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RV Solar Power, How Does it Work In An RV?

RV Solar Power is created by Sun’s energy. The Sunlight’s energy that comes down from the sun is collected by solar panels that are normally mounted on the top of an RV. The energy generated is transmitted through a series of cables that go from the outside of your RV to modules on the inside. Sunshine can be direct sunlight or partially blocked by clouds thus making the voltage variable.
A solar controller is installed to take variable voltages in, and send usable voltage out to the bank of batteries. Everything in your RV is powered by the batteries. The complete solar system has one job, to charge the batteries. 
Full-time RV life enthusiasts say that converting to solar power is the best decision they have ever made and with good reason.
Finding a way to harness the power of the sun has many benefits. It is green power there for the taking.
Once the system is in place there is very little maintenance.
Most full-timers notice that putting the system together requires few parts and tools. The initial troubleshooting of the solar system sets it up to last a long time.
Finally, there is a sense of accomplishment when you live day to day powering your RV from sunlight, it is awesome.
So let’s start from the beginning. 

How does an RV solar power system work?

The Solar panel system installed on the roof of an RV has one job, to power the batteries. Nothing more, nothing less, just charge the batteries.
The power from the batteries is wired into the RV electrical panel to send two separate voltages,12 volts direct current and 120 volts alternating current. In some cases, these systems can be made portable with the solar panels placed on the ground facing the sun.
Low voltage devices on the 12VDC side and high voltage devices on the 120VAC side. The low voltage devices on the DC side are powered directly from the batteries. An inverter is placed on a second side that converts 12VDC to 120 VAC for higher voltage devices.
So your mind may be wondering, what is the difference between DC and AC devices?

Some examples of low voltage DC devices are:

  • lights
  • fans
  • the water pump
  • powerpoint devices
  • USB devices.

High voltage AC devices include:

  • motorized units
  • the televisions
  • coffee pots
  • and kitchen appliances like a blender.
Remember 12VDC devices can be wired directly from the batteries, 120VAC devices go through the power inverter.
And that, in a nutshell, is How an RV solar power works.
Simply put, an RV solar power system consists of five components:
  1. RV Solar Panels that collect and generate power
  2. A Charge Controller to charge the batteries
  3. Your Battery Bank that stores energy
  4. RV Electrical Panel to disperse and serves as your breaker box
  5. Power Inverter for higher voltage items
Along with a few miscellaneous items including cable, connectors, and fittings
In theory, the energy from the Sun would follow this path:
Solar Panels >>> Solar Controller >>> Battery Bank >>> RV Electrical Panel >>> DC Side >>> to DC Loads >>> AC Side >>> to AC Loads
When configuring a solar system you probably will make mistakes. Rarely are these mistakes detrimental to the system.
With just a few tweaks troubleshooting faults and failures you can remedy the problem.
The end result is usually a much higher amperage rating from the solar panels then you had planned on.
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RV Solar Power Panels

Photovoltaic solar panels generate electricity from sunlight to replenish the DC power in our battery system.
The one function of solar panels is to replenish the solar power you use every 24 hour period during the four to five hours of useful sunlight we have each day. The Photovoltaic cells in the panels absorb sunlight that creates energy.
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Solar panels operate at 100% efficiency with full sunlight and the solar panel squared-up facing the sun.
This can be compared to 25% efficiency in a heavy overcast day.
How are panels measured?
Panels are measured in either Watts, or Amps, or both. The size of the panel determines whether we are using this power source to maintain a high level of power or trickle charge the batteries when we are unplugged from shore power.
For our purposes, we will use Amps, since most RVers have an idea of what their battery capacity is. Multiple panels can be wired in series or parallel to each other to charge the batteries and produce enough energy to power the large draw circuits in the electrical panel.
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Solar panel energy is power with a purpose by reducing our energy dependency on fossil fuels and curb greenhouse emissions. These clean energy benefits are also packed with safety benefits and economic advantages as well. It is green, with less risk of harm from heat, temperature, and fire, and can also save you a ton of money in the long run.
Word of caution!
Shadows can have a dramatic impact on the efficiency of solar panels! A shadow covering even the smallest portion of the surface can have an impact on the power output. There is a large voltage drop acting as a barrier to power usage from shading even one cell. This can result in upwards of 25% less power. In the event of a shadow on your solar panel turn the panel until the shadow is gone.
Some other variables would include:
  • Cloud cover
  • Tree cover
  • Latitude
  • Season
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Charge Controllers

Charge Controllers keep your batteries from over-charging It stops the current when sensing the battery is at full power.

It is not necessary to regulate solar panels that produce less the 1.5% of your batteries rated capacity. Therefore a 1.5 Amp panel is as large as you should use without regulation on a 100 amp hour battery.
Regulators are used when you install two or more solar panels to charge your batteries. These controllers have a rating equivalent to the amps hour maximum in your solar array. Since the power travels one way through the controller it prevents battery discharge.
There are basically two choices when looking into charge controllers, the MPPT charge controller or a PWM charge controller.

PWM – Pulse-Width Modulation

  • more affordable, easier to install
  • direct current from the solar array to your battery bank
  • steps the voltage down to whatever your battery is charging at
  • stops charging when your battery is full
  • works great on smaller systems

MPPT -Maximum Power Point Tracker

  • Costs more than PWM controllers
  • uses the same voltage drop but gives you more amps
  • Converts lost voltage into usable amps which is more efficient
  • gives you a lot more of your solar energy wattage
  • most efficient on larger systems
We suggest using the MPPT charge controller is you can afford the initial expense. Paying $30 for a PWM controller as compared to $200 for an MPPT controller might be a tough pill to swallow. In the long run, over time, you will be much more satisfied with the MPPT controllers efficiency.
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Batteries

Lead Acid or Lithium
All batteries self-discharge, a solar panel can keep a battery fully charged. A 150 milliamp solar panel can maintain a 75 amp hour battery just fine.
This is a good rule of thumb assuming there are no loads on the batteries other than self-discharge, also referred to parasitic drain.
Solar panels put out pure DC power and are excellent chargers as long as there is a charge controller in the circuit.
For the highest efficiency, the batteries in our battery bank should never discharge below 50% of the total rating.

Lead Acid or Lithium Batteries

Lead Acid batteries have a charge efficiency of only 85%.

Lithium batteries have a charge efficiency of nearly 100%.
The allowable depth of discharge on a typical lead-acid battery is 50% or less.
The allowable depth of discharge on a Lithium battery is 80% or more.
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Inverters

Determining the size of an inverter is simple.
The job of the inverter is to convert 12VDC power to 120VAC that comes from the bank of batteries.
The 120VAC power is sent to the electrical panel for use on our higher powered devices.
The inverter simply needs to be large enough for the devices you power simultaneously.
A simple power usage table of these devices will determine the size of the power inverter.
Most RVers have found that 2000 to the 3000-watt inverter is sufficient.
How do I mount solar panels?
Most Solar panels are rooftop mounted on top of the RV on a rail system. Some motorized RV rigs already have these rails installed.
RV Solar panels are mounted securely so they do not break away from the roof during travel  A second option would be to store your solar panels and ground mount the units when you arrive.

What is Solar Prep on new RV’s?

Having an RV with solar prep is a bonus. The biggest challenge to having solar power on an RV is installing the cable entry plate. As you have probably heard “there are RV’s that leak and there are those that are about too!” Drilling holes in your RV is a sure fire way to create a leak.
With solar prep, the work is done for you by the manufacturer. The cable entry plate is drilled, secured and waterproofed on your RV. It is plug and play. With the work done you can by a prepackaged kit and go solar. The installation of the cable entry plate saves money due to the fact that you do not have to hire someone to install it.

Does Solar Power provide enough electricity for my whole RV?

Devices in the RV can be powered by our Solar Panels including your air conditioner. For example, let us say a solar panel is rated at 100 watts of power
six solar panels would provide us with 600 watts of power
To determine how many solar panels you will need you to need to calculate your typical electrical usage will be on a typical day.
As an example, think about the devices you use in a given day and write them down in a column.
We will use a series of calculations to determine your power usage
Device >>> Amperage Draw >>> Hours of Usage >>>> Amp-Hours
Lights                        1                         4                                    4
Laptops                   13                         8                                104
Inverter                     3                        8                                   24
Cooking                 100                        5                                   50
Parasitic Drain        1                       24                                   24
4 + 104 + 24 + 50 + 24 = 206 amp hours of power per day
Our solar panels will need to replace 206 amp hours each and every day in that 7 or so period of direct and useful sunlight
206 hours of usage divided by 7 hours of sunlight equals 29.4 amps in full sun
Solar panels are rated watts, we know the amps
Watts=Volts X Amps
530 Watts = 18 Volts X 29.4 Amps
 This is the absolute minimum wattage of solar panels you are going to need assuming you get 7 hours of full sun every day
Variables= cloud cover, tree cover, latitude, the season
30% factor of safety
let us say we have a 30% variable, so 530 W X 1.3 = 689 Watts required.
So there you have it, RV solar power for RV’s. Please feel free to share!
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