we have Muffle furnace so it can reach 800 degree C.we put a bunch of NaCl (almost 100 g) in quartz cup n melt them.
I am not sure if he was just cleaning the wires or something , but this is what he did and told us , as the thermal battery inside the machine wasn't working.
anyway I read a little bit about the molten salt battery , just wondering how it work and how to design one.