Electricity powers most of the devices in an RV – lights, appliances, the furnace as well as the controls and monitoring systems. Most RVs have separate interconnected electrical systems, 12V DC (battery power) for lights and smaller appliances and 120V AC (shore power) systems for air conditioning, battery charging and larger appliances, making them a bit more complicated than your home where nearly everything runs off 120V AC power.
RV’s have three separate interconnected electrical systems:
- Chassis 12VDC
- House 12VDC
- 120VAC
We’ll go into detail on each of these below.
Chassis 12 Volt DC
This is what powers the “car” portion of the vehicle. In a motorhome it includes a separate battery that runs the starter, headlights, signal lights, radio and other accessories. This battery is recharged by the engine through the alternator, just as in a car. In a trailer the chassis power comes through the electrical connection at the trailer hitch to run the signal lights, brakes, etc. in the camper. In both cases the chassis power usually has a connection to the house batteries that run the RV systems to help maintain them.
House 12 Volt DC
Most of the electrical devices in an RV are powered by the 12VDC system. This includes the lights, entertainment systems, refrigerator (unless it’s a residential model – usually only in larger RV’s), roof fans, slide motors, etc. The 12VDC system usually includes a deep cycle battery (or batteries) to store electricity and a converter that charges the battery when connected to 110VAC (shore) power. Batteries can be either lead-acid (the old standard) or lithium (LiFePO4) which are similar to the batteries found in phones and laptops. Lithium batteries are much better suited to off-grid use (boondocking) because they don’t mind being drawn down to very low levels and can be charged at a high rate until nearly 100% full. Lead-acid batteries can be damaged by discharging them over 50% and when recharging the converter needs to slow down charging after they reach about 80% full. In some units the 12VDC can be connected to an inverter, which takes DC power and turns it into 120VAC power, allowing the batteries to run some of the high power devices such as microwaves.
120 Volt AC
The 120VAC system in a motorhome or trailer is essentially the same as that in your home with the exception of having a removable cord to plug it into the grid. 120VAC typically runs the higher power devices such as air conditioners, residential refrigerators, microwaves and electric hot water heaters. Most RV’s have either 30 amp or 50 amp service. The larger 50amp service is required to run two air conditioners simultaneously. When 120 volt power is available, the RVs converter is able to provide power to the DC systems and charge the batteries as well. Most motorhomes and some trailers also have an on-board generator which is capable of running most if not all of its electrical devices.
More Posts
This is just a basic primer on RV electrical systems. Look for upcoming posts with additional details.
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