Free RV manual
How the RV Electrical System Works
30 amp and 50 amp shore power, the 12 volt battery side and the inverter. What runs on what, and how not to trip a breaker.
Two systems in one
Your RV runs on two kinds of power. The 120 volt side is like a house. It runs the air conditioner, microwave and wall outlets. It needs shore power, a generator or an inverter.
The 12 volt side runs off the batteries. It runs the lights, water pump, fans, furnace fan and the control boards on most appliances. When you are plugged in, a converter charges the batteries and feeds the 12 volt side.
30 amp and 50 amp
Look at the plug on your power cord. A 30 amp plug has three prongs. A 50 amp plug has four and is much bigger. Most campsites have both outlets on the post.
A 30 amp RV can run one air conditioner and a few small things at the same time. Run the AC, the microwave and a hair dryer at once and the breaker will trip. Turn one off and reset it.
You can use an adapter, called a dogbone, to plug into a smaller outlet. You just get less power. You can use a 30 amp RV on a 50 amp outlet with an adapter too.
Plugging in safely
- Turn the breaker on the park post off before you plug in or unplug.
- Plug a surge protector into the post, then your cord into that. Many protectors will also catch a wrongly wired post.
- Turn the post breaker on and wait for the protector to clear.
- Inside, check that the lights and the microwave clock came on.
Batteries and the inverter
Lead acid batteries do best if you do not run them below half charge. A reading near 12.2 volts at rest is about half. Lithium batteries can go much lower, but still need to be charged before storage.
An inverter turns battery power into 120 volt power for outlets. It drains the batteries fast. Turn it off when you do not need it.
Most RVs have a battery disconnect switch near the door or the tongue. Turn it off for storage so small loads do not drain the battery.
When to call a shop
Call a shop if a breaker trips again right after you reset it, an outlet feels warm, you smell hot plastic, or the cord end looks brown or melted. Those are wiring faults, not user error.
The maker's own manuals
These guides cover how most RVs work. Your own rig may differ, so check the manual for your make and model.
- Lippert · Slides, awnings, jacks and leveling
- Winnebago · Operator manuals and diagrams
- Every maker we link to