hole flow". But electrons actually travel from - to +.
As to the OP; I still think it's more of a physical deformation than electrical. Maybe relative tightness of shrinkwrap in the center vs the ends? Maybe the straps slowly over time squeeze the middle more? Maybe an inner cell puffs under usage, and since they are all stacked up, the tightness of the heatshrink causes that bulge to squeeze the material of adjacent cells around? Since lipo cells are long/wide layers of material, any gas expansion would affect the entire surface area of the cell, and would tend to bulge in the middle.