# Vacuum formed battery boxes



## Zak650 (Sep 20, 2008)

Hi,

I've been involved in vacuum forming for 40 years. Deep boxes are't really a great application for vacuum forming. You wind up with thin corners. You can help some with and assist over a male mold then transfering to a female cavity. Over a male form tends to make webs at the corners. I see some people fabricating boxes with glue which if you go that route a lap(overlapping) joint is way stronger than a butt(edge) joint.

Zak


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## Ziggythewiz (May 16, 2010)

What's the goal? Are you trying to reduce weight, cost?

Most batteries have channels to promote air flow which vaccum forming would hamper.


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## skooler (Mar 26, 2011)

Hi Zak,

The idea was from seeing bathtubs being vac formed on TV (random I know!) If I was to make an MDF mold in the car, get it vac formed and then support with steel do you think it would be strong enough? The most weight I'll be putting into a single box is 150KG. What material and guage/thickness suits best? or is it a no go?

Ziggy,

Inspired by dtbakers plastic boxes:

http://www.diyelectriccar.com/forums/showthread.php/upgrading-miata-lead-lithium-79061p5.html

I like the idea of using something non conductive for battery boxes.

Cost isn't really an issue, I just want something to contain the batteries effectively and actually surround them to prevent moisture and debris getting in.

The main consideration is ease of creation/ installation.

My current steel boxes literally took 3 weeks for me to build (never really worked with metal before though!).

Cheers,

Mike


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## RIPPERTON (Jan 26, 2010)

Im currently making boxes from 6mm acetal plate and using m4 countersunk screws to hold the corners together.
Acetal has good thread holding as its harder than nylon but almost as expensive as aluminium.


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## mizlplix (May 1, 2011)

Harbor freight-plastic welder....Uses hot air to melt the plastic.








Looks like a big soldering iron.

Cut plastic to size with a circular saw. clamp together (or make a wooden battery size model to clamp it around) and weld the corners. Makes it like a solid piece. GREAT for batteries.


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## Caps18 (Jun 8, 2008)

Or you can buy a Pelican case in the right size...  I'm not done yet, but it should work very well. They come in a whole bunch of different sizes. But airflow will be non-existent (or will have to be added on later). This picture is of the biggest 1690 case that will hold 45 100Ah LifePO4 batteries in a 9x5 array.


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## Ziggythewiz (May 16, 2010)

skooler said:


> Inspired by dtbakers plastic boxes:
> 
> http://www.diyelectriccar.com/forums/showthread.php/upgrading-miata-lead-lithium-79061p5.html
> 
> ...


I think the primary benefit of vac forming is the ability to fit odd shapes, which batteries are not. 

If you like dt's approach, why not copy it? To me the only drawback is the cost, so if that's not an issue, go for it.

For forming the strength would depend on the material used, but I think it would be difficult to get both good strength and good forming around the corners.


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## Zak650 (Sep 20, 2008)

Hi All,

Skooler, when you are thinking about vacuum forming it's really a manufacturing/production situation. One offs aren't in the picture. I designed and built all the tools and manufactureing systems to make Vetter Winjammer motorcycle fairings. We could make them in very large volumes but to make one or two molded items means doing almost all the work in making thousands but then only making one or two. Bathtubs, spas are great for making a cosmetic skin and then backing it up with fiberglass for strength but even a smooth, gently curved shape will require a lot of R&D. 

The non conductive plastic route is excellent idea but I would think of it more in the vein of insulating the inside of a fabricated aluminum box. These lifepo4 batteries are fantastic but charging below freezing is really something that needs to be addressed. I'm using a small 25watt outdoor warming pad placed in the bottom of an aluminum box with foam or plastic lined walls and lid. The K&H small animal heated pad, # KH1060, $24 on ebay free shipping. Attach one or two of these to an aluminum sub floor inside the box and a thermostat and that issue will be solved.


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## skooler (Mar 26, 2011)

Thanks for all of the input.

As I said in the first post, it was just an idea, seems as though it isn't a very good one!

I did a small amount of vacuum forming when I was at school and thought it was relatively easy. I wasn't sure about larger applications, hence the question.

I think I'll go down a similar route to dtbaker and use a plastic welder with polycarbonate sheet.

Now to find a UK supplier.....

Thanks again


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## Batterypoweredtoad (Feb 5, 2008)

I think DIY vacuum formed thermoplastic would be great for a Flat-inum style A123 pouch cell pack. Plastic is light enough that the relatively large surface area of that style of pack wouldn't cause such a weight hit that other materials might.


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