flyyy

I have around twenty different lipo packs from like four different mfgs. Due to circumstances beyond my control my building and flying schedule has been delayed. The only thing I have done with these packs is test run engines and periodically balance charge the packs to ensure that they don't drain too low. I know not to store the packs at full charge and none of the packs have been discharged beyond thirty percent charge. Several of the packs are slightly puffed in the middle even the newest packs that I have only charged to keep them about eighty to ninety percent charged. I have goggled around and have found advise from is the middle is hard they are ok to seal them in concrete immediately and call the hazmat crew. What is the real deal. If they are really that damaged without really using the things I don't think I can afford this sport.

The oldest is a couple of years and the newest is a couple of months.
1300 to 2200 mah 25c and 30c. Mostly 2200mah.

fhhuber

"minor" puffing will indicate the pack can no longer safely deliver full rated current or capacity.

Its impossible to predict the real effect. Some minorly puffed packs can give reasonable service for a year or more... some are time bombs waiting to go off.

Its always safer to recommend disposal.

I have gotten away with assigning some slightly puffed packs to low current demand. I've also had to yank one and toss it in a fireproof container when I saw it puffing more under 1C charge rate.

You have to treat any puffed pack as if they could burn with no warning.

I note that the cheaper SkyLiPo packs I bought have resisted any sign of puffing better than the more expensive brands...

You can expect packs to degrade just from age. >3 years you can expect significantly lower current delivery even with the best care and your first warning that you are stressing the pack will usually be puffing.

Sir Crash-A-Lot

For me I will still use slightly puffed packs as long as they remain balanced and the IR of the packs has not changed. Both my chargers can read the IR of the individual cells so I am comfortable with that. If you can't check the IR and the balance of the packs the I would not use them. I think some people toss packs that can still be used but my method works for me.

Pictures would help.

Mike

Sir Crash-A-Lot

As a side note storing my packs in the refrigerator seems to be helping with the life of the batteries as well.

Mike

JetPlaneFlyer

Any 'puffing' indicates that the battery is damaged, how bad the damage is is hard to say. Providing they are stored in a safe place then there is no reason to throw them away right now. Give them a try in the plane when the time comes, if they perform ok and the swelling gets no worse then I'd say they are ok to use but with a little extra caution when it comes to charging.

By the way.. storing at 80-90% charge is too high, that probably explains the damage. You should be storing at about 50% charge give or take... that's about 3.85 volts per cell.
You cont need to routinely 'top-up' lipos when in storage (that's a sure way to kill them) they don't lose charge when stored. A check of voltage every few months is all you should need to do.

JetPlaneFlyer

PS.. what brand are they? I've had bad experience with HobbyKing lipos (specifically Nanotechs) puffing prematurely in the past. I'm currently giving another Nano a try to see if I'd just been unlucky, too early to call as yet as I've only put a few cycles through it.

CHELLIE

A slight amount of puffing is normal for a lipo over time, from Charging and discharging, they produce some gas inside of them, as long as they charge ok, and are balanced and dont smell like Bubble Gum IMHO they are ok to use, Most of my Lipos have a slight puffing to them, and they work Just Fine, Just be very careful with them and store them in a Fire proof Container like a clay pot or Lipo sack, If the lipo starts to get weak or Really Puffed up, then its time to dispose of it.

flyyy

As for the brands Blue Lipo, E Power, Sky Lipo, and Rhino seem to be about equal. The best I remember I read somewhere out there when I first started with electric to store at around 4.12 per cell. Of coarse before I ran across that I thought that the best thing to do when they arrived was to fully charge them because they didn't arrive at full voltage. As for keeping them in a safe place I don't suppose putting them all in the same bucket is a good idea is it?

One other thing . If you only use 80% to keep from damaging the battery say with a 2200mah pack, that would leave 1760mah usable current. It has been my experience that upon running a motor while watching the mah counter, and in recharging and monitoring the mah put back in the battery I don't get that much juice without the voltage of the pack getting too low for comfort. I suspect as a rule that batteries are overrated as for the capacity. U think?

JetPlaneFlyer

There is your problem, that's far too high for long term storage. Aim for 3.75 to 3.9v per cell. Most chargers in storage mode are set to 3.85v

Steve

Panther

I have a 3S 2200 that puffed up a week after I bought it and the LHS didn't want to know. (2nd and last time he has done that to me) However it is now 6 months old, balances perfectly and goes to 99% on charge so I still use it. BUT I am scared of it but just can't afford to just throw it so I take exxtra precautions with it.

solentlife

I have a couple of packs that puffed slightly shortly after they arrived. I use them in low demand situations like sett8ing up gear etc.
A pack that is losing it's high output capability is usually fine for lighter use. ie my EDF packs get hammered and soon start to show signs of shorter runs ... so they get put in my Cessna and other less demanding models ... one pack is near 2 years in that mode ... still delivering.

Nigel

RihhanaNZ

Hobby king lipos are not so efficient; it ruined my device.

Bub Steve

Puff the Magic Lipo, most of mine that are 6 months old or so are puffed a bit,, I 've got some that are abit puffy and 5 years old that still charge and fly fine, bubsteve

r_kopka

I am/was at one with that. But lately I had a not so funny experience.

TREX700 12s5000 (6s+6s) max.current about 80A

I had an older pack with one battery slightly puffed. I just wanted to try it a last time and didn't expect much. But the pack was good. Full flight time, nearly full power. Discharged about 60% and landed. Carried it to the bench and then I heard a slight fizzling. Got the cables disconnected and the canopy down. The one battery was VERY thick, outer tube open, one cell open. I just got it out and put it away. You could see some liquid boiling(?) inside. Some time later a second cell broke open - no fire.

The airstream during flight must have cooled it until landing. The voltages of the remaining cells are still OK, as were all before the flight. So just measuring the voltages wouldn't have helped. Maybe a charger which shows inner resistance of each cell. But the IR will always change, i.e. get worse over time.
If you have some other usage for such cells (nothing flying, especially no heli) it would be safer.

RK

kyleservicetech

Yup
That's why I use the 35% heavier 2300 Mah A123 cells. They don't seem to wear out, even after 5 years flying with them. They don't care if they are stored at full charge, half charged, just don't discharge them below 2.5 Volts per cell. They can be safely charged at 10 Amps without issue, and don't get much more than warm after a flight.

They have metal jackets, and their insides is solid copper sheet with the chemicals coating the copper sheet. (Don't ask!)

But, with these A123 batteries, you pretty much have to buy the battery, then try to find an airplane that can carry them.

All of these models are A123 powered.

Great Planes Giant Big Stick Electric Conversion
http://www.wattflyer.com/forums/showthread.php?t=65052

Giant Scale Cessna Model
http://www.wattflyer.com/forums/showthread.php?t=66414

Thread on 70 size glow engine conversion to electric
http://www.wattflyer.com/forums/showthread.php?t=45222

Hacker 6S2P A123 powered Models
http://www.wattflyer.com/forums/showthread.php?t=44686

Hangar 9 Kantana Model
http://www.wattflyer.com/forums/showthread.php?t=68844

Hanger 9 Twist 40 Model
http://www.wattflyer.com/forums/showthread.php?t=70548

Panther

To kyleservicetech. I didn't know any such thing existed. Obviously not LiPo? Can you provide a link so I can have a sticky at them. Thanks mate.

kyleservicetech

Certainly
I buy mine through www.voltmanbatteries.com here in the USA. Good company, and I've purchased over 100 cells from them over the past few years. But, they only ship to the USA.

Can't vouch for this place, but they ship world wide.
http://www.ebay.com/itm/8-A123-2300m...item2ec825dbd5

Note that these cells MUST have welded solder tabs installed. Soldering directly to the cell case is very difficult, and requires a high powered, temperature regulated 100 watt soldering iron (NOT soldering gun), along with special soldering flux.

We had a case in the USA last year, where a modeler used two of these cells for receiver power. An aileron servo dead shorted out. The A123 battery responded by melting the insulation completely off the aileron servo lead wires, resulting in bare wires. You don't want to short these things out!

Most newer LiPo chargers with balancing capabilities can also charge these A123 cells plus their very similar LiFe chemistry cells. Those I've seen spell out A123 directly in the programming guide. If your receiver and servos can handle a 5 cell Nickel Hydride receiver battery, the A123 and LiFe are direct drop in units. A lot of guys in my club are going to these type cells for their giant scale models. They work, and work very well. The A123 cells will hold 95% of their charge during a storage period of a half year. Not bad.

njg

Great thread by the way. very informative.

I have a PZ 1300 3 cell pack that is not puffed but feels a little more "spongy" in when I squeeze it compared to another PZ 1300 3 cell pack I bought at the same time.
Size wise they look and measure the same. Also, each individual cell are the same for both packs (My charger shows individual cell voltage as it's charging)

Is that what you mean by puffiness? or is this normal?
Would discharging/cycling help? My charger also allows for discharge cycles.
Also, I always charge at 1C (meaning if the pack is a 1300, I charge at 1300, if a pack is 2000, I charge at 2000. Is this correct or am I screwing the pack up by doing this?

Thanks for any help you can give
n

quorneng

njg
A LiPo does not have any memory problems so there is no benefit from cycling.
All you do is use up one of its available charge/discharge cycles.
Charging at 1C is correct & safe providing the balance port is connected so the charger will stop the full rate charge once any cell reaches its 'full' voltage. It will then continue to slowly charge the remaining cells through the balance leads until they are all at the same 'full' voltage.

A LiPo is not self regulating when full so it continues to accept a charge and quickly get terminally damaged just as it does if the voltage drops too low.

Slight spongy is probably ok but it may mean a cell is getting weak. Keep a careful eye on it. If it does not change over the next few flights then its fine.
With a LiPo puffs up the shrink wrap feels like a balloon. It will happen quite quickly and is the result of the electrolyte breaking down into a gas due to a cell itself degrading and getting locally too hot during a high discharge current.

When it puffs up it is no longer safe to use the battery at either its full rated current or capacity and should be disposed of.

Panther

A good charger will have an internal resistance checker built in. This can show if 1 cell or more are a problem. I haven't had a lot of experience with mine yet but I have 1 puffy battery so I did a internal resistance check on it and a good one to compare.
The good (new) one had a resistance of .001 ohms on all cells. The puffy one had a resistance of .03 on cell 1, .02 on cell 2 and .01 on cell 3. I think cell 1 is the positive end one.
Maybe someone has more experience with this and can enlighten me.
Obviously when you discharge a cell with high resistance heat is going to build up and may cause problems.
Anyone with experience care to comment when a cell should be retired (at what resistance)
My 'puffy' battery still charges up perfectly (or so it seems)

quorneng

Panther
The slightly raised internal resistance on one cell is unlikely to effect the ability to accept full charge but as you suggest that cell (or parts of it) will get hotter causing further degradation and still higher resistance.
With this sort of 'exponential' failure mechanism the point at which a battery becomes too badly effected to be no longer safe to use can arrive with little warning.

Panther

Thank you quorneng. I think I will delegate that battery as power for my FPV screen now. I had been using it in a glider with only short power bursts and short runs.

njg

Thanks Quorneng I appreciate your quick response.
Very helpful.
njg

r_kopka

I have a very puffed battery at my working place for years now for quick tests. FPV is another usage for low current. Others are e.g. lighting systems.
From a current viewpoint also RX supply would be OK, but we generally prefer very safe systems for this usage.
Big cells could be used to power chargers if no other powersource is available. I've seen that several times now.

RK

fhhuber

I generally take the badly puffed batteries out to the flying sit... and in the middle of the runway I stick a screwdriver through them.

Hard to start a fire in the middle of a 50 X 300 ft paved runway.