Please help me build a wooden battery box

[JinbaIttai]

With the recent talk of pouch-type LiFePo4s requiring compression, I have decided I will build a box for my 48V 20ah when it arrives.

I'm thinking of picking up a board of relatively thin wood from a local hardware store, cutting it up, and making a box out of it.

I am probably going to have to pick up some new tools. I have a decent collection of automotive tools, but am severely lacking in the woodworking department.

I live in a small apt. so space is a premium. I have a wood hand saw and a miter box, but I'm pretty sure that isn't adequate. What setup would you recommend purchasing so I can build a battery box out in my parking lot? I'd prefer as inexpensive as possible, so sawing by hand is fine, as long as I can somehow do it accurately.

Should I use glue? Nails? Screws?

 

[TylerDurden]

Good questions...

I'd suggest (@ bare minimum):
Black&Decker Workmate folding workbench/vise
Decent Saber-saw
3/8" VSR electric drill/screwgun

Screw+Glue can be very strong; metal cornerbracing or wood cleats are advised for thin sheetstock.
Threaded-rod & metal angle can also be used to maintain compression.

 

[etard]

If you purchase your wood at home depot, they can do all the cuts for you for a small price, then just borrow a drill or buy one at a pawn shop for cheap. Or buy one with bits already, cuz you will need to predrill your holes. You can either use screws or wood dowels with glue and some clamps. Corner bracing is a good idea, and wood filler.

Have you thought of working with fiberglass? Seems like it would "hug" your battery much tighter than any box you build.

 

[Eric G]

I live in a small apt. as well and have done woodworking in the living room after each cut I use one of those hand held dustbuster type vacs.
Eric

 

[John in CR]

I'm not sure what you mean by "requiring compression". I believe that, especially the foil pouch type cells, they require the ability to expand, because the cells are physically slightly larger when fully charged.

With my original Ping packs I protected them with an exterior covering of epoxy impregnated 3mm plywood, which is very strong yet lightweight and very easy to work with compared to composite structures. I had this left over from a sailboat build, where I learned just how strong a thin plywood can be, especially if bent into a curve.

A battery box built specifically for your pack can easily be built with no new tools required other than a squeege for less than $1 to spread the epoxy and minimize any excess on the plywood. It's quite easy to rip before or after the epoxy impregnation using a simple handsaw. The main issue would be how to make a nice pretty joint at the corners, but the easy solution would be to use a thicker wood for the end and bottom plates, which you screw and glue together first. You could also forgo the the more expensive and messy epoxy treatment, though you do lose some strength, water resistance, and ease of finish at the end.

My plan for my current build, which will include built in battery compartments integral to the bike structure, is to use a very thin balsa wood, which I will impregnate with epoxy and reinforce on the interior with fiberglass and epoxy. I'm going with balsa because I want to get away from sharp rectangles and the balsa I can steam into curves and bend, and use just a razor knife to cut before I get into the epoxy phase. Then once reinforced on the interior properly with fiberglass, I end up with a structure that is very strong and light yet slightly flexible, and that I can easily get a good exterior finish. I'm also experimenting with bamboo strips as part of the interior strength reinforcement to add a bit more local flavor to the materials I use, and it appears that I can get the equivalent strength to aluminum in less weight and a form that I can easily create myself without thousands of dollars in metal working equipment that I don't have.

FWIW, you could take something like a Ping pack at full charge, and just do a couple of layers of fiberglass and epoxy to end up with a strong and easy to finish lightweight pack. I would however recommend a bit of practice first before doing the pack itself. I mention full charge since that will be the maximum size of the pack, and the fiberglass epoxy combo will allow sufficient flexibility to deal with the expanding and shrinking pack.

John

 

[Zoot Katz]

. . .
My plan for my current build, which will include built in battery compartments integral to the bike structure, is to use a very thin balsa wood, which I will impregnate with epoxy and reinforce on the interior with fiberglass and epoxy. I'm going with balsa because I want to get away from sharp rectangles and the balsa I can steam into curves and bend, and use just a razor knife to cut before I get into the epoxy phase. Then once reinforced on the interior properly with fiberglass, I end up with a structure that is very strong and light yet slightly flexible, and that I can easily get a good exterior finish. I'm also experimenting with bamboo strips as part of the interior strength reinforcement to add a bit more local flavor to the materials I use, and it appears that I can get the equivalent strength to aluminum in less weight and a form that I can easily create myself without thousands of dollars in metal working equipment that I don't have. . . .
John

Eureka! Wicker/willow, rattan or bamboo baskets would make perfect battery boxes.
Ghetto points, shock absorbtion, ventilation, non-conductive, corrosion and rattle free, rugged, cheap, stylish and stealth. Relatively primative DIY construction besides being Gaia friendly.
What's to want?

 

[dnmun]

Jinba, i think the duct tape should keep it tight enuff. did you ever try to solder the broken lead back onto the tab? it may be that the swelling only happens when the tape is removed, i still think the balancing leads may be too tight when they pull the ribbon cable tight across the battery and then bend it over the edge and secure it. i sent ping an email asking him to look into it and give him a heads up that his people may be pulling that cable too tight since there have been a few failures where the tabs have pulled out. did ping send you new parts or offer to take the battery back?

 

[JinbaIttai]

I thought the same about the duct tape being enough to hold the cells, but it swelled and stretched right through the duct tape. I haven't bothered with the old battery. There were a lot of swollen cells; it was under warranty and I ended up sending it back.

I'm not too concerned about finish or seal as it will be in a waterproof pannier, likely wrapped in dense foam or bubble wrap.

Impregnating balsa wood with epoxy sounds a little over my head, unless it is easier than it sounds.

Is it possible to make accurate cuts with a hand saw and one of those Black&Decker Workmate folding workbench/vises? The prices look decent.

Saber-saws--are these the same as reciprocating saws?


Is 1/8" too thin to use screws?

 

[TylerDurden]

Sabre-saws have reciprocal action:
View attachment Bosch1587.jpg

You can cut straights and curves very accurately using guides clamped to the work.

Thin plywood can have high tensile strength, but screws can rip or pull through, unless you use a lot of them (plus glue). If you look at continuous-hinge at the store, you will notice the screws are quite small, but spaced closely (enough strength to hold the heavy lid on a piano).

 

[TylerDurden]

here's the most rudimentary model, 1/4" ply & aluminum angle

 

[dnmun]

maybe you should just measure the dimensions of your pack and then go to target or walmart or kmart or wherever they sell little storage boxes, or maybe the container may be part of something else you can take apart, you never know what application they may be sold for, but you may find a small plastic container the perfect size to squeeze the battery into. just a thin layer of polyethylene will stop penetration of sharp points, which is your big risk with the duct tape pack. i don't think any wooden box is gonna be as tight as a molded plastic box, so just waste the time looking for the right fit, even 1/2" plywood will not hold a screw strongly enuff. imho, BOL,dm

 

[JinbaIttai]

Maybe putting compression on the box is too much, I can aim for preventing expansion, with all the other benefits of having a hard shell. Thanks for all the advice so far.

 

[marty]

How about a box like this?

Build these your self. I bought parts for equipment boxes like these at a music / theater place.

Hundreds of cases here http://www.casesbysource.com

 

[JinbaIttai]

Thanks for all the suggestions. I ended up buying some 1/4" x 3" x 4' oak for the bottom and top, and some 1/4" x 2" x 4' oak to make the sides. I'm going to make it crate-style, so there will be air gaps in between, and it is all small enough to cut up in my miter box. I'll hold it all together with gorilla glue and wood screws (I have a drill). I'll post pics when I start. I have to wait for the battery to arrive.View attachment Ceramic Wood Crate.jpg

I'm inspired to get a beach cruiser and do a beach-theme pannier build now. I visualize weathered wooden crates on the panniers, a battery inside, wrapped in burlap & stenciled with some kind of food name (maybe Thai Jasmine rice), the wires cleverly tucked away and everything lashed down with fishing net...

 

[Toorbough ULL-Zeveigh]

Eureka! Wicker/willow, rattan or bamboo baskets would make perfect battery boxes.
Ghetto points, shock absorbtion, ventilation, non-conductive, corrosion and rattle free, rugged, cheap, stylish and stealth. Relatively primative DIY construction besides being Gaia friendly.
What's to want?

waterproofing?
that's what's giving the most difficulty.
trying to figure how to provide ventilation & weather worthiness at the same time.

 

[torrent99]

Maybe putting compression on the box is too much, I can aim for preventing expansion, with all the other benefits of having a hard shell. Thanks for all the advice so far.

Compression?
Use a sheet of plywood as a plate at each end. Reinforce with a couple of bits of batten glued & screwed lengthwise along each end. Then use 4x threaded bolt & nuts between each plate to compress the pack. Then build a box around that.

 

[Zoot Katz]

Eureka! Wicker/willow, rattan or bamboo baskets would make perfect battery boxes.
Ghetto points, shock absorbtion, ventilation, non-conductive, corrosion and rattle free, rugged, cheap, stylish and stealth. Relatively primative DIY construction besides being Gaia friendly.
What's to want?

waterproofing?
that's what's giving the most difficulty.
trying to figure how to provide ventilation & weather worthiness at the same time.

Coat the battery in Eulachon grease if a little bit of precipitation or ocean spray is going to bother you.
Baskets can be woven to hold water. Substitute hot rocks for batteries and you can cook soup in them.

Thinking about it; the harder it rains, an un coated covered basket would become more water repellent as the fibre swells to exclude the air spaces. The excess water would drain out. Conversely, the basket could be soaked for natural evaporative cooling for desert riders.
This makes baskets more perfect all the time.
Go nuts!

<insert appropriate ASCII gesticulations here>

 

[Toorbough ULL-Zeveigh]

i was thinking heat sink compound but replacing a cell or doing any kind of battery maintenance is difficult enuf.
slathering it with grease would make it a royal PITA, so that's out.

there's no such thing a little precip.
electricity & water don't mix (in fact right atm homer simpson is proving so by driving an electaurus thru the ocean with disasterously humorous results. mel gibson guest voice).
even moist humid air would be good to shut out preventing corrosion & premature failure.

 

[MitchJi]

Hi,

This link is for a site on building wood canoes with strips of wood and he also documents building the body for a 3-wheel Electric Vehicle using the same technique:
http://members.peak.org/~innercom/index.html