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        Near Lipo Disaster

#1 Tigger Feb 09, 2004 12:40 AM

Near Lipo Disaster
 
1 Attachment(s)
Flew indoors today. Brought 5 different airplanes 4 of which sport Lipos. First flight was my Fantastic Models GeeBee. I used an Irate 1100mah 2cell pack on it for the first time. Flew great and did several take-offs and landings. My friend Megawat was there and I noticed he ahad a nice little metal box for his Lipos. I remember thinking to myself " I need to get one of those." Anyway after the GeeBee I flew a Horsefly Hobbies Mini Geebee, a Lightened MSW, Megatech Diversion, and finally my Cox Viper Conversion. Had a great day flying a wide variety of indoor aircraft. :)

After the GYM closed I demonstrated my MSW outdoors for a father and son who were curious about the hobby.

What a great day!

Loaded up my little foam airplanes and headed home. Had to make about 3 trips through the house and back to my shop to put things away. After the final trip I grabbed the GeeBee..when I got in the shop I went to hang it in it's prominant place ion the ceiling. I'm standing on this tall stool looping a string under the belly when I feel this sharp pain in my right index finger. 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!
Guess who owns a metal box now?


I'm not 100% sure as to he exact cause of this but I have a good idea.


I can't say for sure in all the excitement that I even unplugged the pack from my GeeBee. My GeeBee has a little on/off switch which is really "handy":rolleyes: ...Flip the switch and the GWS 4RP stops it's nasty servo chatter. This little switch turns off the receiver but as I recall there is still some current draw happening. I'm thinking that the Irates were being sucked down for about 2hours after that last flight and just happened to be at critcal mass about the time I was hanging the airplane.

Just thought I would share this...

I can assure you all I have a heathier respect for the dangers of these cells.

No lectures please.


tIgGer

#2 Tigger Feb 09, 2004 12:48 AM

Lucky GeeBee
 
1 Attachment(s)
If you look closely you can see where the wire insulatation from the pack melted onto the edge of the batterry compartment. You can also see the switch That I should NEVER use with Lipos.

#3 wacko Feb 09, 2004 01:09 AM

i'm really glad to hear that you've only lost a lipo pack, and nothing else...

#4 mjdoz Feb 09, 2004 02:10 AM

Is this normal behaviour for over discharged cells? I thought from the many threads that you actually had to do something to the cells to cause this to happen such as deform or over charge or shorted.

From your description it sounded as though the leads were hot which suggests that there may have been a short somewhere in the wiring.

Just curious and concerned.

Glad to see that you got them out in time.

Michael

BTW I own 5 packs and think they are great just curious that there maybe another gotcha that I was not aware of.

#5 Tigger Feb 09, 2004 02:36 AM

Cause??
 
1 Attachment(s)
mjdoz,


That was my other theory.

It may well have been a short . Something got so hot so fast that the jst connector slipped right of the end of the of the leads...I'm mean right out of the clips!

I just was thinking about that darn switch and trying to remember whether or not I disconnected the pack. It is my understanding that these packs will balloon and vent when overly discharged.


tIgGeR

#6 747drvr Feb 09, 2004 07:50 AM

As far as I know, cells wiill only do this if they are overcharged , shorted or traumatized . I'm pretty sure that over discharging will not cause what happened. Did you build the pack yourself ? Is there any chance that there might have been a short ?

Marc

#7 Andy W Feb 09, 2004 08:35 AM

Wires don't melt off insulation unless they are shorted.
..a

#8 747drvr Feb 09, 2004 09:51 AM

Andy's right. I should have picked up on that. You had a short of some sort. Check all wiring through your switch , esc and motor. To be on the safe side check for the short in your wiring with a voltmeter set to measure continuity.

Marc

#9 Jiwer Feb 09, 2004 11:06 AM

Having decided to get back into r/c planes and now reading these posts, I'm thoroughly spooked. I've read back as far as I could go through these forums and I still feel as though I have no better understanding then when I started. I've already ordered a plane with a li-poly and feel like I have a stick of dynamite on the way.

#10 mkirsch1 Feb 09, 2004 11:20 AM

LiPolys do not, and never have, spontaneously combusted. There is always some external source of trauma that has caused these failures. In this case, there was definitely a short. What kind of connectors were on this GeeBee?

Simply leaving the battery connected didn't do this. Even though the ESC is still powered when the receiver is off, it's not drawing nearly as much current as it does while the motor is running full throttle.

Overdischarging will not cause the batteries to fail catastrophically. However, overdischarging through a short circuit or through an excessive load is accompanied by excessive current, which causes the battery to heat up, which in turn will cause the battery to fail.

Yes, you have a stick of dynamite on the way, but if you don't light the fuse, it can't hurt you!!! Treat them with all due care and consideration, and pay attention while you're using the batteries, and you'll be fine.

#11 hoppy Feb 09, 2004 11:33 AM

mkirsh1,
reference "However, overdischarging through a short circuit or through an excessive load is accompanied by excessive current, which causes the battery to heat up, which in turn will cause the battery to fail."

Point me to some cases of this happening-
hoppy

#12 luc Feb 09, 2004 11:33 AM

I guess that when you grabbed the plane, you shorted the 2 wires of the cell. That's the only explanation. Leaving a cell being discharged for days will never make it smoke.

#13 hoppy Feb 09, 2004 11:51 AM

tigGer, do you have a guess on how far the battery had been discharged from flying?
hoppy

#14 Fishnut Feb 09, 2004 01:12 PM

Boy that was a close call
 
I'm getting back into the sport because of how far e-flight has come as well. Looks like we still have nitro--it's just in another form LOL. My buddy makes LiPo powered bicycles and oh does he have stories of the development process :eek:.

I'm going to setup a dedicated (fireproof) charging and storing station in the garage (has smoke detector) as well as follow strict procedures of transporting batts in a fireproof box. I plan on keeping the batts out of each plane until flown, then back in the box after I'm done.

Fishnut

#15 unbalanced prop Feb 09, 2004 02:47 PM

Re: Boy that was a close call
 
Quote:

Originally posted by Fishnut I'm going to setup a dedicated (fireproof) charging and storing station in the garage (has smoke detector) as well as follow strict procedures of transporting batts in a fireproof box. I plan on keeping the batts out of each plane until flown, then back in the box after I'm done.
I do all this stuff too and.................... so far so good!!:D


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