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Batteries & Chargers Discuss Li-P, Li-Ion, NiMh, Nicad battery technology and the chargers that juice 'em up!

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Old 02-05-2014, 05:44 PM   #1
maxflyer
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Default What Constitutes a Puffed Lipo?

Every time I go back and review the horror stories about damaged lipos going off, It gives me a renewed sense of fear and dread. I have especially become fearful of storing a good number of the batteries I have been using regularly, which not that long after use have developed a slight puffiness. My battery habits are good except for one area...I am guilty of leaving charged batteries unused for periods of days-to-weeks. If my batteries are indeed puffed, I would suspect this may be the cause.

My problem is that I am not sure how one defines a battery as being swollen, or puffed. These batteries exhibit no real operational issues, and seem to charge and discharge in a normal manner. Is an acceptable battery considered to be one that exhibits absolutely NO swelling at all? Does even a slight bit of puffiness dictate disposal?

The half dozen batteries in question get regular use, and all have developed what I would have to describe as a very slight bit of puffiness. If I squeeze them, they depress perhaps 1/8" to 3/16." They seem to have settled into their current state, and don't appear to show increasing puffiness.

The photo shows a disassembled DBY 3S 30C 1000mah battery, one of two that I fly frequently. Both exhibit the same degree of very slight puffiness. I also show the other battery on it's side. The puffiness is hard to detect, and is most evident by squeezing it. The other one is a Turnigy nano-tech 2s 950mah 25-50C that exhibits the same very slight puffy condition.

Even in the split battery it is hard to see the puffiness, and it's more evidenced by squeezing. A slight bit of the "puffy" look of the middle cell is actually from the force of pulling the cells apart and freeing the adhesive.

So I guess the essential questions are, Does a truly healthy battery remain absolutely flat throughout most of it's life? Is even a slight puff a sign of danger that requires disposal...even though the operational characteristics appear normal?


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Old 02-05-2014, 06:49 PM   #2
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what can i say max? the question is a good one and has been asked many times in the past in the "battery/charger thread section.

skim through them and you'll get many differing opinions on puffed batteries.

being totally spent from shoveling a new 6inch of wet snow i figured I'd type ya my feelings.....if i fly the parkjets/funjet ultra and the packs get warm and puffy,i wait to see how they are after cooling off. the slight puffy feeling goes away and i lock em up with my other lipos. if it remains puffy i keep it separate till confident it won't burst. if after a day it's still puffy i will trash it.i do this because i can afford to buy new bateries as needed and it dosn't break the bank.

this is a picture of my lipos in storage and all are at storage charge levels. none are puff even in the leastand some have outlived theyer usefulness as they droup charge under stress of wot. i only fly zippy batteries from hk and they replaced one that arrived with a bad cell for free and no return of the bad battery. just needed to supply them a picture showing front and back of the battery with a volt meter on it.

max,don't take chances,keep puffed batteries in a fire proof place so your house doesn't go up in flames. hope this helps and read the other threads to get many responses from others here at wattflyer. stu

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Old 02-05-2014, 06:51 PM   #3
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picture didn't come through...here it is.


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narrow is the place to land...wide is the space to crash....choose the narrow way!
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Old 02-05-2014, 06:57 PM   #4
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The best battereies will never feel like there is any air in them at all... until they are worn out and ready to be retired.

Some of the cheaper batteries will have a SMALL amount of puffing as early as the first discharge and still be OK... Never really good for high current applications though.

When any cell is double initial volume, its time to call it done.

Remember that all cells in the pack have been through the same service and were made at essentially the same time. (rare for cells in one pack to be from a different batch) So you can figure that even if only once cell is puffed the others are just as worn out as the worst one.
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Old 02-05-2014, 08:16 PM   #5
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Thanks. I have been flying the batteries in question for probably a year or more. They don't seem to worsen, so I have kept flying them. Starting to wonder if I'm pushing my luck though. Having been at this for only a couple years, I haven't tried more than a couple brands. Most recent purchases are from HURC, where I buy most of my supplies, including the DBY batteries. Gonna try some other options (just ordered a batch from Chinahobbyline), and see if I can make a better effort at keeping them at storage levels when not in use. That can be tough if you like to have a couple batteries ready to go all the time.
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Old 02-06-2014, 04:46 PM   #6
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Found this on Battery University site:

"Gas buildup during charge can cause some Li-polymer in a foil package to swell, and equipment manufacturers must make allowances for expansion."

If this is true than I must believe that the very slight puffing I seem to be experiencing may be within normal parameters for battery health. Especially since I don't notice any unusual characteristics in operation.

Reading about LIPOs again has me thinking I should start storing my batteries outdoors. I currently store them inside my studio/workshop in an open-top ammo can on a concrete floor. This however, would not prevent the escaping gasses from a lit off battery from rendering the space toxic, and I might never get rid of the smell.

Outside storage for me would mean that batteries would cycle from a possible below zero nightime winter temp, to a daytime high of up to the fifties (F). In summertime, daytime temps could commonly reach into the high nineties. Info from the Powerstream website indicates storage temp range of -20 to 25 C. Anyone have experience with this kind of wildly swinging storage temperature environment? Has it resulted in damage to your LIPOs?
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Old 02-12-2014, 08:20 PM   #7
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Do you believe NO LIPOS are ever shipped or stored in frreezing temperatures all around the world ?
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Old 02-12-2014, 08:33 PM   #8
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Not talking about those modes. Talking about a regular cycle of freezing and thawing. Seems that might have some effect on the battery chemistry over time. I would be pleased to find out my concerns are unwarranted. Especially since I realized our stainless steel barbecue with the rolling cover would make for ideal storage.
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Old 02-12-2014, 08:59 PM   #9
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My lipos stayed in my garage. it got down to -18f outside. non insulated garage, definitely reached 0f. We also got over 100f and flew several times.

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Old 02-13-2014, 04:26 PM   #10
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I think this is where storing a battery at 50% is SUPER CRITICAL.

Storing a 100% battery ACCIDENTLY.....in a freezing area for a night, could cause it to become OVERCHARGED. That could then start the Puffing routine. My stretched out logic.

LIPOS hate to give anyone a second chance.
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Old 02-13-2014, 05:17 PM   #11
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Keeping mine in an Ammo can.

Puffing? I equate this to pregnancy. 3 months - Okay 6 months- some concern, keep your eye on it and maybe just use for bench testing. 9-months- sound the alarm , evacuate the building ! I drive a stake through em.

I have witnessed what they can do when they explode. Not a pretty site. A well cared for lipo stored at the proper storage level is perfectly fine in all temps but I do keep mine in the detached garage just in case.
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Old 02-13-2014, 06:53 PM   #12
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A weather proof DOGHOUSE. With a lock on it, would also be fine. FAARRRR enough away from things that burn.
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Old 02-13-2014, 06:57 PM   #13
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Dog house? LOL I know about being in the dog house all too well. UPS man expected today with new Tucano PC-9. Could be a night in the dog house !
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