using carbon fiber kit on lipos ?

[nechaus]

I am making a battery box.
I was thinking of a real simple method.

Assemble my lipos with tape,
paint with resin, apply carbon fiber cloth more resin ect...

Let it set and never bother opening it up.

I have not ordered the carbon fiber kit yet, but will do soon.
I seen some ebike batteries sellers on ebay doing it now.

[Ypedal]

make it with a lid.. you WILL need in there at some point.

[voicecoils]

It's also worth remembering that carbon fibre is electrically conductive.

kapton tape around the batteries or a layer of kevlar before the carbon would help.

[kfong]

Use a layer of glass first, that will insulate it from the carbon. You could design it with a weakened seem that can be torn open when you do need to get at it. I would cycle each pack a few times before you do this to verify the capacity and that all the packs matches. I would also incorporate balance taps and use a DB25 female connector or some other connector to bring out the balance pins as one common connector. I've done this with all of my lipo packs, and it works out well with the Hyperion chargers. Don't forget to leave a vent hole, you don't want pressure to build if it does go bad. I would also incorporate mounting points while you at at it. I will be encasing mine as well on my DH build but it will have access covers. The carbon fiber makes an excellent fire proofing material, a metal box would be the only other material that would come close. Keep the carbon layup section from being too soaked with epoxy, since epoxy does burn. A vacuum bag and peel ply does a great job at removing excess epoxy.

[marty]

Look here:
Re: box for ping battery ?
viewtopic.php?f=14&t=8659&p=132328&hilit=harris#p132328

Copy text.

Jeremy Harris wrote:Marty,

The box was made using the "lost foam" method. I hot glued two bits of 60mm thick extruded polystyrene foam insulation together (the pink or blue stuff used as house insulation) and just carved it to shape (the outside of the foam becomes the inside of the box).

I covered the foam with brown plastic parcel tape (the 2" wide stuff) then laid up woven glass cloth with epoxy resin over the lower half, leaving the top face uncovered (you have to use epoxy as polyester attacks the foam). Once this had gone hard, I trimmed the edges so they were flush with the uncovered top face and then parcel taped over the newly laid up glass fibre. I then laid epoxy glass over the top and sides (to about half way down the sides) and let that cure.

Once it was all hard, I drilled a hole on the lower half (at the end where the wires come out) and poured petrol (gasoline) in. This melts the foam and the pretty horrible sticky mess runs out (it takes three or four goes to melt all the foam). The two halves of the case then pop apart, with a reasonably good internal finish, due to the shiny surface of the parcel tape.

The last thing to do is to trim the top part edges, fill and sand the outer surface and give it a coat of paint. The top is a tight sliding fit over the bottom, as it was moulded on top of it, with just a thickness of parcel tape as clearance. This makes it fairly watertight, but to be sure I put a wrap of PVC tape around the joint as well.

The longest job was filling, sanding and painting the outside, the actual carving and laminating is pretty quick. I did this because I wanted a box that would fit exactly into the limited space I had. You can use this technique to make pretty much any shape box you like. I've made odd shaped fairings, aircraft fuel tanks and even an inlet manifold for an experimental fual injection system using this technique. You can make the shape as complex as you like, as long as you can get the glass cloth to drape over it OK.

Jeremy

[dogman]

Why carbon? Why not just cheaper fiberglass and resin? Leave at least a vent hole where the wires come out.

Why would conductivity matter? The packs already have non conductive shrink wrap on them.

[Ypedal]

exactly, if you short out a cell on the outer box, you already got problems on your hands lol..

I've built all sorts of boxes over the years, the black metal cans i used on the chopper with 12ah lifepo4 prismatic cells could have survived earth orbit re-entry ( ask Karma how much fun getting into one was !! )

Now i use pvc and tape, filament tape keeps the package tight ( no strech ) and the pvc provides impact resistance, i can open one up in a matter of minutes and re-seal it easily.

[dogman]

Yep, PVC, cookie sheets, plastic plastic boxes, coroplast, all make great matieral for cut, fold, and tape battery protectors.

Nothing wrong with carbon or fiberglass battery enclosures for looks and weatherproofing, but inside more protection from easliy worked materials is the way to go.

[kfong]

For fire saftey carbon fiber or metal enclosure works best if using lipos

[dogman]

Like, it will contain the fire? Don't contain it too much. If it's going off, you want to let those gasses expand. If it's going off, the fact the pack has puncture protection that could be ignited will be 1% of the flames you are seeing.

I do agree, a metal box will really help prevent punctures in a crash, but mine are all wide open on the top. In theory, I'll be able to go grab a stick, and yank out the burning pack by the wires. If it happens, more likely is that at least all the batteries in that box will be goners, and the heat may even transfer through enough to ingite the packs in the other side box. I expect it will detemper and ruin the frame.

[kfong]

With so much battery capacity installed on the bike. If these lipos ever go off. I'm not looking to save the bike or the batteries. It's the house I'm worried about. A metal enclosure or a carbon fiber one is the only thing I can think of that can contain the fire. The enclosure will need just enough venting to release the gases. The fire from the lipos should not get out of hand due to the lack of air. You are basically creating a large lipo sack, which has been shown to work, but one that is permanent to the bike. I have gone this route because removing the battery from the bike was not an option for me. Trying to do a quick disconnect did not seem reliable in an emergency and still be solid on the bike. Removing the batteries from the bike each time has it's problems. The only setup I do use this for are the rear rack non suspension ebikes.

An open lipo setup, the flames will be too large to even get near let alone find time enough to get a long stick that just happen to be nearby. I'd rather have the fire contained from the very start.

[Kingfish]

Thinking outside of the box (sorry – bad pun), we’ve discussed metal and carbon fiber and fiberglass… each has their merits. But what about a Kevlar/Aramid bag? I’ve been looking at Aramid fibers as an alternative to CF because it is not conductive, though likely stronger than FG. I can order sheets of this material in two or three densities (weaves); combine that with Aramid padding (similar in composition to Panaracer Tire Liners) and you could have yourself a soft-sided incredibly strong breathable bag that has a complimentary artifact of repelling moisture.

Material Reference: Tap Plastics (my local).
You’ll need some tough thread to match and an industrial sewing machine (or epoxy!) for binding.

Anyway, that’s me thinking out loud. I’ll go scurry back under the mushrooms now.
~KF

[Ypedal]

If epoxying the fibers, it will no longer breath and allow gas to pass... just a thought.

[Jeremy Harris]

I've used Kevlar in composites, it's nice and light and has amazing resistance to abrasion and penetration. Despite it being that good, I have half a roll of it sat unused, because it is a complete and total PITA to cut. The only tool I've found that will touch it is a pair of electric scissors with tungsten carbide blades, nothing else has a hope of cutting it neatly. It would make a great battery bag though, literally bullet-proof....................

[Ypedal]

Will tin snips cut thru the stuff ? or a blade knife ? *( prior to epoxy )

[Jeremy Harris]

Will tin snips cut thru the stuff ? or a blade knife ? *( prior to epoxy )

Not really, the fibres just force the blades apart so that they can't cut. The same goes for scissors, even really sharp ones, or a craft knife that just sort of smears the fibres. You can cut the stuff with a carbide roller cutter, I believe, a thing that looks a bit like a pizza cutter, but I've never tried it. The only job I did with the stuff I used a borrowed pair of cordless scissors, that had carbide inserts in the blades. These were OK, but not that fast.

[kfong]

I took a torch to Kevlar, it burns as well as fiberglass. The fireproof stuff nomex was rated only to 700'C. and would not be much different. Carbon fiber was the only thing that didn't burn with a torch that I could mold. Kevlar can be cut on a CNC mill once molded. Since we are making these enclosures to perform much like the lipo bags, the heat output probably is less, and carbon fiber might be overkill, since we are basically smothering the fire. I'm using it for it's structural qualities and weight savings as well.

[Kingfish]

If epoxying the fibers, it will no longer breath and allow gas to pass... just a thought.

Epoxy the seams-only is what I meant

I have one of those electric shears with the self-sharpening carbide blade, and I used that to cut some of the fiber-reinforced material for my custom farings and battery covers. Here’s the one I purchased last year:


Yamata WDJ8-1 fabric cutter

Be very careful using these!

I also have an industrial walking-foot sewing machine, but finding aramid thread… I just thought epoxy for the seams might make better sense cos a needle might have the same problems going through Kevlar as would bullets

~KF

[nechaus]

iv order 3 meters of carbon fiber, 1 meter wide, cloth tape 50mm, 5L of resin + fast hardener as its getting cold here atm

http://www.carbonfiber.com.au waiting on my order to arrive, cost about $350 ..

Yeah im thinking ill now make the box first to size and just a bit bigger, then put padding inside and stuff it with lipos, make a cool lid with lcd panel for cell voltages.

Its really not that expensive for what im doing, i think this stuff will go along way, i think i could make atleast 3 battery boxxes or more.
im also going to use it to wrap around my rear forks on my new build, just to give it a carbon look..
making a whole bike would be a different story id imagine


The stuff will polish up nicely

Once i make it ill post some pics up on here, might give you guys ideas for something for yourself to build, who knows..

[nechaus]

id also like to make like a dashboard kind of thing for some of my ebikes..
something to hold switches, CA, lights, wiring and possibly a small battery to power lights.



im not to worried about lipo fires..
the most action i got from a lipo was when i charged a cell to 12ish volts, cant remember exact voltage, but i chopped it in half with one clean swing of a machete.
The smoke was really dense, could not tell if their were flames or not because of the smoke.