# wood batt box?



## onegreenev (May 18, 2012)

What type of batteries? Lead Acid? Wood is fine for them as the wood is strong but you will need to protect and seal the wood on all sides and from any intrusion of water. If lithium I'd use aluminum boxes. Wood boxes take up a bit of precious space but ply has been successfully used for a very long time. Marine is the best and most expensive and strongest ply.


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## Ziggythewiz (May 16, 2010)

I've heard people complain about it...mostly for looks and non-OEMness. Others claim it's a fire hazard, but I don't think it would contribute appreciably as a fuel. I'd feel much better with a plywood box than with the aluminum or steel ones I've seen that look so nice.

I replaced my electronics board with plywood as a temp job while putting some new holes in the aluminum one, but it went in so easy it's still there 16 months later. When I ever get around to making battery boxes they'll just be plywood covered in marine carpeting or somethin.


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## Jamie EV (Oct 3, 2012)

That's my thinking as well. I was thinking of doing a plywood with rino-coat sprayed on the outside to repel water as well as give it a more pro-oem sort of look. How structurally relevant is it anyhow? Other than insulating and keeping the fingers out, does it have to have some incredible crash worthiness? I mean...metal, wood, plastic...it all buckles in a crash. Marine ply is probably as safe as anything else and insulates better than aluminum...lead acid for sure btw


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## Jamie EV (Oct 3, 2012)

Oh and that brings me to a second thought....insulation for heating in winter...I'm thinking fire proof fibrerglass batts. Styrofoam would kill the occupants if it burned so no way....

thoughts?


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## CFreeman54 (Jan 14, 2009)

If you ever plan to put the vehicle on a racetrack it is structurally relevant. I believe NEDRA requires the battery box withstand 6 Gs of force...or was it 9? One of the NEDRA guys on the forum can confirm the number.

Also, in the event of a battery pack fire metal will slow/contain the blaze some. With wood or composite your car is history in minutes unless you have a fast and efficient fire suppression/extinguishing system.


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## Jamie EV (Oct 3, 2012)

vaporized metal will kill you a hell of a lot faster than wood smoke.


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## Jamie EV (Oct 3, 2012)

I also don't think that there is such a thing as an effective fire suppression for a lithium runaway. Unless you're driving around with compressed liquid nitrogen lol


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## Jamie EV (Oct 3, 2012)

CFreeman54 said:


> If you ever plan to put the vehicle on a racetrack it is structurally relevant. I believe NEDRA requires the battery box withstand 6 Gs of force...or was it 9? One of the NEDRA guys on the forum can confirm the number.


I should think that a plywood box can take lots of Gs if properly engineered....perhaps with steel strap and external dampers? After all, wood is strong, flexible and vibration resistant.


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## PaulS (Sep 11, 2012)

Jamie,
Plywood will splinter and shatter once it reaches its maximum load point. Wood is a natural insulator but it has almost no crash resistance at all. Aluminum will be lighter and you can still use the Rhino-liner to coat it. Wood and sulfuric acid (the acid in lead/acid) don't live well together. I have seen a few shelves for UPS's that rotted away in six months and the batteries were a total loss when they fell to the floor.
Get some high-density foam board (the kind they use when insulating foundations) and make a sandwich with aluminum epoxied to either side. Then use your Rhino-liner to seal it and protect it from the acid. It should be lighter than 3/4" plywood and it is better insulation. I would be willing to help with the design if you want someone to assist. I would hate to see you build it with plywood and then lose your batteries six months down the road.


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## CFreeman54 (Jan 14, 2009)

If you are still sitting in the car by the time the fire breaches a metal battery box you are either trapped, unconscious, or really dumb. The point is the containment gives time to get out of the car...or extinguish the fire. 

Have you never heard of halon fire suppression systems? They are used in drag cars and recommended by the FAA for extinguishing Li fires on airplanes;

http://www.jegs.com/p/Stroud/Stroud-Safety-Fire-Systems/1014849/10002/-1


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## Duncan (Dec 8, 2008)

Wood is good!

My battery box is a type of treated MDF - very strong, totally waterproof, superb insulator
And best of all I didn't have to pay for it!

Much better than metal or plastic.
I am even going to use some for the sides of my car


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## Jamie EV (Oct 3, 2012)

Do you mean styrofoam on the inside of the aluminum box or the outside?


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## Ziggythewiz (May 16, 2010)

PaulS said:


> I would hate to see you build it with plywood and then lose your batteries six months down the road.


The plywood should not be supporting the batteries. Angle irons are used for that. A plywood battery box will easily outlast the lead acid batteries it holds.


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## dtbaker (Jan 5, 2008)

by the time you build the steel/aluminum rails and paint the inside and out you've invested a ton of time... less expensive to go with 1/4" think polypro sheet which is easy to work with, non-conductive, and can be heat-welded (not glued). It is acid and moisture proof and requires no paint.


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## Jamie EV (Oct 3, 2012)

Ziggythewiz said:


> The plywood should not be supporting the batteries. Angle irons are used for that. A plywood battery box will easily outlast the lead acid batteries it holds.


That's what I've heard...and no of course the plywood would not support hundreds of pounds of battery weight. You still need angle iron frame!

Plywood is relatively cheap and easy to mill compared to plastics, metal or some sort of composite. I've heard good things about it provided it's engineered correctly...as for wood splintering...my thinking is that if you're putting the car in a situation tha tis causing your wood to splinter, you've probably got more serious immediate concerns than your batt box....like your driving style

For my purposes the box would be for electrical safety, heat insulation, acid spill protection and overall aesthetics. Metal supports beneath the box and laterally would reinforce the box at key stress points of course (perhaps with rubber isolation) 

A well built wooden box will take a pounding. The frame of the Morgan Speedster was and continues to be all wood...food for thought.

For me it comes down to dollars and sense. If I can find a decently priced truck bed box made of plastic, I might go for that as well...maybe even an agricultural feed bin (they're very tough. but they tend to be pricey as well.


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## dtbaker (Jan 5, 2008)

the 1/4" polypro is $100 for a 4x8 sheet, but completely acidproof, and doesn't require painting. as easy to work as plywood.


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## Jamie EV (Oct 3, 2012)

dtbaker said:


> the 1/4" polypro is $100 for a 4x8 sheet, but completely acidproof, and doesn't require painting. as easy to work as plywood.


How rigid is that? 1/4 inch doesn't sound too robust.


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## onegreenev (May 18, 2012)

I would still assume it would need external frame support.


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## Jamie EV (Oct 3, 2012)

onegreenev said:


> I would still assume it would need external frame support.


I should say so....

speaking of boxes , is it strictly necessary to use a framed box in the trunk? I mean...it sort of IS a box....mind you it would need sealing and venting and insulation but what's the matter with just stuffing the trunk full of batteries (load limits permitting of course). I have seen a few setups like this. I've also seen people cut out the rear trunk and then weld and drop in a deep box so that they can have a regular boot-space (trunk-space). Neat idea and the box probably only weight slightly more than the oem trunk.

with SLA or AGM it's even simpler I suppose. No venting during charge.


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## dtbaker (Jan 5, 2008)

Jamie EV said:


> How rigid is that? 1/4 inch doesn't sound too robust.


its pretty stiff... stiffer than 1/4" ply or waferboard. going one cell width it won't bow, going more than 2 rows its best to add a vertical rib internal or external to stiffen it up.

going one cell width, you really don't need steel or AL frame for Li cells as long as you have good attachment points that keep the stresses in tension/compression rather than bending.

when I upgraded from lead to lithium, I was able to ditch my steel angle frame in the front and just make a plastic box... which is bolted thru the bottom to a steel U member, and attached in the front to the hood support.


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