RVs may benefit from solar electricity the most since they can sustain large systems that supply the necessary comforts and conveniences of a mobile home. Solar is a natural fit for living on the sea as well because of its mobility and quiet operation, and since shading and module location issues can often be resolved because the sun is always shining there. You can carry power to a job site, campsite, picnic spot, or even simply far into your own backyard with portable solar systems, including tiny, pull-along carts and bigger, trailer-mounted sets. Small systems may also be wonderful do-it-yourself projects for learning the fundamentals of battery-based solar electricity. The primary parts of a simple DC system for an outbuilding are the same as those of mobile PV systems, which are generally 12-volt systems. The system capacity is determined by the output of the modules and the storage capacity of the batteries. The only safety devices required are fuses and possibly a breaker or other type of switch for cutting power from the modules. One or more modules are used to charge batteries via a charge controller, and the batteries supply power directly to DC devices or to AC devices via an inverter.
Although they only make up a small fraction of the overall solar business, RVs dominate the 12-volt solar equipment market. This implies that you have a wide range of options for items and system setups. There are times when what works well on a house or outbuilding also applies to an RV. In other instances, the finest items to take into account are determined by the particular installation and operation environment, in addition to the reality of the road.
Solar Modules & Mounts
Standard stiff modules are often the best option for RV installations because to their robustness and reasonably good efficiency. For items to withstand various storms, tree branches, and other natural threats, they must be durable. Due to space constraints, efficiency is crucial for RV applications since it allows for the production of more power from smaller, more efficient modules. Metal brackets that hold the panels a few inches above the roof surface can be used to install framed rigid modules to roofs. As a result, an air gap is made, which aids in lowering the extremely high temperatures on vehicle roofs that impair a module's effectiveness.
On sloping or curved roofs, level installation is possible thanks to adjustable mounts. To optimize solar potential, tilt the modules up using mounts that can do so. Flexible modules are no longer sold for use in residential systems, although they are still popular in the mobile industry for a number of reasons. They are lightweight (only a few pounds for a full-size module) and thin (about 18 inch thick), and they can bend up to 30 degrees to fit curving rooftops. Grommet systems, glue-down, and screw-down installation techniques are available. They are strong enough to withstand being stepped on, hit by hail, covered with snow, etc., but they aren't as strong as stiff panel surfaces made of tempered glass.
There are further issues. Although these figures pertain to amorphous construction, some more recent flexible units are constructed with crystalline silicon and have slightly better efficiency. Flexible modules typically only give 6 to 8 percent efficiency, compared to 14 to 18 percent with rigid modules. Additionally, flexible modules are not tiltable, which reduces their overall output capability.
Charge Controllers & Inverters
To manage the flow of power to the batteries in all battery-based solar systems, a charge controller is required. Among other things, charge controllers aid in extending battery life, avoiding overcharging, and enhancing system performance. Your daily electricity budgeting can be significantly improved with a decent controller. Shunt-type, or "On-Off," charge controllers have long been the industry standard for 12-volt RV systems. However, more recent series-type controllers with pulse width modulation (PWM) offer some benefits, such as maintaining the batteries at a higher charge and minimizing issues with water loss and sulfation that are typical with shunt-type controllers.
The charge is maximized early and late in the day, when the modules are relatively cold and the battery voltage is low. Series controllers with maximum power point tracking (MPPT) are capable of charging "boosts," which employ extra voltage from the modules to enhance the charging amperage. An inverter must be placed on your system if you wish to use any equipment that plugs into a typical 110/120-volt wall socket, such as a laptop or mobile phone for charging. RV inverters are the same kinds found on several other 12-volt systems. The best kinds are pure sine units, which can supply regular home power to any AC equipment.
Although modified sine inverters can be roughly half as expensive as pure sine inverters, many appliances, including electrics, microwaves, and refrigerators, don't function as well or effectively when powered by modified sine. Based on the combined power requirement of all the appliances you want to operate simultaneously, select an inverter size. The electricity will be cut off if you go above the inverter's wattage rating or amperage limit.
Battery Remotes & Monitors
The charging amperage, battery voltage, and charging status of your batteries are all conveniently shown on a battery remote meter that functions in tandem with the charge controller. A battery monitor offers considerably more information about the state and health of the batteries, such as the percentage of capacity, the precise voltage for numerous batteries, and real-time amperage, which displays the watts or amperage as it enters and exits the batteries. Turn a device on or off and observe the change in discharge rate to determine how much electricity each light or appliance is utilizing.
In order to measure lifetime amp-hour discharge and evaluate the history of recent charge/discharge cycles, monitors also store data. Battery monitors are optional but are highly recommended for long-term solar off-grid living. Monitors assist you avoid excessive discharge, which significantly reduces the lifespan of your pricey batteries, by providing precise information regarding charge/discharge status. They also let you know how much reserve power you always have. A battery remote and battery monitor are available for purchase separately, or you may select a single device that performs both of their roles.
Lead-acid AGM batteries are still the most common kind of battery used in RV solar systems, however lithium-ion is increasingly gaining market share. True deep-cycle lead acid batteries are required; marine batteries, which are made for starting motors as well as operating lights and appliances, are not acceptable. RVs, unlike boats, often contain separate batteries for the vehicle's motor and the "home" electricity provided by the solar system, so they do not require a starting or cranking battery. Over lead acid batteries, lithium batteries have certain important advantages, such as longer life, deeper discharge, quicker charging, and greater capacity in a smaller size. Although lithium batteries don't need to be kept in ventilated spaces, they should be kept at the right temperature to guarantee the longest possible battery life. If your vehicle will be exposed to significant temperature swings and abrupt climatic changes, this is a crucial factor to take into account. The expense of lithium is by far its biggest drawback, coming in at two to three times that of lead-acid batteries.
Sizing an RV Solar System
Similar to sizing for home electricity, sizing a solar array for an RV involves considering your typical consumption patterns and calculating the amount of solar power required to supply that amount of power. When it comes to a house, you can simply check at your power bill; but, when it comes to an RV, you must consider how rapidly your batteries deplete on an average day. Simply start with fully charged batteries, use electricity as usual until the batteries are discharged—down to around 50% for lead-acid batteries or 80% for lithium-ion—and then turn the power back on.
For instance, if your battery bank has a 200 amp-hour capacity and it takes two days of average use to reach 50% capacity, you normally require 100 amp-hours of power per day. Make that amount your solar system's minimum production target. This easy approach works well for approximate estimation, but installing a battery monitor before your consumption test will give you far more accuracy. Your findings won't be based on the projected capacity of your battery bank because the monitor will show you exactly how much power is consumed by the batteries. Before deciding on a system size, you may also find out how much power is used by various appliances, which is useful to know in any event and also helps you decide whether to maintain such products or replace them with more efficient versions or alternatives. Use a reliable battery monitor that has a shunt built into the wiring. Calculating energy usage is challenging with certain other voltage meters that simply provide percent-charge readings.