R/C Tech Forums - Is this how Lipos work?

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Is this how Lipos work?

So, this was a while back, but just had a question. I had a dispute buying a touring car with a lipo in it. It was very puffed when I recieved it and in pictures it looked fine. I belive they were old pictures because there was a sticker on the picture online but when I got it the sticker was gone. I am unsure of that though. When I said that to him, this was his response:
Him:

its only the case. i have more like it that run fine. heat gets trapped inside and puffs the case

Me:

I also checked the voltage and it is pretty high, like 8.3, which is not a very safe voltage to send it out. That is probably why it puffed because of being on full charge for a while

Him:

He probably stored his lipo with too much charge or even fully charged, and no, lipo cases aren't airtight so they can't get swollen because of heat.

He was also fairly irresponsible to ship a swollen lipo battery.

No, it shouldn't have been sent at such a high voltage. You are right, storing and sending a battery fully charged (which it must have been to arrive at 8.3V) will cause it to puff.

The way he tried to explain it sounds very condescending and is also just incorrect. Clearly he treats all his batteries this way.

I'd suggest requesting a partial refund or ask to return the car minus lipo for a full or mostly full refund and be done with it. Or if you're happy enough with the car, just don't deal with this guy again and post to a RC Good/Bad List on facebook to help others avoid this seller.

Quote:

Originally Posted by ljl23 (Post 15513618)

its only the case. i have more like it that run fine. heat gets trapped inside and puffs the case
No. This technically isn't possible as all lipo cases are very thin and never air tight. Not to mention this implies the battery would be a constant source of radiant heat to energize the O2 molecules inside. This implies the battery is either charging, discharding(both at high rates) or burning up... which I'm guessing was not happening while it was shipped.

Me:

I also checked the voltage and it is pretty high, like 8.3, which is not a very safe voltage to send it out. That is probably why it puffed because of being on full charge for a while

Him:

Physics 101 8th grade. what happens to air when you heat it. it expands. any mositure trapped in during assembly process will also expand. this will puff the plastic case only until the hot air finds a way out. push on the case in middle u can even feel the big gap now there. if the lipo was puffed it would be solid. cant explain it any better at a low level of knowledge .
This is crazily wrong. Lipo batteries puff when the aluminized plastic inner casings(the individual cells themselves) become filled with pure oxygen as the electrolyte inside catalyzes. During normal se with a good battery this effect is usually not noticeable, but the oxygen can build up over time when the cells themselves are either too charged or discharged, and enough oxygen will collect that it cannot go back into "solution" with the electrolyte and it will be permanently puffed and lose punch.
Does this make sense? Because I decided to agree with him, and the first run out I pulled it out of the case and the lipo had popped the case open. I then disposed of it. It was definitley a hard puff, no air inside there.

Hope this helps! I'd be asking for a refund.

Absolutely correct with the answers above. The cases are not air-tight at all, most are held together with the sticker and a plastic lip that can be cracked open with a flathead screwdriver. Lipos puff due to over-discharging, drawing too much current for extended amounts of time which exceeds the max "C" limit, and from being stored with a full charge for long periods of time. They will also develop a slight puff just from usage, but usually this starts in the 100's of cycles or so. Different for different packs.

I'd be asking for a refund, partial, or just don't do business if your otherwise happy with the car.

Never buy a used LiPo, I consider them disposable after 6 months old. If I include them in a used car deal, I don't give them any value and just include as a way to sweeten the deal.

Most of the hard cases on my budget brand batteries tend to swell after 6 months to a year of use... however if not properly cared you can cause them to swell on the very first use. Very easy to do if you charge them in a cool A/C house, then take them outside in extreme heat where heat causes voltage to increase. There was a guy on URC (TheJANG) who charged his batteries at home, placed the batteries in the trunk of his car, then went on a 2 hour drive to the beach and when he got to the beach all of his batteries were swollen and completely ruined, all brand new packs too!

If the guy shipped your car in the middle of summer and the delivery guy left your box inside a hot delivery truck for hours on end, would not be surprised if that damaged the pack too. I try to have my packs shipped in cooler months when possible.

Who did you buy it from, just so we all know who to avoid?