Electrical systems inside a van can be a bit intimidating to figure out. I'll use this page to explain a little bit about 12 volt and 110 volt systems, specifically, how to install them. I'll try to be as basic as possible here, as there is a ton of information on the Links page.
How your vehicle produces power
For those who don't know how a vehicle's power system works, it's relatively simple. When you start the car, power flows from the battery to the starting motor which turns over the engine. The main belt on the engine spins up your alternator, which is a small generator. The alternator then provides all the power your car needs to ignite the spark plugs, run the various pumps, lights, stereo, and recharge your battery. The main purpose of the battery your car has is to provide enough power to the car until the alternator takes over. The whole car runs on 12 volts DC if you're in North America, or 24 volts DC if you're in Europe or Australia.
RV Electrical Systems
An RV, unlike a car, has two separate electrical systems. The first, which is the starting system, is identical to one in a normal vehicle. It provides the power for everything involved in running the vehicle under the hood and in the cab. Since most smaller RVs use the same chassis as a truck or a van, there is very little variance in these systems across the board.
Since the starting system is only really designed for the chassis, this does no good for everything inside the RV. An additional, completely separate system is used in RVs. This system and its components are called the house system.
A very technical, but thorough discussion of these types of systems and their components is on The 12 Volt Side of Life page. I recommend you read this first, as it will explain the concepts much better than I can here. I'll go over how some of those principles apply to vandwelling instead of a full sized RV.
House System - Components
House systems have a few different components. The first one is a battery or a battery bank used to store power. These batteries differ from the ones used in the starting system. Starting batteries are not designed to be drained of power and recharged repeatedly - their purpose is to provide a boost of electricity to start the car and that's pretty much it. If you end up draining a starting battery completely (say, from leaving your parking lights on) the life of the battery is shortened considerably.
House batteries are a heavier duty type called Deep Cycle batteries. They are designed to be drained and recharged repeatedly due to their thicker and heavier components. These batteries are rated not just in amperage like a starting battery but in something called Amp Hours. A good detailed explanation of Amp Hours and types of deep cycle batteries is on the links page, under The 12 Volt Side of Life.
Basically, the more Amp Hours (Ah) your system has, the better your storage capacity, and the more expensive your system will be.
If you have more than one deep cycle battery, make sure the entire battery bank is still delivering 12 volts. Most RV batteries or hybrid Marine batteries are 12 volts, but more and more individuals doing conversions are wiring 6 volt golf cart batteries together so the entire bank produces 12 volts. RV appliances and inverters will need this amount of power to be used effectively.
Batteries should be in a separate compartment and vented to the outside of the vehicle. When batteries charge or discharge, they bleed off hydrogen. In a sealed enclosed space, this can cause an explosion hazard. Remember the Hindenburg?
I would not recommend sourcing these batteries from Amazon. You can order them through automotive stores, RV/Trailer stores, and you can find them off the shelf at Wally World.
I'd like to share one last note that I have learned about deep cycle batteries from the last year and a half I have lived in my van. Deep cycle batteries used in a typical RV can last years, because in reality they aren't used much. A large RV will spend most of its time hooked up to outside electricity or have a generator running, thereby lowering the stress on the battery. People also rarely use their RVs year round, further extending the battery's life.
In a van where this isn't an option most of the time, your batteries get drained and recharged constantly. My rig can use quite a bit of power. After a year and a half, the efficiency of my batteries dropped off considerably until they would barely hold a charge. After confirming this with a few experts, it turns out that under the constant heavy use a battery is subjected to in this situation, you can realistically expect the battery to last for eighteen months to two years at the most. Once this happens, you may have to spend a bit to replace these batteries - mine cost $160. Save the receipt! You may be able to get a good deal and get a discount on a new set of batteries.
Another component, called an inverter, will take that 12v DC from your batteries and turn it into usable 110v AC current like you would find in a wall outlet in your house. This power is used to run anything in an RV that needs household current such as laptops, TVs, computers, gaming consoles, washers and driers, microwaves, and anything that you would normally plug into a household outlet that you would now take with you
All inverters will take the power from your battery bank and turn it into 110v AC, but not all of them put out current that is identical to what you would find coming out of a wall socket. To understand this, take a look at this graphic:
Normal household current that you would find coming out of a wall outlet produces a certain type of power curve as it alternates between positive and negative at 50-60hz. The current switches from positive to negative and back again fifty to sixty times a second, in a smooth curving motion called a sine wave. This is shown on the chart in red.
There are three types of inverters you can buy that will turn your battery power into household current that alternates at that magical fifty to sixty times per second, but not all of them do it the same:
Square Wave Inverters: These try to simulate household current by rapidly reversing the polarity from full positive to full negative, as shown by the green line. This can cause havoc with electronics, causing TVs to flicker, clocks to malfunction, and some appliances will just not work or in a worst case scenario, even be damaged. Fortunately, these are very hard to find because of their numerous drawbacks. Should you actually come across one, you should avoid this type of inverter at all costs.
Modified Sine Wave or Modified Square Wave Inverters: Shown in blue. These inverters are better quality than square wave. Instead of just rapidly switching polarity between positive or negative, the unit will "step up" or "step down" the polarity in order to closer approximate the sine wave of a household current. A period of full positive polarity will then have a period where there is no polarity before switching to full negative, and vica-versa. The entire cycle will still occur at the same speed as household current.
Some higher quality modified sine wave inverters may include a few more steps along the curve for better results. These inverters cost a bit more than square wave inverters but are much more common. They will run most appliances in my experience with no problems. (I've run my HDTV, my Playstation, fridge, microwave, laptop, external HDs, and power tools all for more than a year and a half on this type of power and I haven't had any issues.)
If you've ever seen or used an inverter that plugs into a cigarette lighter, unless specifically advertised as something different, it's a modified sine wave inverter.
Modified sine inverters will not run high end precision electronics equipment such as a heart monitor or an oscilloscope where so many of the device's functions require sine wave output. Some people also claim that desktop computers and clocks or appliances with timers may not function properly on modified sine wave inverters. Tube TVs flicker and speakers have a low underlying buzz or hiss. I have not personally experienced any of these problems, but I cannot discredit those that have had them.
The general consensus among the RV bus conversion community is that any electronic device that has an in-line transformer (X-Box 360s, laptops, battery chargers for powertools with wall transformers) should be fine on modified sine wave power since the transformer will convert the current into whatever the appliance uses with little difficulty. This, like all things, is not absolute, but given the amount of small cigarette lighter inverters that are marketed for running these specific appliances, it can be a fairly safe bet.
Sine Wave Inverters: These are the most expensive inverters you can buy, at twice the cost of modified sine. The advantage is that these will produce a sine wave identical to household current. These inverters will run anything, including sensitive pieces of electronic equipment, with no difficulties whatsoever. If you can afford it, this is the way to go.
If you need to run a sensitive piece of equipment, some people will actually use two inverters - a small pure sine wave inverter just for the one sensitive appliance, and a larger one with a modified sine wave for larger, less finicky appliances.
More on inverters further down the page.
An RV system will also have a converter/charger. When an RV is in a campground, it can plug into a 110v electrical line (called "shore power" in RV lingo). This will allow everything in the RV that runs on 110v power to do so without putting any drain on the inverter or batteries; however, they need to be recharged.
The charger portion of this unit is just what it sounds like - it's nearly identical to a battery charger you would find in the automotive department of a big box store. When an RV is hooked into shore power, the charger will use some of that electricity to recharge the batteries.
The converter portion of the unit is similar to the power supply in your computer. It also takes some of the 110v AC current and steps it down to 12v DC current to run anything inside the RV that requires 12 volts. Some examples would be the lights, water pumps, or fans. This frees the load from the battery allowing it to charge faster.
It can be a nightmare to wire up and remember to flip all the switches needed to switch back and forth between shore power and the inverter when switching between the two. Fortunately, RVs will have a transfer switch that will do this automatically.
If you're running on batteries and the inverter when you plug in the RV to a shore power line or turn on the generator, the transfer switch does several things. First, it turns off the inverter and allows the power to pass through to the outlets and anything else that uses 110v inside the rig - it's now using external power instead of inverter power. Secondly, it will also turn on the charger/converter unit to begin immediately charging the batteries.
When shore power is cut or the generator is switched off, the transfer switch will do the opposite - turn on the inverter and shut off the converter/charger. This may happen nearly instantaneously or could take a few seconds depending on the transfer switch.
Finally, an RV will usually have a generator. The generator takes the place of a shore power connection so you can and charge your batteries when you have no electrical source to plug into. On an RV, some higher wattage appliances won't run without them. An air conditioner will not run without the generator, and running the generator while using the microwave or another high wattage appliance will ease the strain on the batteries. Very few vandwellers use generators, but if you're going to be off the grid for long periods of time and not have a friend/family/coworker/campground to plug into once in a while, a very small one may be worth the cost and effort.
More on Inverters
Inverters are mostly sold by watt ratings. Every 110 volt appliance you run will consume a certain amount of wattage. Clocks may only use a few watts, while power hungry appliances like toaster ovens and microwaves can push over a thousand. The wattage rating of an inverter is what an inverter can safely put out continuously.
When buying anything larger than a single outlet cigarette lighter inverter, you'll notice the inverter will also have a second rating. This second rating is called a surge or peak rating and is significantly higher than the normal rating. When certain appliances kick on (such as microwaves, compressors, or the motors used in power tools) they will draw up to twice as much power than their wattage rating for the first second or so they are on. An inverter with a higher surge rating will be able to produce that much power for a short amount of time (usually a minute or two) before it will shut itself off to avoid damage. Surge ratings for an inverter will usually run from 150% to 200% of the inverters normal rating.
The easiest way to avoid stressing your inverter is to figure out your power needs. If you're running a few appliances at once, never have a high watt appliance running with anything else, such as using your microwave when your TV is on. Inverters have built in safety features but if one should go bang you're left with a useless piece of equipment and possibly damaging anything else connected to it.
All in One Inverters: A Vandweller's gift from God
The best type of inverter for my needs and for most vandweller's needs will actually combine the charging/converter unit, the inverter, and the transfer switch! There are two that I've personally handpicked in the store right now, one rated for 750 watts and one rated for 1250 watts! BOTH ARE AT AN INCREDIBLE PRICE RIGHT NOW AS WELL!
These inverters are very similar to mine except are produced by a different company (the company that made my inverter unit does not sell it on Amazon, or has it at this good a price)
These particular inverters produce a modified sine wave, so they will run your appliances as my inverter runs mine. They both have a 110VAC input for shore power - when you plug it in to an extension cord, it will charge your batteries and run any 12VDC appliances in your van!
These units even have a built in transfer switch that will allow shore current power to pass through when plugged in (at a pure sine wave output, too!) and will automatically switch to drawing power from the batteries when no longer plugged in.
This type of inverter is perfect for most vandwellers! It combines all of these in a relatively compact unit, much smaller than you'll find on a typical RV which requires alot more power. These units cost no more than $400 depending on the sale price, while a pure sine wave version will run close to twice that.
These all in one inverters are more expensive than straight inverters, but once you add in the cost of a comparable converter/charger and transfer switch (not to mention the hassle of hooking all the components up properly, I've found the cost for a good all-in-one inverter runs about a third less than a system with individual components. In a van, it also takes up alot less space, which is something to consider as well.
There is only one drawback to these types of inverters, but very easy to avoid. When plugged into shore power, make sure the wattage you are using does not exceed the continuous rating of the inverter. Even though you aren't using any battery power and the inverter is allowing the shore power current to simply "pass through," the sensitive electronics inside the inverter will not be able to handle anything higher than its rating. The inverter could fry if the power you're drawing exceeds that rating since all voltage is still passing through it.
I did not know this, although in retrospect it should have been obvious. One night at a campground I was plugged into shore power and running a 600 watt space heater. I turned on the microwave to heat up some soup and bang, no more inverter. While it was still under warranty, the wait to get it repaired was a long and miserable one.
So now that we know how the 110v system is going to get its power (from the all-in-one inverter) we need to know how to charge the batteries when we're NOT plugged into shore power.
Charging Your Batteries When on the Go
We didn't build our vans to park at campsites all that often...we built them to be completely self reliant machines! While most vandwellers have relatively small energy needs (I will admit I tend to be on the power hungry side) there needs to be some way to put electricity back in the house battery while driving.
Behold the battery isolator. A battery isolator is available from most RV suppliers or car audio shops for under $30.
You can purchase my battery isolator (the one in the photo) from the store.
A battery isolator is a huge relay (also called a continuous duty solenoid) that will connect your starting battery to your house batteries when the engine is running. This allows the alternator to charge all of your batteries at once. When you park for the night or turn the engine off, the isolator will break the connection so you can draw power off your house batteries while leaving your starting battery untouched.
In an emergency situation, this will also allow you to start your engine off the house batteries, say if you leave the parking lights on and kill your starting battery. I have been stupid enough to do this before.
Your isolator should come with instructions, but here's the general gist of it. In order to hook an isolator up properly, you need to ground your house battery bank and run a heavy wire (at least 4 gauge) from the positive terminal of your starting battery to your isolator, and then from the isolator to the positive terminal of your house battery bank.You can see this in the above photos - the wire runs from the positive terminal of my starting battery, attaches to the isolator, and then the second line disappears into the firewall. The relay portion of the isolator can be hooked up to your ignition circuit so it comes on automatically, or you can run it to a separate switch like I did. Some isolators can be grounded by anchoring them to the firewall like mine or may require a separate wire.
When connecting these components, you can buy professional inverter cables designed to handle the load, or you can make your own. Just make sure you use the right sized wire for your application, and when in doubt, overbuild it.
Doing this properly will allow you to charge your batteries while driving! This gives you two methods of charging batteries - being plugged in or running the engine. You can also add solar, but the information on that is elsewhere on the site.
My own electrical system
Like some other sections on the site, I'll show you how I wired up my own electrical system in addition to the general information above. While I can't give a step by step instruction on how you may wish to set up yours, the information provided thus far should be enough to understand what I'm talking about in the following section. Send me an email or leave a comment if you have any questions and I'll do my best to answer them!
I keep 2 Group 29 deep cycle batteries in a custom built box behind the drivers seat. This gives me 250 Amp Hours of storage. These batteries were purchased from Wal-Mart. The box is vented to the outside of the van. I replaced the batteries after eighteen months or so with two smaller Group 27 batteries from Autozone. (see above for notes on batteries)
Although you can't see it from the photos since I didn't get a chance to take one during the construction process, the first step was to drill a hole in the side of the van and install an electrical hookup. You want to find a 15 Amp outdoor receptacle. This can be found at or ordered at most RV supply places. You can skip all that and order one here.
I found mine at a local RV shop, but it was a bit hard to track down as most RVs in the US are wired for 30 amp service. In the photos of my van, this is the gray box behind the bay window on the drivers side.
This inlet is wired to a standard 2 receptacle GCFI outlet inside the van. While a normal outlet will work and costs less, a GCFI outlet will give you added protection. If you only install one GCFI outlet in the van, make sure it is at this connection.
My inverter is not one sourced from Tripp Lite like the ones in my store are. Mine was sourced from a different company that does not sell this model on Amazon. My inverter is much longer but flatter than the ones in my store, making it perfect to mount to bulkhead behind the drivers seat. The wires from the battery bank end up going to the bottom of the inverter, as you can see to the right of the photo below.
The line from the battery isolator (shown above) runs through the firewall, down through the drivers footwell, and back to the battery box. The switch for the battery isolator is mounted next to the steering column. Instead of wiring up the isolator to the vehicle ignition circuit, I ended up hooking a switch to it directly, giving me a little more freedom when I park and drive and how I manage my power. The thick wire running down the footwell is the 4 gauge wire from the battery isolator that heads back to the house batteries.
Since the outlets were in relatively inconvenient places on the inverter, I decided to run Romex wiring (same as in standard houses) to the outlets in the van. I installed three pronged plugs on the end of a few short strips and plugged them in, and then wired up the switches above the inverter.
I should have done this with a small breaker box, but at the time I didn't know much about them. The wires then go down to the different outlets scattered throughout the van. If you go the route I did, go slowly and double check everything. Oh, and just in case you aren't doing this already, make sure that the inverter is turned OFF and the van's shore power outlet isn't connected to outside power.
So why the switches? One of the biggest problems in RVs are something called "vamp loads." These are appliances that will draw power even when turned off, such as TVs, microwaves, computers, etc. You may also want to lump appliances that are "always on" in this category, such as a mini fridge.
When I was initially building my van, I had imagined three major appliances: a microwave, my refrigerator, and my computer. You can actually see the framing for the desktop computer next to the refrigerator. As such, I decided to put the outlets for these areas on their own circuits with their own switches and I recommend you do the same. That way I could control which outlet was on at what time.
The leftmost switch controls the microwave outlet. The middle switch controls the back outlet that was going to run my computer (instead it now powers my desk area for my laptop/cellphone charger and box fan when I have it in the back window) and the right switch controls the outlet to the refrigerator.
There are three more outlets in the van that are always "hot" if the inverter is on or the van is plugged in which I use for lights, power tools, and now my TV/Playstation area. Having each appliance on its own individual switched circuit has been very helpful for controlling different aspects of my power use. There's no need to have the microwave on if I'm not using it, and if there's no perishable food in the fridge, there's no point in having it use power either.
All the outlets in the van use shallow gang boxes designed for adding outlets to existing walls. If you need a deeper box such as the one I used above my inverter, look for gang boxes that are designed for "old work." They fit into a cutout and have small flaps that rise up and bite into the back of the plywood when you tighten their screws.
Here you can see the microwave circuit next to two of the "always on" outlets next to the cabinet and above the sink. The third outlet is in the "bedroom" and I added it for a nightlight or something, but now it powers my entertainment center. I just ran the wiring for these from the junction box above the inverter under the van floor.
Finally, here's an electrical diagram of everything in my van (before adding the solar panels - more information is on the solar panel page)
An air conditioner is by far the most power hungry appliance any vandweller or RV owner has, whether it's a wall mounted window unit for household use or a rooftop one designed for an RV. The surges on these things can top 3,000 watts. It is just not practical to run an air conditioner off of an inverter and battery bank, as the size of the bank and the cost required is less than the space and cost of a generator. ALL commercial RVs have the air conditioner wired up to the shore power or the generator circuits because of this.
My air conditioner is no exception. I had tried to find a small room air conditioner on Craigslist and stumbled across an older Montgomery Ward model for $20. I removed the bulkhead next to the bed on the drivers side and cut a hole in the side of the van to mount the air conditioner stealthily and securely. The air conditioner plugs into the second receptacle of the shore power outlet (the inverter plugs into the first) so I can only use it while hooked up to shore power. The unit is a bit older and doesn't work as well as it used to, but in 60 square feet, it works beautifully. I also gained a desk!
12 Volt systems
12 volt appliances are much more energy efficient than their 110 volt counterparts, especially when you power them on an inverter. As a result, most items inside an RV run off 12 volt DC power and for items inside a van, this is also the norm. The standard items that you may find in an RV that run off 12 volt power would be lights (either the dome lights or any other lights you wanted to wire), a range hood above the stove, a water pump, and any fans installed in the roof or windows.
Fortunately, 12 volt DC wiring is easier than 110 volt, but still must be done carefully.
At present, there are only two things I have added to my van that use 12 volts. The first is my water pump from JC whitney, and the second is my Fantastic Fan Vent Fan installed in the roof. I simply ran wires from the battery to another terminal/fuse block, then ran the wires from there to the fan and the pump/faucet.
If you don't use an automotive fuse block, at least make sure you run inline fuses in the wiring. 12 volt appliances are a bit more expensive than their 110 counterparts, so it's well worth the extra few dollars to protect them.
You can also purchase a ton of 12 volt items online and from the store, from small toaster ovens to coffee pots to hair curlers. Whether you use them or not is up to you, since they may end up providing as big a drain on the batteries as a similar 110v appliance. They mainly exist for long haul truckers, who need convenient appliances but don't have a built in inverter in their trucks.