JonesN2Travel
Choosing the right solar charging system comes down to the power you need for your RV systems and/or electronics.
Words by Perry Mack
We live in a world of solar energy and advancements in technology over the last few decades now allow us to harness and effectively use portable, clean and free power on- and off the grid.
Solar panels are an exceptional accessory to your battery system. Staying in remote areas for a week or two fishing, hunting and camping are now even more enjoyable and convenient. You can keep beverages and food cold and fresh, play music in the evening, keep your electronics charged and even maintain the starting batteries of your tow vehicle or RV.
You can buy solar panels as a kit or individually. The former will include a solar power converter with either a Pulse Width Modulation (PWM) or Maximum Power Point Tracking (MPPT). In simple terms, both control how the power is delivered to your batteries.
Pulse Width Modulation is less sophisticated, cheaper and most often found in portable power systems. Maximum Power Point Tracking is ‘smarter’, more efficient and expensive, and usually designed for larger systems. The PWM works great since the maximum power voltage of the solar panel is 1.5 times the battery being charged (for example, 18 V for a 12 V battery).
Choosing the Right Solar Charging System
This answer comes down to the question of power. You’ll find most portable panels, whether you mount them permanently on your rig or carry them around, are described in Watts (W). An average panel is 100W while 200W is a popular option.
Several electrical phrases are worth defining, then we’ll cover what it means when you’re camping in the real world.
photoschmidt
Understanding solar power and all of its components will help determine the right system for your RV.
Ampere or amp (A)
This is the measure of electrical current. To use a water analogy, it’s the amount of water flowing through a hose.
Amp-hour (Ah)
The amp-hour is used to determine the capacity of a battery and the amount of energy that allows one amp to flow for one hour.
Think of a large dam next to a small one, each draining through a pipe into its own river.
If you start draining them at the same flow rate, the large dam will have water flowing in the river longer and for more hours. How big is your dam battery?
Most automotive batteries are 40 to 65 Ah, which describes the capacity of the battery to deliver a certain current for (usually) 20 hours. As opposed to Cold Cranking Amps (CCA), which is the maximum current the battery can deliver for 30 seconds, it’s enough to (hopefully) get your combustion engine started.
Volts (V)
In simple terms, the volts are the difference in electrical potential between any two points in an electrical circuit, similar to water pressure in a hose. Pressure is the force that moves the water through a hose similar to voltage pushing electrons through a wire.
Ken Suarez
If you want to run your 50W laptop for one hour a day, you’ll need 50 Wh. If you want to run it for two hours it will need 100 Wh.
Watt (W)
This is power and the rate of power flow. A watt is when one amp flows through an electrical difference of one volt. Returning to the hose analogy, you can increase the power of the water coming out by increasing the water pressure (volts). Think of a pressure washer or the amount of water coming out.
When you are trying to determine how large of a solar system you need, think about how much power each device or system in your RV requires. For instance, an average laptop needs 50W to run.
Watt-hour (Wh)
The watt-hour is a unit of energy equivalent to one watt of power expended for one hour. If you want to run your 50W laptop for one hour a day, it will take 50 Wh. If you want to run it for two hours it will need 100 Wh.
Now, armed with a basic understanding of the electrical jargon, we can finally get back to choosing a solar panel.
Battery Size Always Matters
Determining the size of solar panels comes down to two factors including how big is your battery and how much power you need. You want to be able to keep your batteries at full power to use the necessary devices during the day while having enough to use them into the evening after the sun sets.
You want a battery large enough to meet your needs for the day and night (24 hours) and still be able to start your vehicle in the morning (if you’re running on the same battery). In a perfect world, you would have two separate battery systems including one for your vehicle and a separate battery - or power station - for everything else.
Courtesy Campendium
Battery size matters and you want to be able to keep your batteries at full power to use all of your necessary devices.
A 100W solar panel is your lightweight, small, and budget-minded solution. If you add up all of the devices you need to use and how long you’ll use them each day, you can get an idea if 100W will be enough.
It’s called a 100W solar panel because that is how much energy it can produce under ideal circumstances, which means a bright sky and the panels are angled properly at 90 degrees to the sun. How many amps it produces will depend on how many hours of sun it gets. This means power production depends on the weather and the length of the day.
Since this can change with every trip (and day to day), it’s best to work with averages (be sure to check the links at the end of the article for the highs and lows for your location or destination). Let’s work with an average of three sun hours per day.
How Much Will You Use?
Power consumption of electronics varies by make and model. So, look at your devices for greater accuracy. For now, let’s consider some typical numbers for portable electronics you may want to power during your RV trip.
How to Choose a Solar Charging System
In this example, there’s enough power in a 100W panel since it will generate 300Wh (100W x 3 hours) per day. However, with a few overcast and shorter-than-average days and a few people using similar devices for the same amount of time, you may lose the ability to keep everything running. On a positive note, many destinations during peak summer have seven or more sun hours per day. In this case, the 100W panel will do the job.
Battery Charging
Earlier, we mentioned batteries and how they are rated in amp hours. But how do watt-hours convert into amp-hours? It’s a very simple calculation:
Watt hours/voltage = amp hours
So, if we generate 300Wh with our 100W solar panel per day, then divide by 12V (battery) it equals 25 Ah. Oh, this could be a problem especially if your 65Ah vehicle battery suffered a parasitic drain while parked and it could take days to recharge. For these instances, always be sure the cooler is full of ice.
Power Storage
It makes sense to separate automotive and device power storage. We say ‘power storage’ since your vehicle will have an automotive battery. However, power storage for your devices could be a type of automotive battery such as lithium or a portable power station.
Let’s look at the cheaper lead-acid battery solution first. Choose a deep-cycle and not a starting battery. Deep-cycles are like marathon runners and are designed to deliver sustained power with low current draw over extended periods, which makes them great for RV and camping applications.
photosbyjim
The number of choices can be overwhelming but buying the right system will provide seasons of convenience.
Starting batteries are like sprinters and specially designed to start your engine, work as a voltage stabilizer and run accessories when the engine is not running. Lead acid batteries shouldn’t be regularly drained below 50 percent capacity. Doing so will dramatically reduce its life.
As a result, opt for a battery that can store at least twice the output of your panels on an average day. For instance, a 100W panel can provide 300 Wh/day. So, you should have a 600 Wh battery.
Watt hours/voltage = amp hours
600 Wh/12V = 50 Ah
If you think you’ll use 300 Wh or less per day, this works out to a very affordable solar system.
Lithium batteries are a different beast and can almost be completely discharged, which means you only need one slightly larger than your panel output. They are much lighter than lead-acid batteries and offer more stable power but are five to ten times the cost.
Depending on your needs, perhaps consider a portable power station, which incorporates a lithium battery and power inverter. This type of device not only outputs DC power but AC as well.
Courtesy Honey Trek Relion
Lithium batteries are lighter than lead-acid and offer more stable power. However, they are much more expensive.
Learn About Solar Power from Experience
Our first portable power system consisted of two Coleman 40W panels with their accompanying seven-amp charge controllers, which we bought at Canadian Tire for $300 CAD. It’s better to have some solar than no solar. With a max power output of 40W and 2.3 amps under ideal conditions, one panel could essentially trickle-charge an automotive battery while the second could charge a smartphone (with the right cables).
These charge controllers aren’t attached to the panels so as a result, I lost one while moving them from storage to the RV. The best thing about this experience is we learned what to look for when shopping for a new one.
We soon realized this wasn’t enough power since we work on the road charging cameras and enjoying our portable fridge freezer (490 Wh). Our daily average power consumption is roughly 1000 Wh.
We live, work and play in the Okanagan during the summer, which has about seven sun hours per day and an average of five. So, 200W of solar power provides us with an average of 1000 Wh per day.
Now that you are armed with the knowledge of how to choose a solar charging system, you’ll be properly prepared to enjoy all of the benefits of harnessing the power of the sun during all of your RV adventures.