Talking about solar and RV’s first is premature. Solar Panels (Photovoltaic Panels – PV’s) are a method of generating energy for storage. They are only one of a number of options to generate electricity with a RV.
We should understand energy first. There are three components regarding a RV.
- Generation (production)
- Usage (consumption)
There are two types of electrical systems in an RV.
- 120 Volt – Home electricity
- 12V – Car battery voltage
There are specific areas where energy is used and generated
The chassis generates electricity (12V) with the alternator. (generation) The chassis has a battery (storage) that is utilized (consumption) to start the vehicle, run the radio, illuminate the headlamps, extend the coach steps, extend the slide, etc.
The chassis supplies 12V energy to the coach when the alternator is generating energy. A voltage regulator modifies the energy going to the chassis battery so the chassis battery can be charged (storage). Energy (12V) produced by the alternator is passed through a relay to the coach.
The coach obtains electricity by operating a generator or plugging into the electrical grid (120V) (generation), or by energy being provided by the chassis alternator (12V) (generation) or by solar (PV) panels (12V) (generation).
You are unable to store 120V energy. It is either is or isn’t available. 120 V energy can be produced by an inverter which takes energy from the coach batteries and converts it from 12V energy to 120 V energy. If you run a 120V fan that consumes 2 Amps, using the inverter, you would need to draw at least 20 amps from the batteries because the battery voltage is 1/10th that of electrical grid voltage. ( 12V * 10 = 120V). If you ran the fan for an hour, you would consume 20AHr from the battery.
The coach has a charge controller that charges the coach batteries (12V) (storage), either from the electrical grid, or the generator. It will transform 120V energy into 12V energy and provide energy to the 12V system in the RV, so that you can use 12V energy for the lights, and other 12V systems, and charge the batteries at the same time.
The coach has two power systems, 120V (Home electricity) and 12V (Car battery electricity).
120 Volt Appliances
- Air Conditioner
- Refrigerator (also works on propane, some work on 12V energy when the chassis is running. New RV’s have compressor refrigerators that work off battery (12V) power, and don’t require a 120 V AC Connection.)
- Heat Pump
- Outlets in the coach
12 Volt Appliances
- Interior Lights
- Propane Valve (later models)
- LP Detector
- Propane Furnace
- Interior Fans
- Water Pump
- Television (some versions have a 120V AC television that requires the Inverter to be turned on).
Usage (Energy Consumption)
Prior to considering additional energy production, it’s important to determine the usage (consumption) for the RV. Energy consumption is generally not a problem when plugged into the grid, or when running the generator, as long as you do not exceed the amount of electricity the RV can handle, generally 30 Amps 120V AC. (home electricity).
Using too much electricity, (running the AC, microwave, coffee pot, hair curler, hair dryer, electric grill simultaneously will trip a circuit breaker. On the power post, or in the house for home electricity, or on the generator (small black switch on the side near the on off switch – propane) )
Tripping a 120V circuit breaker will not shut down any 12V system in the RV. Energy will continue to be supplied from the batteries (storage) until the batteries are discharged.
Plugged into the grid, or running the generator, supplies both 120V electricity directly and 12V electricity indirectly with the Charge Controller.
Table of 12V Consumption
|Category||Quantity||Watts||Amps/Hr||Hours per Day||% of Time||Amp Hours|
|Television – Older||1||100.0||8.33||4||100.00%||33.33|
|Inverter (98 to 70% efficient)||Watts||120V Amps||12V Amps||Loss||Hours||Amp Hours|
|Television – Samsung M5300 32″||27||0.23||2.25||50%||4||13.5|
Batteries store energy. The amount of energy batteries can store is measured in Amp Hours (AHr). Look for the Amp Hours (Ah) @ 20 Hr rating to see how much energy the battery can store.
Batteries used in most RV’s are either 6V batteries, or 12V batteries. 6V batteries are combined in series to make one 12V battery. Two (2) 250 AHr 6V batteries combined together make one (1) 250 AHr 12V battery. Two 12V batteries are combined in parallel and make one 12V battery. Two (2) 100 AHr 12V batteries combined in parallel make one (1) 200 AHr 12V battery.
Combining in series increases the voltage, combining in parallel increases the amperage.
There are, generally, three type of batteries. Lead Acid (wet) Batteries, AGM (Absorbed Glass Mat) Batteries, and Lithium Batteries. Lead acid batteries need to be vented as they can emit hydrogen and oxygen. AGM’s and Lithium’s do not need to be vented. AGM’s and Lithium’s are sealed for life.
Led Acid batteries need to have the electrolyte checked periodically, and generally cannot be discharged past 50% 0f their capacity.
AGM’s need no maintenance and generally may be discharged down to 80%
Lithium’s need to be in a conditioned space, as charging and discharging is affected if they are too hot or cold. Lithium’s have the ability to be discharged rapidly without damage, and may be discharged almost completely without damage.
|Duracell – Batteries Plus||SLIGC145UT||Flooded||77||6||255||10.25||7.13||11.88||128|
|US Battery||US 145 XC2||Flooded||70||6||251||10.25||7.13||11.88||126|
|US Battery||US RE GC2H XC2||Flooded||68||6||242||10.25||7.13||11.88||121|
|Duracell – Batteries Plus||SLIGC125||Flooded||68||6||235||10.25||7.13||10.88||118|
|US Battery||US AGM 2224||AGM||67||6||224||10.20||7.09||9.96||112|
|Deka||Solar Battery GC15||Flooded||73||6||215||10.50||7.10||10.90||108|
|Duracell – Batteries Plus||SLIGC110||Flooded||60||6||215||10.25||7.13||10.88||108|
|US Battery||US 250HC XC2||Flooded||77||6||280||11.63||7.13||11.63||140|
|Duracell – Batteries Plus||SLI6V225S||Flooded||73||6||250||11.75||7.00||11.60||125|
|Duracell – Batteries Plus||SLI6210S||Flooded||67||6||235||11.75||7.00||11.50||118|
Do I Really Need Solar?
Having solar today has a ‘cool’ connotation. Deciding whether you need solar panels on the roof to charge your 12V system is a combination of how and where you camp, how far you travel every day, and your energy consumption.
|Do I need Solar Panels?|
|I Camp at campgrounds with electrical hookups exclusively||I camp occasionally at campgrounds with no electrical hookups||I camp exclusively at campgrounds with no electrical hookups|
|NO Panels||Do you drive more that 100 miles every day?|
|Do you run lights, television, inverter the propane furnace or use a C Pap in the evening?|
|Solar Panels are a good option to assist in keeping the coach batteries charged.|
Solar System Components
Solar Panel System Components
Solar (PV) avoids the onboard charge controller, and utilizes its own charge controller. There are essentially four components to a solar system.
- Collection – Solar Panels converts sunlight into electricity, and passes the energy to the charge controller to charge the batteries
- Management – Charge Controller takes the energy from the solar panels and regulates it in a manner to efficiently charge the batteries.
- Storage – Stores the energy collected by the solar panels until use.
- Distribution – Inverter/12V System. Converts 12V energy stored in the batteries into 120V energy for use in ‘normal’ electrical appliances. It requires 10 Amps of battery energy to supply 1 Amp of 120V AC voltage.
Collection – Solar Panels (photovoltaic array)
Monocrystalline – manufactured from a silicon ingot, more expensive than polycrystalline, efficiency in the 18% range. Less effected by heat than polycrystalline panels.
Polycrystalline – manufactured from a poured silicon block, less expensive than a Monocrystalline panel, efficiency in the 14% range. More effected by heat than monocrystalline panels.
Output in volts – panels are sold with a watt rating. IE: 100 Watt Panels, 170 watt panels, 320 watt panels. The output of the solar panel is managed by the charge controller so as to properly charge the house batteries.
Watts = volts * amps
You have to charge a battery at a higher voltage than the voltage level in the battery. Typically the charge controller will charge the battery at a voltage of over 14V. As the voltage increases, the amperage decreases. Generally, on a sunny day, with a balanced system, the batteries will be fully charged before mid-afternoon. If you have a 200Ah flooded battery system, you can safely use 100Ah a day. The 100 Ah must be returned to storage either by the solar panels, alternator, or from the charge controller being connected to 120V AC.
A 300 watt system, charging at 14.1 V, at maximum efficiency, with optimal sun angle, optimal sun visibility, and length of day, will able to return to storage about 20 Amps per hour. Therefore it would take at least 5 hours to fully charge the batteries.
12V Batteries are provided by Winnebago for powering the 12V systems in the coach. There are two, and generally, but not always, they are located under the steps to the coach. There are a few models where additional batteries can be mounted. All batteries should be securely restrained, and those batteries that require venting (flooded) should not be placed in enclosed spaces. The OEM Batteries are not Deep Cycle
Wet cell or flooded batteries produce oxygen and hydrogen as part of the charging process. As a result they must be checked periodically to make sure that there is sufficient electrolyte. In case the electrolyte is low, add distilled water, readily available at a supermarket (for ironing). Flooded batteries require periodic maintenance, are generally less expensive than other types of batteries, but can not be discharged as much as others. Flooded batteries can be generally discharged to 50% of their storage capacity.
AGM – (Absorbent glass mat) AGM batteries differ from flooded lead acid batteries in that the electrolyte is held in the glass mats. They are sealed for life, and do not require venting. They can be located in closed spaces. There is no maintenance on them. AGM batteries can be generally discharged to 80% of their amp hour capacity.
Lithium – Lithium Ion batteries are sealed for life, require no maintenance and can be discharged to almost 100% of their amp hour capacity. One drawback is that high amp hour Lithium Ion batteries can cost to $1,000. They do not operate well in temperatures below freezing or in high temperature environments.
The RV has two discreet power systems, an AC, 120V system and a DC system generally used for the TV, lights, fans, propane furnace, propane refrigerator, compressor refrigerator, gas valve solenoid and entertainment system. Some of the later models have 120V AC Televisions. Older RV’s came with high light output halogen lamps. These lamps used a significant amount of energy to light the RV. LED lamps come in a variety of heat colors (warm and white) and supply an equal brightness for far less energy. If you have halogen lamps, I strongly advise you to switch them out for LED’s.
They manufacture 12V appliances, fans especially, that can run directly off battery power. Female 12V receptacles can be added by tapping into the power source of 12V switches and lamps.
The microwave, heat pump, air conditioner and refrigerator use 120V AC power. 120V AC power can be supplied by the generator, line voltage from the power grid (plugging in) and an inverter. An inverter is connected to the batteries and converts stored 12V electrical energy into 120V AC energy.
With an inverter, rule of thumb is that if an AC appliance requires 5 amps, you will need at least 50 amps from a DC source to run the appliance. The amount of energy used to power the device is constant, so 120V * 5A = 600 Watts; 12V * 50A = 600 Watts.
Inverters are measured
Size the amount of watts they will provide for an AC device. Typically inverters are 100w, 500w, 1,000W, 2,000W. A 2,000W inverter will power a 1,500W microwave for a short period of time. (1,500W = 120V * 12.5A; 1,500W = 12V * 125A) Running your microwave off the inverter for 15 minutes will require about 32 AHr from the battery.
Form – AC power alternates. The alternation should be smooth, like waves far out at sea. The alternation is referred to as waveform. Smooth waveforms are described as sinusoidal. Electric Utilities supply sine wave electricity. A true sinusoidal inverter should be used. Other waveforms output by inverters are Modified Sine Wave, and Square Wave and stepped wave.
Efficiency – There will always be loss in the conversion of electricity from AC to DC. Depending upon your inverter the loss may be as much as 50%. Read the literature for your inverter to determine the most effective use and sizing of your inverter.
One of the questions about solar installations on an RV is “Can I run my Air Conditioning off the batteries?”. The answer is not effectively. The batteries will run the AC, but for a VERY short period of time, if the batteries have a high enough capacity and the photovoltaic array is properly sized to restore the used energy.
A 100AH battery system contains about 1,200W. A 3,000 BTU converts to about 880 Watts.
In dry climates, a viable alternative may be an evaporative cooler (swamp cooler) air conditioner. The Colorado Plateau, parts of the western Midwest and sections of California are compatible with an evaporative cooler. Some evaporative coolers require only 10Ah (12V) to run.
There is a possibility that RV’ers do not look at all aspects of a solar system, and are disappointed. A solar system is a balance of solar input energy to the battery, battery storage energy and battery energy use.
Think of a RV solar system as a checking account with direct deposit. Solar input is direct deposit, the account balance is useable battery energy (with a minimum balance), and debit card purchases are battery energy use. Not enough direct deposit (Low/no sunshine), the balance is low (Battery voltage), impeding the ability to make purchases (turn on lights, run fans). Low account balance requires alternate income (running the generator or alternator on the RV), to bring the account balance back.
Ongoing automatic payments from a checking account can’t be avoided. It’s the same with an RV Solar system. The refrigerator, gas valve, propane sensor, thermostat, use energy (make withdrawals), and can total 85 AH, or more, in a 24 hours. Turning on the lights, running water, running fans are all optional uses of energy.
You can only spend what balance is left after the automatic payments. If you have a useable capacity of 120AH, and need 85 AH for systems, you’re left with a balance of 35 AH.
So, there has to be a balance between the amount of energy collected and the amount of energy you are capable of storing. Five hundred amps of storage would require more solar panels for charging them than could be mounted on a View/Navion.
We are generally limited by space regarding the Amp Hours you can store or collect. Without modifications to your battery storage area, (with the exception of select M Models) the maximum is about 180 AH (usable), the minimum shouldn’t be lower than 100AH (useable), simply because there are so many good batteries out there capable of storing that amount.
The flooded 6V Golf Cart Batteries generally have the most robust construction and amps for the dollar. They should be checked periodically for low water, especially if they have been severely discharged and recharged. They can be can be discharged to 50 percent
AGM (Absorbent Glass Mat ) Batteries require no maintenance, they are sealed for life. They can be charged up to five times faster than the flooded version, and they have the ability to deep cycle. AGM offers a depth-of-discharge of 80 percent; versus the flooded, which should only be discharged to 50 percent
Gel batteries have the acid mixed with silica gel. A gel battery generally lasts longer than an AGM battery. AGM Batteries are superior at low temperatures than Gel Batteries.
Lithium Batteries have the lowest weight, highest price and are capable of being almost completely discharged without damage. There are issues charging them in lower temperature conditions, and you need a charge controller capable of charging lithium batteries.
The roof of a Navion/View is about 190 SqFt and generally capable of holding about 400 watts of solar panels at a maximum. There are always ways to achieve something, provisioning your roof with more is possible. You will also need a charge controller to handle the increased load.
The 150 amps of battery storage would require about ten hours of sunshine from three 100 watt panels. Using the maximum battery capacity of 180 amps per day would require about 400 watts of solar. Adding over 400 watts of solar panels on the roof would only shorten the time required to charge the batteries and only if you used enough energy to discharge them to their safe discharge level. Lower solar collection ability i.e.: fewer solar panels on the roof, would not collect enough energy to fully charge the batteries.
Solar System Wiring
How to route wiring from solar panels – Generally the most difficult part of running wiring is determining a route from a location on the roof to the batteries. Some RV’s don’t have locations from the roof down the wall. Preplanning is critical
Through the roof with a new fixture – Amazon sells a receptacle that attached to the roof and has two waterproof compression fittings. A new hole can be drilled into the interior of the RV, and the wire run the batteries without disassembling the interior of the RV. There is room between the floor of the RV and the frame of the RV. If the solar cables are properly attached and covered with coilex the wires can be located under the floor..
Through the refrigerator vent – Older RV’s had the refrigerator vent on the roof. Later models have it located on the side. A fixture on the roof over the side heat discharge for the refrigerator is an option.
Through the entertainment system antenna – I’ve installed several solar systems using the rear entertainment system antenna hole in the roof. The hole generally has to be enlarged, the wires run in at an angel, the space between the wire and antenna cable filled with caulk and then covered liberally with dicor.
Exterior with wiremold – wiremold is a plastic channel that can be affixed to the exterior of the RV. There are no holes drilled into the RV, the channel encloses the wire and protects it from snagging, and the cable is run under the RV, and then to the charge controller.
Rear corner post – The rear corner posts of the RV are made of heavy aluminum to protect the relatively soft corners of the RV walls. There is a chaseway inside the posts, and wire can be run under the upper decorative trim, down the corner post, under the bumper fascia and to a location. They can be especially useful if the solar panels are mounted in the clear area at the rear of the RV.
Zamp port on the roof – Winnebago has been selling RV’s with a roof appliance capable of attaching three solar panels. There are cables that can be utilized that can combine multiple panels for one Zamp port. The port is limited to 500 watts of solar; each port is limited to 150 watts of solar. The wiring in the appliance and the rest of the RV is robust enough that 170 W panels can be affixed.
Unfortunately Zamp panels are about twice the price per watt of most panels on the market. They also have a SAE connector and reversed polarity, than industry standard panels with MC4 connectors. There are cables that allow standard panels to be used with a Zamp system. There are specific mounting brackets that make mounting additional offset Zamp Solar Panels very easy.
Where to locate charge controller
I have installed the majority of Charge controllers under the cabinet forward of the sink. They have also been installed flush on the bulkhead for the dinette by the entrance in an H model, and in the space between the slide and the speaker compartment under the refrigerator in a J. Ideally, the charge controller should be located close to the batteries or inverter. A close examination and pre planning of the RV ensures a professional looking job.
Where to connect leads to battery
The cables from the charge controller can be connected to either the battery, or the inverter. In many later models, the inverter is located in the cabinet to the rear of the side entrance. The inverter is connected directly to the batteries and fused. You can use the rear of the inverter as a bus bar to provide a charge to the battery. Make sure to protect any cable coming from the positive terminal of the battery or an added cable to the inverter, with a fuse. A 20A or 30A is suggested.