Designs for battery box behind rear axle?

[RoundOut]

With both of my batteries located in the forward drivers side of the engine bay, there's almost 100 pounds forward of the front axle and on the outside edge. My truck has a slight tilt that way and I hope moving the batteries back behind the rear axle will reduce the tilt, lower the overall center of gravity, and improve the balance of the truck over both axles. (The tillt couldn't be because the driver weighs in at +/- 200 lbs. - ) The relocation will also open up a nice venue for on-board air at some point in the future.

Has anyone else done a relocation of batteries behind the rear axle? If so, what design elements did you incorporate? I am looking for ideas to make access to the batteries simple and secure (physically stable, safe cable runs, and protected from theives). Any advantages of having Optimas on their side versus vertical?

So far, I am leaning on putting them in a marine (USMC) ammo container designed for two mortar shells. I need to get my hands on it (it is currently a prop in a retail store we have) and make sure its dimensions work, but I am pretty confident it will make an ideal "case" for the batteries to protect them from the elements, and still allow easy enough access. I'd have to drill appropriate holes for my cable runs and use adequate grommets to prevent insulation chafing. If I could figure out a way to mount it lid up, with the lid's hinge forward, I could secure them inside the case to the bottom, put a locking hasp on it, and they would be pretty well protected.

Any other ideas are welcome!



.

 

[RoundOut]

I got it...

Here's the Ammo Can picture. 25"x13.5"x7.75" Dimensions.

Mark had an great idea. Use the ammo box so the hinge is forward. Bolt the air tank to the ammo box on the side opposite the hinge (the front of the box that will face rearward on the vehicle). Cut cable holes in the side facing forward. Construct a stronger hinging bracket to lower the whole assembly, with the hinge forward. Use the winch for the spare tire, to lower the assembly for inspection or maintenance.

I love the spare tire winch idea. That is AWESOME.

I think I'll have him make the hinged drop bracket with a locking hasp and then fab up a skid plate for the whole thing, one that can serve to hide the posterior gizmos and offer some rock protection, too.


.

 

[ntsqd]

One of those exact ammo cans is bolted to the tongue of the C.U.T. as a lock box to hold all of the coupler/chains/wiring stuff. It's frankly a bit light to hold a vehicle battery w/o some added structure. I don't think that covering the batteries is too important. I suspect that the corrsion protection is debatable. Though some sand/rock blast shielding is probably a good idea. There are any number of various pre-fab'd Optima holders that could be used.

In a dynamic loading situation I usually design (SOP) for 4X the static weight. So for those times when you didn't realize how steep that vado really was, those batteries then weigh about 400 lbs.

I know of a certain DuraMax that has 10-12 major Baja trips under it's belt. It has done those trips with 2 upside down yellow tops simply bolted to a load spreader plate on the bed floor.

The DM's original owner previously had a well built T-100 that used the tire winch to lower the rear of the rear skidplate, that curiously enough, had a spare tire on top of it. The front of the skidplate's frame was hinged (2.25" x .25" wall tube spinning on some 1.75" tube) on the air tank's support frame. 805Gregg, if you see this it's that built burgandy T-100 that wanders around your home town.

 

[RoundOut]

change of direction

Out with the ammo box idea, in with a fabrication project. We are cutting out the X-shaped cross member that exists in stock Tundras to support the spare tire, add some re-inforcement to the area under the bed, and to add some rigidity to the rear of the frame. We will replace the cross member with a rigid box, made from angle-iron and thin gauge plate, except for the lower surface, which will be of skid-plate quality. Inside the box forward, we will locate the two Optimas. In the box behind them, will be a rib that also supports the 4-gallon air tank. The forward surface of the box will be accessible from an inspection port to enable quick reconnection of loose cables, etc. Below the air tank's drain port will be a hole in the skid plate to allow easy draining of any collected condensation, too.

 

[sami]

just make a trunk where the spare tire used to sit under the rear... IMO better for structure and more secure. When i build mine, i'll put atleast one battery back there.

-Jason