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Dec 31, 2004, 04:31 PM
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Experimental Ignition of a LiPo in a Brinks Box


The setup: 3S Gen1 3270s overcharged by a 20CC 30CV PS. An 800mah 3s pack was placed in the box, to get some idea of survivability of adjacent non-exploding packs.
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Dec 31, 2004, 04:39 PM
one game away...
PerfectStranger's Avatar
Well how did it all work out?

matt
Dec 31, 2004, 04:42 PM
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Hay is definitely non-flammable, correct?
Dec 31, 2004, 04:42 PM
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The charging current was set @ 10 amps (~ 3C) and the voltage set all the way up, to allow it to drift up to the amplifier's limit. The amplifier LED readouts were visible during the demonstration and, as Charlie Wang said in another thread a day or two ago, the pack blew up as the voltage climbed past 16 volts.

As far as I am concerned, we can drop the silly euphamism "vent with flames". The explosion sprung the box's locking tang and blew the lid open. It dropped back down into the closed position and the pack continued to burn for about a minute.

The burning haybale demonstrates that the box must be sitting on a non-combustible surface, to avoid collateral damage.
Last edited by RD Blakeslee; Dec 31, 2004 at 04:56 PM. Reason: typos
Dec 31, 2004, 04:48 PM
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Other unprotected packs in the box will not survive, as Ted surmised from his experiments with steel-tube containers.

I'm going to add a steel hasp to each of my Brinks boxes. The lock-and-key with tang is a pain, anyway, and not strong enough.

The box itself did very well - just burned paint.
Last edited by RD Blakeslee; Dec 31, 2004 at 04:58 PM. Reason: completeness
Dec 31, 2004, 07:08 PM
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Fantastic test, RD. This is very useful data to all of us who purchased the Brinks box as a cheap and effective container to safely charge and store Li cells.

Quote:
Originally Posted by RD Blakeslee
As far as I am concerned, we can drop the silly euphamism "vent with flames". The explosion sprung the box's locking tang and blew the lid open.
Vent with flames still holds true for an uncontained LiPo cell. We've seen enough videos to know that they don't explode when out in the open. What you've just shown is that trying to contain a venting LiPo in a container without adequate pressure relief may result in an explosive opening of the container.

Think in terms of a firecracker. If you light a tightly wrapped firecracker, it explodes with a loud report. If you strip open the paper containing the pyrotechnic powder before you light it, it flares up a lot like a burning LiPo with no explosion.

So the next question is, what's the best way to have the Brinks box relieve itself of the internal pressure of a venting LiPo with minimal collateral damage. My initial thinking based on your test is that I want to vent the flames straight up where they are not likely to ignite anything rather than letting the lid fly open and have flames erupt in all directions.

Keeping the lid tightly closed could have some interesting side effects. The pressure has to go somewhere. Hoppy has pointed out that you can run wires to a charging LiPo pack right through the seal where the top closes over the body of the Brinks box. That suggests that flame could vent around the edges of the lid and set fire to any combustibles nearby, such as a conveniently located hay bale.

Anyone else have thoughts on this?
Dec 31, 2004, 07:40 PM
Space Coast USA
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Good show RD! That's a good point about adding to the Brinks box latch. Perhaps some addtional vent holes in the top might also be effective in allowing pressure relief but preventing free access of air to the interior. Thanks of the info...........
Dec 31, 2004, 07:43 PM
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As i have posted several times.... For whatever fire-flame proof container you're using needs to be pressure-proof latched closed AND the indivual LiPo pack sub-containers seperately vented with some type of adequate flow rate flame quenching-detonation arrestor(s) to safely allow the container over-pressures to be instantly cooled, debris filtered and safely vented to prevent pack-to-pack overheating and possible co-ignition ........Slightly modified 6 HP gas engine, 1 inch diam screw-on pipe pancake mufflers filled with steel BB's and shreaded stainless steel ("ChoreBoy" brand) between the perforated baffles makes an excellent flame-detonation arrestor/filter vent per indivual LiPo container......... kw
Dec 31, 2004, 07:44 PM
Lawn darts, anyone?
Since you asked...
A cheap lawn mower muffler comes to mind. Could serve as pressure relief
as well as dampening of sudden venting. Just a thought.
JB
Dec 31, 2004, 07:55 PM
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IA-Flyer's Avatar
Fine steel wool makes a very nice spark / flame arrestor when glued and screwed over small vent holes. A large tube filled with steel wool, exiting a tightly sealed ammo box should work nicely also.
Dec 31, 2004, 07:59 PM
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Q: Is the "fire/explosion" of a lithium cell proportional to the degree of charge abuse?

In other words, you did this test by charging not only at too high a voltage (common cause of lipo failure) but also at 3X the normal current.

Would the same explosive reaction occur using a 1c charge current?

Great test and documentation!!
Dec 31, 2004, 08:14 PM
I don't want to "Switch Now"
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I would like to know what would have happened at 1C as well.
Pat MacKenzie
Dec 31, 2004, 08:23 PM
Registered User
Quote:
Originally Posted by clearconcepts
Q: Is the "fire/explosion" of a lithium cell proportional to the degree of charge abuse?

In other words, you did this test by charging not only at too high a voltage (common cause of lipo failure) but also at 3X the normal current.

Would the same explosive reaction occur using a 1c charge current?
I defer to anyone with greater Li cell knowledge than I have. But it's my understanding that the object of the test is to put the cells into a thermal runaway condition, and that it makes no difference how this is achieved. So I don't believe there is any significant difference in explosiveness due to different charge rates. It's the thermal runaway condition that creates the fireworks.

KillerWatt, your solution does sound effective. Filtering the pressure relief has the benefit of preventing flaming embers from being blown out under high pressure, which could result in them traveling pretty far and landing on something combustible. What I think might come out of this discussion is that there might be several alternatives available at reasonable cost that already exist for other uses.
Dec 31, 2004, 08:29 PM
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Quote:
Originally Posted by IA-Flyer
Fine steel wool makes a very nice spark / flame arrestor when glued and screwed over small vent holes. A large tube filled with steel wool, exiting a tightly sealed ammo box should work nicely also.
Steel wool is VERY flammable, is it not???

Dadgummit, after all that work obtaining haybales and moving them into my workshop, now I find out they aren't ideal charging bases..


Bill Davenport
AMA 28141
Dec 31, 2004, 08:34 PM
Registered User
[QUOTE=Dave Hederich] So I don't believe there is any significant difference in explosiveness due to different charge rates. It's the thermal runaway condition that creates the fireworks.
QUOTE]

That's what I wanted to know. The videos I have seen don't look to be explosive enough to blow the "lock" open. If the brinks box was sealed air tight, I would understand how the pressure would create a bomb out of the box.

I have done this with dry ice, water, and a plastic pop bottle. That sounded like a bomb.

I thought perhaps this lipo "vented" more fiercely than "normal", but apparently not.

Thanks.


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