Enclosure for Charging Large Lipo Pack

[Patriot4]

I was thinking of this- http://www.cabelas.com/product/Cabe...t=wood+stove&WTz_l=Header;Search-All+Products to store and charge a 12s 44 volt 30 to 40 amp hour lipo pack.

I believe most powerful explosions happen from the Hydrogen gas that is formed when the electrolyte degrades as the battery goes into thermo runaway and then ignited by the heat of the battery. So I was thinking of adding a large computer muffin fan to the smokestack to vent out the gas in case the battery goes up. This would be in a garage.

What do you think?

 

[kfong]

Cheaper to get a used metal file cabinet and cut your own smoke stack. Be sure the smoke stack opening is large since the venting can be quite violent and secure the file cabinet from opening. I've thought of doing the same, but could not commit to cutting a hole in my roof. The idea of having a wood burning stove as heat source in the winter is appealing though, but no real placed for me to put it. I don't ever plan to leave the charging process unattended and always balance charge. I plan to enclose my packs in a fire safe shell. If something does go wrong, hopefully the only thing that will happen will be a garage full of black smoke that can be soon cleared by opening up the garage door. You definitly don't want this venting in the house, the smell and black soot gets everywhere and takes days to clean up.

 

[Ypedal]

most cheap file cabinets likely wont hold up to a full pack meltdown, the stove has a much better chance of survival.

Woudl be neat to hook up a smoke detector to trigger the fan, must be a metal bladed fan or push positive pressure into the stove to vend heat without melting said fan.....

never a bad idea to plan for a worst case scenario... i'm guilty of severely not planning that atm... :lol:

 

[neptronix]

Sorry to be a bit contradictory to your whole idea here... but the best defense against lipo fires is:

1) cycle test your packs a few times as soon as you get them, to rule out any bad cells, or puffing exploders from the get go.
2) don't abuse them ( if you need to know what qualifies as abuse, i can get into that ).
3) don't store them at over 70% of their charge for long periods of time.
4) Inspect packs every once and a while for swelling and discontinue the use of packs that have significantly swelled packs.

I have not seen anyone have a lipo fire who has followed the above procedures.

The reason i mention this, is that it is quite easy to get lazy and stop using your lipo protection stuff, particularly if you use the battery pack multiple times a week. The best prevention is proper lipo management.

 

[kfong]

That only accounts for things to go perfectly. The fact that you can have packs with impurities or a charger that fails badly or in my case, since I trail ride agressivly most of the time. Physical damage due to a harsh enviroment. This is difficult to detect till it's too late. I thought I was quite safe with my Konion setup, till I damaged them this year from trail riding. This was due more to many hours of pounding abuse, causing a weld tab to break. That is one reason I will never bulk charge lipo's, like I do with konions. I did not detect the problem till I noticed capacity had really fallen. If this had happened with Lipo's I might have easily had a fire by bulk charging. Having loose connections or shorts are a big possibility. My spare lipo pack had this problem in the summer, where both the main positive and negative leads made contact. Worn through due to constant rubbing. I did not catch this till I took the pack out during an inspection. Ran several cycles with out knowing since the contacts were intermittent. Mainly vaporised during contact. Although the HK 10awg wire is very flexible, I no longer use it for any areas with high friction. Having been around electronics all my life, it's best to err on the cautious side of things, especially when dealing with voltages and currents that can be used as a portable welder I would feel better if these batteries were hard cased. I'm still not convinced they can handle trail riding like my konions. That is why I'm doing as much as I can to avoid such a fire. If it wasn't for the price and the added capacity I would stick with konions or A123, eventually a safer chemistry will be available.

 

[Patriot4]

Maybe I am being paronoid. The point about the fan is good, I will have to think about that. The practices factor I totally agree with and will diligently do. I am fairly sure if the pact does go all 12 to 20 pacts will follow. Lots of gas, soot, heat and flame.

Will be using this pact, when finished alot, as I live in a small villiage and the nearest big town is 14 miles away. Abuse won't be from C rate.

Thanks for the comments and ideas.

 

[neptronix]

It's smart to be paranoid when you're dealing with the most dangerous battery that the hobby market will let you get your hands on

You might think i'm crazy, but this is how i roll.. double padded triangle bag plus lipos permanently fixed to the bike, and i charge in my kitchen.
I feel it is safer because if a pack is going to puff, i will see it and be able to catch it.
I have no suspension and hit rough stuff often.
I bulk charge 99% of the time. This is because i picked only the best packs to be part of my daily driver, and balanced them 1 time in a ~9 month period..

As long as you know what you're doing.. know what to look for.. and aren't using packs that are even a little dubious, you should have the same results as me.

Maybe I am being paronoid. The point about the fan is good, I will have to think about that. The practices factor I totally agree with and will diligently do. I am fairly sure if the pact does go all 12 to 20 pacts will follow. Lots of gas, soot, heat and flame.

Will be using this pact, when finished alot, as I live in a small villiage and the nearest big town is 14 miles away. Abuse won't be from C rate.

Thanks for the comments and ideas.

 

[kfong]

I can't roll that way I've had a lipo fire and have dissected many lipos during my RC days. They have very little support structurally for me to trust them in a vibration prone environment. The power tabs are thin foil soldered to a pcb board. If they get constantly stressed, they have a tendency to shear. They are easily punctured, so having them in a bag is not an option for me during trail riding. I've had countless crashes and have gone over the handle bar more than 3 times in the past three years. Those crashes usually gets the bike rolling pretty good. A durable shell is needed for my use. I won't trust any pack that is not locked down since friction is really more of a problem over time, also loose wire movement can stress the packs due to their weight. The movement gets transmitted to the pcb board and then directly to the tabs. This may not seem like much but I have had several packs from my RC days break this way as well as many of my friends having similiar problems. My riding is a bit more extreame than just regular commuting, but over time many of these issues become pronounced and apply to ebikes in general. I don't want to worry about problems that develop over time. While your practice may work out, it would never fly in a production type setting.

 

[Patriot4]

The pack I am building will be on another thread when it gets close to completion (estimate a month) and I hope people will like my ideas.

I guess I am asking if this is a viable idea in case catastrophic failure happens for whatever reason? The cost is small compared to a garage or house or me.

The idea is two fold, vent gases so there is no explosion from them, also resulting flames are also vented out and not in the immediate area. Something that can withstand the heat.

The other thing about this is that it is relatively portable.

 

[dogman dan]

Since this is what you will be trying to contain.

I'm happy I still charge my lipos 4 at a time, on two chargers, leaving a two pack fireball my only likely possibility. I charge on my firplace hearth, but not actually in the firebox. I have a smoke alarm right there, a flat shovel and a door to outside 3 feet away.

I think the stove is not a bad idea, provided you have it actually hooked up to a proper stovepipe to vent the hot gas out, just as you would for a regular fire. A file cabinent isn't going to contain a really big fire.

I store em in ammo boxes, that have some vent holes in them. 8 packs per box. This works fine for me, since I don't try to use the lipo daily. It's for the race bike or the trail bike mostly.

Lipo is carried on the ride in these boxes, some good dents in them now, after various crashes. The packs are held in mostly by friction they don't come flying out when I go over the bars. But at the same time, its quite easy to remove them to charge and store.

 

[kfong]

Containing the fire from these large packs is going to be a problem. I really have not seen a good solution, the fire from the Grange race would not be something I want. We know a lipo sack can work with small packs, can this solution be scaled up to the sizes we are using? Having a large release of smoke is a much safer alternative. This is what I hope if my packs do burn up.

 

[BATFINK]

Look for an old fireproof safe on ebay, nothing will burn through one of them:

something like this http://www.ebay.co.uk/itm/S-M-P-fireproof-telford-safe-/250966438643?pt=UK_HaG_Lock_Safes_GL&hash=item3a6ec3f2f3#ht_500wt_1258

 

[nechaus]

why not just use the fireproof bags?
i have not actually used them myself.

 

[dogman dan]

To my thinking, once you have a larger pile, if it really goes you might not contain it in a bag, even a fairly large one. Too much gas. A fire safe, or such could just become a pressure vessel. My ammo cans I store lipo in have holes drilled in the end, and the holes are kept pointed towards the fireplace.

I like the idea of containing the gasses, while still letting them vent to outside. A wood stove could do that.

That pic from the grange was not a charging accident btw, but a dead short, a KFF situation.

I'm not very worried about my lipo during charging, because I pay a bit of attention. Since I remove it to charge, I notice a hot pack after a ride. So I get some warning that something must be wrong with a pack. If charging a suspect pack, and the weather outside is bad, I put a barbeque grill lid over the pack, which is charging on a tile surface. Charging paired parallell lipo, I could use fire sacks if I got a large one.

 

[Ypedal]

file cabinets are too thin ( and the stink of burning paint would add to the ick factor.. ) , bags are only good for tiny RC packs.... the stove with vent pipe is about the only thing i imagine would hold up ( short of a bunker made from cinder blocks, might be cheaper than a stove ) but would still need to vent it somehow.

 

[kfong]

From the lipo fires I've experienced. If kept from open air, the venting looks controllable. With the large packs we use, I don't know if this is the case. No one has tried on ES that I know of at building anything that can contain it on an ebike. I've been thinking of compartmentalizing the packs so it does not all go off at once. A quick release would be nice, but I have yet to come up with a workable solution that is also secure for trail riding. My current plan is to separate each pack with a layer of nomex/Kevlar and an use a hard shell out of the same material, maybe fiberglass g10 as a separator and support structure. Unfortunately, I will have to hope my solution works, since testing out on such a large pack is too costly.

 

[Ypedal]

I have a growing collection of duds that i can make into a sizable pack ( a dozen cells ) and see what it does to sheet metal

 

[kfong]

Yes, we need more examples of contained fires that are more ebike specific. What happened at Grange could of been a lot worse if it was under a tent or surrounded by people in a tight space. Fires like this should never be allowed to get to this large. A wrapping of fiberglass matting material seems like a simple solution to me. It's the stuff we use for glass laminates. Whether it hold up to large packs, I don't really know?

 

[pyrogaz]

Heavy duty welding drape, usually made from a kind of woven mineral wool might be a better option that laminating fabric. I've used them as a liner for ammunition cases used to transport fireworks to displays, in tests a double layer is enough to prevent a 1kg gerb burning through the case; without the lining a 16g steel case is holed in less than 10 seconds.

As there no oxidant in a Lipo cell it may be that welding drape material would prevent a fire even getting beyong the stage of smouldering.

 

[kfong]

I did some material burning with a small torch. Kevlar burns easily, Nomex must be some other type of aramid fiber. When I looked at its properties it does fail at 700 degs. The fiberglass cloth did not catch on fire as much but I was easily able to burn holes in it. A thin sheet of aluminum worked out better. A g10 fiberglass plated would not be very effective as well since the epoxy gave it fuel to burn. So there goes my plans of a fire resistant shell. Looks like a fire blanket over my bike while charging is a better solution. You end up with a loss of a bike but better than a garage. A metal enclosure looks to be the most effective way currently if you plan to house your battery and charge your battery on your bike. Having to charge the packs away from your bike and everything else is the safest and best approach.

I'm now curious as why a lipo sack works so well. Is is a matter of not allowing enough oxygen to get a pack going in the first place? If that is the case then I might still be able to count on a composite shell to do it's job. The lipo sack looks to me like it's made of only fiberglass cloth and some fire resistant outer material similar to duct tape? Does anyone have a clue of the actual materials used?