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Old Mar 14, 2004, 08:55 AM
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Pat Daily's Avatar
United States, VA, Chesterfield
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Another Lipo Fire -- Etech cells

I have been using lipos for over two years and am very careful about setting the charger up correctly (learned that the hard way a year ago), but yesterday I was charging some 3 cell Etech packs--here is the description of what happened from an email I sent to my flying buddies:


One other thing--I found out first hand about Lipoly fires. Was charging my 3 cell packs of Etechs -- the Kokam chargers were set properly (11 volts, 1 Amp). Plugged them in correctly and they were charging fine and watched them for about 20 minutes. Went in the house to answer the phone. Came back out and one had already burned --was sitting on the workbench and there was black **** everywhere--must have exploded. Burned the surface of my workbench and some papers nearby--can't figure why it exploded unles it was unbalanced--although I had only used that pack about 8-10 times. No significant damage -- just a mess to clean up. Learned a cheap lesson--I do have one of those fireproof boxes (safe) that I haven't used yet. You can bet I will in the future. Kinda scary.

Pat Daily
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Old Mar 14, 2004, 09:35 AM
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Walled Lake, MI, USA
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Pat, thank you for sharing this. It's a perfect case of Murphy's Law that it would "wait to happen" until you went to answer the phone! You are obviously a safety-conscious person since you had already bought one of the fire-resistant boxes. I'm very glad that your loss was minimal compared to what it could have been.
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Old Mar 14, 2004, 09:50 AM
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Pat,

Thanks for sharing and glad to hear you were doing this outside. I have to admit I'm aware of the dangers but I've still been charging indoors (basement) and sometimes I go upstairs after starting the charger. Sounds like you did everything right and yet you still had a fire. Things are going to change from this point on for me, I'm going out to get a fireproof safe today...
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Old Mar 14, 2004, 09:58 AM
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Marshfield, Wisconsin, United States
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I use a mini weber grill in my basement. Takes up a bit more room, but.....with the lid ...
A hibachi should be good, and smaller ones probably use space on work bench better.
Thanks for sharing. I'm thinking a lot of these catastrophies represent shorting, internally or otherwise, and even factory made ones are vulnerable.
Take care guy. Hope your wife lets you back in the house. LOL
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Old Mar 14, 2004, 10:04 AM
Nimble with Gimbals
San Diego, CA
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I'm glad you're OK, Pat.

As an aside, what's with the rash of lipoly fires? Have the planets aligned or something?
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Old Mar 14, 2004, 10:23 AM
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One question (anyone), after seeing some of the quote "explosions" on video do you think that would blow the top off of the little Weber grill or a firesafe?
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Old Mar 14, 2004, 10:48 AM
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Sal

I don't know what the explosions are like--I didn't see or hear it--but the contents of the battery were in about 3 foot circle on my work bench and bits of metal and cinders were on the shelves above the bench--so I assume it must have popped. I have been using lipolys for a long time and will continue to use them, but I have not used many 3 cell packs--the possibility of "out of balance" worries me a bit. Not sure if that caused the problem--the pack I was charging had not been run much after the last charge (maybe 5 minutes of engine time) and it was partially charged as the Kokam charger middle light was on too (both the red and yellow lights were on when I plugged it in).

What I learned is that I will not charge any lipolys in a plane (in this instance they were out of the plane anyway)--but I often charge small packs in my microflyer plane--will now take them all out) and I will use my fire safe in the future. I will also start checking all of them with my multimeter before charging--although I can't really check individual cells in commercially made packs. I wish the manufactures would make multicell packs with some soprt of tabs or connectors so you could check individual cells without tearing the pack apart.

I think I was fortunate that I came out to the garage while it was still smoking and that it was a pretty small pack (1200x3) -- A larger cell pack would do more damage. I have a formica top on my work bench and pressed wood base--these probably burn slower or require more heat to ignite than wood. Nevertheless it burned throught the formica where the pack was sitting on the bench.

My wife is a saint and just said "oh that is too bad" when I told her of the fire. I am a lucky man to be married to her.

As I sat and drank some wine, I mulled over the fire and began to wonder about how I store my shoe box full of unused lipoly cells and my other shoe box full of nicads and nimh batteries. I think I will get rid of a lot of them. I used to buy batteries to keep a stock available and therefore have a lot of early Kokams and others that I won't use because of advancements. I think I will now order only what I need for a particular plane and keep track of how many times I charge them.. Not sure when one should discard lipoys after extended use. Comments?

Pat
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Old Mar 14, 2004, 11:14 AM
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Pat,

The Tanic packs do have a super system you may use to check and balance individual cells. Brian has added one JST connector for each cell and very neatly secured these with heat shrink into the pack shape so that they are protected and take up hardly any room. It is also easy to use the taps with Suzanne's lipo balancer circuits while charging as a *s pack and thereby balance with virtually no extra effort at all. On top of that they are made from the same cells as the Irates and can put out in a similar outstanding fashion.

Hugh
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Old Mar 14, 2004, 11:18 AM
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Marshfield, Wisconsin, United States
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Was the pack in question home assembled Pat?
I use a smoke alarm over my workbench and a fire extinguisher inteh basement as well. As to the cover coming off, well, who knows, but Im not about to test it!. The cover vents are released a bit for venting purposes.. Take care
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Old Mar 14, 2004, 12:36 PM
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Hugh

I don't have any tanics just yet. Maybe I will look into them. What is the lipo balancer from Suzanne? I am not familiar with it.

Did you get my pm about the outrunners?

Stuka -- these were commerically made packs.

Pat
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Old Mar 14, 2004, 12:59 PM
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Switzerland, near Zuerich
Joined Mar 2004
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Hi Pat,

I'm new as a member in the R/C groups but during the past year, I read thousends of posts, - everything about foamies , brushless and Lipolys - It's a great opportunity to learn so many good things from others discoveries and also from their failures, - I'm glad your are ok Pat . It's just fascinating what can bring together this web-linked community for everyone share the experience as yours .
For me also to improve my english because my mother tongue is German .

30 Years ago I jumped into the E-Flight with Graupners Moskito very first E-model airplane, but after to many crashed and repair actions of the fragile balsa structure with the heavy NiCad and the terrible low climb power, I gave up this hobby; just one year ago I restarted with the Zagi-400 and get hooked . Therefore my username ELRush.
I crashed my Zagi, upgraded him with brushless motor, crashed again - reinforced with carbon fibers , upgraded with 2packs 3S E-Tech LiPos - great power now. I'll be very happy to go flyghing again when springs come back soon.
But after your report of E-Tech fire I have to change my behavior and my mechanical setup I fixed two 3S E-Tech packs in my Zagi - a way to comfortable but very risky too I recognised now by all the warnings from you guys - Thanks for all.

Mike
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Old Mar 14, 2004, 01:19 PM
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Switzerland, near Zuerich
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Pat,

A LiPo Balancer is a clever tiny electronic circuit which is connected and wired directly into the Lipo pack: during charging and on the end of charging it hold the earliest full cell to 4.2 V by a soft decharging current till all cells have reached this level visible on LED's for each cell .
When pack is charged and disconnected from charge the Balancer will only eat few microamps similar as self discharge current of every Lipo himself .

The circuit is designed / produced by the clever German electronic engineer - ( Lady ? ) Suzanne !

pls search under Suzanne , Lipo balancer as I have done

http://www.rcgroups.com/forums/showt...+lipo+balancer

I also have to modify my 3S2P E-Tech 1200 packs with such a circuit , to sleep i a way better and to see whats going on in my Power Lipo setup.

Mike from Switzerland
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Old Mar 14, 2004, 06:24 PM
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Sal C (re post#6),

The Brinks Home Security box is quite heavy - it has a steel liner and steel exterior with insulation between. The lid is loose-fitting and has no gasket, so the charger wires can run between the box top edge and the lid without pinching. Also, the lid locks down by means of a tang which rotates into a slot in the liner, and the tang could be bent to give additional relief.

The loose fit should give plenty of pressure relief and the flange around the lid would direct combustion products downwardly around the box. The Sentry is also the cheapest of the charging boxes, I think, and it's available at WalMart.

- RD
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Old Mar 14, 2004, 06:37 PM
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Re: Another Lipo Fire -- Etech cells

Quote:
Originally posted by Pat Daily

One other thing--I found out first hand about Lipoly fires. Was charging my 3 cell packs of Etechs -- the Kokam chargers were set properly (11 volts, 1 Amp). Plugged them in correctly and they were charging fine and watched them for about 20 minutes. Went in the house to answer the phone.

Pat Daily [/B]
Two questions for you that may help to find out the cause of fire.

1)How many percent of the battery capacity was remain in the battery before charging.

2)How much time into the charge that it caught fire (20 minutes plus what ever time you were on the phone).

Hope we can learn more from your answers.

Regards,
Charlie
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Old Mar 14, 2004, 07:15 PM
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Ft. Lauderdale, Fl
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firesafe boxes - how much room around them

Very interesting to read about your experiences. I have been using a firesafe box (I think I got it at Target) for a while now. But I am always wondering how much space I should keep around it. Obviously I do not want the surrounding to catch fire if a cell blows up in the box. (I keep the lid lightly open to relief pressure in case of an explosion but I figure that the lid would probably fully open and then the fire would reach a certain circumeference around the box.) Does anyone have any idea how large that circumference might be?
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