He puts foam padding all around the cells and then what seems like a fiberglass card over that. If the fit is too loose you could always add more foam layers over the cells. The only 40 BMSs available are 14s (58.8V off the charger) and 10s. There is a 13s but its kind of wimpy - 14ga discharge wires :|
...as you can see, the BMSs in question are the "Li-Ion" type: http://em3ev.com/store/index.php?route=product/category&path=42&sort=p.sort_order&order=ASC
...as you can see, the BMSs in question are the "Li-Ion" type: http://em3ev.com/store/index.php?route=product/category&path=42&sort=p.sort_order&order=ASC