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Automatic Lipo Fire Extinguisher

Old 06-21-2007, 09:08 AM
  #1  
orionRider
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Default Automatic Lipo Fire Extinguisher

Take a non-flammable container (Pyrex is ideal because you can visually check your battery while charging).
Never use metal as a battery container: it causes electrical shorts.
Now put any kind of metal grid on it (with large holes, a fine mesh won't do). A big bag full of fine sand goes on top.
You now have an automatic lipo fire extinguisher

If the lipo ignites, the platic bag burns and the sand immediately fills the container. It won't stop the fire, but it will contain most of it.
Leave a small opening somewhere to pass the charge cables and avoid pressurisation of the container.

If you don't see what I mean, the attached picture says it all

Of course, a smoke alarm and a (real) fire extinguisher in the vicinity is not a bad idea to complement this contraption...
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Old 06-21-2007, 09:56 AM
  #2  
Don E
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Great idea! I once saw a similar thing using cinder blocks, but I thought that they would scratch the floor. I like your Idea better.

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Old 06-21-2007, 10:44 AM
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I see ceramic floor and all non-flammable containers - thus use of the sand seems to me void . It can not stop Lipos burning, neither stop smoke from filling the house..
Well, balancer like LBA10, with safety disconnect circuit (in case of any cell voltage gets too high) is much better than sand bag. It can save the charged pack in case of charger error(or wrong setting), issue warning that something went wrong, or in case of overdischarged pack or in case of occasional unbalance.. Simply it will help with treating Lipos right. That way, You can use Lipos to power RC model, instead of thinking about fires. And note that pleasure of power achieved from healthy pack is much better than confusion comming from weak, lazy, damaged Lipos ald the price of new Lipo pack every 20 flights or so. Regardless of the risk of fire.
Lipos are burning if overcharged. But beware of slightly overcharged Lipos - they will baloon and may burst into flames after couple of minutes after charge - thus safe place to put them after charge is important as well. Flying plane is not right I guess.
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Old 06-21-2007, 12:21 PM
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It can not stop Lipos burning, neither stop smoke from filling the house..
Indeed, it won't stop the burning but it will certainly contain the flames.

balancer like LBA10 [...] is much better than sand bag
If you think you are immune to lipo fire just because you use a balancer, you'd better check the Lipo threads on RCG...
Besides, nothing prevents you from using a balancer AND sand bag.
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Old 06-21-2007, 12:31 PM
  #5  
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Default Lipo Fire

This is what happens when a 60gr (2 oz) 2S 1000mAh Lipo ignites in open air.

Picture with lots of flames is taken 2 seconds after the first cell blows. The second shot comes a few seconds later, exactly when the flames from the first cell were dying and the second cell went off.

The barbecue plate the lipo is resting on is 35cm (1ft) long. Gives you an idea how big the flames really are

I think it would be less spectacular with a few kilograms sand above it
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Last edited by orionRider; 06-21-2007 at 12:53 PM.
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Old 06-21-2007, 02:18 PM
  #6  
Red Scholefield
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The sand bag technique is a practical system for containment of LiPo fire hazzard. Depending on some kind of "smart" charger/balancer isn't! Something can always happen in these instances that can produce an incident.
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Old 06-21-2007, 07:58 PM
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Hi Red, thanks for contributing

Maybe you could answer one question for which I found no answer:??

When a lipo 'puffs' slowly with every charge, I understand it is caused by lithium plating on the anode. The gas released is Oxygen.
This is confirmed by the yellow/red color of the lipo fire (oxygen fires are yellow/red).

But when a lipo comes down from a flight hot and completely 'ballooned' due to high discharge, some people say it contains Hydrogen. Is this correct?
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Old 06-21-2007, 09:10 PM
  #8  
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Well, Picture at the start of this thread did show charging Lipos by Robbe charger (multi chemistry in addition) without any balancer or charge protection.
In that situation, balancer with safety guard feature is far better than any sandbag, isnt it? That was my point.

IF user keeping normal safety, using any cheap but well working - trusted one - charge system, will STILL keep being concern, THEN sandbag may come into focus.

But that was not on the picture. Very bad charge setup was pictured, supplemented by sandbag... Well, non-flamable surface is enough to avoid burned house. Can You picture the same size lipos burning below sandbag? I am allmost sure that fireball will be exactly same size.


Second point was about fire that may happen couple of minutes AFTER charge, - where the Lipos will go after charge below sandbag? Highly flammable aircraft?
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Old 06-21-2007, 09:37 PM
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Hi Coro,

I will probably surprise you but I don't use a balancer. However, I check the voltage of each cell before every charge via the 'balancer' plug.
Guess what? Since 4 years and 30+ different lipos, I have not had a single cell that was 'a little bit' out of balance (meaning between 0,05v and 0,5v difference). It was either perfect or too different to be safely corrected.
So I believe all a balancer does is let you abuse lipos too much or even worse: keep charging batteries that are too damaged and should in fact be trashed.
The day I will discover a small balance problem, I will just charge each cell separately to correct the problem... and the pack will definitely be labeled 'SUSPECT'.

Note that:
I charge my lipos to 90%, no more.
My lipos are sized to allow for 15 minutes flights.
I stop flying when there is 30% left in the lipo, NEVER when the ESC cutoff.

It may explain why my lipos don't need a balancer.

As for the Robbe Power Peak 'Fun', it is the perfect charger for me because it is all manual settings and very, very simple to use (no risk of using the wrong memory or program). Besides, it goes in safe mode if the cells are out of balance or compromised in any way because it checks the internal resistance of the pack every few minutes. Trying to charge a 4S as a 5S would simply not work.
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Old 06-21-2007, 10:28 PM
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Red Scholefield
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Originally Posted by orionRider View Post
Hi Red, thanks for contributing

Maybe you could answer one question for which I found no answer:??

When a lipo 'puffs' slowly with every charge, I understand it is caused by lithium plating on the anode. The gas released is Oxygen.
This is confirmed by the yellow/red color of the lipo fire (oxygen fires are yellow/red).

But when a lipo comes down from a flight hot and completely 'ballooned' due to high discharge, some people say it contains Hydrogen. Is this correct?
I really don't know what it is, I doubt if it is hydrogen however. I seem to recall someone telling us it was gasification of the solvents used. I doubt if there is a hydrogen generating mechanism present in LiPo chemistry. I do know that in the case of Ni-Cd generating hydrogen in severe overcharge that the result was more of an explosion than a fire as some have seen in LiPos. I afraid I am somewhat of a failure when it comes to getting LiPos to explode, either from over charge or heavy discharge to Zero.
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Old 06-23-2007, 09:34 PM
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orionRider
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Thanks for your input

I would also think the 'gas' is basically solvent boiling on contact with the hot electrodes because most of the time, the 'ballooning' disappears when the lipo cools down. It would also explain why this condition is less dangerous/leads to less fires than overcharging.
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Old 06-23-2007, 10:43 PM
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Here is a pic of my set up. Not sure if my block with a bag of kitty litter would work or not but I can't imagine it making it worse so I use it.

There was a thread similar to this a little while back and everybody seemed to be leaning towards ammo cans lined with foam.
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Old 06-23-2007, 11:00 PM
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How thick is the plastic that contains the sand?
Also how long does a Li-Po burn?

I've never seen a video of a Li-Po blowing. I seem to remeber somebody saying it's a quick but intense fireball.

I've thought about the sand but question whether the fire would burn long enough to open a bag.

So I now charge in the middle of my garage. Although in a small cooking pot. Guess I better charge that, I never thought of the metal \:
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Old 06-27-2007, 03:52 PM
  #14  
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The 60gr 2S lipo burned intensely for about 10 seconds (5 seconds/cell). There were some small (<1") flames for about 1 minute after that.

The heat is enough to burn the wet grass under the aluminum plate you see on the pict. and even melt some of the plate, so I think a plastic bag won't resist very long...
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Old 07-04-2007, 05:00 PM
  #15  
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smokejohnson,
That is a very nice table to be using outside.
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Old 07-04-2007, 07:34 PM
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That was just for the pic. I live in an apartment and set it outside on the patio table when I charge.
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Old 07-04-2007, 07:42 PM
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smokejohnson,
I knew you knew better than charge inside.I just couldnt pass up the chance to tease you a little.
Same setup I use except I use sand. ( Got birds ,so no cat litter around.)
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Old 07-05-2007, 05:29 PM
  #18  
vax6335
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Originally Posted by fr4nk1yn View Post
I've never seen a video of a Li-Po blowing. I seem to remeber somebody saying it's a quick but intense fireball.
Here are links to some good lipo burning videos.
The website: http://www.utahflyers.org/ <-Go to the video list on the left side.

The Videos:
http://www.utahflyers.org/movies/Lipofires.wmv

http://www.utahflyers.org/movies/Lipo2.wmv

http://www.utahflyers.org/movies/lipo3.wmv
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