My solution to Li-po Fires

kfong

100 kW
Joined
Sep 2, 2008
Messages
1,957
Location
SE Michigan, USA
Since I'm not willing to use another battery technology due to the weight savings. I had to come up with a way to prevent my packs from starting a fire. I can accept smoke damage but since I charge in the garage, opening up the garage door should minimize that problem. I have encased my lipo packs in carbon fiber, I'm also hoping full vacuum will provide a good compression to the packs extending battery life. Only time will tell if this is true. This also provides the protection I need for the type of trail riding I do.

Link to the build
http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=12654
 

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Nice box that should greatly help prevent one of the possible causes for a fire, chafing and dings caused by dropping or crashing the bike, or a pebble getting into the enclosure, or a bolt head rubbing a hole.

And looks like it will provide good compression, as the packs begin their normal swelling with age. Well done.

But I don't see how it will keep the garage from burning down, if the bike is parked less than 3 feet from anything flammable, or the roof is within the usual 8 feet.

Isn't carbon and the resin used a flammable material? Sure, maybe a lot less flammable than shit like coroplast, and it should direct the flames out the top pretty good at least in the beginning. So why is that safer on your bike? What prevents the fireball from igniting roof framing or just the paint if your garage is sheetrocked and painted. Lots of garages are bare framing, is yours?

It could help to put a lot of sheet tin on the ceiling where you park. Or some cement based siding. I am not getting how you have any protection from a fireball if the pack should go off.

I'm sure you already do the real fire protection stuff, weeded out any bogus packs before you boxed them, stop before you wreck them with overdischarge, balance when needed, etc.

Since I remove my packs to charge, I notice anything wrong, like a cell got all hot. Add a temp sensor so you won't charge a pack that had an unexpected problem. Just check for heat before you plug in.

My own garage has a more or less valuable car parked too close to the bikes, too much junk that can burn around, and a painted sheetrock ceiling. That paint will burn way too good, and spread the fire if I charged in there and had a problem.

Of course, regular cars burn all the time too. At least my garage does have a fire block wall between it and the house attic. But the house was designed with few exits that aren't right by the garage. First week in the house, I was sawing a hole for another exit, on the far side of the house from the garage.
 
just install one automatic sprinkler above where you park the bike. how easy is that?
 
Should be code for all new construction, since many house fires do start in garages. Cars start fires, as does various bad ideas like storing the oily rags. Then, who's garage doesn't have leftover paint, solvents, and piles of flammable shit in boxes.

Water cannot put out a lithium battery fire at all, but a sprinkler would prevent that fire from burning the whole house pretty darn good. The lipo would burn merrily away, but not ignite the room.


Just don't try it in Ypedals garage though. Unless the water pipes can be empty till the fire triggers the valve. I bet it's still freezing in his garage every night.
 
It pretty much works like the fire safe lipo bags you buy. Without a good source of oxygen, you only get smoke. There is only a small exit from where the leads come out. Combined with my CF battery covers, I'm pretty confident the only issue I will have is just smoke damage. My setup uses a balance charger during each charge cycle and my smart switch to prevent full discharge. I charge my bike without removing the packs, so I needed to be sure I had a good fire safe setup. The amount of trail abuse I put on the bike, requires a pack that can also withstand the crashes.

You can't burn through carbon fiber. Basically it been burned. The epoxy bonding it will burn off. This was the only material other than metal and ceramics that could be exposed to a torch that I found fireproof. Nomex and fiberglass could not handle the torch test I used.

I still have yet to test out the setup on a bad set of lipos to see that I have not inadvertently created a pressurized fireball. I could design it with more vents if this is the case, since the scenario of a fire could happen in the middle of the pack and has no pressure exit. Some real world testing is needed before anyone copies what I've done.

The strategy I’m using has not been done to my knowledge and needs further exploration by myself and others.
 
Yeah, I figured the fibers were pretty hard to burn, I just had no idea about the resins. So I had to ask if you knew. Torch tested, very good!!!

But if it works as good as a lipo bag, great. I just consider them a joke for a bike size pile of cells. Mines 48v 25 ah. I can't imagine what would contain it all.

It looks great to me that it's in three separate packages. That's good strategy for sure!!! My 25 ah goes into 4 metal boxes for storage and charging, trying to isolate it in sections in case of the worst. That has a good chance of working to limit the size of any unexpected events.

But, continuing to bust your chops, go to where you park your bike and look up. Will it burn?

And, how do you know your packs are safe to charge when you plug them in? Did a plug come undone and one pack get discharged to 0v? You sure know if you touch it, or have a thermometer in the battery bay.

I know I'm nit picking you, but I've torn apart a lot of burned houses to rebuild them. In my experience, there simply is no such thing as a "little" smoke damage.

I would love to see it tested, by overcharge till it goes.
 
kfong said:
You can't burn through carbon fiber. Basically it been burned.

Plasma from high current electrical arcs burns through carbon fiber like a fat kid with cake. It does survive most normal material burning, but as fire is conductive plasma, and the cells can dump high current into it, you may find it's more difficult to contain than expected.

I'm curious to see how it handles the cells expansion and contraction over there cycle life.
 
Luke, all new territory, but it's the approach that makes the most sense to me. We will see if it does what I hope. I've been happy with the current setup, this is one extra level of precaution. I have some bad packs to test out, when I get a chance this summer.

Had not thought of the plasma, I do have a thick layer of formex on the top, bottom and in between the two packs, before I wrapped them in CF. It's claimed to be fire resistant and highly insulating. Maybe next design will I cover the sides as well. Maybe that can prevent the plasma?

I don't see much arcing with the lipo fires shown, not sure you can classify them as plasma fires?
 
Hence the double cavity and 3 compartments


Hillhater said:
kfong said:
It pretty much works like the fire safe lipo bags you buy.
I hope it better than those ! :shock:
They may be useful for something like a 2Ahr single cell, but the videos i have seen with 5Ahr multi cell tests, the bags were a waste of time !
 
I was musing the other day what would have happened to the invention of the motorbike if they had stopped development due the the presence of a fire onboard the bike. They just designed around it being present 100% of the time.

I'm assuming that if you try to contain the gas in a lipo fire via a smaller exit hole you cause a high pressure jet to shoot out further? Or is the reaction slowed?

Luke, I'd never realised fire was a conductive plasma - simple when you think about it. Priceless quote on the cake/kid line BTW.
 
Some real world testing is needed, as soon as I find some time I will post the results.
 
Got some old packs around? I'd love to see one intentionally overcharged to failure. If it merely controls the direction of the fire, that's still a huge plus. With the garage door open, you might have that metal straight above the bike.

I think it's a great idea on several levels, despite my busting your chops on it.

Love the idea of two packs per section. Try to limit the fire to two packs, rather than spread to the whole thing.

Love the compression, it's got to be better than some coroplast. Keeping those corners square is the key as Dnmun always says. Once they start swelling, the shrink crushes the corners.

I have lots of experience with nomex, used for near the throat of hot air balloons. Yes it fails the torch test. Especially if the torch is the 13 million btu torches hot air balloons have. But nomex still works on temps under 1000F, and you might consider three nomex bags outside the boxes. Additional separation of the sections can't be bad. A dead short might weld right though, but a ball of fire at less than 1500F will have some additional burn through time with the nomex. It can scorch real bad, and still hold up. Between two boxes, you'd have two layers of it.

Similarly, each section could be put in a lipo bag. How can you do too much?

Look into making your garage more fire resistant. I worry if it's the typical bare framing. Or just cardboard nearby.
 
I'm always open to feedback, or why bother posting. I have plenty of old packs since I'm replacing them with the current ones, as well as misc. packs I've collected over the years.

No rounding of corners with this method, the results with 2 layers of CF and formex spacers creates a solid structure, perfectly fitted to the packs. I know from doctorbass that packs expand and contract when charged. The big question I have is, will constricting this have detrimental effect on the cells or improve them. The only expansion possible is in the center, but CF properties do not allow for any stretch. I bet the center might bulge, putting strain gauge on this area would be a simple way to monitor the packs and give me a hysteresis curve on empty and full charge. That is next on my list.

CF only glows with the torch test, I need to see how formex does.
 
I've been riding with the packs, I'm getting an IR measurement of 21 milliohms, with 13 usable ahrs. The packs is charged to 95% and stopped at 32 volts. The packs are balance charged during each cycle. So far things look good. I picked up some strain gauges, but not sure if I will try them on this setup. I'm putting together my Dirtsurfer with a similar setup, so I can plan on having them on that to test out.

Hopefully I can find the time to do a fire test, since I'm already committed to doing my batteries this way.
 
I had a small battery fire it wasn't the fire damage that did the damage but the heat and smoke damage. When they got the water on the small fire but the heat and black smoke that made the damage of fishing poles, gaphic and titamiun skis that melted from heat and most went to trash from smoke damage. Trashed to the dumpester. Don't fool yourself. Trashed.
Charge outside of garage in barbaque.
 
When it comes to fire, being able to buy more time via protection can make all the difference, so can't see the harm in building a carbon fiber container.

I noticed on hobbyking they got some new lipo safe bags.
Some look pretty funky
http://www.hobbyking.com/hobbyking/store/__1114__85__batteries_accessories-lipo_safe_bags.html
 

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Charging outside was never an option unfortunately.

999zip999 said:
I had a small battery fire it wasn't the fire damage that did the damage but the heat and smoke damage. When they got the water on the small fire but the heat and black smoke that made the damage of fishing poles, gaphic and titamiun skis that melted from heat and most went to trash from smoke damage. Trashed to the dumpester. Don't fool yourself. Trashed.
Charge outside of garage in barbaque.
 
Yeah i'm curious too. I'm building a pretty big pack and have all the equipment to do similar vacuum bagging/resin layup. I'd definitely go to the trouble if it kept the pouches happier. The formex stuff looks interesting too, i could cut them out on my CNC die-cutter and make little boxes in no time.

I do a lot of resin casting too, i wonder if anyone's experimented with stuff like http://www.innovative-polymers.com/plastic-urethane-liquid-resins-cast-fire-resistant-parts Wouldn't be hard at all to resin cast some boxes.
 
No unfortunately I have been too busy with projects. The only good news to report is this seems to help with the IR. I even vacuumed packed the one on my utility bike, but used cheap fiberglass matting and formex. Doubt I will get around to any burn test. Someone else will need to pick up where I left off if interested. If I do get a failure, I will definitely report it. If anything, I'm hoping I might have extended the life of the packs, being compressed this way. I'm not on this forum much. My conversion van has taken all of my time.
 
Ive never put enough drain on a pack to see it expand but ive read they will expand slightly, maybe with gas, and then subside again. If there is nowhere for the gas to go but maybe one small area maybe the pressure in that one area would be too much and blow a hole innthe envelope?

I covered a couple packs with carbon to protect them from flying debris on the bottom of my skateboard but was told it was a bad idea for the reason above
 
A bit worried about some assumptions...
Carbon fibre can't burn, it's already been burned. The classic fossil fuels, coal, coke, anthracite - basically pure carbon. The industrial revolution was fuelled by this stuff.
A vacuum will prevent a LiPo fire, 'cos there's no oxygen. I seriously doubt this, batteries only work at all because they carry all the reactants necessary to output a bundle of energy, with no external oxygen input. I don't think a Lipo fireball is due to Lithium burning in oxygen.
 
kfong said:
My conversion van has taken all of my time.

Electric conversion, or camper van?

-JD
 
bobc said:
A bit worried about some assumptions...
Carbon fibre can't burn, it's already been burned. The classic fossil fuels, coal, coke, anthracite - basically pure carbon. The industrial revolution was fuelled by this stuff.
A vacuum will prevent a LiPo fire, 'cos there's no oxygen. I seriously doubt this, batteries only work at all because they carry all the reactants necessary to output a bundle of energy, with no external oxygen input. I don't think a Lipo fireball is due to Lithium burning in oxygen.

Huh?, don't think I implied it was a vacuum. You are reading too much into it. As for CF not burning, try taking a torch to it. Would be great if I could use ceramics, but impractical. I'm also not advocating that this works, since I have no test results to back it, just something I've experimented with.
 
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