Part of: Guides
Campers come equipped with to two separate electrical systems. The AC (wall power) system, and DC (battery power) systems. AC power is used to power most high-power electric appliances, like the microwave, air conditioner, fridge, TV, and outlets. The DC system is used to power the lights, fridge (yes, most fridges run on both systems, more on that later), furnace, water heater, fans, water pump, auto levelers/jacks, and much more.
The DC system runs from battery power, which is why these appliances can be used when not plugged in. When your camper is plugged in, the power converter uses some of that AC power and converts it to DC power. This accomplishes two things, firstly, it powers the DC appliances from shore/generator power, and second, it charges the batteries.
Most campers out there can only make use of the AC power system when the camper is plugged into shore power, or a generator. That means no microwave, TV, or air conditioner unless you’re at a campsite with electric hookups, or you’re running a generator. Unfortunately this also means no battery charging too. Some trailers and fifth wheels can also charge or maintain the batteries from a 7-pin trailer connector, and most RVs will charge the house electric system from the engine alternator after some time, however all of these solutions prohibit extended boondocking without running a motor, either a generator or a vehicle engine.
Installing solar power on your camper is the only way to passively and quietly regenerate your batteries while boondocking or camping without a hookup. A standard solar system consists of two main components, panels and a charge controller. The charge controller uses energy from the solar panels to charge the batteries. There are many different types of charge controllers, however they all serve the same general purpose, to charge batteries safely and efficiently from solar power.
Some solar systems, usually marketed as “portable” solar panels, contain a solar charge controller and solar panel or solar panel array, integrated into a single product. Usually, if a solar panel is not meant to be permanently affixed to something, and uses an SAE connector, then there is a good chance it is an integrated solar panel and charge controller. These products are meant to be connected directly to a battery.
As mentioned above, the AC electrical system in a camper is usually powered by an electrical hookup, or a generator. An inverter can be used to power AC appliances (microwave, TV, etc.) from battery power. An inverter draws power from the battery bank and converts it to AC electricity, just like the power from a wall outlet.
In conjunction with solar power, an inverter is extra useful when boondocking. It gives you an indefinitely renewable, and virtually silent source of energy to power everything in your camper. You’re not dependent on fuel for your generator, and you won’t wake up others when using appliances late at night or early in the morning.
An inverter by itself can’t be used as a stand-in for a generator. Campers contain a power converter (see above), which is used to charge the batteries from AC power. If you’re powering the AC system from the batteries and charging the batteries from the AC system at the same time this will usually result in a blown fuse or worse a blown inverter.
To get around this, the system must be set up so that the power converter is only active when the AC system is connected to utility power or generator power, but is disconnected when on inverter power.
The inverter could be connected to the AC system by plugging the shore power into the inverter, however there is no way to ensure that the power converter is disconnected, other than by doing it manually. The inverter could also be directly connected to the power panel, but you’d end up with an electrocution hazard whereby the male prongs of the shore power cable will be energized with 120V of AC power.
The connection of the inverter to the AC system can be done with an automatic transfer switch. This automatically chooses which power source is connected to the AC system. It also isolates each source from the other. The inverter can be on, and the shore power connector will not be energized. Plugging in the shore power will cause the transfer switch to switch inputs – the entire camper will be powered from shore power, despite the inverter still being on.
This solution on it’s own does not fix the issue around the power converter. The simplest and most cost-effective solution is to use an inverter/charger/ats unit. These units integrate the inverter, power converter, and automatic transfer switch into one product.
For an in-depth explanation of 30 amp vs 50 amp service in campers (see here).
50 Amp service in a camper refers to how much shore power your camper is capable of drawing. Campers typically come with either 30 or 50 amp service. 30 amp service is very simple, with a three-prong outlet: live, neutral, and ground. 50 amp service is a little more complicated, as it contains two live wires, one neutral, and one ground.
There is virtually no reason a 50 amp trailer can’t be powered from an inverter, however the difficulty comes when finding or using an automatic transfer switch. An ATS for a 50 amp trailer must be capable of switching two poles, and rated for 50 amps. Most units are not. Victron is one of a very few manufacturers who make a single inverter capable of switching 50 amp service.
Alternatively, an independent transfer switch, relay, or contactor can be used to switch two poles between a single inverter. In this case, rather than having two 120V RMS poles 180 degrees out of phase, you will have a single 120V RMS pole. This may become an issue if your inverter is capable of outputting more than 50A, as you may overload the neutral.