best material for shock absorbing custom battery case

[CrossRoads]

I need to build cases for my cheap but very bare bones Unit Pack Power batteries. They have no shock absorbing bases for the cells and come with a very minimal plastic case that appears to be mostly waterproof but has zero structural protection. I want to use marine grade mahogany ply (hydratek) for the box, for durability and aesthetics, but i'm going to build it with about a 1/2" larger all around (sorry i'm from amurica, 1 to 1.5 cm) to line the interior with something shock absorbing. My question is has anyone done this sort of thing and what do you think is the optimal material? Rigid expanded polystyrene? Neoprene? packaging bubble-wrap?

 

[HumanPerson]

I use the green stuff from lowes https://www.lowes.com/pl/Board-insu...ing-supplies/4294858106?refinement=2526185591

1" for the tops and bottom and against the seat post tube.

For the sides i use the same thing except it's only 1/2" thick.

Hope this helps ya

Ride Safe

HP