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12 Volt Electric System

12 Volt-Direct Current (DC)

12 volt is the type of electricity automobiles use. The battery is the foundation for the 12 volt system in an RV. A fully charged battery will operate the 12 volt electrical equipment in the unit until the battery becomes discharged. Each piece of equipment will discharge the battery at different rates.

These are typical running amps on components that are commonly used in an RV.

Appliance or Accessory AMP Draw

  • CO Detector 1 Amp
  • Fluorescent Light 1-2 Amps
  • Furnace 10-12 Amps
  • LP Gas Leak Detector 1 Amp
  • Overhead lights (Per Bulb) 1 Amp
  • Porch Light 1 Amp
  • Power Roof Vent 1.5 Amps
  • Radio/Stereo 4 Amps
  • Range Hood (Fan & Light) 2-3 Amps
  • Refrigerator (LP Gas Mode) 1.5- 2 Amps
  • Television (12 volt) 4-5 Amps
  • TV Antenna Booster <1 Amp
  • TV Antenna Booster 12 Volt outlet Up to 8 Amps
  • Variable Speed Ceiling / Vent Fan 4 Amps
  • 12V Fridge 4-5 Amps
  • Water Pump 4 Amp

(Note: These are “typical” amp draws from common components. Each component can vary based on many factors.)

(Note: Many of the above accessories will cycle through running/not running. This means their amp draws will vary throughout their running cycles. Examples of these types of accessories would be the 12V fridge, water pump, furnace, etc…)

To get a true amp draw number while camping, use a multi-meter on the main battery lead with different appliances/accessories on

RV Battery System

RV batteries store charge to run the 12V electrical system in the RV. They will need to be charged with either the solar system or the converter from shore power if they are fully discharged. The most common setup is (2) 12V deep cycle batteries that are wired in parallel or (2) 6V deep cycle batteries (often called golf cart batteries) wired in series. There are two main types of batteries that are commonly used in RVs, lead acid and lithium-ion. The main difference between the two types is the larger number of charge cycles that lithium-ion batteries can hold in their lifetime and the time it takes to charge them. The amount of charge in a battery is measured in amp-hours. The amount of time an RV 12V system can run without shore power is greatly affected by the batteries that are chosen.

Differences Between Automotive & Deep-Cycle Batteries

An automotive type battery, like in a car, is designed to provide high amperage (required during starting) for a short period of time and to be recharged continuously.

A deep-cycle battery is designed to be slowly discharged (like during camping) and recharged over and over. While an automotive battery will work in an RV, the life expectancy is short compared to the deep-cycle battery which was designed for this type of use.

To predict the amount of time an RV can run on the 12V system alone, divide the amp-hours of the battery system by the amount of amps being drawn. Example: A 100 amp-hour battery could theoretically output 10 amps for 10 hours (100 amp-hours/10 amps = 10 hours). For (2) 12V batteries in parallel, the total amp hours are added together for the total charge. For (2) 6V batteries in series, the total amp hours are the individual charge of each (not added together).

Inverters

Inverters turn 12V DC electricity from the battery to 120V AC electricity when the RV is not plugged in to shoreline power. The inverter will power a circuit of receptacles so that 120 AC electrical components can be plugged in and operate while the RV is not plugged in to shoreline power. Receptacles that are on the inverter circuit will be labeled. The air conditioner(s), microwave, or fireplace will not operate on inverter power. For some RVs with a residential refrigerator and no solar panel, the inverter will only operate the refrigerator when the RV is not plugged in to shore power. Most inverters in RVs will be installed near the front of the RV and can be accessed through an internal cabinet door or an external trunk door. The inverter will have an on/off switch, usually located near where the inverter is installed.

These are typical running amps on components that are commonly used in an RV.

AMP DRAW COMPONENT

  • 10 amp 13.5k air conditioner
  • 0.6 amp DVD player = 70 watts
  • 15 amp Microwave
  • 5.5 amp Refrigerator
  • 11.6 amp Water heater on electric
  • 11 amp Vacuum Cleaner
  • 7.5 amp 2 Slice Toaster
  • 15 amp 4 Slice Toaster
  • 7.5 amp Coffee Maker
  • 10.8 amp Griddle
  • 12.5 amp Hair Dryer
  • 0.70 amp Curling Iron
  • 1.4 amp Flat Iron
  • 0.5 amp Satellite Receiver
  • 2.5 amp 19" LCD TV
  • 0.2 amp LED Alarm Clock
  • 7.1 amp Printer
  • 0.75 amp Laptop
  • 1.7 amp Computer
  • 0.25 amp Play Station 2 Gaming System
  • 0.6 amp X-Box
  • 1.4 amp X-Box 360

To determine how much a 120V appliance/accessory will draw from the 12V system, multiply the 120V amp draw by 10. This means that an accessory that draws 5 amps at 120V (5 amps X 120V = 600W), will draw 50 amps at 12V (50amps X 12V = 600W).

Solar

All RVs that have a solar panel installed will charge the battery while the solar panel is receiving light. A solar controller will be located inside the unit and its display will show how much electricity the solar panel is generating and the level of the battery. The solar panel strictly charges the battery, components then run off the battery. The solar controller can also change the type of charge, based on the type of battery installed. All RVs that have solar installed will also have an inverter that will power a 120V circuit.

Note: The solar panel/solar controller does not run 12V appliances/accessories in the RV, it only charges the battery. Without a battery, the solar system cannot power 12V equipment in the unit.

Each 190W solar panel can output up to 9.45 amps at 12V to add charge to the battery. The solar controller will display the total amount of amps coming in from the solar panel(s). The amount will vary greatly with the time of day, weather, time of year, obstructions to sunlight, etc…If the amps drawn by the 12V appliances/accessories are less than the input from the solar panel, the battery is being charged.