Portable 12v Pie Warmer

For hygienic reasons, foods should be held above 140°F = 60°C. Thus I would target the cabinet for 65-70°C. The dimensions and R-value of insulation will determine the heat input needed. I'm too sleepy/lazy right now to estimate that, but this will give the heater wattage required. From there, just use Ohm's Law. Skip all the crap about converting to 120/240 volts. Just get a heater with some extra watts, put a thermostat on it, and run it off the 12-vdc batteries (or other voltage as applicable.)

Bingo! William Tell hits the apple right in the core.

I don't mind building something if I have to. But if there's an easy way to do something, I'll take that route every time.

Nice find Kramarat

Bullseye

Next up, a 12v Peltier fridge to keep the beers cool, as a complement to the meat pies. (I'm crappy at golf, but these ancillaries don't sound too bad.)

You can keep the pies. If it weren't for cold beer and golf carts, I'd never bother with that silly game.

My claim to fame in golfing, is that I always come home with more balls than I left with, because I spend more time searching in the woods than on the course.

I come home a winner every time!

12v Peltier devices work just fine as heaters, too.

Yeah, but nichrome is cheaper.

I'm not thinking too clearly myself (as someone else mentioned (about theirself)), but I know a Peltier device can be run in reverse to create heat.

Wouldn't it also be more efficient than a resistance heater as it is, in essence, a solid state heat pump?

I'm not sure about that. From what I understand, Peltier/Seebeck devices are not particularly efficient. Their advantages include simplicity, compact size, and no moving parts. This is all to the good, and useful, but not the same as energy efficiency.

Ok, thanks--I think you're probably right--I've never seen them described as high efficiency. And some quick googling seems to confirm that.

I have a buddy that uses one to keep beer cold. It works great, but it will only keep the beer a certain temperature below ambient. If it gets too hot outside, he gets beer that's about 20° below that. Pretty limited in Atlanta.

Peltier devices create heat normally - one side hot the other cold.

The 'hot side', is the applied potential energy plus the heat drawn from the cooling.

Much the same as reverse cycle air conditioning is a 'better heater' than 'cooler' because the pump energy adds to 'heat' and subtracts from 'cold'.

Great Find! Kramarat, unfortunately they're out of stock.

I certainly like doing it simple, and cost effectively, if I can, however, due to being located in Hanoi, Vietnam, such items are usually very difficult to obtain and often attract exorbitant Import duties, on account of being electrical/electronic items.

as for food temp, anything that can operate between 50 deg. C and 110 deg. C is certainly within the ball park.

Any food kept longer than 4 hours in such a device ought to be thrown away anyway, but food safety regulations as they might apply in different regions of the world are not the primary subject of this discussion, interesting as they may be...

Thanks for the prompt replies guys, I appreciate the interest shown so far, but on the surface, it looks like this is gonna have to be something I build, rather than order, "off the shelf." :-(

Maybe these guys.

Too bad this isn't until Sept.

Many of these things are actually manufactured a lot closer to you, than us.

If you could just get them to sell you one.

http://www.alibaba.com/product-gs/248795543/food_warmer.html

Use a water cooled cart with petrol engine, run the cooling water (thermostat set at desired temp... I used 210°F) through a small heat exchanger with a 12V motorcycle cooling fan blowing the air into the insulated compartment.

I designed/built many many many food delivery vehicles using this technique, with outstanding success.

If You have ever seen the Meals on Wheels trucks, Harras casino trucks, Pizza Schmizza, Burrito boy etc etc etc, that's the system they all use (yep, built em all). The great thing about it is the simplicity, and the ability to use the heat that otherwise would simply be wasted to the atmosphere.

We had less success using a 12V system, or propane system (although we did employ both) the reclaimed waste heat method was leaps and bounds above the others as far as reliability and maintenance were concerned.

Hi guys,

thanks for the feedback. I've since taken a look at the electric cars that are currently running around Hanoi, unfortunately they don't have a cigarette lighter socket, or any other mechanism of tapping power, so the pie warmer would have to be self-contained. As such this project has now fallen of the drawing board.

I do like the inverter idea the best, but would still have liked to build a 12VDC dive just for the fun of it. If anyone does come up with a circuit diagram, please feel to post it up.

Thanks again, have fun.

Installing a 12v power socket is really easy.

http://oreilly.com/pub/h/3611