Doing your own electrical systems for your homemade camper isn't as difficult as it might sound -- especially if you commit to keeping it extremely simple!
You can think of an RV or camper electrical system as made up of just three components:
The Battery (a.k.a. the "House Battery", as distinguished from your "starting battery"
The DC Circuits (direct current)
The AC Circuits (alternating current)
Keeping things simple...
I'm sure you know what a lead-acid car battery is, right? OK! You'll need one of those. (There are matters of the best battery type for a camper, but that can wait...)
The DC circuits are those wired to run 12V devices that can run off a car battery, i.e. from your car's cigarette lighter. These circuits are connected directly to the battery, just as your cigarette lighter is wired directly to the battery.
The AC circuits are those wired to run standard household plug-in devices. If it has a standard plug, then it is an AC device, and it requires an "Inverter" to be placed between it and the battery. The inverter turns standard "flat" direct current into the special"rippling" AC current that household appliances require.
Camper electricity revolves around Battery Powered DC Wiring. While it's in many ways easier for a beginner to implement, it's different enough from standard household wiring that it can be very confusing at first, even for electrical engineers! To help wrap your head around it, a crucial point to "get" is that...
An Inverter Is A DC Device!
(That is used to run AC Devices)
It might be easiest to think of camper wiring as implemented in layers:
First you have DC layer, which at it's simplest is a lot like wiring your speaker system together, or more accurately, like wiring a high-end car audio system.
You first connect a set of cables from the battery to a hub, i.e. set of "distribution blocks."
From there you branch off wires to DC devices like DC fans, LED lights, cigarette lighter outlets for plugging in your phone, AND... an Inverter.
Once you have an inverter connected (to a branch of the DC circuit), you can then plug your AC household appliances (portable fan, clock, heater, coffee maker, mini-refrigerator, etc.) into the inverter. Simple right?
That's really as complicated as it gets, ie. not very complicated at all!
Have you ever wondered if it's possible with a bit of DIY hacking to Build Your Own Air Conditioner?
Maybe even one that saves energy?
Check out this instructional video by Amit Ranjan showing how he made his own "poor man's air conditioner" out of a few spare parts.
Here's another variation
Watch how desertsun02 creates a Simple Homemade Air Conditioner using essentially the same setup as above, but quite a bit neater, and in a way that separates the parts in a way that makes it easier to see what's happening.
As explained in the video, the whole setup uses only 45 Watts, suggesting that unlike a typical energy-hogging air-conditioner, this one could conceivably be run off the grid on battery power or solar panels.
So, how does it work?
Copper is a great conductor of heat. When ice-water is pumped through the copper tubing, the heat within the warm forced air from the fan tries to equalize with the cold water in the tubing. In a sense the ice water in the tubing steals the heat from the air and delivers it back to the ice box. In doing so, it melts the ice, but if you have enough, you can keep this effect going long enough to get to room feeling comfortably cool again.
Instead of using water as a coolant, a typical air conditioner uses a gas refrigerant (like R22) to absorb heat from the air.
But instead of sending the heated refrigerant to an "icebox," an air conditioner has to pump the heat outside using a complex compressor and coil system, fueled by electricity.
Refrigerators and air conditioners run on a "heat pump" principle to pull heat out a cold place and pump it into a warm place, using knowledge of what happens to liquids and gasses under different pressures. This takes quite a bit of energy, which is why air conditioners use so much electricity.
In the case of the homemade AC unit, you applied this energy before you started, by making the ice water!
So in some senses, you've actually cheated. You haven't really saved any energy -- you've just borrowed it from somewhere else. This might not be a big deal in your apartment, where the cost for the ice is measured in mere cents, but if you're attempting to boondock in a camper... well, you can't! Not for any length of time, anyway, without running out of ice. So this system is good for a day, maybe two, so you're talking... about $1-2/day for the ice + gas for the commute!
But it raises an interesting question...
Can you actually make a self-running air conditioner that uses less power... that could potentially be run on energy from, say... the Sun?
It's an interesting question. It turns out that because the concept of a heat pump is so straightforward, it's possible to play with different combinations of liquids, gases and materials that boil and condense at temperatures and pressures that can be hit without requiring so much energy.
In fact your typical propane RV refrigerator uses exactly this idea. In any type of refrigerator, the freezing is accomplished by part of a chemical cycle in which the refrigerant absorbs enough heat to cause it to evaporate. But in a Dometic style camper "absorption refrigerator", rather than use an electrically-driven mechanical compressor (like an air compressor for the gas refrigerant) to return the evaporated refrigerant to liquid form, it uses the science of chemistry to do the job. Instead of electricity, an absorption refrigerator uses propane to boil an ammonia-water-hydrogen mixture, pushing it through a series of tubes that causes strategic pressure and temperature changes that continue the refrigeration cycle.
It's a bit ironic to realize that refrigeration can be accomplished by adding heat, but that's how an absorption refrigerator works! Unfortunately this old technology is less efficient and convenient to maintain than using an electric compressor, so it's only seen its revival in RV refrigerators. But to someone interested in renewable forms of energy, it's natural to wonder if instead of propane, you could use heat from the sun to do the same thing. And in fact, some researchers interested in helping communities in developing nations have been rediscovering and trying to adapt this idea with new combinations. A promising one uses the class of volcanic rocks called Zeolites, and a few companies have actually started selling expensive solar camping coolers that run on a simple system using a zeolite/water mix. You can imagine that the air conditioning applications could be just around the corner.
Of course, if you're strictly interested in low-power air conditioning, then it will pay to become familiar with evaporative coolers (a.k.a. "swamp coolers"). Those who live in a dry climate like the Desert Southwest grew up with evaporative cooling systems, which cool the air by blowing hot dry air across a water-soaked mesh. As the water evaporates into the air, it takes the heat with it.
Traditionally the limitation of evaporative coolers is that they don't work in humid climates. But a number of researchers have come up with clever ways to pre-dry the air using "desiccants", so that evaporative coolers are evolving so that they one day might be feasible in any climate.
And once you've solved that issue, then (provided you have a source of cheap water) you've got yourself a source of low-power cooling, requiring no more than a fan. You can read more in my article about evaporative air cooling by clicking below: