Electricity in the Van

[NOTE: I’ve blogged all these “how-to” posts before, but am gonna re-run them on occasion, since folks may have missed them, and many of them have been updated or expanded since they were first posted.]

Back in my younger days as a backpacker, we used almost no electricity at all. I sometimes carried a small flashlight with me (good for reading paperback books at night), and some of the people I knew would carry small battery-operated transistor radios (to get the news and weather).

But today, the electronic revolution has changed all that. Once dismissed as “flashpackers”, today’s hikers are normally armed with a variety of electronic devices, from GPS navigators to cellphones to small “netbook” laptops.
Van campers of course have the advantage of not having to carry everything on our backs, so we can have even more gizmos and gadgets. In a well-equipped Class B camper van, you can find virtually every electronic device that any apartment would have, from a microwave to a TV set to a Playstation. There will also be electric LED lights and perhaps an electric fridge, plus normal 110-volt outlets for anything else you want to plug in.

Those of us, however, who are converting their own campervan will probably be less lavish.

Your van, of course, will have its own battery, which is constantly recharged by the alternator. It also has a “cigarette lighter” outlet in the dash, into which you can plug charging cords for a variety of devices, including cellphones, GPS, and laptops.

For most people, however, this will not be a workable system to meet their needs. Car batteries are not designed to give repeated long periods of power; they are only designed to give short intense bursts of electricity sufficient for starting the car engine. External devices plugged into the cigarette lighter will steadily drain the battery and, unless you are constantly driving the entire time (and recharging the battery with the alternator), you will quickly end up with a dead battery.

Instead, you will want to have your own independent source of electricity that is not configured to the car battery. There are three options for this: a dual battery, a generator, or a solar panel system.

The dual-battery setup consists of adding a second battery in the back of your van, to be used as your “house” source of electric power, and connecting this to your alternator so it charges up whenever the van is running. For this, you will need a “deep cycle” battery, which, unlike car batteries, is designed to give a steady electric current over a long period of time, and to last through many hundreds of cycles of draining and recharging. Deep cycle batteries are used to power electric motorboat engines, and can be found in virtually any marine supply store.

These batteries come in a selection of sizes and power outputs, measured in “amp-hours”. They also come in different types. Some deep-cycle batteries are “wet”; they use diluted sulfuric acid and lead plates to store their current. They are very heavy, and they need to be periodically opened and filled with water. Since wet-cell type batteries can release sulfuric fumes which can be harmful in an enclosed space, and since they can sometimes leak acid, they are not really suitable for use in a camper van. A much better option are the “sealed” batteries: the “AGMs” use glass-fiber mats soaked with acid, and the “Gel” batteries use a thickened jelly to contain the acid. These are also very heavy, but they don’t leak, don’t release fumes, and don’t need to be topped off with water. You will want to get a sealed deep-cycle battery with the highest amp-hour rating that you can afford.

Wiring this system is complicated and can be dangerous if it isn’t done right, so you will likely want a mechanic or electrician to do it for you. You will be stringing cables from your van’s alternator to your house battery, so the alternator feeds electricity to charge both your van battery and your house battery, and you will be wiring up some sort of plug to your house battery (the most commonly-used is a cigarette-lighter type outlet) into which you can connect your electric devices like phone chargers or laptops. To prevent the house battery from pulling electricity from your vehicle battery, it will be isolated by a switch or a solenoid, allowing you to draw power only from the house battery whenever you are parked.

The dual-battery setup has the advantage of being inexpensive—all you need is an extra battery and some wiring. But it has severe limitations: your house battery will only be charging when the engine is running, so if you park for a period of days at a time, you will wear down the battery. This made it unsuitable for me. And the system is good only for producing and storing a relatively small amount of electricity. If you plan on using a number of electric devices with large power requirements, this system will probably not be able to handle it.

Larger amounts of electrical power, therefore, can be produced using a generator. Generators are, essentially, small gasoline engines that turn a wire coil inside a magnet to produce electric current. These come in a variety of sizes and produce different amounts of electricity. The greater the amount of electricity you use every day, the more powerful generator you will need. Most generators have built-in electrical outlets—these provide the same 110-volt electricity that your home outlets do, and you can plug anything into them which you can plug into the wall at home.

Generators are far more useful, however, if they are set up to charge a “battery bank” instead.

Without getting all mathy, every electric device you plug in consumes a particular number of “amps” per hour. So you must have sufficient battery power to provide all the amps you will need for the number of hours that you plan to run your devices in between charges, and that usually means more than one house battery. Some devices, such as small fans or LED lightbulbs, use less than one-half amp per hour. Most laptops use about five or six amps per hour. Other devices, like microwave ovens, can use several hundred amps per hour (but of course you will only be running it for five or ten minutes a day). So you will have to figure out the total amps that each of your devices will use, add them all up, and that will determine how much battery capacity you will need.

Let’s say that your total amp usage will be 10 amps per hour, and you plan on running these devices 5 hours a day for two days before recharging the batteries again. That gives a total of 100 amp-hours. However, since deep-cycle batteries can be damaged if they are discharged below 50% of their capacity, you will want to save your battery life by providing a capacity that is twice what you expect to actually use—so in this example you will actually need 200 amp-hours of battery storage. You can obtain this by wiring two 100 amp-hour batteries together or with one larger 200 amp-hour battery.
The idea is to run the generator to charge up the battery bank (your generator must be large enough to quickly recharge the batteries), then run all your devices from the batteries. If you use less electricity than planned, you can go longer between charges. If you use more electricity than planned, you will need to recharge more often—or you will have to add more battery capacity to your bank.

But you are not finished yet….

Deep-cycle batteries produce a DC current at 12 volts of power. Nearly all standard electrical devices, however, are built to run off ordinary household AC current at 110 volts. (There are a variety of devices specifically made for RVs, such as fridges and microwaves, that run on 12 volt DC, but these are found only in specialty shops. Some people, though, equip their entire van setup with 12v appliances.) You will therefore likely need to connect your battery bank to an “inverter”, which will transform the current from the batteries into ordinary household 110-volt AC. The inverter will provide you with a number of standard electrical outlets, into which you can plug your devices just as you would at home. (The inverter itself will also use up a non-trivial amount of your electricity, so you should keep it turned off any time you are not actually charging something up.)

The generator/battery bank system is a workable one, and is used by many people, especially in large RVs. I, however, don’t like it and don’t use it. The disadvantages of the generator are many; it is very loud when it runs (it’s like running a lawn mower), and you will annoy everyone within earshot whenever you charge your batteries. Another disadvantage is that the generator requires gasoline fuel to operate, which is just another thing that you have to periodically run out and get, and takes up storage space (and I don’t like the idea of having a gasoline can inside the van). And generators are big and take up a lot of room. On a big Class A motorhome, the generator is usually mounted outside. For most people in a camper van, they will simply not be a usable option.

Fortunately, there is a better (and greener) alternative for the smaller van camper—the photovoltaic solar panel.
In years past, solar panels were horribly expensive. But in just the last few years, the price has plummeted dramatically as more and more people have bought them to use in their homes. For the van camper, a solar panel system can provide all the electricity you need, quietly, steadily, and, once installed, for free.
The solar electric system consists of four basic components. First is the inverter—this is where you will be provided with the 110-volt outlets that you can plug your devices into. Next is the battery bank—this is where the electric current produced by the system is stored until you use it. Then there is a device known as the “charge controller”, which regulates the amount of current flowing from the solar panel to the battery. And finally the solar panel(s), which produce all the electricity you will use.

The size of the battery bank is, again, determined by how many amp-hours you will actually be using each day. The size of the solar panel capacity is determined by the size of the battery pack you need to charge. Most solar panels come in standard 100-watt and 200-watt sizes. As a very rough rule of thumb, 100 watts of solar panel power is usually enough to recharge 100 amp-hours of battery capacity in a typical summer day. So if, as in our example above, you have 200 amp-hours of battery capacity, you would need to put either two 100-watt panels on your van’s roof, or one 200-watt.

But there’s a catch (and here comes the disadvantage of a solar panel system over a generator)……

The bane of any solar panel array is rain and cloudy weather. While most solar panels today are efficient enough in their capture of light that they can still produce electricity in the rain (mine even produces a small charge if I park under a bright streetlamp at night), this will be much less than the charge produced on a sunny day (and keep in mind that the shorter days and less direct sunshine in winter produces much less charge on the panel than in summer—and some geographical areas, like the Pacific Northwest, are notorious for their lack of sunshine). So you will want some extra capacity, at least double, in both the battery bank and the solar panels, to get you through cloudy days. In our example above, where you are using 200 amp-hours of battery with a generator, you would need a total of 400 amp-hours of battery capacity with solar, and then two 200-watt panels to charge it.

In my case, my need for electricity is pretty small: I have my laptop, which I charge every night; a small electric fan which I use on hot nights; my camera batteries, which I charge every few days; a couple of small LED “hockey puck” push-lights for the van interior, which run on AAA batteries that get recharged once a week or so; and my electric razor, which gets used each morning. In total, these add up to about 6 amps per hour. So, running these for a total of four hours a day means I draw 24 amp-hours in a 24-hour period, meaning I require a minimum of 48 amp-hours of battery capacity to last me one day. My actual battery bank therefore consists of just a single 105 amp-hour marine battery. (I do have the option of expanding the system whenever necessary in the future by adding solar panels and batteries.)

So my electrical system consists of a single 100 watt solar panel on the roof, which runs inside to a charge controller that regulates the current to the battery. When the battery is low, the charge controller sends current from the solar panel to charge it; when the battery is full, the controller shuts off the solar panel. The battery in turn sends current to the inverter, which is where I can plug in my laptop, camera battery, etc, the same way as an electrical outlet at home. A full charge will give me about two days’ worth of typical electricity usage. In periods of cloudy weather, I can temporarily run the battery right down to the absolute minimum and get four days on a full charge. The only time this system has ever let me down is during the rare periods when it has been rainy and cloudy all week.

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