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Old Feb 10, 2004, 05:19 PM
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I have crashed and burned with a lot of factory LiPo packs and haven't had a problem. I think the home built versions have a problem because it's tough with the small tabs and criss crossing the wires. Also, manufatures use shrink wrap to hold all of the batteries together which keeps everything from moving around.

LiPo fires can be serious business. I had a fire over a year ago in my house that caused 30k worth of damage. It was caused by a digital charger that miss-read the number of cells putting too much voltage to the batteries. At the time I was unaware of the hazards of LiPo's and charged the batteries inside a foam plane leaving the house for an hour, ouch. So, everything went wrong that possibly could. Thank god we had a monitored house alarm.

It wasn't a fun thing to go through and we even had to move out of the house for 3 weeks. There wasn't any structural damage, but the stink and mess the fire caused was unbelievable.

At the time there wasn't much printed or stated about the do's and don'ts of LiPo charging. Since then the manufactures appear to have been better about warning people.

I'm not trying to rehash old war stories, just warn people so it doesn't happen to them.
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Old Feb 10, 2004, 07:29 PM
Does anyone hear a cat?
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whew, that's a sobering picture... i think i'm gonna go check my packs right now just to be sure they aren't about to burn my house down...
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Old Feb 10, 2004, 07:51 PM
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Quote{{{(I flip over the plane and see the insulation on the lead wire is gone...quickly I grab the now hissing pack and toss it outside my shop....within seconds it's ballooned and and on fire!...I kicked it a little further from my shop and watch as it smokes, smolders, and hisses. Al little nasty smell in the shop but I escaped unscathed. I'm truely lucky this didn't happen in the GYM, unattended car, House, Garage, or unattended shop!)))To all the guys that say fires only start wene over charging.
And to the distributers Lawsuites are coming sure as spring.
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Old Feb 17, 2004, 09:26 PM
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Guess I'll add my experience here so others may benefit.

I have read all the warnings about LiPo's and take a due amount of care in handling and storing them. I do sometimes leave them unattended while charging. If I didn't I'd never get to fly, because I can't spend several hours a day in my shop sometimes. I usually keep an eye on NEW packs pretty closely the first couple of charges.

Today, I was planning on some indoor flying, so I got up and started an E-tec 2x700 on my Triton. I have a charging station set up in my basement shop that has a small power supply with a cooling fan housed in a plastic box. The cooling fan doubles to cool the packs if they get a little warm while charging.

Went upstairs, took a shower and was getting dressed when I heard the Triton's alarm, but instead of the usual few beeps, it kept beeping. About that time I smelled the smoke. I hurried downstairs, but it was already over with. There were the extremely charred remains of my pack sitting on the melted top of my power supply. Black soot was everywhere and little ember ashes were spread far and wide. I can only imagine the intensity of the fire that took place, aggravated by the steady flow of air provided by the fan.

All in all, I got off pretty easy on the deal. My JR tx charger got charred pretty good, but I think I can salvage the wart part and just splice in new cords. The cord to the power supply was charred, but it didn't get through the insulation. I cut away the melted part of the case, and the power supply still works. My charging lead from the Triton and the charger itself were fine. Best of all, it did'nt spread and burn down my house.

What was the cause? When I later went to charge my remaining pack (still gotta fly) I noted that I had chosen a preset for a 3-cell pack for my 2-cell. IE, charging was set to 10.8 volts. What will I do differently?

Going to re-do my presets and number the packs accordingly.
Going to order the temp sensor for the Triton
Going to refine the surface for charging the packs (fireproof)
Adding a fire extinguisher and smoke alarm to the shop

Karl
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Old Feb 17, 2004, 09:37 PM
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Karl, it's awfully hard to admit making a mistake in public. So I really appreciate you sharing in such detail what went wrong. If others learn from your mistakes, then it will not only have been a fairly cheap lesson for you, but for others, as well. Thanks goodness it was a fairly cheap lesson this time, as the potential for a far worse outcome was clearly there.
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Old Feb 17, 2004, 10:08 PM
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I have a slow charger for lipo batteries which I built from an rcm 2/2003 article. I have been using it in my garage and in the house while Im there. But I want to put it and the batteries outside to charge overnight in a metal trash can.
Unfortunately at this time of year the temp is between 10 and 20 deg F. Is this a problem to get full charge or to damage the lipos?
Thanks for your help.
Tom
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Old Feb 18, 2004, 06:38 AM
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A Repeated Observation:

If LiPos packs are constructed for charging their cells in parallel, it's impossible to set the charger wrong - it's always at 4.2 volts.

- RD
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Old Feb 18, 2004, 08:05 AM
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And JJ Hong in another thread said that Kokam would add a single-cell, 4.2V Safety Guard to the lineup. If you always charge single or parallel cells through a 4.2V Safety Guard, you would be safe even if the charger or DC power supply were set to a higher voltage.
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Old Feb 18, 2004, 11:12 AM
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Quote:
Originally posted by RD Blakeslee
If LiPos packs are constructed for charging their cells in parallel, it's impossible to set the charger wrong - it's always at 4.2 volts.

- RD
Well is anything really impossible?

The problem with this statement which has been proven over an over is that given more than one setting choice combined with a LAPSE OF ATTENTION nothing is impossible.

I do think the safety guard has some merit if people chose to use them. Somehow I doubt that the people that really need them will use them.
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Old Feb 18, 2004, 06:32 PM
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Quote:
Originally posted by headless
s'why i only buy premade packs; i don't trust my meager soldering abilities with my life or my house...or my car... or my family's lives...

makes the 15$ it costs for a pack seem pretty cheap.
I consider myself an average in soldering skill, but both of the packs I made for my MM Cessna last spring balloned on me. They were the Kokam 560 cells out around that time. Since then I buy premade packs, just so I know they are done by someone who knows what they are doing. I never liked those tabs...just too close together.

I charge mine in a Pyrex baking dish and never store or transport them in the model. I am also on the lookout for a fire safe too. You never can be too carefull, but these stories should not keep people from using these wonderfull batteries just think about what you are doing before you do it.
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Old Feb 19, 2004, 04:16 PM
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charge,store,transport in one box

Here is a link to the set up I have been using to charge, store, and transport Lipo's.

I have added color codes on the ends of each charger connector to identify them with a particular type of pack. Other than that, it has been pretty hard to mess up.

http://www.rcgroups.com/forums/showt...hreadid=199854
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Old Feb 23, 2004, 09:35 PM
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THANKS FOR YOUR RESPONSE!
Tom
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Old Feb 23, 2004, 10:41 PM
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Your incident

I shan't speak for Irate; but a Li Po does not ignite from overdischarge. It sits there quietly and bleeds to death! Experience has shown almost as surely as fingerprints, what has a happened. Overcharge (i.e., overvoltage during charge) creates a "silver sausage" that, if permitted to go too loong can cause venting with flames. Overdischarge or overload, creates the "silver prune" that shows a deformed and wrinkled envelope. From appearance, I am guessing that the wiring shorted in some way and burned into the envelope to short the cell. When you short a cell internally as I once did with a T-pin, the release of energy is instant and very high. Anything in the way is gonna get hot. If the wire , glowing red, melted through the Li Po envelope and shorted the plates, it would create what you show. If in doubt, remove the pack from the plane and secure when you finish flying. Inspect wiring each session.

TIP: Demonstrate the following to yourself. Take a piece of scrap sheet rock, light up your propane torch and direct it to one side of the sheet. Touch the back of the sheet and you will find it is warm at most. Sheet rock is an excellent insulator. Cut out what you need to CA together a box and you have a dirt cheap safe. If you don't like ugly, buy a cheap tool box and line it with sheet rock.
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Old Feb 24, 2004, 08:03 AM
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Re: Your incident

Quote:
Originally posted by electroman
IOverdischarge or overload, creates the "silver prune" that shows a deformed and wrinkled envelope.
Now there's a description that's not likely to be forgotten. Good one, Electroman.
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Old Mar 12, 2004, 08:48 AM
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Echt, Netherlands
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http://www.modellflugjugend.de/archiv/user/lipo2.jpg

Happend in Germany. Savety first "always"

http://www.modellflugjugend.de/archiv/user/lipo1.jpg
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