There has been a great deal of talk about LiPo safety, but one thing that no one has addressed, is LiPo battery fire suppression.

There are many types of fire extinguishers available - which is best and why? A suggestion has been made that a bucket of dry sand may be best, it won't spread the chemicals all over.

From : Don Stackhouse

All the evidence I have seen indicates that the fire from the battery itself is over in a few seconds at most. It flashes in a big fireball and then it's gone. You will not have time to use a fire extinguisher. Any remaining fire will be the burning of whatever else was close enough to the battery to get ignited by it. Base your choice of fire extinguisher on those issues. If you follow the right procedures, there won't be anything else combustible near the battery in the first place.

The oxygen involved in the battery combustion comes from the air around it, not from anything inside the battery itself. Thus, if you really want to suppress the fire, remove the battery from the airplane (which is precisely why we developed our little "Quick-Change Battery Mounting Kit", see our website for details) and put it in a small fireproof container, so there is not much air available to support combustion.

A few months ago I experienced my first and only experience with a Li-poly battery fire. It was because I followed Fred Marks' advice of sticking the battery in the oven (another good example of a fireproof container) while charging. Yeah, I know, gotta blame someone else (after all, it's the American thing to do these days!). Since the wire from my old Plantraco charger to the battery was too short to allow the charger to sit outside of the oven, the charger was also in the oven along with the 3-cell 250 mah pack.

It had been in there long enough to get to the "topping off" stage of the charge while I was busy in the kitchen taking care of some other chores. I needed to bake some cookies for the kids' lunches, and I absent-mindedly turned the oven on to preheat it to 375 F, forgetting about the battery in there. Yes, I know, the first thing that goes with age is the memory, and I forget what goes after that....

Well, it was some time after that when I suddenly realized my mistake. I opened the oven and discovered that (as could be expected) the battery was a little pile of ashes on the bottom of the oven, and the charger was a melted lump (from the heat of the oven, not from the battery fire). The battery had incinerated itself inside the oven without making any commotion that was observable from the outside. I was in the room right next to it the whole time, and I did not hear anything when it "went off", whenever in that 10 to 15 minute period it happened to occur.

Needless to say, I don't charge batteries in the oven anymore! I'd been planning to change anyway because I felt the volume of air in the oven just opened the possibility for a bigger flash. If I'd made the switch sooner, at least I would still have the charger. OTOH, that was one of the old chargers that could not tell the difference between 2 cells and 3 cells, so maybe it's just as well.

In any case, for a while I started using a covered Pyrex casserole dish to contain the batteries. The only problem with that is the risk of accidentally knocking it over and breaking it.

Recently, I found an old Brinks fireproof insulated lock-box about 4" x 8" x 12" at a garage sale. The sellers had lost the key for it, making it pretty useless as a lock-box, so they let me have it for a dollar. However, here was an insulated, fireproof metal container with a tight-fitting gasketed lid (and enough room around the edges to bring the wires to the charger out of the box without kinking or damaging them), and a restricted volume of air inside, enough room for several batteries, but not enough oxygen to support a significant fire. That's what I use now.

The only other thing that would be nice would be a window to see the battery inside the box before I open the lid, in case there is a still-hot battery inside. I may add one eventually, but in the meantime I just open the lid slowly and carefully when taking out a charged battery.

BTW, after I blew up the battery and charger in the oven, I just removed the charred remains, then ran the oven through the cleaning cycle to get rid of any residues. It cleaned up just fine, and the cookies I baked in there right after that came out perfect, no funny smell or taste, and no unexplainable residual electric charge!

Don Stackhouse
DJ Aerotech