puffy lipo question
 

i have an older maxamps 11.1v 8000mah that i recently bought on here. ive run it like 6 or 7 times since i got it, but i never used more than half of the pack. (i ran with my friend, and his couldnt last:lol:) anyways, this morning i was out driving it around, just bashing about. i have my lvc set at 9.6v. well, i noticed it getting a bit sluggish, so i figured it was going to cut off. what i found was a slightly puffed pack. it was minor and still came out of my t4 easily. so i was like crap, the lvc didnt work. so i put a meter on it, and it was at 10.1v. it was warm, but not even close to hot. say 125, maybe. so i left it outside all day, out of the sun. when i got up this afternoon, i went out, and to my surprise the pack had shrank back down to normal size, and i couldnt feel any puffy-ness at all. i rechecked the voltage and it had gone up to 10.3v. i put my balancer on it, balanced it, and then left for work. im now charging it outside, just in case. im new to lipos, but from what i gather, once it puffs, it doesnt go away. info please!!!

im using an xcelorin esc with their 6400kv motor. stock (as far as i know) spur, which is 87t, and a 19t pinion.

The way you are driving driving might be working the batts a little hard. ive had lipos get warm but not puff. just keep an eye on it.

If a lipo is puffing it's just about gone. Won't be long till it goes up in flames. Call Maxamps and get them to handle it.

The cell that puffed is prob a weak cell and is struggling under the amps your ride is pulling. If its the puffed cell is returning to normal, its right on the edge of going bad. Ck voltage with dvm and then again early in a run. You'll prob see its dropped relative to other cells.

I'm guessing MA is not going to do anything for you except offer to sell you another.

ill make sure to check it. and your probably right, because i didnt buy it directly from them.

well i ran it down to 11.4v. barely even warm, altho its pretty cool out. no puffing at all. 2 cells were at 3.83, and one was at 3.82. hummm....

When you had it puff - what were you doing - high speed runs? Did you take it easier this time?

If you were running about the same amp draw as when it puffed initially, then ambient temp may be the diff. How much cooler?

Thats not enough voltage diff to worry about. I've read that the hardest thing on a lipo is running it to the lvc - beginning to think thats what's going on here, if you had run it to the same voltage as the initial run, prob would have had it puff again and get hot.

Def wouldn't run it to the lvc next time out just to check. Maybe you need to raise lvc?

when it puffed i was mostly just messing around. never really mashing the gas, but i did get it going pretty quick a few times. mostly just mobbing over grass and the street. i drove it pretty much the same. the ambient temp was the same because i drove it both times in the morning, around 7, so it was like 65 both times. i know the normal lvc is 9.0v, but from what ive learned with one of my other hobbies (flashlights. i know, dorky, lol) you dont want to bring a li-ion or a lipo below nominal if you can help it, so thats why i have my lvc at 9.6v as opposed to the normal 9.0v. i know thats still 3.2 per cell, but thats still higher than 3 per. like i said, when it puffed, there were at 10.1, so they were fairly close to nominal voltage. im going to take it out in a few and see what happens. its 90 something right now, so that could effect it.

I have all my lvc set at 3.2 - 3.4v cell, so I have a safety margin. Using brakes a lot will also heat one up since these depend on motor braking versus mech brakes.

Since this lipo goes a while between runs, how are you storing/maintaing it between runs?

yea brakes definitely do draw some power, altho i barely use mine. i use mine pretty much everyday, so i keep it mostly charged.

Sorry, my dumb, I read your op wrong or something.

Best way to maintain a lipo is to use it regularly, sounds like you're doing all the right things. I'd keep a close eye on it over the next several cycles and if its ok, I'd just run it.