Li-Po Safety

civdef

Given that Li-Po batteries can be fairly nasty if you're not careful, what sort of precautions do forum users take with them?

Link to reported incidents on RCGROUPS
http://www.rcgroups.com/forums/showpost.php?p=15776103&postcount=4



Charging bags seem to be popular, but this video indicates they aren't all equal:

http://www.youtube.com/watch?v=ZEkewCjiDs0

I like this approach, though you'd need to make sure no curtains, furniture etc were in the vicinity:
http://www.mrcss.org/articles/9-howto/134-making-a-lipo-battery-bunker


Generic safety video from the nice people at New Zealand Fire Service:
http://www.youtube.com/watch?v=9Be-RgRZTfs

Kashkai

I post on a rc related forum in the UK and there's one guy based in New Zealand that narrowly escaped with his life when an unattended lipo cooked off and set his house on fire. He just about managed to get the buring lipo out of the house but he had to be taken to hospital after inhaling the toxic fumes.

I charge my lipos in my fireplace so if it goes up, well its in a place designed for fires with a chimney overhead to take the fumes away. I have those lipo bags and while they may stop the fire from spreading, they won't keep in the fumes.

The best advice is to always monitor your lipos while charging them, i.e. never leave them unattended. Charging them outdoors in a garage on a non combustible surface would be best.

T-Maxx

Metal money box

Alan b.

I don't take any precautions what so ever for lipos over any other batteries.

I charge my batteries in a military ammo can though, lipos or otherwise. Everything but phone batteries.

Considering the abuse lipos get in phones without blowing up, I've never been too worried about em.

Bruthal

Alan b. wrote: »

I don't take any precautions what so ever for lipos over any other batteries.

I charge my batteries in a military ammo can though, lipos or otherwise. Everything but phone batteries.

Considering the abuse lipos get in phones without blowing up, I've never been too worried about em.

Batteries in models would be subjected to far higher current loadings than the lightly loaded phone battery would be. Phone batteries dont really ever get much abuse either. They are well protected inside the phone casing.

coolwings

There needs to be a distinction made between safe storage of lipos and safe charging of lipos.
This is standard in liquid fuels, but you take it for granted and don't think about it as two processes that must be done right. And the similarity is necessary because of the first time we have electric batteries which have a similar energy density to flammable fuels.

The first point is that lipos are better stored in a 50% full state for longevity reasons. That is to say they should not be put away empty, but they keep better if they are not full too. So why store them with more (dangerous) energy inside than you have to? If case of a problem arising for whatever reason, the energy becomes heat, and the less energy there is inside at the time, the smaller the problem.
So don't store them fully charged.

The next point is the charging itself. You don't smoke in the filling station with petrol around, and you don't fiddle pouring liquids into your car, it is all done in a sealed environment, tank underground to pump to tank in car, then all sealed up again with a screw cap.
So if this kind of safety practise is used the situation becomes clearer.
The battery should be in a fireproof place with nothing nearby that can provoke a fire by itself. In batteries this means metal things that can short out the battery terminals by contact and bridging those terminals.
I once had a NimH model battery in my pocket and my car keys bridged the connectors for a second or two. It got hot really fast!
So while charging the lipo should be on a non metal surface, ideally ceramic or fire clay, with nothing that can burn overhanging it or proximate if heat comes out or rises vertically. I consider tiles, bricks and pyrex as suitable materials.

The next point I'd mention is that human error usually triggers unfortunate events. We may be technically capable, but some day we might just make a mistake and start it ourself by overruling the charger safety system, or another silly mistake out of character for us. We have to make it safe for us, even when we do somthing silly.

And one point that gets forgotten is this: when power surges into or out of batteries, the heat created is related to the internal resistance of that battery. High discharge batteries have low resistance and run cooler. Old or cheap or high capacity batteries have a higher resistance, and make more heat, which is the beginning of an "event". The lesson here is buy better batteries, not ones the maker says are better, but ones that are really better with low resistance inside, and also destroy the old ones instead of trying to eke out a few more "last cycles" from a puffed up damaged pack.

The money saved by getting those last few charging cycles will be easily outweighed by smoke damage to furnishings in a room in your house, even if you have done things right and nothing further occurs when that old battery goes kaput. The last few cycles are not worth it. Replace the pack when your common sense says to do so, junk the old pack now and don't wait until your wallet feels full enough to replace it.

Usual disposal technique I use up to now is a nail through the discharged pack and a drop into a bucket with some salty water. It is safe after that.

Bruthal

So good you had to say it twice:D.

Probably the slowness of the server tonight.

coolwings

robbie7730 wrote: »

So good you had to say it twice:D.

Probably the slowness of the server tonight.

Thx for the heads up ... I never noticed. Duplicate post removed !