Unleashing the Power of Solar and Battery Systems: A Use Case for Electric Consumption in RVs
As the world moves towards sustainable living, more and more people are turning to renewable energy sources like solar power to meet their energy needs. This shift towards clean energy is also evident in the recreational vehicle (RV) industry, with RV owners increasingly exploring the use of solar and battery systems to power their adventures on the road. In this blog post, we will delve into the development of a use case for electric consumption, specifically for the specing of a solar and battery system in an RV.
Why Go Solar in an RV?
RVs are a popular choice for travelers who seek the freedom of the open road and the ability to explore new destinations at their own pace. However, traditional sources of power in RVs, such as generators or relying solely on the RV’s engine, come with their drawbacks. Generators can be noisy, require fuel, and emit harmful emissions, while running the engine for prolonged periods can lead to increased fuel consumption and wear and tear on the engine. This is where solar power can be a game-changer for RV owners.
Harnessing the sun’s energy through solar panels on the roof of an RV can provide a reliable and sustainable source of power. Additionally, coupling solar panels with battery storage allows for energy to be stored and used even when the sun is not shining, providing power during cloudy days or at night. This combination of solar and battery systems allows RV owners to enjoy the benefits of clean and quiet energy, while also reducing their environmental impact and saving on fuel costs.
Developing a Use Case for Electric Consumption
When it comes to specing a solar and battery system for an RV, it’s crucial to develop a comprehensive use case that takes into account the specific electric consumption requirements of your RV. Here are some steps to guide you through the process:
- Assess Your Energy Needs: Start by evaluating your RV’s energy consumption requirements. Consider the appliances, devices, and systems that you will be using in your RV, such as lights, refrigerator, air conditioner, water pump, and entertainment systems. Note down their power ratings, usage patterns, and estimated daily energy consumption.
- Determine Your Solar Panel Capacity: Once you have a clear understanding of your RV’s energy needs, you can calculate the solar panel capacity required to meet those needs. Consider factors such as the location and orientation of your RV during travel and camping, the average daily solar insolation in those locations, and the efficiency of the solar panels you plan to use. You can use online solar calculators or consult with solar experts to determine the optimal solar panel capacity for your RV.
- Choose the Right Battery System: Selecting the right battery system is crucial for storing and utilizing the solar energy efficiently. Consider the capacity, type, and voltage of the batteries based on your energy requirements and the available space in your RV for installation. Lithium-ion batteries are a popular choice due to their high energy density, longer lifespan, and lighter weight compared to traditional lead-acid batteries.
- Plan for System Integration: Once you have determined the optimal solar panel capacity and battery system for your RV, it’s essential to plan for their integration into your RV’s electrical system. Consult with a qualified electrician or solar installer to ensure the safe and efficient installation of the solar panels, charge controller, inverter, and battery system. Consider factors such as wiring, mounting, and protection against overcharging, over-discharging, and other electrical hazards.
- Monitor and Optimize Your System: After your solar and battery system is installed, it’s crucial to monitor and optimize its performance regularly. Keep track of your RV’s energy consumption and the performance of your solar panels and battery system. Make adjustments as needed to optimize the system.
This Specific Use Case
It took us about four months to develop a use case that was workable. Some of the challenges were changing expectations of what is possible and normal, and personal behaviors of consumption, and maintenance. A simple difference between home vs RV life is that at home, people typically let the faucet run while brushing your teeth, where as in an RV with only 50 gallons of fresh water and perhaps days until you’re at a place where you can refill, the behavior is modified to just get the brush wet or use a glass of water for the whole process. The same goes for electricity. Turn things off while not using them, turn the heat down, turn the cooling up, etc.
In the end, it was decided upon the following:
- Batteries should have enough capacity for three days without sun.
- Air Conditioning could only be run for short periods of time on batteries to initially cool the area.
- Install more efficient air-movers to help circulate warm and cool air.
- Technology such as internet, monitors, etc. are required and thus their consumption 24×7 must be taken into account
- Solar panels should recharge a minimum of 30% batteries in six hours of good sun.
- The Inverter should be able to run everything in the trailer, not all at once, but at a minimum, all minor loads and one major load such as the air conditioner, microwave, or electric heater.
It was decided to go with a 24v system. There are advantages and disadvantages with this. The primary advantage is efficiency and lower current. Following Ohm’s law, V * I = P where V is volts (the amount of electricity), I = current or amperage (the flow of that electricity), and P for power in watts (the amount of work that the supplied electricity can do). So increasing the voltage from 12 to 24 volts, in turns reduces the current by half while still providing the same amount of power.
The number of batteries, it was decided, were six 100ah @ 12v Battle Born LiFEPO4 batteries. These are arguably at the top of the industry, much of the price of them is for the name. But they work, and that was very important to GLRay. These batteries (more tech talk) were to be configured in three parallel lines of two batteries in series – yeah, it’s a mouthful and the head needs to be wrapped around that. Basically it means that the two batteries in series will bump the voltage up to 24v. You put three of these series together in parallel and that changes to available amperage up to a whopping 300/600 amps. Not that this system would ever use that, but hey… it’s available. We actually limited it to 200amps, as there is nothing in the trailer that would ever exceed that – not even if all of the loads were turned on at the same time.
These batteries will provide 300ah @ 24v of power or 7.2kwh. That’s a lot of power, but not enough to run air conditioners all day long.
As the use case stated, we needed the batteries to be charged a minimum of 30% in six good sun hours. That would call for a minimum of 450w of solar panels on the roof. That would be the bare minimums. There is also an arbitrary rule of thumb ration of ah@12v : 2x w for batteries:solar. So for this ratio, for the 300ah @ 24 or 600ah @ 12v, we would need 1200w on the roof. Since solar panels are inexpensive, we went this route. We have six 200w panels on the roof feeding the batteries and they generate quite a bit of power.
Since I have experience with Victron Energy components in El Alebrije, we decided to go with Victron all around – well… almost.
The SmartSolar MPPT controller is a 150/70. What this means is that on the input side, it can convert up to 150v, and on the output side, it can convert up to 70amps to charge the batteries. So min-maxed this SmartController could support up to 2000w of panels on the roof. We only put 1200w up there – so room to expend if we need to.
The next thing would be the Orion DC-DC charger. This device functions to take the 24v battery power and convert it to 12v for the trailer. All of the components in the trailer are 12v. This is a little bit of added complexity, but the trailer would always have the required voltage to run everything there – without having to worry about the voltage fluctuation of drawing directly from a 12v source.
Next is the brain of the system – the Victron MultiPlus-II 24/3000 2x120v. That’s a mouthful. This device is both an inverter and a charger. It will take shore or generator AC power and convert it to DC @ 24v to charge the batteries. It will also take the 24v DC power and invert it to 120v AC to power things like the air conditioners, the microwave, and laptop chargers.
The system monitor is a display or UI that is installed in the trailer and relays pertinent information regarding the electrical system, holding tanks, and temperatures to the user. This is important for a variety of reasons, primarily to give information and knowledge. And as we all know, informed people and knowledge lead to power. With this information, we are able to adjust behaviors, change itineraries, etc. Without it, we would be surprised when we ran out of power or water – which would be a bad thing.
We chose to go with the Simarine Pico Blue. Made is Slovakia, they primarily focus on leisure water craft. It’s a pretty nice system, although there are some software issues – which, with time, are getting remedied.
Ironically, the main issue on the maiden voyage had to do with the Pico not reporting correct SOC (State of Charge) for the batteries, thus giving false information and a false sense of security – and a bit of frustration. That problem was fixed right away.
One thought on “Owlbear Solar and Electrical Use Case”
One of the self imposed build constraints is size. 30′ for an RV in Mexico is pretty limiting, and there are places it can’t go. However, it was also the shortest RV size that met all the use case parameters, namely having a full time living space with a dedicated “lounge” area. You could go 25′ without that extra piece. A fifth wheel would have been more comfortable and probably shorter, but it’s height is a serious limitation in Mexico. This was it. A 30′ box of some variety. I looked at 27 different models.
When it came to electricity, we quickly came up against some space limitations, before we even hit a cost ceiling. Six batteries is really pushing the space and cargo weight capacity. This particular trailer came with two, and its on board systems are power hungry. I expected four batteries, but the first two didn’t really count. So 2+4. The roof can probably accommodate another two panels. I consider the electrical build to be adequate to what was discussed, definitely not overkill. There needs to be a lot of continual thought about its use, if we’re boondocking. A few rainy days and you are done.