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        Be careful with LiPo packs

#1 Joe Bennett Mar 08, 2004 10:51 AM

Be careful with LiPo packs
 
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Group,

One of our group had a Slow Stick go in this morning. Fortunately our flying field is fairly large, and little damage was done when the LiPo pack went off. We have since sealed off the impact area, and should be able to use it again in about 10,000 years. ;)

Joe

#2 SlowRider Mar 08, 2004 10:58 AM

LOL :D ! Does this mean the site qualifies for Superfund status?


Andy

#3 Joe Bennett Mar 08, 2004 11:20 AM

It might at that....:)

In all seriousness though, both myself and my next door neigbor have both had LiPo packs go off on us. Both in our garages, and fortunately the damage was confined to a small area on our work benches. Not sure why Scotts went (still trying to figure it out), but I know that mine was my own stupidity. I had just finished charging a 3 cell pack, and put a 2 cell pack on without remembering to switch the charger to 2 cells again (it was a Kokam 402 charger, and MY fault, not chargers). Within 45 minutes, the pack decided it had had enough of my abuse, and burst in a nice ball of flamming debre. I was very lucky that nothing else caught fire, as I was in the house at the time. Wife came into computer room and asked, "Joe, is there supposed to be alot of smoke in the garage?". I went out, and sure enough, garage was full of smoke. Pack splattered in about a 6' radius, but only the immediate area caught fire, and went out quickly. When pack went, it took out itself (a 2s1p pack), two full size servos, a pack of heat shrink tubing (used for making other battery packs), my Kokam 402 charger (its wiring shorted and smoked the circuitry), and miscellaneous small components on the work bench. All in all I lost about $200.00 to damaged and lost items, but consider myself VERY lucky the garage did not go. I have since built a charging station out of fire bricks, put a smoke detector just above it, and an exstinguiser within reach. All charging is now done while I stay in garage. I now use a Triton charger also, and pay MUCH more attention to settings. Going good so far....:)

Joe

#4 Joe Bennett Mar 08, 2004 04:27 PM

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Group,

Here is a photo of my charging station now. I know, seems like overkill, but it really is not. I feel 100% safer now then before, and it stands as a reminder to NOT become to complacent with the new chemistry of these batteries too. Would I abandon LiPo's? Never. Even with the dangers and past experience, they are far superior to NiMh and Nicad, and getting better every day..............................

Joe

P.S.

The two bricks in front are stacked one on top of the other to close the opening when a pack is being charged. Not airtight, but still a good flash barrier seal.

#5 Dax Mar 08, 2004 08:05 PM

that is overkill. I use a coffee can on the bench. I tested it by burning some gas in it and the table dosen't scortch and the flames don't hit the cealing.

#6 Joe Bennett Mar 08, 2004 09:35 PM

Dax,

I agree it is overkill, but when I saw the distance the battery threw hot stuff, I decided to err on the side of caution. Bricks cost about 31 cents each, so for under $10 I built the charge station. I needed a smoke detector in the garage anyway, as well as a fire extinguisher too. It does make me feel lots better knowing that in a worst case, the only thing that will escape will be some smoke, and I can live with that. Scott's battery moved about 2' when it vented prior to burning, so containment of some sort appeared to be in order. Not recommending that everyone should use my method, but only presenting it as an alternative others might consider. Thanks for the comments Dax...........

Joe

#7 steve ypsi mi Mar 08, 2004 11:59 PM

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You might want to try millitary ammo cans, the 30 cal cans, they are 3 X10 x about 8 high, just put 3 inchs of sand in the bottom, I also cut a piece of galanized metal to keep the battery off the sand, the sand will keep the bottom from getting hot in case of fire, I would still keep it a ways from flamables on the sides, I just did this tonight, I am going to cut a small slot on the side below where the can latchs down just big enough for the wire to go thru and still not let fire out, I am also going to tape the slot so it wont cut the wires causing a short, I also bought one of the 18 pound letter safes for 19.00 to store my battery's in, when you close a ammo can there is no way the fire can push it up and the small slot will act as a saftey valve letting a very small of pressure out in case of a battery fire, I am really leary of the batteries so I am taking as many precautions as possible. these cans cost some where from 3 to 5 dollars at gun shows, They are portable

#8 gouch Mar 09, 2004 05:24 AM

When some guys talk about sealing off the containers, I would think this to not be a good idea. Doesen't it then become a bomb?

Kind of like gunpowder on the floor, sure it burns but put it under pressure in a container that may not be strong enough and see how it goes off. Maybe some testing needs to be done, I.E make one go off in a sealed ammo box etc, and see what happens under pressure.

I have only just converted to Li-po and have yet to fit them in a plane (slow builder) so they sit uncharged till then, so I am a newby with these packs, so I ask about the sealing as my knowledge is limited with this idea.

Also if it's sealed would you have the possibility of a "backdraught" effect due to the lack of oxygen in the sealed container?? It could be fizzing away unknowingly with no oxygen, open the container and well..... refer to the movie.

Can someone theorize or otherwise what would happen to a pack going off in a closed vessel.

Dark overlord: I like the brick setup. My theory is that if it's gonna go, let it, but control the fireball, rather than try and stop it.


DAX: there is no such thing as overkill when your house and family are at risk.

I have seen the videos of guys setting off li-po's via an overcharge and after watching the resultant fireball, I repeat, there is no such thing as overkill. I prefer to call it safety.

Also burning fuel is nothing on the li-po fire video I saw. Fuel only burns in vapour form, meaning only the evaporating gas is burning, not the whole lot at once, quite a difference.


I understand the horror stories told are user error and I'm yet to hear of one going off without overcharging/ crash damage so I'm not "freaking out" about them, just cautious.

Cheers
Paul

Edit, I just reread the bit in the last post about the small vent to allow venting. I would be very careful where this vent was pointing too, as I would imagine the stream of "nasty" would be quite a vicious concentrated shot of "nastiness". I still think dark overlord has the best design I have seen yet.

#9 RMihara Mar 10, 2004 01:08 AM

Hi Joe,

knock on wood I've only had witnessed two 'puffed' incidents. And both were flight related. Hope I never witness/experience a fire...

You may want to check with your insurance company. I got an added discount for having fire extinguishers in my garage and kitchen (small one in a cabinet).

Roger

#10 steve ypsi mi Mar 10, 2004 05:32 AM

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Here's another way to make a container to charge in, I used a 2 pound Coffey can for the outer shell, the inside one is a 28 ounce tomato can, I placed 2 1/2 inches of sand blasting sand or play sand in the bottom of the Coffey can and then set the tomato can on top of that, I then poured sand around the tomato can , I have a wire welder so I made a top out of metal and welded a hinge to it, the old grinding wheel in the photo will be placed on top to act as a dampener, not heavy enough to hold it down firm and the lid is not air tight any way.
as far as the ammo can acting like a bomb, I have never seen a battery go off but I doubt it is as strong as black powder which I do know about. all powder has to be compressed tight so it can explode, if it has the least bit of space it will just burn, 40 years ago I made 12 gauge shells with the old felt wads and a hand loader, I didn't tamp the wads tight, I pushed them in till they were snug, well when they were shot the lead shot went about 5 feet out of the barrel and fell to the ground, this was with modern powder.it needed to be compressed tightly to fire right.
Gasoline is a power full explosive, in my work we had a kid that tried to blow up his dads car by placing a rag in the gas tank fill hole and lighting it , it didn't do any thing and I don't know why.
Until I see one go off I can only speculate on what will take place, That's the reason I would have a way to vent the ammo can so it have a way for the fire to escape and not be like a compressed shot shell. the coffey can is no doubt totally safe as far as being a bomb so thats what I am going to use now as the lid can raise slightly to let out pressure

#11 Extremeone Mar 10, 2004 06:30 AM

LiPo Safety
 
I think cooling the cells while charging in a sealed container will become a problem as you get into the bigger packs. I made a cooling tube out of an empty plastic bottle just the right size to put a cooling fan in the end.

The fan is 12v from a smoked computer power supply. Goop a little wire shelf inside and you have the pack suspended so cooling air can circulate all around it. The fan is hooked to the 12v power supply for the chargers so it comes on automatically when I am charging.

The firebrick is the way to go. I feel much more comfortable with that and there is room for air to circulate through it.

John

#12 twinstarchris Mar 10, 2004 04:27 PM

I use a Cadbury Flake tin. Makes me feel alot better.
Hey Dark Overlord, I think I may get one of those brick barrier thingies, when I'm not charging at least I'll have somewhere to hide in nuclear war! :-)

#13 oldfac Mar 10, 2004 06:16 PM

I agree with those who advocate an open top. If you look at military installations that have powder magazines, you will see that the roof of the structure is usually open at the ends as a way of venting and directing material in the event of an explosion. My suggestion would be a four sided enclosure of fire brick with a lawn chair nerby so I can monitor events.

#14 BrunswickOH Mar 10, 2004 06:39 PM

Dark Overlord your charging leads must be about 4 feet long!!!

#15 Joe Bennett Mar 10, 2004 09:35 PM

Well, not quite 4', but close to it I guess. I have switched over to using Anderson Power Poles for connections on most all of my battery and charger hookups. Make life so much easier to hook things up now. I am going to use a Castle Creations Phoenix 35 ESC on my upcomming AP Avenger, as well as on the LIttlebirdz Predator B when its released, so have just recently placed one of the USB programming interfaces on order with CC. Just got an email yesterday from them saying it will be SEVEN weeks until they will be shipping!!!!! Oh well, being able to program and review my ESC's settings from the computer will be worth it. Anyway, I like the ideas people have been sending regarding charging stations for LiPo's. Keep them coming, and hopefully it will raise the level of understanding on all of use regarding this new technology, for the better I think.

Joe


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