"John Stumbles" wrote in message

If the OP really goes off running in the midge-infested wastelands of the
north with long-suffering spouse in tow on a whim, without time to fill a
couple of flasks before he goes (though presumably time to take some cold
water and cold soup :-) then he could do with something more than the
standard wimpy cigar-lighter 12V immersion heater. How about (a) fitting
inside the car a socket of decent current rating wired back to the
alternator or battery terminals in heavy gauge wire (b) some sort of
resistive heater to connect up to this socket. If the heating element were
about 0.5 ohm, taking 30A at 14-15V (with the engine running) giving a
power of about 400W then you could boil a cup or two of water in a
reasonably short time (I'll leave calculation of the exact figures as an
exercise for the reader :-). Question is how to make the element? What's
the resistivity of stainless steel? Would a length of thin s/s strip bent
into a U shape do it? Or a coil of thin s/s tube? Or some sort of closed
end tube (like a test tube) with a heating element inside, embedded in
ceramic (how?) or maybe tube packed with carbon making the resistance
element (would it be low enough R?) and central electrode connecting to
it?

Come on you d-i-y-ers!

If Spouse saw this he'd whip his pencil from behind his ear and start making
marks on a dismantled cardboard box ... :-)

Mary