Can a LiPo battery go "puffy" ? NEW! photos added

[GordoSH-3]

Hey everyone:

Can LiPo's go stupid in storage and puff up? I have two Apex 2100 mAh/15C LiPo battery packs that I'm a bit hesitant to use because the outer heat shrink feels like there is a "cushion" or "pillow" under the heat shrink (not sure exactly what constitutes "puffy; I've never seen a bad or puffy pack in person).

Background: Both packs were purchased about 8-10 months ago but have not been used in 6+months. They were only used/charged 2-3 times prior to storage for the non-flying season and I gave both of them a full charge using a Triton charger just before storing them away in a fire-proof porcelain container. When I looked at them this weekend to do some flying, they both felt soft or slightly padded. I compared them to a a set of similar looking/shaped DN 2150 batteries (never charged/used) and the DN hat shrink is absolutely flat against the cells. Comments? Opinions?

Thanks,

[M Carr]

I think where you went wrong was storing them at a full charge. I believe you are supposed to store them at slightly under full charge. I store my 3s packs at around 11.8-11.9 volts. I would be hesitant to use them also.

I may be wrong but I have had no problems yet.. Maybe someone else who is better knowledged can help you better.

[WayneBrown]

from the description, I'd think they were okay but had a little trapped vent gas inside the outer cell.
Charge slowly and outdoors, and fly with a minimal load for a couple flights and feel them out.
The typical puffed cell will be more rounded, say more than 5mm down the center, and more likely than not be hard, not soft.

[Pinecone]

a) Proper storage is about 3.8 - 3.85 volts per cell.

b) APex packs can puff from looking at them. :)

c) Follow Wayne's advice and try them in controlled manner.

[GordoSH-3]

Wayne:

I've added photos to help with the analysis/further comment. One yr old APEX packs (yellow/2100mAh/15C) vs. new DN packs (black/2150 mAh/20C). Sorry for couple of pics out of focus; I'm trying to show swelling and curve of the packs compared to the DN packs.

As I said, I've never seen a LiPo pack swelled up or puffed out in-person. They are not puffed out by 5mm, more like .50 to .75 mm per side (1.5mm total). I'll try your advice about the careful charging and use for 5-10 flights.

Thanks for the feedback.