In a post dated November 2 2014, I detailed the fabrication of a battery box modelled after one I saw online. It was based on the stated dimensions of the PC680 battery, but when I finally purchased the battery a few weeks ago, it became clear that I had oversized my battery box a bit.
For this retaining design to work, it has to hold the battery tightly against the firewall, so dimensions on every axis had to be trimmed down a bit.
So I took the original part and cut off some of the flanges, and made up some new parts to get the fit just right.
Two key changes to the design were to 1) introduce a hinge at the top (image 1) and 2) reinforce the bottom attach with some L-angle.
The L-angle is much stiffer and provides a rock-solid shelf for 15 lb battery weight. The 0.050" box is then rivetted to the angle as shown in Image 2. You can see the outboard vertical retaining flange had to be trimmed off and I rivetted on a new flange; it now sits snug against the battery on both sides to prevent lateral movement.
The two AN3 bolts attaching the top of the battery box to the firewall are intended to always stay attached (could have used rivets). The hinge on the top allows the whole box (with the battery) to swing up and away from the firewall and the battery can then be dropped out from the box for sevicing.
The 4-door cowl certainly made work very easy here, so I'm reaping the rewards adopting that cowl design as well.
L-angle and AN3 retaining bolts with nutplates on firewall