Everybody's powerwall build is going to be different, and everyone's budget is different, but I thought I'd bring this up. I'm planning my build in modular packs using the 4x6 18650 cell holders, on shelves for each series. Turns out reclaimed pallet boards are exactly the depth needed for the 4x6 packs. For 4 cells deep, not 6, though there are various pallet sizes and some of the wider boards probably could accommodate 6 cells deep. And it's not hard to find used pallets for free, if you don't mind breaking them apart yourself. Just wanted to share for other people that could use that information, since it's a great option for a build on a budget, not to mention fits in with the theme of "second life."