When designing the camper’s subframe, 730mm was the absolute maximum width that I could make the battery bays. Luckily, this is just wide enough to hold four AGM Deep Cycle house batteries, which is what I intend to use.

The more available power you have, the more things you can run without overtaxing the batteries, but that’s a discussion for another day…

Like the truck battery frame, the frame for the house batteries is also made from 50mm x 5mm angle.
Making the frame itself was quite straight forward, but finding a method for securing the batteries required a bit more thought. The reason for this was because four batteries only just fit within the available width; there is no extra room for a standard battery bracket, like the OEM one used to secure the truck’s batteries.

The design I ended up with involved a single bracket that secured all four batteries by clamping them down along their centrelines.
To secure the batteries a combination of angle and flat bar was used. The centre part of the bracket is made up of two pieces of 40mm angle, welded together to make a T. A similar arrangement is at either end, but this in “notched” to give clearance around the air filter bracket.
Between the angle pieces are lengths of flat bar to add additional clamping force onto the top of the batteries. A length of 25mm x 12mm flat bar was used to to join everything together and give the bracket sufficient strength along its length.

To hold the battery bracket to the frame I manufactured some custom T bolts. This involved making some 8mm studs that had 30mm of thread at either end. The nuts were made from 15mm round bar with a hole drilled and tapped in the middle. A spacer, made from 12mm round bar, was also needed to give clearance between the nut and the lugs on the frame. The spacer allowed for a lock nut to be used at that end.
All of the T bolt components were made from stainless steel.

On the base of the frame there is a sheet of 2mm stainless steel, which gives the batteries a solid platform to sit on. At the rear there is a piece of folded stainless steel angle which acts as a battery stop. Holes were drilled on both sides of this angle bracket, allowing for the use of two different sizes of batteries; 305mm (105 Ah) or 330mm (120 Ah).

When test fitting the battery frame in the truck, and during construction, I used some old lead acid batteries I had acquired for that purpose.
These are not exactly the same size as the AGM batteries I intend to buy, but they are close enough to do the job. I simply allowed for the difference in size during manufacture of the frame and bracketing.
It is pretty tight at the front, but there’s still enough clearance around the air cleaner bracket and clips not to cause any issues.

Update – 13 June 2012

Here are a couple of additional images of the completed battery frame.