Phil Addison wrote:


Now, just how DIY do you want this? There is a copious supply of piping
hot water in your vehicle cooling system. Surely someone/somewhere has
rigged up a means of routing that through a mini heating coil which
could be dunked in a steel flask heat up or keep hot the contents? I bet
google has some designs already!

Just look up "calorifier" - boats use them all the time for hot water
supplies.


--