RC smoke filter

So lets assume you are planning for the eventuality that a LIPO battery may eventually go thermal and create a large amount of toxic smoke and some flames. If you have a jet airliner, you can just vent it out a nice titanium tube to the atmosphere. If on the other hand, the batteries are not able to be vented outside (and yes I am taking about the bike with lipo batteries in my garage!), how do I make a filter to trap the flames and fumes and vent the residual gases into the living space? All the filter material I can think of will burn. (plastic, steel wool, paper, etc). Ideas?

-Warren.

charge inside a sheet rock lined cabinet and have a thermal switch activated fan and sprinkler system.

make sure all the inside surface have only sheet rock and no lumber exposed. since it is cold outside you want the exhaust vent to have a flap on it like a vent for the fan over the stove does to the outside. you can buy in line 5" duct fans that have enuff moxie to push open the flap to exhaust the smoke. then when it starts smoking it will push the smoke outside and the sprinkler will cool the fire down enuff it may not expand to the other cells.

i recommend using a BMS during charging to avoid fires.

How about a wood burning stove? They are proven to hold fires and duct the smoke away.

A friend sells a rig extinguisher that is a glass bottle that smashes open when it gets hot. I think the liquid goes everywhere and gasses off, smothering the flames. IIRC lipo is self fueling though, it would keep going in a bucket of water. Could be wrong, It was just something I read.

activated carbon maybe ?.. they use the stuff to filter all sorts of nasty chemicals on industrial smoke stacks..

http://en.wikipedia.org/wiki/Charcoal

also used for .. uhm.. other things..

http://www.hhydro.com/Can-Fan-Filter-100.html

Any filter that could make gases safe for inside the house would be ridiculously expensive. It would have to have a particulate filter (probably several in layers) and appropriate adsorbents for removing gases. Activated carbon is relatively cheap but will only remove some compounds and probably not the ones that would be most toxic. There are other materials for that but they are expensive. A conventional house HVAC filter will take out a lot of the larger particulates though. If you ever have a fire in a house and then look at the HVAC filter, it will be black. The very fine ones work the best, but a stack of progressively finer filters would be helpful to keep them from clogging.

I like the ideas posed by others; the wood stove is the best I think, vented outside. If you are lazy like me, you don't have to build anything and you can probably get a used one super cheap. It sounds like, however, you might be trying to find a way to keep the batteries on the bike. A noble goal but difficult.

Some people recommend water for battery fires but MAKE SURE THERE IS NO HOUSE CURRENT TO THE BATTERY (such as a connected charger)! Water will not smother the fire if the electrodes ignite; as LiCo oxide fires evolve oxygen, but water has a high heat capacity and it can conduct heat away fast enough to stop the thermal runaway. Or that is the theory anyway. Other people recommend a dry chemical extinguisher but you need to have one large enough for the task. Many home ones are designed for stovetop fires that burn on atmospheric oxygen and are too small to get enough material on the fire to conduct the heat away. In any case, if the electrodes are ignited, could be difficult to put out until they burn.

Practically speaking, if a garage was filled with smoke and you opened the garage doors shortly after the smoke got in there, you would not get much in your house. The problem is that in most any garage, there is not a large enough space away from combustibles to store something that might catch on fire, if you are trying to keep from removing the batteries from the bike. Then you end up with a car fire or worse, if you have a natural gas water heater in your garage as I do. If you don't mind taking the batteries off, a small fireproof enclosure made of cinderblocks and topped with a piece of sheetrock would work nicely.

There is a nice link to a battery expert's explanation of LiPO battery fires in another thread; you probably saw it. If not, reading that was very useful to me. It describes the physical effects to LiPO of over and undercharging, as well as shorting. It also discusses manufacturing faults that cause internal shorts. That part was a bit scary as there is nothing you can do about that.

Let us know what you come up with.

i recently snagged some old metal filing cabinets. the kinda which have the vertical files and latching drawer. like they were trash and the guy wanted them gone. yes sir.

i am gonna put sheet rock on the inside on the bottom of each drawer and in the sides too.

i don't have an alarm yet but am thinking i should find some of those thermal switches that are NO and close at 70oC or maybe 50oC. rig the alarm in parallel for all the cabinets.

The amount of smoke from a 10ahr pack would be enormous. I would never charge in the house because of this. Even if you contained the fire the smoke damage is just as bad as if you had a fire. Since I do not have a place outside, my garage is my next best option. My current trail bike, the packs are enclosed in a carbon fiber cover. This will not burn, I even throw a fire blanket over it to be sure. It will not contain the smoke, and the smoke is actually corrosive to equipment. Those who have had lipo fires have pointed this out on RC groups. My plan is to open the garage door if I ever have a fire. I store my lipos in a metal file cabinet, large ones used by business.

My current pack, even with every precaution taken and balanced charge during every charge is displaying a large imbalance overtime. These are not the best quality packs. I plan to disassemble them this winter to see each packs actual capacity and IR. This was the packs second season. I would complain if it wasn't for the price. I'm getting 10ahrs out of a 15ahr pack, haven't seen a serious drop from any banks, so I can only assume the losses are from use and aging. Anyone bulk charging packs are just asking for a fire if they are not monitoring each balance port.

How about a smoke alarm Dnmun ? Many are designed for linking now, so probably provide the relay switching you require, and an audible alarm. They are extremely cheap, and in many skips too. If it's just a typical stand alone battery operated one you had, I'm sure you could get it flicking a relay with the sounder wires as your easy way in. Even the test switch would work. It's almost professional.


How do smokeless fires work? Is it wet sticks?
I think venting it out is the way. Scrubbing it to the level where you wouldn't mind it staying indoors is going to be a nightmare. Many filters, including coal based carbon for it's range in pore sizes. A sealed container would mean the fire drove the smoke out so it could be intrinsically safe. Problem is the heat. Even the carbon wouldn't like it as it messes with the pore sizes.

I'm trying to score one of these from work
Its even bigger than this one fits my bike no problem .
I'm going to vent it with a fan triggered by a smoke alarm somehow.
I'd like to insulate it and put in some type of safe heating to store the bike outside..

A sound activated switch would be easy if you don't want to mess with the alarm. Cool ebike garage

mushymelon said:

I'm trying to score one of these from work
Its even bigger than this one fits my bike no problem .
I'm going to vent it with a fan triggered by a smoke alarm somehow.
I'd like to insulate it and put in some type of safe heating to store the bike outside..

Click to expand...

lipo bags anyone?

http://www.hobbyking.com/hobbyking/store/RC_PRODUCT_SEARCH.asp?strSearch=lipo+bag

they contain the fire from charging and failures.

i think lithium and water is not good i think it is better to let it burn it's self out.

I'm confused here, wouldn't you want to vent the smoke out of the garage? Positive pressure from the house to the garage would greatly help vent the smoke to the outside, keeping inside the house clean. Some heating cooling systems do this, but not all by a long shot.

Hard to implement though, unless the outside temperature is perfect, and there is no wind. In a fire, likely your garage door opener is not working, and you won't want to go in there to yank the red handle to open manual.

Best possible idea remains the woodstove, or some other type of vent, such as a stove hood. If you own the place, either could be installed in a garage. Worktable, top and back wall made of non flammable, non conductive sheet such as cement based panels or tile backer. Then put the stove hood on top, and put it on a timer so it runs till your pack is done charging. When done, store in the lipo bunker which might be a box sitting on the same table. Overkill, maybe have a lower power fan that is always on.

dogman said:

put it on a timer so it runs till your pack is done charging.

Click to expand...

This might want tweaking a little. The story goes that high voltage sets off the fire. High voltage is right at the end of charging. Thermal runaway takes a time period. This means you could hit critical voltage, the charger stops, then the fire starts.

ejonesss said:

lipo bags anyone?

http://www.hobbyking.com/hobbyking/store/RC_PRODUCT_SEARCH.asp?strSearch=lipo+bag

they contain the fire from charging and failures.

i think lithium and water is not good i think it is better to let it burn it's self out.

Click to expand...

\

I am not sure how effective the bags are on large packs. Someone posted a link to a store that sells the bags with some pictures of "saves", batteries burnt in the bags. None of the batteries were the larger ones most people here use and in the case with the largest battery, I would say the fire was only barely contained. The bag was adjacent to a wall and the wall was scorched. The bags are better than nothing, but it appears that you still need to put the battery away from flammables. The bags are helpful, but I don't think they should be used indiscriminately. And they don't contain the smoke, which in the event of a fire in a house can be the bigger problem.

For now I charge outside in the barbecue, but I plan to charge in the fireplace w/smoke alarm relay triggered to start a fan poised high in the chimney to suck all the fumes straight out the chimney. I will test this periodically to make sure it works, and I will use 2 smoke alarms for redundancy.

This way the fumes are released up high in the air, so anyone outside will not be overcome or impacted by the fumes releasing either. The fan is up high away from immediate fire and smoke to prevent ignition of the smoke fumes too. I'll use solid smoke/fireproof door-blockers to seal the front fireplace off from the inside house. There is enough gap in the door bottoms to allow airflow into the fireplace for proper suction up the chimney. I suppose I could improve it further by also using a low-volume slow fan to force a small amount of positive airflow pressure in from the front into the fireplace through the door closures.

Obviously, I don't use my fireplace in the traditional sense.

deVries said:

For now I charge outside in the barbecue, but I plan to charge in the fireplace w/smoke alarm relay triggered to start a fan poised high in the chimney to suck all the fumes straight out the chimney. I will test this periodically to make sure it works, and I will use 2 smoke alarms for redundancy.

This way the fumes are released up high in the air, so anyone outside will not be overcome or impacted by the fumes releasing either. The fan is up high away from immediate fire and smoke to prevent ignition of the smoke fumes too. I'll use solid smoke/fireproof door-blockers to seal the front fireplace off from the inside house. There is enough gap in the door bottoms to allow airflow into the fireplace for proper suction up the chimney. I suppose I could improve it further by also using a low-volume slow fan to force a small amount of positive airflow pressure in from the front into the fireplace through the door closures.

Obviously, I don't use my fireplace in the traditional sense.

Click to expand...

Why the fan? A well-designed fireplace is supposed to contain and vent fires. I know sometimes they don't work perfectly, but as long as the vent is open and you have smoke alarms in the house itself, I'd have thought you'd be fine. With a screen in front of the fireplace, nothing can get into the room if the cells pop so no fire hazard inside. I'm not saying it is a bad idea, I'm just curious.

pdf said:

deVries said:

For now I charge outside in the barbecue, but I plan to charge in the fireplace w/smoke alarm relay triggered to start a fan poised high in the chimney to suck all the fumes straight out the chimney. I will test this periodically to make sure it works, and I will use 2 smoke alarms for redundancy.

This way the fumes are released up high in the air, so anyone outside will not be overcome or impacted by the fumes releasing either. The fan is up high away from immediate fire and smoke to prevent ignition of the smoke fumes too. I'll use solid smoke/fireproof door-blockers to seal the front fireplace off from the inside house. There is enough gap in the door bottoms to allow airflow into the fireplace for proper suction up the chimney. I suppose I could improve it further by also using a low-volume slow fan to force a small amount of positive airflow pressure in from the front into the fireplace through the door closures.

Obviously, I don't use my fireplace in the traditional sense.

Click to expand...

Why the fan? A well-designed fireplace is supposed to contain and vent fires. I know sometimes they don't work perfectly, but as long as the vent is open and you have smoke alarms in the house itself, I'd have thought you'd be fine. With a screen in front of the fireplace, nothing can get into the room if the cells pop so no fire hazard inside. I'm not saying it is a bad idea, I'm just curious.

Click to expand...

Every time I built a fire in a fireplace it takes about a minute or so for the heat flow to draft up the chimney at the very beginning of starting a fire. Some smoke/fire smell gets into the house during that initial start-up, and if the LiPo goes off it usually is a big time event with lots of concentrated smoke that will expand rapidly within seconds and burn like gunpowder. It's a very fast reaction that can't be stopped. You don't want to take any chance of that flammable smoke and nasty stink overflowing into the house.

Also, I do epoxy & fiberglass work, so I work right by the fireplace to draft those fumes up the chimney too.

Thanks for the ideas. Nothing really seems viable down this alley of thought. From the posts I have read it does seem like most if not all of the lipo that has gone exo was abused in some way, or was defective from the factory.

I do mostly bulk charging, with chargers that shut off of go into hickup mode at 48.9V. My Turnigy packs are 3 years old now, with over 300 cycles on the packs (I don't keep track). I balance charge a couple times per year. The cell balance wanders by as much as .1 volts after bulk charging for a while. I undercharge the 12s pack to 48.9V, and it discharges down to about 45V after the commute. My controller cuts off at 39V, but I have only gotten it that low a few times when I forgot to charge at work. This seems to work well as the batteries have lasted well.

As they get older though I get more wary. I now have cell voltage monitors I use check the cell voltage more often without taking the packs apart. The batteries are well protected in a padded aluminum box on the bike. It has holes in one side to vent, so if there would be a problem that would contain it to some degree. I think I am doing everything right, and I love the high current LiPo allows, I just wish I didn't have to treat it like a potential b0mb.

-Warren.

If you like to barbecue or just cook outside, then put that cooker in your garage. Buy one with a chimney which you could rig for a slip on tin pipe for venting outside the garage when you store or charge the LiPo. Simply put on a slow low cfm fan when charging or storing. Use a smoke alarm to alert you too. LiPo won't burn down your BBQ pit, and the low cfm fan will be already on if something happens to vent the smoke outside thru the sidewall or roof vent.

Maybe a drop down curtain with vented 'cone' above, or shower curtain style that joins with magnetic strip?

[youtube]g1eUIK9CihA[/youtube]

A cooker hood extractor is one of the cheapest sources for duct fans on the 2nd hand market. $30 gets a fan worth $100 new and comes with speed control that won't make it hum. Many are new at that kind of price too, just damaged cosmetically. Something like a neff will be all metal construction and could actually take a flame short term. The motors have thermal trips that would be the problem. Cheaper brands will be all plastic with pvc wires. You shouldn't really run them hot, but way up a flue should be ok. Or pull an old boiler to bits as balanced flue systems have a small fan that really will take some abuse.

I live in apartment, and its the first time i "Play" with lipos....so, I take all the precautions.
I charge and store my batteries, in my fire-place...

Take care,
Luis Costa.

My observations of burning Lipos is there is an initial flare/fireball that only lasts about a second as the chemically released oxygen gets used up. After that, the majority of the fire is the solvent and plastic burning with atmospheric oxygen. If the batteries are contained such that the flare can escape, but no oxygen can enter, and the container can withstand the heat of the cells discharging their energy, I think the amount of smoke/fire would be greatly reduced.

I'm working on a pack using a surplus .30cal ammo can. Heavy, but will contain the fire I'm pretty sure. I plan on drilling out a hole on the side for a vent, and having a spring loaded flapper door that will self-close after a vent. A good impact is a good way to get them ignited too. The steel can will provide good crash protection.

I've seen cells that spontaneously puffed and ones that have spontaneously ignited even when not charging, though this would be much more rare than ones that go off when charging.

That's a good idea. My storage is also ammo cans, with holes drilled to vent in one direction. I point the holes towards the fireplace.

That's my hope too, that if something happens in the night, the initial fireball is contained, but not too much. Then the can might not let enough oxygen in to combust as much.

Only the lipo used regularly is in the house, the rest is outside in an old fridge.