This clamp mechanism uses 3 X 3/8" bolts and two pieces of 3/4" thick HDPE board to clamp around the battery cases bottom draw bar. A slot was routed into each clamp at the perfect height to fit the battery case.
The battery case draw bars fit into the notches in the battery cells and compress the cells with 5/16" SS threaded rod. The square aluminum bars are 1/2" aluminum square tube which locks the cells in place and fits this hold down clamping mechanism. The battery can not move when installed.