2S pack swells after run

[sailr]

The shrink wrap is so tight on some packs that the air heats up inside and puffs out the wrap only. When it cools, it goes back down. Not a battery problem. I have actually 'carefully' punctured just the wrap before and watched it go down immediately. This was not on a hyperion as I haven't had a hyperion puff.

There is no PERFECT battery out there. Regardless of the brand or price they are all susceptible to failure either through improper charging, storage, or usage...OR...simply a bad pack! The cheaper the packs, the more often this is likely.

In my opinion you are using the BEST packs out there.

This is interesting. I was going to post about this and forgot. My Hyperion start out a nice flat top side, and than puff a tad, then go flat. I was worried. Pat at RcLipo said that any puffing is bad. What should I do?

[Steven Vaccaro]

Thanks for the info Jim. I will look at that.

I do not preheat. But do balance charge on each and every charge cycle.

[sailr]

No need to preheat in Florida!

[SweetZ28]

Reason why they start to puff is due to temps 140 deg or greater or if you are over draining the lipo and it can't supply the amp draw ... you need higher C rated packs.... they puff up because the chemicals inside break down to a kind of liquid that's why they get soft so a soft lipo is a bad lipo a lipo should always feel hard a bad one you can smush it around a bit and it feels puffy.