I previously showed the main battery racks (metal frames) being made and mounted in the back seat. Since then I've wire-brushed the surface rust off and primed and painted them with Rustoleum. The next step is to fabricate the wood pieces that will form the box that will keep prying fingers from high voltage connections and passengers from breathing battery fumes.
I chose to use 3/4" plywood for the base of each box to minimize flex from the battery weight. Actually, I really splurged and bought oak plywood. Nice and flat. For the sides I'm using 1/2" pine plywood. I'm relying on the steel angle framework to keep the batteries contained in the event of an accident, so the strength of the wood sides isn't really important.
Here's a view of the two main boxes with the wood pieces set in place.