when does a LiPo take to puffing?

[Skipster]

I have had four 2s LiPos puff recently
mild puffing but worriesome.

Batteries where made by different manufacturers
PolyRC, and Flightpower.

All puffed NOT while running but being charged
by a LiPo charger .
2 had the balance tap plugged in and in use.

two different chargers actually
Hot Power and a another China equivalent.

Both were set at 3A on batteries with a 5000 mah 20-30c rating.


So they were being charged below their max charge rates.

I fail to understand whats happening.

I understood they would puff when driven beyond their max amp rating.

The more I learn, the more I know I don't know.

__________________

[Chilli]

Were you running different packs (type, C-rating, manufacturer) at the same time?

Were the cell voltages similar while charging?

[Fluid]

What were the voltages of the packs/cells when removed from the charger? Cells can puff if overcharged above 4.2 volts per cell.

Since you had puffing on two different chargers, the cause might lie elsewhere. If you have over-discharged your packs in the past they can be damaged and may respond by puffing on a charger even if the charge parameters are within reason.


.

[SweetAccord]

Fluid is right. Also, what is the history of these packs? How many runs, how old are they, what's the amps you are pulling through them, what was the voltage before they were put on the charger, what was the voltage after the charge? All these or any one of these may contribute to this. It's tuff I know. Sorry for the loss.

I have had one Turnigy Lightmax puff on me. I'm still not sure why. Strange is that I have other ones running in the same setup and charged on the same charger and no issues and I baby everything. I leave it to be that some cells are a little better than others in a batch when you pay a lot less than you should.

[Skipster]

Thank for the replies guys.
Sorry for the delay, problems with the laptop
(power supply if you believe it!)

I will attempt to answer in hopes of helping anyone else that reads this.

The packs were all purchased used from the SS.
Thus I am not sure of their history.
Pigs in a poke obviously.

The two Flightpower were run once by me for a total of about one minute
in a 25" mono with an Ammo 36-50 on 2s2p
the prop was a 437/3
It was just a test and a toad so I brought it in. Nothing was hot.

The PolyRCs were never run just added deans and put on charge.

I did not think to check the pack voltage upon completion
But the chargers both turn off (beeped "full")

My chargers do not tell individual cell voltages while charging.

I checked the voltages on the cells today and they are as follows

__________cell 1 ..cell 2
PolyRC #1 ..4.29v ..4.29v
PolyRC #2 ..4.31v ..4.32v

FP #1 ........4.21v ..4.18v
FP #2 ........4.21v ..4.22v

So as Fluid says maybe they were all over charged by the two
chargers (both are the same charger wrapped in different cases)

Both chargers have been in use for about a month with other LiPos.
with no problems .. plus
I charged two other FPs today (same type LiPo) they are fine.

Thanks again for taking the time to reply.

[Himalaya]

If the Flightpower and PolyRC packs are older than one year they are very likely to have same cells made by enerland, known for great performance when new but very afraid of storing. All my enerland cell based packs include Hyperion and PolyRC built up extremely high IR after several months of storage, even in perfectly 3.85V/cell condition. Many high end lipo brands if not all suffered from this before they found new cell vendors in China. And then Hyperion G3 and other high performance long life "new generation" lipos appeared.

As long as they work, use them to maximize their value.

[GP73]

Also make sure the chargers are calibrated properly.

If they are IMAX B6 clones you can find the instructions here:

http://www.rcgroups.com/forums/showthread.php?t=827821

[pyroM!KE]

Always time your runs and stick with the 80% rule...Never discharge lipo packs lower than 80% of the rated capacity..So a 5000mah pack discharged down 80% you would have used 4000Mah...So when you charge it, the pack should only take in 4000mah..Ive been using this method for years now any my packs seem to outlast what everyone else says..Also..When I run, I never see the cuttoff from the esc using the 80% method..
Also,I balance charge my packs every time their charged..

[Skipster]

thanks again for the input

Pyro - good advice that and I will use it in the future
I do not run long run times but will keep it in mind

GP73 - I will have to research to see if they are a IMAX 6 clones,
quite the thread you linked to thanks.
The voltages shown show them to be charging a few 10ths high.
but
Himalaya - I believe you hit the wood holder on the cranium
(nail on the head)
These are older and have been in "storage" for some time.

I have charged many other LiPos with these chargers and none have done this.

The PolyRCs continue to swell (just sitting on the bench)
They are at a very scary size now.
Time for the salt water drowning I suppose.
(now stored in my charcoal grill)

Shame is I have two more from the same deal waiting for me to put
bullets on them.

The Flight powers continue to provide power and charge totally
balanced. No more puffing.
Two other from the same deal are normal.

Somebody build a better power source please!

__________________

[norbique]

Dear Skipster,

You should absolutely make sure your chargers aren't charging your cells above 4.20 Volts! You could have burned down the house with those! Either calibrate your chargers somehow, or have someone fo it for you as other suggested, or get a decent calibrated charger.

I use a Junsi charger (208B) and I set the charger up so that it "undercharges" the cells to 4.15V instead of the factory default 4.20 volts. This way I'm loosing 3-5% of the capacity of the battery, (charging it up only to 95-97%) but they don't puff on me. This approach also extends the battery cycle life by some.

[Skipster]

Thanks for the warning Norbi
much appreciated

I do not charge in the house I use a charcoal grill in the driveway.

But I have since learned, thanks to Mike Chilli Nautiboyz
my charger does show individual cell voltages

I now monitor them and turn it off at 4.18 - 4.2 v /cell.
I have not seen it charge above this but ....
why take chances.

I have charged many other cells many times with these
chargers and these are the first to do this.

Enerlands may have some problems after sitting
as Himalaya said.

[Mel279]

Skipster

charging at a rate of 3A would be not a good idea for a puff lipo. I usually charge my lipo's at 1A, eventhough it takes time to full charge but my lipo's are all in good health. I use a cheap Imax B6 balance charger which is the only charger I have.

[Skipster]

Thanks Mel

I will do this in the future for any suspect batteries.
Plus monitor the voltage.

I have "puffed" six (6) batteries in the last month
all were 2s and
all are Enerland cells that were stored before I got them.

Some made it a couple runs, some puffed after the first charge.



I run at least one of my boats almost everyday
and therefore do a lotof charging.

I never run the same packs twice.
I do not over run them and monitor
motor ESC and Battery temps after every run.

On the average I only put about 1500 mah back in each pack.
No pack has ever exceeded 120 deg F.

The thrifty man spend the most.