Heat makes them swell. Hard cases do not let them get cooled off. The battery's need cooling just like motor or esc. Hard cases on the battery's is not smart. It's a scam. You have been duped. I have a mountain of lipos. (Car planes Heli) most if not all have puff! There's a bunch of info about cooling discharging Lipo cells. http://ideaexchange.uakron.edu/cgi/v...earch_projects And many others. But whatever.