Your RV has two different electrical systems onboard (or three counting the automotive electrical system in your motorhome or tow vehicle). The 120-volt alternating current system (AC) will be familiar to you, because it is the one that most closely resembles the electrical system in your home. The electricity is supplied by an external source that you “plug” into, at an RV park or in your own driveway. You will also hear this referred to as “shore” power by veteran RV owners.
The motorhome or trailer also has a 12-volt direct current electrical system powered by batteries you carry onboard. This system lets you operate lights and 12-volt appliances in the RV.
The automotive power system is obtained from a gas-powered engine that drives an electricity-producing alternator. It runs the fans, headlights, and radio, and it also charges the automotive batteries that provide power to the ignition.
If you are a dedicated do-it-yourselfer and experienced in working on electrical systems, you may want to add additional outlets to your rig. You should be able to obtain a wiring diagram from the manufacturer or dealer. Just remember that any modifications you make may void a warranty.
When you stay in a campground with hookups, one of the first things you will do is plug into the outlet located at your campsite. This electrical current charges the RV batteries and powers all electrical devices on the RV, including the air conditioning. The amount of electricity your RV is drawing cannot exceed the amount that is available or you will have problems. Overloading your RV circuit can damage your equipment and wiring along with the power outlet and power meter for the entire campground. To increase your chances of having an enjoyable stay, you will need to understand how much power you have available and also how much power your RV draws.
All electrical appliances and devices in your RV have a rating of the amount of power they are drawing. These numbers should be in your owner's manual for devices that came with your RV and will also be on a label on the actual device itself. Don't forget “add-on” things that run on electricity like personal computers, electric shavers, and hairdryers. You might also add in two or three amps for good measure.
You will also need to know a campground's power limit (how much you can draw). Campgrounds with electric hookups will have one or more levels of electric current available: 15-, 20-, 30-, or 50-amp service are the options. Some newer or upgraded campgrounds will provide more than one level of amperage, while older or public campgrounds are more likely to have only 15- or 20-amp service available.
Each type of service requires a unique plug in order for you to hook up. Camping supply stores carry adapters that will enable you to use the service that is available. Some campgrounds will also “lend” them to you for your stay for either a price or a deposit. While these adapters allow you to draw amperage, they do nothing to increase the amount of service you have.
Plugging into 15-amp service gives you 15 amps; if you are running appliances that are trying to pull 20 amps, you will have problems. You may need to ration the use of appliances in a camp where only 15-amp service is available. You should be able to run the air conditioner with 15 amps, but it should be shut off when using another high-draw appliance like the microwave. Fifteen-amp, 115-volt power sources take standard three-prong plugs (the same plug you will see on standard home appliances).
Twenty-amp outlets are very similar to 15-amp outlets. If you have this type of outlet available, you can use either a 15-amp plug or a 20-amp plug in the outlet. The extra 5 amps adds a little more power to help prevent brownouts. You will still need to ration use of high-power-use devices when hooked up to 20 amps.
Most new RVs are equipped with 115-volt, 30-amp service. Newer and updated campgrounds will also usually have this type of service. A 30-amp plug is round with two flat prongs in a V-shape and one round grounding prong in the middle toward the top. With this service available, you should be able to run your microwave while the air conditioner is on, but you should still be careful. If you try running too many devices, you will pop circuit breakers and fuses.
Fifty-amp service is usually found in only the most expensive rigs, such as top-end Class A motorhomes and bus conversions. With this much power, you can run one or more air conditioners along with a microwave, TV, and computer all at the same time without any brownouts. It can be difficult to find RV parks that have 50-amp service and when you find one you will pay a premium price for it.
The exclusive camps that cater to the RV owner with a bus conversion are most likely to provide 50-amp service. They may bill for this power separately, over and above the space rental charge. The plug for 50-amp service is round and the same size as a 30-amp plug. It will have three flat prongs and a round grounding prong. If you own one of the ultra-expensive RVs with 50-amp power and decide to slum it, you should carry adapters for either 30- or 15-amp power.
If you need to use an extension cord to hook up to the campground power source (this happens), make sure you are using one that is adequate for the electric load. Get one rated for outdoor use and 5 more amps higher than the power your RV will draw. They are more expensive but worth it.
The 12-volt power in an RV comes from a deep-cycle battery, also known as the house battery. A motorized RV will also have an automotive battery. These batteries are different from one another and have different functions and should not be interchanged.
Deep-cycle batteries discharge slowly and deeply and can be recharged many times. Smaller RVs, including foldup trailers, will usually have only one house battery, while larger RVs will often have two. The large bus conversions will have up to eight batteries. Different deep-cycle batteries are used, and each carries a group designation; Group 24 and Group 27 are the most common ones you will see in RVs.
The group designations indicate amp-hour capacity and reserve capacity — basically, an indication of how long they will provide power. For most RVers, the most important thing they need to know about these different groups is which one fits their rig. Group 27 batteries are larger and may not fit the battery case.
The batteries are charged while driving through a connection to the vehicle alternator in both motorized RVs and in trailers. The connection is either permanent in motorized units or temporary when the trailer is hitch to the tow vehicle.
Batteries are useful when not connected to AC power or when there is no AC hookup available. Running a high-power air conditioner or microwave is usually not practical, but you will have enough power for your basic needs for at least a short period.
The other important component of your RV electrical system is the converter-charger. Most RVs will have this device. It is activated when you plug into shore power and basically converts AC power for use by 12-volt devices, thus eliminating draw on the battery. At the same time, it recharges the house batteries.