Most of the 12-volt appliances at truck stops (and at many RV stores) are just crap. The reason that coffee maker takes for-
ever to heat water is it has to be a small enough amp draw not to fry the wires of the 12-volt socket. I think that one is an 8 amp (100 Watt) coffee maker. Bigger ones will draw 13 amps (150 Watts). Those 12-volt sockets are fused at 15 amps.
If you want a really good 12-volt coffee maker, the
Power Hunt 12 Volt Single Cup Coffee Maker is the best there is. Their products require a special
12 Volt Power Port plug (or 2-outlet strip which you supply the cables) that connects directly to the battery using heavy cables, instead of a normal 12-volt socket. That's because their products are high amp draw units. The coffee maker draws 25 amps, for example, but it'll make a cup of coffee in 3 minutes. The 10-cup version draws 45 amps, and takes about 19 minutes to brew a pot. Once you have the power port connected, then all of Hunt Power's appliances can connect to that same port, so you only need to buy one power port. They only plug in one at a time (or two if you have the strip). Coffee maker is $60 and the power port is $50.
My aunt in Tucson lives mostly off the grid, using solar power. She has a Power Hunt coffee maker and a grill. The Power Hunt products are somewhat popular in RV conversions, because they're located in Tualatin, OR (suburb of Portland), the same town where
Upscale Auto (Sprinter accessories - and a repair shop) is located. The Sprinter RV conversions are very popular there. They have a club with rallies and everything. They're moving into accessories for the Promaster van, as well. It was my aunt where I first saw one, and then I saw a couple more inside some Sprinter conversions when I visited Tualatin with a delivery.
But man, you've gotta be a real coffee devotee to spend that kind of money on a coffee maker when truck stop coffee is so close by. Then again, I don't drink coffee, so what do I know?
The Coleman and Igloo electric coolers work pretty well. But they'll only keep things about 40 degrees cooler than ambient temperature, so there's a limit to what they can do. They will draw 5 amps, though, so they shouldn't be run off a cranking battery, either. For a real 12-volt fridge that will also work as a freezer if you like, you'll need an Norcold, Whynter, Engel or Sundanzer unit. They're not even remotely cheap. But, you get what you pay for - a real fridge for 4 amps. Don't run one of those off a cranking battery, either.