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Old Sep 28, 2003, 07:58 PM
MKH
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Ohio
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Gary, thanks for stressing the point so well. I admire your willingness to take responsibility for this, but don't beat yourself up over it. It sounds like you did everything right, except to be there to see it go wrong. I've been wondering about one of these big multiple series, multiple parallel packs burning up, but didn't want to ask aloud. With that much potential energy for flames, my real concern was for a large 1/4 scale job or large aerobatic plane augering in and damaging that big pack of lipo cells. This was a different kind of accident, but I think it answered my questions anyway. Thanks for sharing the details.
Marcus
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Old Sep 28, 2003, 07:59 PM
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San Diego, CA, USA
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Quote:
I'll never really know what happened,..if it was charger, battery pack,..etc
Lithion Ion (LiPo's are a subset) cells catch fire while charging when a cell goes over the safe voltage period!

The chargers that we currently have available are not able to check the voltage on each cell like the chargers in laptops do. There were laptop fires until the industry adopted safe chargers.

The charger/battery pack system is at fault in this situation, not one or the other.

Until we get better chargers than we currently have for hobby use there will continue to be fires. I believe that the chargers need to monitor the voltage of each individual cell during charge and shut down when any one cell reaches 4.2 volts.

I know of one rc flyer who had a fire while he was charging his large pack in the bedroom, while asleep at night. He woke up to a room full of smoke, the battery was exploding all over the place. The wall, carpet and many other things in the room were burned. Had he not awoken when he did we would have a sad statistic.

Gary was absolutely "WRIGHT" when he said:

Quote:
... Something we do know is that there is the POTENTIAL for real danger. ...
Chuck
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Old Sep 28, 2003, 08:59 PM
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I can think of dozens of things I'm around every day that could hurt someone if proper care is not taken. Thanks to these discussions, we have a pretty good idea of the care that must be taken to avoid lithium cell failures escalating into more serious problems. Those who do not take all reasonable precautions and suffer a cell failure that leads to collateral damage are very courageous to admit to their mistakes here and share with us the results. These are the experiences that remind us all to be more careful.

The problem here is not lithium cell failure. The problem is in not taking proper precautions to mitigate against collateral damage from lithium cell failure. Those who understand the risks and take proper precautions should face no more risk from dealing with lithium cells than with any number of other potentially harmful situations we deal with on a daily basis.
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Old Sep 28, 2003, 09:24 PM
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1st, let me say to Gary how VERY SORRY I am for your loss. Your Funtana was absolutely my favorite of all your airplanes and I know you had a lot of work and a lot of $$ tied up in it.
2nd, how thankful I am that only property damage occurred.

This is certainly a "wake up call" that hits close to home. I hope all of us will redouble our resolve to take extra care when handling Li-Po's .....charging and otherwise. I certainly won't be charging any of my Li-Po's unattended (even for a few minutes) in the future.
Ed
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Old Sep 28, 2003, 09:26 PM
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Quote:
The problem here is not lithium cell failure. The problem is in not taking proper precautions to mitigate against collateral damage from lithium cell failure. Those who understand the risks and take proper precautions should face no more risk from dealing with lithium cells than with any number of other potentially harmful situations we deal with on a daily basis.
You are correct, however, there are many people that do not read these threads and are not aware of how to take the proper precautions.

Since this technology is new, most of the people who are using Lithium cells are not really aware of the risks like we are with the other things that are dangerous that we use every day and have been for years.

Chuck
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Old Sep 28, 2003, 09:36 PM
GBZealous
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Western Mass
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So Laptops sovled the multi cell imbalance by monitoring and charging each cell individually?
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Old Sep 28, 2003, 09:56 PM
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Lipolys

Chuck, while what you say is true this forum only reaches a small section of the electric RC Airplane pilots world wide. One thing to remember is that those people might not try these new batteries without first learning of them on this forum or others like it. I for one will spread the word among my friends and I will never leave a Lipoly pack unattended while charging. Also I believe a very small part of the electric community is even using this technology due to price and availability. I do believe that more safeguards could and probably will be built into future batteries and chargers. Until then if we choose to make use of this advanced technology its clear that we all need to be aware of what we are doing at all times and willing to put in the extra time and effort needed to make sure we use the technology safely.

Gary's loss, while a terriable thing to happen could have been much worse and I know that I for one will be extra diligent around any Lipo packs I might use in the future.
JMHO
Joe
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Old Sep 28, 2003, 10:52 PM
Scott Black, Montreal
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montreal quebec Canada
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Quote:
Originally posted by rcelectfly

I know of one rc flyer who had a fire while he was charging his large pack in the bedroom, while asleep at night. He woke up to a room full of smoke, the battery was exploding all over the place. The wall, carpet and many other things in the room were burned. Had he not awoken when he did we would have a sad statistic.
Now that has to be one of the most bone headed moves I have heard in a while. I thought I was dumb for trying to fly my Sabre with the motor running backwards, but this takes the cake!

So until new fancy technology comes out, we have to charge outside of the airplane, in a safe place, and if we don't want to stand over the charger for an hr we need to put it and the pack on some sort of surface that won't burn - like a patio stone or a firebrick and obviously away from 5 gal. cans of gas, cases of dynamite and the new Porche.

I certainly don't want to stand around for an hr at the field watching a charger, so perhaps that is a way around it - make it so that if there is a freak fire it is managed.

There is risk with this stuff at this point in its development, but we can manage that risk with a few extra precautions.

But going to sleep with a charger on???? After all we've been hearing? Wow. A certainly a Darwin nominie!

sb
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Old Sep 29, 2003, 12:26 AM
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Quote:
Originally posted by sblack
I certainly don't want to stand around for an hr at the field watching a charger, so perhaps that is a way around it - make it so that if there is a freak fire it is managed.
The most fire safe place in my house is the fireplace, which I've converted to a charging station. IMHO, it has the necessary precautions; heat and flame resistant, smoke exhaust, mesh and glass spark arresters and nothing flammable nearby.

Daren
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Old Sep 29, 2003, 02:08 AM
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Quote:
Also I believe a very small part of the electric community is even using this technology due to price and availability
Not so here in San Diego. Many people are using them and they are available at the local hobby shops right over the counter. They can be expensive but people seem willing to pay the price.

Chuck
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Old Sep 29, 2003, 02:28 AM
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Quote:
Now that has to be one of the most bone headed moves I have heard in a while.
sblack,

Yes, we all do stupid things every now and then.

Chuck
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Old Sep 29, 2003, 04:41 AM
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First let me say that iŽm real sorry for your loss Gary. What bothers me is the question if we just wittnessed the natural end of a LiPo Pack without any kind of cell balancing electronic built in.

Personally iŽm holding back from purchasing packs because iŽm waiting for this kind of packs, with built in safety circuits.

Right now our chargers will take our word for the voltage of the pack, when one or more cells get imbalanced theŽll puff and will cause fire finally when this happens unnoticed.
What happens when a pack reaches end of its life? I guess not all cells will die simultaneously, so one or more cells WILL start to imbalance.
Next time trying to load...youŽll get the picture.

Currently only way to hopefully avoid this is to check voltage of each cell from time to time manually, just recycling till the end of life seems dangerous.

Gary, do you know how old the pack was, how much cycles it did?

Best regards,
Thomas
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Old Sep 29, 2003, 11:15 AM
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Melbourne, FL
Joined Feb 2002
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I can't believe how much press this has gotten in such a short time. This is Mike Weiss, the friend that got to the fire first. I wanted to comment on the fire extinguisher discussion. My fire extinguisher is perfectly suited for kerosine fires, but did almost nothing to put out the Li-Poly's. I definitely plan to keep a more appropriate extinguisher handy in the future!

As has been stated in earlier posts, different extinguishers are used for different purposes. Make sure you have the right one for the potential application at hand.

It's a real shame that the charger burned with the airplane. I would really like to find the cause of the fire was (especially since my Shultze charger is in the mail!). I have a new respect for this technology. From now on I'll be charging in the middle of my garage under supervision! I can't even describe the feeling of walking around the corner and seeing Gary's airplane in flames (the flames were so hot that they melted the carpet in the trailer!).

I can't imagine not using this new technology, but the what if's definitely go through my mind often. I think we can enjoy the benifits of this new technolgy, we're just need to stay diligent with our safety considerations.
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Old Sep 29, 2003, 11:49 AM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
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In terms of fire extinguishers-

It sounds like a low tech approach might actually work quite well here. Part of the problem with any fire extinguisher under pressure is that it can blow flammable materials around. (We actually got a bit of practice putting out fires- the fire department decided that as chemists- we were likely to see some nasty ones, so a little practice was in order.)

Might I recommend a bucket of sand? This has several advantages- it's non toxic- which most of the dry chemical ones aren't.-
it's cheap-
it doesn't operate under pressure, so it will minimize spraying burning battery goo everywhere.
it will work very well on nearly any kind of fire-it's what we kept on lab benches. Might be problematic for large volumes of kerosene though- works better on compact fires which it sounds like these li-battery fires are.

Make sure you have enough sand, and a shovel if you're flying larger stuff so you don't have to get too close.

In terms of the fire extinguisher that didn't work- I'm taking a guess that it was a CO2 extinguisher- that's what's often reommended for flammable liquids. CO2 extinguishers can be very hazardous on certain metal fires (I don't think li is one of them, but I still don't think naked li metal is what's burning- doesn't really matter though) but you must get the extinguisher at the base of the flames. If you aim above- it does no good- these fires are too hot, and blow the CO2 away allowing fresh O2 to keep the reaction going. Hence- sand- doesn't blow off- can be applied liberally, and as long as it's on top of the fire (not off on the side) it'll do some good.

Sam
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Old Sep 29, 2003, 12:20 PM
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Laurel, Maryland USA
Joined Aug 2000
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Sam, I think your exactly right. The bucket of sand is probably the best idea. It is very effective and it is cheap. If we recommend an extinguisher that costs more than $50.00 I doubt many will actually buy it. The sand is literally "dirt" cheap. I know that's what I'll be using in the future.

As a side note: A simple precaution to solve the cell imbalance problem is to have taps on each cell. Every LiPo pack I build has small very thin gauge wire attached to specific points in the pack. These wires have very small insulated connectors on the end that allows me to charge each cell individually. Every month or so I charge each cell to 4.2 volts exactly regaurdless of what its voltage is. I think this method will solve alot of problems. That's not to say this fire was due to imbalance, it may not have been. But it certainly appears that way.

-Jim
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