For most of us, off-road travel requires electrical power for an ever-increasing number of electrical devices.
There’s the fridge-freezer, of course. But also, a laptop (or two), GPS receiver, two-way radios, air compressors, air pump (for mattresses), power tools, and such.
Power consumption isn’t an issue while the engine is running: The alternator keeps the battery charged up. However, if you plan to stay in camp for several days, a constant drain on the battery can leave you unable to start the vehicle or run devices. A solar power system keeps the deep cycle battery charged up. Keep in mind, a typical lead acid battery discharged too low can shorten its life. Thus it is better to keep it charged up.
Important components of a solar panel charging system
Typical system for off-Road
Let’s look at the components of a typical solar charging system. While this topic can be very technical, I won’t go too deep. Even so, you will develop a solid understanding and feel comfortable buying the necessary components. Check out the internet if you need more on this topic.
The solar arrangement discussed here is designed to charge a deep cycle battery.
Solar panel: There are two types of solar technology, monocrystalline and polycrystalline. Mono panels look black while poly cells have a bluish color. Mono panels are 15 -20% more efficient. Therefore, their footprint is slightly smaller for the same wattage. Either style should last for at least 25 years if properly cared for. Check the size and weight difference to see if mono or poly makes a difference for your application.
Solar panels come framed or foldable. Framed panels weigh more and take up more space when stored. The foldable style is easier to store, but may not be as durable. How you plan to use a solar panel will influence which format is better for you.
A typical 100-watt mono framed panel is about 21 inches by 46 inches and weighs around thirty-five pounds. A 100-watt foldable can be folded to about 21 inches by 21 inches and weighs just under 8 pounds.
Brands to consider
I have purchased panels from Ramsond and Renogy. Each has a 25-year warranty on the rated power output. All four companies are reputable brands. I tend to rely on Powerwerx for accessories, wire and connectors.
Controller: A 100-watt solar panel produces energy at a higher voltage than batteries can handle. A controller is required to regulate this energy and keeps the battery from over charging.
Controllers perform this using one of two processes, PWM (pulse width modulation) or MPPT (maximum power point tracking). You don’t need to know the science behind these processes. Either type will work well for your application. MPPT controllers, which are more expensive, tend to squeeze more power out but are only worthwhile if you have two or more panels. I have been very happy with the inexpensive PWM controllers. I recommend you buy two controllers. The second one is a backup and can also be fitted to provide you flexibility to charge stray batteries (like your buddy’s car battery).
At $19.99 this is a basic PWM controller. Buy two.
A PWM controller costs $20 to $30, while an MPPT unit runs $80 to $100.
This 10-watt PWM at $19.95 is a better buy with more functions but not quite plug and play.
Connectors: Solar panels use MC4 connectors. Remember to buy a bag of MC4 connectors with the other gear. You will need at least one pair (male and female) to connect to the panel. Once you have that connection, I recommend you use Anderson power poles for your other connections, unless you need the watertight protection the MC4 affords. MC4 connections are a bit more difficult to work with. Some foldable panels assume you will not need the water tight properties and are supplied with other types of connectors.
Don’t care to build it yourself? Powerwerx has a solar MC4 to Anderson Powerpole Connector Adapter Cable for $19.99
Additional items to buy include an extension cord at least 30 feet long, a stand for the solar panel, and wire to connect the controller to the battery. Install the controller in your vehicle wired directly to the battery. This allows for convenient connections between the controller and the solar panel.
Positioning the solar panel
Multiply the solar panel wattage to get a total solar harvest for one day.
This chart has influenced how I think about deploying a solar panel. It provides the average results for four strategies for deploying the panel. It also shows the difference between winter, spring/fall and summer sun.
- Straight up – meaning the panel is lying flat.
- Perfect tracking – constant rotation and elevation to face the sun.
- Repositioning the panel every two hours to face into the sun and adjust the elevation.
- Placing the panel in the ideal location for noon and leaving it there all day.
How you position the solar panel determines its effectiveness. Reviewing the options above:
- Mount on top of the vehicle. I don’t recommend this, because the panel will take up valuable cargo space unless you have a Hummer. Plus, the vehicle would always have to be parked in a sunny spot. That could be challenging in a wooded area. Also, parking in the sun warms the interior of the vehicle, causing the refrigerator to work harder (among other issues).
- The second option entails a surface mount and repositioning every two hours. Place the panel on the ground (or other surface) at the proper azimuth and elevation. Reposition the panel’s azimuth and elevation every two hours to maximize the energy collection. Ideal if you plan to be in camp all day.
- If you’ll be away all day, say on a hike, position the panel so that it will be in direct sunlight at noon. That way it will receive pretty good exposure from late morning into early afternoon.
- Attach the solar panel to a rotator. The panel automatically tracks the sun throughout the day. This is the most effective process but entails the added cost, weight, and space of the rotator.
You’ll note that options 2, 3 and 4 allow you to park the car in the shade. Remember to pack an extension cord. Fit the extension cord with Anderson power poles for easy connect and disconnect. Use it to connect the solar panel to the controller, which is kept in the vehicle attached to the battery.
My recommendation for a solar panel charging system
To help you get started, I recommend a framed or foldable 100-watt mono panel with a PWM controller. Add in the MC4 connectors and an extension cord, and you’re looking at something under $200 for the package. Of course, if you don’t own a deep cycle battery, you’ll need to buy that too.
Armed with the information from this article, you can now design your own solar charging station. And start enjoying the benefits that solar power offers for an outdoor adventure.
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I hope to see you on the trails!
Tom Severin, President Badlands Off Road Adventures, Inc.
4-Wheel Drive School
Make it Fun. Keep it Safe.