The R100GS takes a huge battery, so I figured I could save some weight and make more room for a bigger tool tray if I fitted a smaller one, with the expectation that I would replace it more often to keep it up to peak capacity.
I looked through the Yuasa battery catalog
and found the YTX14AHL-BS which seemed like it might be enough. Its used on some other big displacement bikes. Here's how the specs compare to the 53030:
model AH CCA acid weight L W H
53030 30 ? 1600ml 7.3kg 186 130 171
YTX14AHL-BS 14 210 660ml 4.1kg 134 89 166
With a little searching I found one advertised cheap locally so picked it up to try it out. Here's how it compares to the original GS battery.
To start I made up a paper model to find the best fit in the frame and get an idea of styling that would look good.
Here's a slightly revised version of the battery tray drawing
for the unfolded sheet metal. As seen in the photos following my original design didn't have the full front panel this drawing has.
I used some 16 gage aluminum sheet I had that was left over from the dash, and after a quick layout with a Sharpie marker I used this holesaw and drill press to make the big side holes. These holes were bigger in my original design, and I found they removed too much material which left the sides a bit too flimsy.
I could make the smaller holes with this rotex sheet metal punch
Here's the plate with the main holes. I don't have a photo of it, but next I punched four very small holes at the intersection of the fold lines then used a corner notcher to cut out the corners. The holes help to make a smooth bend.
I used a sheet metal brake
to bend the panels up. Also shown are the mounts I cut from aluminum angle. To be safe I made the mounts a bit longer than I measured was needed with the intension of trimming them down after welding and fitting.
Here's the finished tray with the corners and mounts welded, and mount holes drilled.
The old and new parts compared.
Here's how the tray fits in the frame. It leaves a lot of room for a big tool tray, exhaust pipes, and muffler. I still need to clean up the mount ends and add a hold down strap.
And a view with the battery. This photo doesn't really show it, but the contrast between the dark battery and the shiny aluminum makes the strip and five holes look really good.
As mentioned, this first version is a little flimsy, I think the new version of the drawing will be enough in 16 gage aluminum, maybe with a slightly stronger attachment of the mounts to the tray panels.