Puffed Up Lipos

[Chris Reid]

I have 4 lowish capacity BRC Hobbies HiModel  (1700mAh) 3S lipos. Over two years of occasional use, 3 out of 4 have puffed up.  This occurred early in their life mainly while in storage while charged.  They have always been balanced charged on a lipo charger at 1C, and never exceeded 85% of their rating on discharge.  I use a Whattmeter, and prop motors to load the batteries appropriately.

 

The query is, are they still safe to use?  They charge and discharge ok, and still fly the small models for which they were purchased.  BRC Hobbies say they are probably ok, but forums are full of tales of doom, and my club leccy experts don't really know either.  Better safe than sorry is the usual advice, but it'll be a fair sum to replace them. 

 

Chris Reid

[winchweight]

I'd not risk it as you might have a fire on your hands. Unless they're really specialist lipos they're cheap to replace and not worth risking your expensive model.

 

To dispose of them, cut off the leads and immerse in a bucket of salty water in the garden for 48hrs. Then check the voltage has dissappated and dispose as normal rubbish.

[Pete B]

I had two 2S HiModel Li-Pos which both puffed within the first half-dozen cycles (neither was abused). I've never had it happen to any other brand so I assume I look after the packs correctly.

 

In view of what happened, I wouldn't rush to buy another.I've settled on Zippy's or Rhino's now and am very pleased with them. LoongMax are OK, too.

 

As Shaun says, it's not worth the risk, Chris..........

Pete

[Erfolg]

At the flying field I have seen the puffing phenomena quite a few times. It does not seem to be restricted to any one band or cost.

 

It does seem though, that the harder they are pushed, the more common is the puffing. The trouble with this observation is that it is an observation of how models appear to be  flown and not measured values

 

Strange thing is we all claim to be conservative in our usage, me included. Yet I have models where the battery and motor become warm to handle at the end of a flight. Yet the amps drawn seem well within the rating of both motor and battery.

 

Erfolg

[Andy Freeman]

Another Hi-model "puffed up" for no apparent reason here. I have had two that have gone that way. Was a couple of years ago now but would be very reluctant to buy another one..

 

They were 3S 1800 and used in a vintage style cabin thing that never went past half throttle and only pulled 10A at WOT

[Tim Mackey]

Discharge them fully first, via a car headlamp bulb or similar, then cut the leads off and dispose as Shaun suggests.

The cost of replacing them is miniscule compared to replacing your home.

[Simon Chaddock]

Chris

The way I look at it is if a LiPo has puffed up then something has gone wrong with the chemistry in one or more of the cells.

LiPo are not self healing in any way so continued use is likely to make the puffing worse which could have serious consequences.

In my fairly limited experience of puffed up cells they seem to have a higher internal resistance so not only does the voltage sag more under load but they tend to get hotter as well. Not a good combination.

Why do they puff up? I have no idea!

I have had one puff up in a matter of days others still as new after a year.

 

Take the advice and dispose of them as suggested.

[Peter 'Ivanna Crashalot' Savage]

Is the risk where the pressure inside them gets too big and they pop? surely as long as the pressure isn't too high it should be alright should it not?

[Brian Parker]

You guys must have plenty of disposable cash.
 Why throw away perfectly good cells?

Just remove the puffed cells, test the remaining cells and if all OK, use them to build new packs.

 I had this happen to me with a couple of BRC HiModel 3S. One outer cell puffing on both batteries (not the inner cells). I put it down (probably) to stress due to the Velcro straps I was using to hold the battery in position.

No further problems after more than 12 months use configured as 2S and a revised fixing.

[Malcolm Fisher]

Pete "Servo scrounger",

 

The major risk is that of fire. Abused Lipos can get to a runaway state and burst into flames with serious consequences for anything nearby.

 

There are some fireproof bags which are used to contain Lipos while being charged.

 

No direct experience, just relaying bits I've read about.

 

Malcolm

Edited By Malcolm Fisher on 17/05/2010 21:00:58

[Peter 'Ivanna Crashalot' Savage]

Yes I understand that when they are open to the air they  set on fire, but is it the pressure that makes them puncture, we have 2 of the bags which we use to charge them in or if we can't be bothered to take some out to the shed!

 

We have a slightly puffed one, still use it on low current models, it is only one cell that has pufffed but if it expands anymore we will get rid of the dodgey cell in a bucket of salty water!

[Doug Ireland]

"Puffed up LiPo's", "charging bags", "Salty Water"; All scary stuff! Stick with IC, can't think of the last time I heard of one blowing up!

[Delta Whiskey]

Very True !

[Tim Mackey]

Well obviously the OP must make his own decision, but I for one wil NOT endorse an inexperienced user ( and we have no idea of assessing his capability on wiring , dealing with aluminium soldering etc ) dismantling and re-assembling Lipo packs.

[Peter 'Ivanna Crashalot' Savage]

They can be quite scary at some times! My OS 48 made an absolutely massive pop sound, I have to say I was worried I had blown it, literally

[Doug Ireland]

Did it catch fire? Probably not. Enough said.

[Pete B]

Nah - noisy, smelly, sticky goo, fuelproofing, can't switch on and off at will (usually) - and I still remember those raps on the knuckles and stinging prop cuts on those cold winter days - oh Joy!

 

I prefer life in the 21st Century, ta...............

 

Pete

 

[Peter 'Ivanna Crashalot' Savage]

Yeah, If your not sure of the lipos, get rid of em

 

And Pete, that is why we use sticks and electric starters  

[Pete B]

Well, life is a richer experience if you learn the hard way.................no pain, no gain! When it hurt too much, I eventually treated myself to a chicken finger

 

Pete

[Peter 'Ivanna Crashalot' Savage]

They do nothing!!! give me a 12" dowel any day!

[Peter Miller]

One of our club members stuffed his electric model in. The doubled up pack of Lipos got their ends bent. He has straightened them out and even though they are 1/4" shorter they have been cycled twice and work well. NOTE He is not keeping/using them in the house.

 

My latest flight box has my built in starter system but now the starter moves back and switches itself on as the spinner is pushed into the cone. No more awkward foot switches.

 

And before anyone says anything, I was hand starting engines from 54 onwards. Among many was a Super Tigre G21-29 speed engine, a 5cc engine that could be hand started on 25% nitro and turning a 7" X 10" wood propeller.

 

Oh, While one may get a hit finger with ic engines they can't start up on their own causing damage or injury.

[Erfolg]

It does not totally surprise me that a bent Lipo may still be usable. When you read the blurb of the primary manufactures of cells, the ability to form the cells into a particular envelope which is a claimed advantage.

 

Most of us now have Lipo and Life in the house these days buried in mobile phones and computers, some power tools etc. and think little of it, even some come in a plastic case, although not all.

 

Erfolg

[Myron Beaumont]

Peter

As I've mentioned before (but for the benefit of those that didn't know) one of my occupations was as lead guitarist in various bands for about 35 years .Now then ,all that time I was hand flicking props . Say no more Eh!

[Tim Mackey]

There is a difference between a slightly distorted battery and one which has puffed. The puffing is caused by chemical reaction, which is subsequently putting the pack at more risk to igniting through the pouch allowing air to enter and react with this affected electrolyte, and likely igniting. I also have some packs which are slightly deformed, but are NOT showing signs of external / internal puncture damage or reaction, and I continue to use them in low power systems.

As with most advice, one needs to be extremely careful to not mislead people into thinking that all is well, when in fact it may be dangerous, even slightly.  For this reason, I maintain my original response, and that is, a puffed / swollen or physically damaged / split LiPo pack should be disposed of correctly ASAP. After all, the price of replacement packs these days is low, and I simply dont think its worth the risk.

The batteries in question in the OP were old and pretty well used anyway, and in fact replacing them all with todays equivalent pack ( actually quite a lot better in many respects ) would cost just  £40 for all of them ! Its a no brainer surely .

So no big loss IMO,  your house / life would be.

Edited By Timbo - Administrator on 18/05/2010 10:51:30

[Myron Beaumont]

Surely possible,loss of life &/or property shouldn't even be an issue ? I have my two lipos in the house at the moment ,They are the correct voltage for storage (Timbo - your info ) but due to fluctuations in temp etc & the uncertainty that folks talk about on various threads ,I am about to put them outside ! Scary stuff I reckon . My fuel will remain indoors like it always has,