Lipo Swelling

[Steve Krug]

I have 2 Zippy H 4S 5000mah lipos...

After running them, my temp gun always says they are between 90-115 degrees F...
Now...

After running the lipos they usually swell up slightly...but they always return to normal after roughly 15 minutes. They also have never gone below safe voltage, in fact, I have never completely run out one of these lipos yet..

Now is it normal for them to swell like this slightly? Its not alot of swelling, just enough that you can notice the cells rounding off at the flat tops just a little bit.