# Battery Box Designs - What steel thickness?



## Overlander23 (Jun 15, 2009)

I ended up using 1-1/2" x 1-1/2" x 1/8" angle iron for my boxes. As you can see, I've kept the 90 degree on all corners for rigidity. They're ridiculously strong for my usage... my rear box carries 19 cells that are underslung between frame rails (they don't rest on anything). Though, my max span is about 8 cells thick. I think the stock is up for it, though. If you need more strength, length-wise, just add triangle bracing.

I don't see a problem with bolting a hold-down bracket on the edges to keep the cells in place, but you have to be careful. My boxes are enclosed, so the tops of the cells sit a couple of inches from the battery box tops. Wood blocks wedge between the top angle and the cells. They wedge the cells from moving.

You can see more detail on my blog... http://adventure-ev.com/?p=181


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## corbin (Apr 6, 2010)

Overlander23 said:


> I ended up using 1-1/2" x 1-1/2" x 1/8" angle iron for my boxes. As you can see, I've kept the 90 degree on all corners for rigidity. They're ridiculously strong for my usage... my rear box carries 19 cells that are underslung between frame rails (they don't rest on anything). Though, my max span is about 8 cells thick. I think the stock is up for it, though. If you need more strength, length-wise, just add triangle bracing.
> 
> I don't see a problem with bolting a hold-down bracket on the edges to keep the cells in place, but you have to be careful. My boxes are enclosed, so the tops of the cells sit a couple of inches from the battery box tops. Wood blocks wedge between the top angle and the cells. They wedge the cells from moving.
> 
> ...


Nice! I will definitely go with 1/8" thick based on that, and I can probably get away with 1", but I'll think about moving up to 1.5" too.

Your website is great! I've been meaning to get some similar "strapping kit" to contain the cells together -- does the ebay seller have more kits? I'll try searching and finding one for myself.

I'm hoping to get my batteries next week. I've been reluctant to make boxes before actually getting the cells, since i'm not 100% sure of the cell size. I ordered the 200ah cells in the "small 160ah" size, however, I have heard they stopped making those size, and I might be getting some that are larger.

corbin


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## RKM (Jun 9, 2008)

Corbin,

I used 1/8 X 1" angle and 1/8 X 1" flat for the skeleton frame, then lined the boxes with 1/8' thick UHMW plastic. I also have a small amount of insulation in each of the five boxes. Three of the boxes house cells arranged 9 wide, the largest holds two rows of nine cells. This largest box is also unsupported from beneath. As Overlander suggests, triangle bracing is a good idea to add strength for the wider span.

I used SS strapping to hold down the cells. There are holes for the straps to pass through the bottom angle irons and small pieces of round iron to soften the radius bend of the straps. The straps have poly tubing across the top of the cells to insulate them from the posts.

I'm convinced that this design is sufficiently strong and reasonably light.

Hope this helps.

Rob


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## corbin (Apr 6, 2010)

Hi Rob -- yes, that does help, thank you! Everyone does such quality work on these forums. I'm always impressed.

--corbin


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## adric22 (Jan 17, 2008)

I used 1/8" angle for my battery racks.. Here's a photo of the rear rack:










Notice one big difference is that I actually put spacing between my batteries. I was using lead-acid, though, which tend to buldge on the sides a bit. So with lithium your design my be even better. Oh, and to hold them in I made a similar rack for the top of the batteries and then they bolted together.


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## Jimdear2 (Oct 12, 2008)

Doesn't appear this material was mentioned, but I may be wrong. I've used it and it works OK.

A good source for battery rack material is bed rails. Goodwill and other places used to have hunderds, now since scrap prices went up they are a bit harder to find. Even so they are still cheaper then new metal.

Most types I've seen are 1.25 or 1.5 inch angle with a 1/8 thickness. 

The advantages are: the metal is designed to take quite a load. I think it is close to spring steel. Slightly lighter then the same sized hot rolled angle. Probably save over 50% on material.

Disadvantages are: harder to cut with a saw, but a cut off wheel does fine, nasty to weld, but a good mig will do it.

The rails are usually bent up from flat stock so you don't have that thickening at the fold point of hot rolled angle. You won't get that step in the corner you can get with 90 degree cuts for your weld. A nice radius lets you get your batteries close to the inner edge without tipping towards the next row.


Jim

Even at


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## corbin (Apr 6, 2010)

Cool! it sounds like the general consensus is 1/8" is a good thickness to use. So, I'm going with that. I'll be picking some up from SIMs metals in San Jose, CA tomorrow.

corbin


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## Ziggythewiz (May 16, 2010)

Corbin,

In my bug I used same as everyone else but wished I had used 1/8" 1 1/2" angle instead of the 1" for the front box piece behind the back seat. It would have fit easier.

For straps, I just used some normal tie down straps, they were cheap and are rated at 800 lbs.


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## dtbaker (Jan 5, 2008)

RKM said:


> I used SS strapping to hold down the cells.


very interested in your strapping method. how do you terminate/tension the strapping? and where did you get the banding material?

I am contemplating running 1/8" all-thread through the ventilation ribs between cells, but the strapping is an option to combine the end compression with holding in the box...


...and in answer to the original thread, my rear battery box I used 1x1x1/8 steel angle edges welded together, then lined with 1/4" polyprop plastic panels which I screwed to the steel rails, and then plastic welded the seams together on the inside. Maybe a little on the heavy side, but acid-proof, strong enough for Lead, and protection from road debris as I live on a gravel road. I have a whole series of construction pictures around here: http://www.envirokarma.org/ev/gallery/090125_rrack02.foam.htm


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## Tug (May 26, 2008)

No ventilation?


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## dtbaker (Jan 5, 2008)

Tug said:


> No ventilation?


...if you are talking about mine... there is no forced ventilation/fans. I decided the time, trouble, and risk of spark from the fans was worse than going with natural venting.

There are a couple 1/4" holes near the top railing, and two 1/4" holes in the bottom to allow natural convection of fresh air to vent hydrogen from gassing with the FLAs. The lid to the cabin which acts as the rear seat, has a layer of foam gasket to provide an air-tight seal so no hydrogen seeps into the cabin. Never had any discrernable odor in the cabin after charging although the garage had a slight sulpher smell sometimes.

no venting required with the LiFePO4 of course.... so I'll seal up the little holes for the winter.


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