Les-Please explain.Yeah newbie to this kind of thing,but I do want to learn more.
I'll try to describe this as best I can.. A Peltier Junction, is an electronic device, sandwiched between 2 aluminum plates. If you apply current to it, it transfers heat from one side to the other, and will boil water on the side heat is transferred to, and freeze it on the side the heat is transferred from. Basically, cold is nothing but absence of heat, and heat is a form of energy. They're not dependent on current only flowing one way, if you reverse the current, it transfers heat the other way. If you purchased some, you could build a thin aluminum plate to serve as a bottom in the cup holder, attach a Peltier to the underside,with a CPU heatsink and fan mounted to it and with a dab of heatsink paste. WIre it up so you can reverse the polarity, you have a heater/cooler for your drink. I had a cooler built with one of these over 20 years ago,that I saw the idea for in Popular Electronics magazine,before you could go to target and purchase one, and I've been wanting to build some cupholders with a couple.....and now you're asking about it, so I thought I'd share... ( hell, someone beat me to patenting it anyway, lol)
A key element, is make sure the heat sink you add will cool it sufficiently, or just like an under cooled CPU, it'll toast itself.
edit*, i'll try to draw a diagram and post it, not sure if I've described it well enough...