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RV power,

What does my Camper use,

AC or DC?

RV power for RV Campers is powered primarily from a 12-volt direct current and a 120-volt alternating current system. The 12 VDC power system is the primary power. This can be sourced from batteries, converters, or generators and even solar. The 120-volt AC current, usually from campground hookups works in resemblance to that in your home. The devices with electric motors usually require more current. Little to no maintenance is required on AC current. 
 
 RV power, what does my Camper use, AC or DC power for electricity?
 
Recently while hooking up my 50 amp shoreline RV power cord to the electric pole at the campground I pondered, if my lights work before I hook up the RV power, what exactly is the campground power for? Does this recharge the batteries?
 
There has to be a reason why I need this. I know that there is a difference between alternating current and direct current but I never really knew enough to explain why. What if somebody asked me what I was doing and why I needed to do it?
 
To save myself from stumbling around such a direct question I then decided to dig a little deeper into the matter and basically get to the bottom of the question.
 
 

How does 120-volt AC power work in my RV?

The shoreline cord hooks up to the campground power pole through a large, awkward looking plug. It can also work from a household 110-volt outlet, like the one in your house with a male-female conversion adapter.
 
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Most shoreline cords come in two varieties:
  1. 30 amp shoreline power cord
  2. 50 amp shoreline power cord
 
As a general rule of thumb, an RV with one AC unit runs on 30 amps and an RV with two AC units works from the 50 amp shoreline power cord. Air conditioning units are usually found on the roof or are rooftop air conditioning units. These are easy to see from the ground.
 
All 120-volt AC wiring for appliances, microwaves, refrigerators, and accessories have protection through a series of circuit breakers. These are located in a separate cabinet, under a piece of furniture and usually found close to the entry door on a wall.
 
This is a low voltage system that connects to the power distribution panel also called the fuse box. These circuits are routed to individual 12 VDC loads. DC current flows in one direction-positive to negative.
 
The flow of positive charges powers the low voltage devices like lights, water pumps, fans, and even entertainment equipment.
 
The devices with electric motors usually require more current. Some examples of higher current consuming low-voltage devices are the slide-out motors, power jacks and even the electric steps.

RV Power 

 
The 120VAC RV power system in and of itself is potentially dangerous due to a high voltage electric shock. Unless you are trained to know how to work on the system limit yourself to just checking the circuit breakers.
 
12-volt DC RV power systems require additional maintenance but rarely offer any danger of shocking you.
 
There is, however, an ever-present danger from the production of large amounts of current from an overloaded circuit.

This can be caused by:

  • Excessive heat
  • Melting wire jackets or insulation
  • Faulty appliances
  • Circuit overload

 

These examples also have the potential for fire danger. For protection, circuits have a required form of OCPD, over-current-protection device that consists of a lower rating than the conductor’s maximum ampere rating. In a perfect world, the OCPD fuse or circuit breaker is installed within a foot and a half of the power source.
 
Interruptions in current are the most common problems faced internally in an RV. Electrical systems as a whole are mysterious, troubleshooting these systems is done by testing the circuits with a simple 12-volt test light indicator or even better a multimeter.
 
The test light checks for power within a 12-volt DC appliance or light fixture. Just be sure you are actually testing a DC device. Sticking the probe in a wall outlet causes a dangerous electric shock as mentioned earlier. To test 120-volt AC circuits for current use the multimeter.
 
Different types of multimeters are able to display the exact voltage and even precise voltage, depending on if the device is analog or digital. Breaks, shorts or interruptions in the current are found using these basic tools.
power converter

RVs are powered with a 120-Volt AC input on a 12-Volt DC system

The appliances and accessories in an RV run off of a 12-volt DC system. The low voltage lights, fans, and smaller units run off of the batteries.
 
The higher current motorized devices, slides, power jacks and steps are utilizing the 12-volts DC and pull a higher current provided by 120-volts AC. This is from the campground receptacle pole or a free-standing generator.
 
To convert the alternating current to direct current RVs use just that, a power converter.
 power converter

RV Power Converters

A power converter consists of two sides, the AC side, and a DC side. The unit changes 120 Volt AC current (high voltage input) to 12 Volt DC current (low voltage output) and supplies relatively clean power. Simply put, 12 VDC devices switch power when you plug in the shoreline power cord.
 
The second option for this power is a free-standing generator. Full-time RV life campers use this option when 120 VAC is not available like in a campground or even boondocking in a parking lot.
 
power inverter
 
Most power converters come standard with a battery “trickle” charger that keeps the batteries charged when connected to shoreline power. This stands true when using solar power as well. Photoelectric power cells use the power of the Sun to produce a 12-volt DC “trickle” charger to re-charge the batteries.
 
The use of multiple panels creates more power, enough to run the whole RV.  As an added line of protection, some chargers incorporate a sensing switch to send a charge but only when the batteries need it.
 
Care must be taken when using a 120 VAC input. There is an ever-present risk of getting shocked.  Never tamper with a converter when it is connected to shoreline power. Many components in an RV are listed by UL (Underwriters Laboratories)  or CSA (Canadian Standards Association) to evaluate the devices for safety. In an RV environment, vibration is a consideration in the listing process.
 
RV’s go through a lot of movement, components should be “listed for RV use” or some similar language.  Where applicable it is paramount these devices meet this requirement. When dealing with converters it is even more important.

There are two types of RV Power Converters

  1. Linear Dual Output Converter
  2. Single Output Converter

 

The Linear RV Power converter is the most widely used in RVs. It is also the least expensive. With two outputs, one for powering appliances and one for charging the batteries they are multipurpose.
 
The drawback to this converter is the fact that the power is often dirty and produces surges. As a result, surge protection is a consideration when installing appliances and accessories. Also, the battery charging side is not the most efficient.
 
Single output RV Power converters are also referred to as battery floater converter and direct all power to the batteries. These converters are heavy, efficient and expensive. Being in a direct line with batteries eliminates surges and “ripples.” Also, as a result of the direct line, the charging of the batteries is limited to the available power that is not being consumed by the lights and appliances.
 
Be aware of the location of the converter in your RV, check it periodically for corrosion. Power converters require proper ventilation, most RV manufacturers take this into consideration.
 
It is rare to have a converter installed in a small space or with other supplies. This is because there is a significant amount of heat produced during normal operation. Always avoid storing anything near a converter.

RV Power: Lead Acid Batteries

The lead-acid batteries in RVs are built to store an ample amount of power and last up to five years. Depending on the amount of care taken. These batteries consist of six cells connected in a series, each of the six cells produces around 2.1 volts.
 
Simple math tells us the 12-volt battery has an output of 12.6 volts. Made internally of lead, plates, an outer shell, and lead oxide. The cavity is filled with a solution that is drenched in an electrolyte made from sulfuric acid and water.
 
Lead acid batteries “store” electricity, not produce it. The thicker the plates, along with an ample amount of electrolyte determine the amount of a charge the battery can store.
 
Full time rv life rv batteries Full time rv liferv battery
 
RV batteries are commonly referred to as “house batteries” and are designed to supply a steady amount of current over a long period of time.
 
The good news about batteries is that they are also a good filter of power. Batteries are a capacitor, not only a requirement for our 12 Volt system but also for their filtering ability. A large portion of DC filtering is through capacitors, simple devices that absorb surges and spikes, the battery is the largest one.
 
One of the drawbacks of batteries is that they discharge and go completely dead. The current is constantly moving through the circuit and wears out the battery.
 
One remedy is installing a battery cut-off switch that saves the batteries. The other, as mentioned previously incorporating a trickle charger. Batteries work better and last longer because the current is consistently moving through them.

Flooded lead-acid batteries 

The most common type used in RVs. These are deep cycle batteries. The two types are “Serviceable” with removable caps and “Maintenance free.” Because they are leak proof they work well in marine applications.
 
Fully charged batteries are impossible to freeze and will not lose any water.
 
Once a serviceable battery is filled with electrolyte from the manufacturer it only requires distilled water when topping it off. A dry cell is the death of a serviceable battery.
 
An important element of RV batteries is how they are discharged. A battery discharged down to 50% and then recharged back to 100% will last the longest. It will actually last twice as long as a battery brought down to 80% and then recharged. It is specifically the amp hour rating that is cut in half.
 
You don’t want the battery to become fully discharged.
 
The larger the battery the more amp hours it has. The drawback to this is space, there really isn’t a large amount of room in an RV for big batteries. If you do have the room it is actually better to have a pair of six-volt golf car batteries wired in series to create a 12-volt battery system.
 
Wiring batteries in series will actually increase the voltage. It will not, however, increase the amp hours, these are set.

What causes RV Battery Failure?

The three most common causes of failure in an RV battery are:
 
  1. Undercharging
  2. Overcharging
  3. Sulfation
 
When your Rig is hooked up to shoreline power your batteries will fully charge. Repeatedly discharging the battery and not recharging it completely between charges is undercharging. This causes the sulfate portion to crystallize and harden.
 
In time the sulfate cannot be brought back to normal and the battery is rendered useless. This leads us to the #1 cause of battery failure, sulfation.
 
Second, only to sulfation is overcharging which results in massive water loss and corroding of the plates. Bear in mind that all of this is avoidable with a little caution and preventive maintenance.
 

RV Power: The Battery Cut-off Switch

battery cut-off switch

 
The battery cut-off switch is a helpful device in your RV. Most of the pull-behind RV’s have one installed from the factory. When connected in the line of the 12 volts DC system the operator can easily “cut” the power which saves the energy stored in the battery.
 
Devices like smoke detectors and carbon dioxide detector are “always on” and powered when the switch is engaged. Turning the device to the “off” position shuts-down these devices and saves power, which is not in safety compliance when the coach is occupied.
 
Having this switch off  when the RV is vacant will save you from walking into an RV and wondering “who left the lights on?”

So there you have the answer!

Your RV Camper runs on 12-volt DC power for electricity. The batteries store it, a generator or shoreline cord connected to a receptacle supplies it and a power converter directs it. The batteries send power to the low current devices and are recharged by the converter.
 
The high current motorized appliances receive the high current from the 120-volt AC source which is converted to DC by the converter. The whole system requires little maintenance.
 
All of that is the answer to my question I asked one day while plugging in my shoreline cord, feel free to share it!
 
 
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