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Old Aug 04, 2003, 05:57 PM
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Colonial Heights, Virginia, USA
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sorry to hear of your property loss of car and model equipment....Could probably happen with any cell chemistry under the right type damage conditions.... Even when all is working properly, sometimes less than 1/16 of an inch of plastic thickness is all that keeps accidents like this even in homes from going up in flames ........... kw
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Old Aug 04, 2003, 06:07 PM
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Walled Lake, MI, USA
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If weight is drastically increased in the name of safety, people will simply remove the "dead weight" as they did (and still are) when stripping Li-ion cells out of their cell phone and computer packs. Any safety solution for e-flight needs to be properly engineered or it will be eliminated by users. It will end up costing everyone more money, though.

You can protect some of the people from themselves some of the time, and you can protect some of the people from themselves all of the time. But you can't protect all of the people from themselves all of the time.
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Old Aug 04, 2003, 06:14 PM
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AMA Insurance?

Ken, are you a member of the AMA? I don't know if their insurance would apply, buy you might want to check. After all it was damage caused by a RC aircraft. Might get lucky and have your deductable covered.

Brad
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Old Aug 04, 2003, 08:32 PM
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Sorry for your loss...

and thanks for the warning..

I hang the lipos at the bottom of my Mini Speedwing and it is subjected to landing impact.. Guess I will have to be much more careful about watching them if I've crashed..
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Old Aug 04, 2003, 08:51 PM
wild in the park?
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McDonough, GA
Joined Mar 2003
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wow that's awful!
glad no one was hurt.
Bil
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Old Aug 04, 2003, 11:41 PM
pfm
Patrick Mahoney
Fort Collins, CO
Joined Sep 2002
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Thanks very much for the warning. I am thrilled with the way my Thunder Power pack flies my planes, but my level of paranoia about them increases every time that I see a thread like this. And I have seen several.

I definitely appreciate the warning and I hope things go well replacing the car and dealing with the insurance company.
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Old Aug 05, 2003, 01:02 AM
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San Jose, CA
Joined Sep 2001
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safety circuits won't help. if the cell smashes in a wreck, so will the protection circuit.

casing the battery? bad. you now have a great source of not only weight, but shrapnel in the event of a vent. now, sausaging a li-poly is bad, but I'd rather a mylar coating popping than aluminum shards being blown apart.

consumer li-ion/li-poly implementations are meant for consumer use. I can almost guarantee a ballasted cellphone dropped from 250 feet up could cause a similar issue with the li-polymer cell is contains.

the best advice? don't crash. batteries are meant for supplying power, as many can attest to, any type can be damaged in an extreme force and cause fires, explosions, shrapnel, etc. if you do crash, be very careful and watch the battery. if you're paranoid, safely dispose of it once it is known to be 'stable' and buy another pack. or, be careful, and watch it as it charges. we are not 'consumer electronics' users here, we have to watch out for ourselves.
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Old Aug 05, 2003, 01:24 AM
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Ken: As someone that has lost everthing to a fire "I understand what your going through" And like everyone else has pointed out "your very lucky that not lives were lost" Where abouts did this happen at (I to live in Portland OR)

Mike
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Old Aug 05, 2003, 02:52 AM
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Virginia Beach, VA
Joined Jul 2003
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This post got my attention. I am a new user of lipos and probably have broken some of the more common sense rules about handling lipos safely. I can tell you after seeing what can happen with an accident like Ken's I will have to change the way I think about these batteries. If my wife ever found out about how dangerous these things can be she would never let me keep them in the house. I hope we can collectively come up with some practical saftey handling proceedures cause lots of modelers are starting to catch on to the benifits lipos.

Ken you have one lucky dog there.
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Old Aug 05, 2003, 04:04 AM
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Let's not go overboard...

First, I too would like to express sorrow for what happened to Ken. And I agree he's lucky as well (no fatalities), but this is the kind of thing that could happen to any one using any type of battery technology. It's just as applicable to glow fliers using a Rx battery.

I've been flying for over 25 years. About 20 has been using one form or another of electric propulsion. If you crash, you need to immediately:

1) Remove the battery (Rx batteries too if used) and check it for damage.

2) Put the battery in a safe place. Not your car. Not in a bunch of flamable material (weeds, grass, etc.).

3) Spend some time with it to verify that it is OK before leaving it alone.

The same basic idea concerns safety checks each flying season, while charging, etc.. Don't charge in your car. Don't charge unattended. Be safety aware. If you don't take the basic precautions to be safe, then it's likely you'll be an accident victim too.

Or is it an accident? - Meaning, if you don't take precautiuons, then who is to blame/be responsible for it?

Art

PS: Many may think it foolish, but I carry a small halon extinguisher in my flight kit in case of fire. Glow or electrical.
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Old Aug 05, 2003, 05:06 AM
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Whilst browsing the Kokam website I found this page on safety testing.

http://www.kokam.com/english/biz/safety.html

also this on precautions:

http://www.kokam.com/english/biz/precaution.html

Clearly, Kokam (and no doubt other lipo manufacturers) takes it's safety responsibilities towards its customers seriously.

However, R/C-ers probably need to work out a safety code of practice appropriate to the way they install and operate lipos.

Would it be an idea for the BMFA, AMA and all other countries national modelling bodies' safety committees to get onto this quickly, and publish guidelines approved by manufacturers?

Perhaps they are already in the process of so.

FWIW

Gordon
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Old Aug 05, 2003, 07:26 AM
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As another poster pointed out, there is probably little that the cell manufactures can do to mitigate catastrophic cell failure after a crash.

- the "soft" cell design will puff up rather than explode like a "hard" cell Lion.

- fire yes possibly, still better than explode, then fire.

- a protection circuit will very probably be of no use if the cell itself is physically damaged.

So it seems what is possible and desired is an educational process on how to safely use and care for Lipo batteries. One thing you can count on is that if there are increasing claims to insurance companies (including the AMA), that they will get involved. At worst with denial or waiver of benefits for Lipo use, at best with a process similar to a "jet turbine waiver".

Education is the key.


Brad
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Old Aug 05, 2003, 07:27 AM
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Walled Lake, MI, USA
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The single most useful piece of advice about Li-poly cells is to always assume that there is a remote possibility that they can develop an internal problem, vent and produce enough heat to ignite nearby combustible materials, such as car seat upholstery, carpeting, curtains, aircraft foam, etc. If you never leave them alone and unattended while in close proximity to combustible materials, it is virtually impossible for them to cause a problem beyond destroying themselves. For instance, if you always keep them on a concrete floor in the basement several feet away from any combustible materials, the worse they can do is put scorch marks on your concrete.

The most common two reported instances when Li-poly cells vent and generate excessive heat are when being charged improperly, either due to a charger problem or charger operator error, and after a crash when they may have internal damage that is not immediately evident. Thus, these are the times when you should be most careful about isolating the cells from anything that could catch fire.

By always assuming that there is a possibility that the cells might fail at any time, you will get in the habit of always storing them in a safe place. If you always treat them with the respect they deserve, there's no reason to fear Li-poly cells.
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Old Aug 05, 2003, 08:15 AM
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Battery safety

The responses and guidance given by all of you is generally good. Some time ago, I made a post on this subject and exhorted you to treat all the cell chemistries as if you had a small stick of dynamite in your hand. I seriously doubt that you would lay a potentially smoldering stick of dynamite in your car.

There are a few tips that can be added:
1. Keith Shaw tells me he examines his packs periodically and discards any cell that has a dent in the very thin metal case. That is because any such distortion has also deformed the cell structure inside.
2. Li Pos are no more and no less hostile than other cell chemistries. They do have the highest energy density, thus the potential is higher if and when ignited.
3. If in doubt,drop the pack or cell that is suspect into a container of salt water. That will stabilize it completely.
4. Never put a pack of any kind into a car or other flammable container under conditions in which the pack has been subjected to a crash until you know it is OK. Come to think of it, wonder why Lexus or any other car manufacturer would use materials in their car that would ignite and burn so furiously that the car is destroyed. And just think what that would do to your body if the car's lead acid battery that generates hydrogen gas when overcharged or overloaded should ignite in a crash (and there are more of them than with model airplanes!) I wondered about this when I saw a brand new Jaguar burning furiously along the highway recently.
5. When you charge any battery pack, do so in a known safe area. The best and the simplest place (unless in actual use) is your fireplace if you have one. Lined with fire brick with a chimney that vents any smelly electrical smoke, and designed to contain flames- what could be better? You can be blase about this because, like me, you have gotten away with it for 40 years to leave the pack in hte flammable airplane, never take it out and check it, and just plug in and charge. In due time, you are likely to have a problem. Safety comes from discipline. That is why the Marine or Army DI hammers so hard on weapon safety.
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Old Aug 05, 2003, 09:33 AM
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hoppy's Avatar
Space Coast
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Here are the safety precautions from Ultralife LiPo batteries.

http://www.ulbi.com/whitepapers/UBI-...recautions.pdf and
Panasonic -
http://www.actec.dk/polymer.pdf

hoppy
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