Living off grid and doing this for years, useing whatever batteries I can find. Currently useing 2volt pb cells from a cell tower back up power system, found out my inverter and charge controler will both run at 56v nominal, for a bigger bank with lower current draw and differentials. Busy working towards an outside power room in a shipping can shop, will be 8'x 8' x 9.5' h, and contain ALL my rather large collection of power equipment, tools, parts, and related electronics, but am very likely to upgrade to new sodium battery cells and build my own bank and aim towards car charging and a two way power link. As to danger, anything sitting there with ~50kw/hrs power in it can easily make you, dead, funny looking, or both and happily turn a wrench into a nice big ball of plasma for your close inspection. It's best to treat a big battery like having a large ambush predator as a pet,nothing personal, but it has certain triggers and is faster than you can imagine, way tougher than you are, and infinitly patient. Or think of it as a gun that can not be unloaded, has multiple triggers, and can be induced to explode. Plus they can just fall on you and crush you. That all said, properly tested, commisioned and maintained, they are as safe as anything else.