What’s the appeal of RV or boat living?
As the cost of living increases, so does the struggle to find affrdable housing. At the same time, many occupations have transitioned to a digital or remote format, or employers have realized the possibility of offing that flexibility to their workers. These factors have increased the usage of RVs, campers, buses, boats, vans and other vehicles as second or in some cases even primary homes. Rather than being saddled with a mortgage or rent with no equity, many people are packing up their lives and hitting the road or water. Of course, that life isn’t for everyone—some prefer to keep their RVs or boats as a parttime or seasonal activity rather than a residence. But whatever the application, electric power comes into play.
How does solar fit into a mobile life?
Most land and marine-based vehicles will need power both for normal operation while in transit and for comfort or recreation when not traveling. Either way, almost all mobile applications can benefit from the addition of a solar electric system. Many vehicles incorporate batteries—whether to start or operate the rig itself or to provide power to loads when the vehicle is stationary. The primary purpose of using solar in a mobile system is to maintain batteries when there is no other source of charging. For those who live full time in their rigs or plan to “boondock” for extended periods of time, a solar charging system can be much more critical compared to someone who is seasonal or may spend most of their time staying at campsites with services and hookups.
Mobile solar systems can be designed in all diffent shapes and sizes—from a small portable 100W solar panel set up on the ground acting as a battery trickle charger for a pickup truck bed camper shell, to a 3000W roof mounted system on a 5th wheel trailer for a family of four who full-time, to everything in between. NAZ specializes in custom system design for RV and marine applications. We work one-on-one with you to understand your wants and needs in order to get you the best solution possible.
What should be considered when designing a mobile system?
There are many factors to keep in mind when designing a mobile solar electric system. Perhaps the most obvious and important one would be the power and energy requirements of the user. Depending on what kinds of loads or appliances need to be powered in the vehicle, and for how long, the size and selection of equipment can vary. Another big factor in this aspect is when these loads need to be powered. For example, if the intent is to power a roof top air conditioner for extended periods of time while boondocking without having to run gas generator, that system size and equipment selection would look quite diffent than needed for the previous scenario.
In addition to what someone uses in their rig, how they use the rig is equally important. As mentioned earlier, a solar electric system for one who’s full time in their RV and depends on the power generated by the system for their livelihood could look very diffent m a system for a seasonal travel trailer that’s only used for a few weekends each year. Understandably, most full-timers opt for larger and more comprehensive systems than people who part time. For those who full-time and prefer extended boondocking over staying in campsites, their system must be able to self-sustain for longer periods of time without external energy input from shore power or a generator. Others who prefer to stay in campsites instead of boondocking could potentially get away with a smaller system altogether. Anything is possible with these types of systems, and each should be built around the user and their needs.
The location of the vehicle or intended area of travel is yet another factor when it comes to mobile solar. Many full-time RVers map out their travel so that they are in a comfortable climate all year long, for instance, going to southern warmer climates during winter and norther cooler climates during summer. This also tends to line up with areas of good sun—so that the solar panels would always see decent solar potential, and therefore a lesser sized-system could be feasible. On the other hand, if someone prefers to take their RV to ski resorts in winter instead of hanging out in the desert, they might require a larger system to supplement for the lack of solar potential. The mounting/placement of the solar panels on the roof in terms of being flat or tilted can also be based on the location or intended travel area of the vehicle. Roof mounted versus portable ground mounted solar panels (or a combination of the two) can be considered as well.
RVs, boats and other vehicles can also qualify as a residence for tax purposes. A 26% federal tax credit available for some mobile solar systems was recently extended through the end of 2022. This should be considered in the budgetary planning stage of a mobile solar electric system.
Another important factor with these types of systems is physical space. Unlike stationary grid-tie or off-grid ar systems, mobile systems have a finite amount of physical space where the equipment can be installed. The most obvious limitation would be the area of the roof or mounting surface where the solar panels would be installed. Often solar panels are contending with rooftop air conditioners, vents, fans, antennas and more, so available space for solar panels and any potential shading concerns need to be considered during design. Even if solar panels are portable and not permanently mounted to the rig, storage space for the panels during transit is also important. In addition to the solar panels themselves, the space for supporting components like charge controllers, inverters, batteries, etc. must also be mapped out. Free space in mobile applications is often at a premium, so deciding where the equipment will be installed while adhering to manufacturer recommended mounting orientations and clearances is an important step in the design process.
What types of mobile systems are there?
- Solar charging system
- Inverter system
- Battery system
- Alternator/tow vehicle/engine system/start battery charging
How does a solar charging system work?
A simple solar charging system consists of nothing more than a solar panel, charge controller and battery bank. A solar charging system can be incorporated with the existing battery system and wiring of most vehicles to allow for charging from the sun when there is no other charging source available. Diffentnds of solar panels can be used in varying quantities and configurations depending on the needs of the user and available space. The solar charge controller is used to manage the flow of energy from the solar panels to the battery bank. This can be a PWM or MPPT-type controller, depending on the solar panels used for that application.
When is an inverter system needed?
The main reason to incorporate an inverter into a mobile electric system would be to provide usable AC power when not plugged into shore power or without having to run a gas generator. Inverters used in the mobile industry (RV, marine, vans) are extremely similar to offgrid inverters but usually smaller. For example, like off-grid inverters, mobile inverters offere sine versus modified, high frequency versus low frequency, and inverter-only versus inverter/charger. Inverter/chargers are extremely common for these types of applications, as well as inverters with AC pass through. A mobile inverter with AC pass through does not charge the batteries like an inverter/charger, but still lets external AC power go straight to the loads without discharging the batteries. A mobile inverter can be configured to power all the AC loads in the entire rig or just a select few circuits like the TV and refrigerator while boondocking.
When does a battery system make sense?
In some cases, it is desirable to be able to charge the “house” battery bank from a vehicle alternator/engine/start battery system. This allows for charging the house battery while the engine is running and the vehicle is in motion. Alternators from tow vehicles can also be used for auxiliary battery charging in the case of 5th wheels and travel trailers. This provides yet another source of energy in addition to solar, shore power and gas generator. Charging from one battery system to the other can be done with a battery isolator or battery combiner. This will temporarily connect both battery banks in parallel based on conditions like voltage or ignition signal from the vehicle. These types of devices usually let a fairly high amount of current pass through—typically 100-300A DC and in some cases higher. There are “smart” battery isolators/combiners as well, which can monitor voltage and charge trends to improve their own operation. These will often allow charging from both battery banks in either direction. The vehicle battery charges the house battery while driving and the house battery charges the vehicle battery from the solar system, shore power or generator. The battery combiner also makes sure loads from one battery bank never discharge the other bank. If using lithium batteries in a mobile application, it’s important to note that they can potentially draw high amounts of current from the alternator in certain conditions, and the isolator itself and cabling should be sized as such. This is especially risky if the batteries have a low SOC and the vehicle is idling when alternator RPMs are low and it can’t cool itself as effectively.
Another method for alternator charging is through a DC-to-DC charger. These usually offer more current limited and precise way of charging the house battery bank. The battery isolator described earlier would simply connect the two battery banks, let the voltage increase to a certain level and remain there for a predetermined amount of time, then deem the batteries charged and disconnect/reconnect as needed. A proper DC-DC charger can deliver a three stage (bulk, absorb, float) charge process to the batteries. The fact that most of these chargers are more current limited than the previous solution, 30-50A, means there virtually no risk of damaging the vehicle alternator. This can be especially useful with lithium batteries which require a very controlled charging algorithm in other to prevent BMS shutdown. Some newer models have integrated Bluetooth programming allowing for a very sophisticated level of control.
It is possible to incorporate all or some or of the above-mentioned configurations within a common system. For comprehensive systems like these, it’s ideal to have the equipment networked together to share relevant information about charging, energy usage, etc.
How do I select a battery?
This industry is dominated by three common battery types.
Flooded lead acid batteries are lead batteries with a liquid electrolyte solution. They have a low upfront cost but require various levels of maintenance and can be sensitive to abusive high demanding applications. Also the maintenance can be an issue for RV applications due to limited access.
Absorbed glass mat batteries (sealed lead acid) are lead acid batteries with the electrolyte absorbed in a fiberglass mat. These are a sealed recombinant battery, they do not require maintenance nor do they off-gas hdrogen but are sensitive to over-discharge and partial state of charge just like flooded lead acid batteries. These batteries are a great solution for less intensive application like weekend camping.
Lithium batteries have an obvious high upfront cost, however, they are extremely safe and offer e best levelized cost of all solutions. They are extremely resilient to the abuse from highly intensive RV activity like full-time living. Also they can accept fast charging/discharging and aren’t affected y partial start of charge. This allows them to be charged up very quickly from a generator in the event solar can’t keep up. They can also be expanded over time, which is ideal for most dynamic projects. The most significant advantage is their weight, they are ¼ of the weight of a similar usable capacity lead acid battery bank and you can get 3-4x the capacity in the same footprint. Lithium battery technology is dominating the RV industry at this point and we have several dedicated solutions specifically for these applications.
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