Larry3215

I tend to agree with that. You do need to be very carefull though.

My recomendations - and my practice - for damaged packs is as follows:

First of all it depends on the type of damage. If the plastic pouches on the cells are not punctured, then I slooooowly discharge the pack in a fire safe area. I usually use one of my chargers set to discharge at the lowest rate with the pack inside a Lipo Sack, outdoors on concrete well away from anything flamable.

Once the voltage is well below 3 volts per cell after sitting for several minutes, I short the pack and leave it for a day or so.

About 1/2 the time the packs puff up when doing this even if they were not puffed before.

If they DO NOT puff you can now toss them in the trash or preferably, recycle them safely. There is no energy left in them to cause a fire.

If they DO PUFF, then the gasses inside the cells are flammable and need to be dealt with.

With puffed packs that have already been FULLY discharged - I punch a hole in using a nail on a long stick. IF the pack is fuly discharged Ive never had even a spark, no flames no nothing. Im still extremely carefull.

After they have holes in them - its perfectly ok to drop them in salt water to be 100% sure all the energy is gone. I dont know if it makes them chemically inert or safer for land fills or not. First priority is to get the energy out of them.

Occationaly I have had a pack that has a tab break off so that I couldnt discharge it. In those cases, Ive discharged the cells that can be discharged by attaching an aligator clip to the ones that still have a conection. See the note above.

After getting as much energy as possible out of the pack - puncture it as above - with a nail in a long stick. THEN drop it in salt water.

The only time salt water does any good is if it can get inside the individual cells. Period.

As Rodneh said - Ive never had a pack flame up when punctured or torn or ripped open, but several of them have gotten VERY hot and Ive had some interesting sparks and spits. You definately want to do it in a fire safe area - the sparky bits can jump several feet - and wear eye protection and have a hose or fire extinguisher handy.

On the other hand there have baan many report over the years of packs going off with a bang when punctured - so there are no guarantees on this. Its extremely dangerous punching holes in lipos. Be carefull.

Sometimes thats the only good choice though in my opinion. If you have a puffed pack - even if its discharged - thoise gasses are flamable. If its also got charge left in the pack, its now a bomb with a detonator built in waiting for the wrong moment.

Murocflyer

.

Rodneh

No Cyclops2, that is not to simple. You are correct, once discharged there is no need for the salt water bath. Salt water is a very poor conductor which anyone can prove to themselves. Just take any battery and put a lead from the negative terminal into a salt water bath. Put the lead from the positive terminal to the positive terminal of an ammeter. Put another lead from the negative terminal of the ammeter into the salt bath and measure the current. You will find it very small, maybe so small you wont be able to get the ammeter to register unless you can get it set to microamperes. Bottom line, salt water baths to deactivate LiPo's is next to worthless. Do the test, prove it to yourself.

Larry3215

Not quite.

In my tests the current that flowed through the salt water was pretty much in direct proportion to the size of the conductor that was immersed as well as the salt concentration.

I did my tests using using a 3S fully charged lipo pack. The salt bath was a 1 quart jar of water with 3 or 4 tbs of table salt dissolved in it. I stripped the ends of some 14 ga wire leads about 1/2 inch and put them into the salt water on opposite sides of the jar.

That produced an initial current flow of 1.7 amps.

That dropped to about .8 amps within a minute or so as the wire quickly corrodes and conductivity drops.

After about 5 minutes the current flow was still .3 amps but still dropping.

After 20 minutes it dropped to .04 amps.

After about 40 minutes it was .01 amps.

Shortly after that, the wire became disconnected and current dropped to zero as it corroded completely through the wire and the end fell off.

However, it had only discharged 169 mahr from the pack. Not nearly enough to discharge any normal sized pack.

Thats a 1/2" long piece of 14 ga wire gone in 40 minutes.

I then did additional tests with large chunks of aluminum to simulate what happens to the aluminum tabs on your packs. The aluminum corrodes away much faster than the copper wired did.

Using some larger chunks of aluminum bar that were several times the thickness and size of battery tabs, they were completely gone in less than 30 minutes.

So - large chunks of aluminum are gone in under 30 minutes. Total capacity discharged under 200 mahr in that time.

Your thin little battery tabs will be gone in minutes when you put a charged pack in salt water.

To repeat - I also left charged packs in salt water for months. Untill the salt water had long evaporated and the tabs were long gone.

It still didnt discharge the packs!!!

Dont use salt water to discharge lipo packs - please

Octavius

Wow. I wouldn't have expected the aluminum to disintegrate that fast.

So this just proves my method is the best:

1. Take to open concrete or dirt or otherwise something that won't catch fire.
2. Hit with shovel or other random gardening implement.
3. Enjoy the show.
4. Toss in trash.

Larry3215

Yup, that will work just fine. You do need to be sure you puncture ALL the cell pouches.

Just leaving them ripped open will kill the cells fairly quickly but if you toss the ripped open pack into salt water it will finish the job much sooner and more certainly.

Packs Ive driven nails through and left sitting have stayed very hot for a few hours.

hillbillynamedpossum

why not just take it to the range and shoot the crap out of it?

Larry3215

LOL

The tree huggers might give you a hard time about that, but I wont

dmarko

'FLY RC" magazine June 2010 Issue Page 60

Article by Scott Stoops [email protected]

has an article on Lipo care and storage.
Picture right in the middle shows a puffed battery and the caption reads something like this:
"This 2S battery is a textbook example of a puffed pack. At this point, it should be soaked in salt water until it's drained to zero volts and then tossed into the garbage."
-------------
FLY RC is a well respected magazine.
They are saying this.

Rodneh

Yes, Fly RC is a good magazine but this is one place they have made an error. If you will check further, you will find ample evidence to prove that. Somewhat similar to the belief that all NiCad have a memory problem, an even more enduring myth. Fortunately, some rather knowledgeable people/labs have proven both of these are just that, Myths. However the salt water bath has a slight bit of truth to it, just doesn't cover all possibilities.

Matt Kirsch

Getting this myth debunked once and for all may not be possible. There are always people who aren't paying attention when "common wisdom" changes, and don't get the memo.

What hurts things further is that there is no truly "authoritative" source for information like this. By that, I mean something akin to an international standards organization, or a respected reference publication.

Sounds like it's time for a letter to the editor.

Larry3215

I agree. I think it would help if several of us sent a letter in to them. It would give the point added weight.

Scott Stoops is well known in RC circles and has written at least one book. Just goes to show how hard this rumor is to kill!.

FlyWheel

uh, Dart, a metal fire in water is not exactly a good thing. For one, it will not stop the fire, I don't care if the metal is lithium, magnesium, sodium or aluminum. Worse, since metals burn at such a high temperature it actually becomes more dangerous!