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First a little background on why I decided to do my battery this way. One of the considerations was that all of the battery boxes I could find in the aircraft supply catalogs cost about $100. Way too much for a little plastic box in my neighborhood. I could have gotten a battery box for a boat a lot cheaper but I would have had to have a way to secure the battery in it as well as securing the box plus it might not have fit in the space I wanted to put it. I also had to pick a size for the mount. It seemed to me that one of the larger and most common batteries (I could be mistaken here) was the Gill 35 so I decided to make my battery mount fit that battery. If I find a smaller battery I can still make it fit securely, I just can't go with anything much larger. Another consideration about doing it this way was that there needed to be a way to evacuate the fumes from the battery if I don't use a sealed battery. Below you will see my solution to the battery fume situation if I should elect to use a vented battery. Since I plan on using an IO 540 (unless something really worthwhile comes up before I get to the engine installation stage) I am putting my battery behind the back seat but close enough so it can be taken out by removing the seat back.

I started by making a rectangular box out .035 tubing. The poster board represents the size of the battery bottom.

Here I am checking for clearance. The aluminum bar on the left of the mount is where the elevator push-pull tube goes. The welding rod going through the fairleads represents the rudder cables.

This is the reinforcement I added to support the weight of the battery. Actually the fuselage as it is would probably support the battery just fine, I just wanted to spread the stress (on the battery) across more area of the battery bottom. I have a piece of 1/4" honeycomb (nonmetallic) that I will put under the battery to help distribute the battery weigh more evenly also.

This is what the mount bottom looks like as it will be installed.

Here is the beginning of my solution to the battery fumes. I started by cutting some poster board to fit all of the caps so I could get the spacing just right.

Then I drilled holes the same size as the caps (slightly larger) in some PVC pipe to fit over the caps.

I took a PVC end cap and drilled it slightly smaller than the tubing I will be using for the vent line.

With the hole slightly smaller the tubing is an interference fit and stays in place just fine.

This is the finished product. All I still need to do is drill a hole in the other end for another piece of tubing to provide forced air to push the fumes out.

Here is how it fits with the battery top retainer in place. I didn't really take any pictures of the retainer because it is just like the bottom except it has a couple of tubes welded across the top to hold the battery down.

The strap that comes on the battery as a handle works great to hold the "chamber" in place.

This is the beginning of a piece I welded on to hold the retainer bolts. I started by drilling a hole through one side of the tube.

Nest I cut out from the hole to the edge and filed it smooth.

Last thing to do was to trim it to the desired length.

Here I am making the retainer bolt. I thought about just buying some "T" bolts but couldn't find any long enough. Maybe I should have looked harder but I like making stuff anyway so why not make this. First step was to drill a hole the same diameter as the rod I was going to use.

This is the rod pushed though the hole. I left it sticking out just a little bit for welding so I would be sure to get good penetration and I wanted it to protrude out a little so I could file it smooth.

This is after welding, grinding and filing.

Here the tube has been trimmed to proper length.

This is how the two pieces will fit together.

After trimming the rod to the correct length needed for the Gill battery I cut some threads onto the end and will use a wing nut (safetied) to secure the top.

After welding the first piece onto the lower battery mount this is how it will work.

Next was to make the retainer for the battery mount top. I started with a piece of square tubing and drilled a hole through it the same size as the retaining bolt.

Then I split it diagonally and cut it to the correct length. I then rounded the corners that weren't going to get welded to the tubes and fitted the other side to fit the curvature of the tube.

Here is what it looks like after welding it on.

This is how all of the pieces fit together.

The finished product before welding into the plane.

Here is how it all goes together.