My understanding is that the cylindrical cells (same as used by Tesla) are the MOST flammable. The downside is that it is slightly heavier and more expensive than some other Li chemistries. I believe it is what the Chinese EV makes like BYD use. The LiFePo chemistry is popular in that it has excellent cycle durability and very low flammability. You will want to read a LOT about Lithium chemistry.there are a number of different lithium battery chemistries in use, which have different durabiltiies, care and feeding habits, costs, and tendency to burst into flames. The battery-blocks run the current through a Neodym magnet for contact? Off-gridders have been building high power batteries (on lead-acid chemistries) using heavy cables, crimp lugs and screw connections for a LONG time and there is a wealth of info on the 'net about that stuff, and a lot of prefab cables and parts available. While it might be possible to source the cylindrical cells for cheap, the whole soldering/spot welding connections sounds like a bad idea (frying the cells, or requiring specialized equipment and techniques). I like the look of this stuff better than your site, since it seems to be bigger cells with screw connectors and commercially sourced battery boxes, rather than little cylindrical cells and custom machined (or 3-d printed?) parts. I found this outfit selling biggish lithium packs in LiFePo: I looked into Lithium for a Hobby-sized off grid Solar system I have (50W panel), when my 100 Ah flooded lead acid battery faded after 4 years of use.