DrMark666 Thank you Potto, that does work. F4.

DrMark666 I have a bank of 4 Li-ion batteries salvaged from laptops with a buck convertor. There's likely to be more later but these are plenty for now.

DrMark666 I think it depends what you put in it - it'll burn a graphite crucible & it likes ferrous stuff, it depends more on what makes it cut itself out, I find - needs to put enough power in but not too much, so size and convection etc matter more for max temp. The actual temp. of what you're heating is a bit irrelevant to this machine, it just puts energy in.