Our solar project this week features customer Jason E., a full time RVer. Jason is a father and husband in a nomadic family of five that travels in their fifth wheel RV full time. His family has been living the nomadic lifestyle for 5+ years but most recently is in the process of putting down some roots, though they maintain traveling is still in their future.

Our solar project this week features customer David G. of Northern Arizona. David and his family purchased property in the high desert of Northern Arizona to be closer to extended family. Their intention wasn’t necessarily to go off-grid with their power needs, however, the location where they purchased their property dictated solar to be their only power option. That’s when David researched solar power and ultimately contacted our team at NAZ Solar Electric.

When looking at what is an ideal full system configuration for an RV, typically one would want to consider the expectations of a system and limitations of the RV, and then build the system around these expectations and limitations. In most cases you want to start from the roof and work your way down. 

Solar for Roof

Roof space is usually the biggest limitation when considering solar power for an RV. Being that solar panels are one of the least expensive aspects of a complete system, maximizing production value for a given space is the most advantageous plan. In most cases putting as many panels on the roof as will fit is the best idea. Measure or use pieces of cardboard, targeting a sixty-cell panel format (~67”x40”). These are technically the best panels and the cheapest, due to the volume of sales these panels enjoy. Other panel sizes are available. Mixing sizes and shapes is complicated so plan wisely. We’ve never had a customer complain about having too much power (because this isn’t possible) but having too little power can result in too little energy production which may not meet your expectations. This can be frustrating and could lead to premature battery failure or other system wide issues. 

Inverter Integration 

Next you need to plan for an inverter if you need to run AC appliances and devices. The inverter converts power from the batteries to your basic household outlet AC power, 120VAC or 120/240VAC. You need to decide whether you want a fully integrated inverter system or a simple stand-alone inverter. In most cases, this decision will be dictated by what you want to power from the inverter. If you simply want to plug in a laptop or charge a phone from time to time, then a stand-alone inverter should work fine. Most of these smaller inverters will have an outlet on the front allowing low power devices to be connected. Anything more demanding than this requires a fully integrated inverter/charger.  These inverter/chargers have a built-in transfer switch and the ability to charge the batteries at a much higher current than a typical converter. These are advanced inverter/chargers with powerful features and thus are usually the best solution for medium to large installations. The inverter/charger is typically placed between the shore power input and the main electric panel, the output from this inverter would go to the main electric panel. This essentially will power up all or most of the electrical circuits within the RV, depending on the configuration of the electrical panel. When AC input power is present from either shore power or generator, the inverter/charger will qualify the input (making sure it’s acceptable) and transfer that power through. It will pull from the AC input dynamically depending on certain limitations to charge the batteries. When shore power or the generator are not present the inverter uses energy from the batteries to power the AC loads. There are many more advanced features available from this type of inverter/charger, but in general if you power to all the outlets and appliances like the micro wave or the air conditioner then an inverter/charger is the way to go. Special care needs to be taken if you wish the inverter/charger to power air conditioners. Air conditioners consume large amounts of energy and need careful planning. 

Battery Bank

The final step in a design is sizing the battery bank. An RV is a terribly abusive environment for batteries. It’s common to have significant deficit cycling (infrequent full charges), over discharge is very likely, and temperature can vary significantly. There are two types of batteries that work for an RV system; lead acid and lithium-ion. Lead-acid batteries include flooded batteries (AGM), or Gel. However, gel lead acid batteries are not designed for the demands present in a typical RV system.  

Lithium

Advantages

• No maintenance

• Lightweight

• Can be placed inside the living space

• Smaller size

• Battery bank can be added to over time

• Low chance of damage if left uncharged

• Higher level of efficiency

• Charges faster

Disadvantages

• Cost- Lithium batteries are more expensive, however, over the life of the system Lithium is cheaper. 

AGM

Advantages

• Low cost

Disadvantages

• Larger and heavier than Lithium

• It’s not recommended to add to a lead acid battery bank after it’s installed

• Life is significantly reduced if they are left uncharged for any length of time

Flooded

Advantages

• Cheapest battery option

Disadvantages

• Must be placed in a vented enclosure designed to handle the gas fumes they create

• Extremely heavy - it’s important to make sure that the location can handle the weight

• Poorly suited to handle the abuse present in an RV system

• Not recommended to add to their battery bank.

It’s important to have an accurate battery monitor installed in the system, one that uses a shunt. This will allow for accurate tracking of the battery state of charge. Regardless of the type of battery bank, this accessory can really help prevent excessive discharge and confirm regular recharging.

Talk to a Specialist

You can do all the research you want but some of the best recommendations you’ll get are going to come from experts in the industry. NAZ Solar Electric has several engineers on site happy to consult and design a system to suit your application, no matter how unique or complicated. Feel free to give us a call to discuss your project today. 

A lot of people assume they need a transfer switch for an off-grid system when they are using a generator to charge the batteries or power loads. If you are using an inverter/charger there is an internal transfer switch to select between the inverter’s output and an incoming AC source. Most inverter/chargers will remain in “Invert” mode unless they see an acceptable AC source coming through (Shore / Grid Power or Generator Power). Once the inverter/charger accepts the AC voltage, it transfers over to supply power to loads and dump excess power into the batteries. Once this AC source is disconnected, the inverter will transfer back to “invert” mode and use battery power to run the loads. Some inverter/chargers will accept two AC sources and transfer between either of those and the inverter’s output. So if this is how your system would be set up, then there is no need for an external transfer switch.

You may need an external transfer switch if you have an inverter/charger with only one AC input and you want to switch between two AC sources like a generator and shore/grid power. This is the case in most mobile/RV applications. Another scenario is when you have a generator that can deliver more power than the inverter/charger can pass through and you want to power some heavy loads. The inverter charger is limited by the rating of the internal transfer switch. For example: Let’s say we have a Schneider 3.8kW inverter/charger with an internal 30A transfer switch with a split phase 120/240VAC output. The max load we can run by passing the generator power through is 7.2kW (30A x 240VAC = 7200 W). If we had a load that exceeded this 7.2 kW, and we had a generator that was able to satisfy this load, we would want the inverter/charger to be bypassed, allowing the generator to power the load directly. In this event we could use an external transfer switch to select between the inverter’s output and the generator’s output. If the inverter/charger is properly sized, this scenario does not occur often.

For more info on this call NAZ Solar Electric 1-800-383-0195 or email sales@solar-electric.com.