Solar Sufficiency: PowerFilm Portable Solar ChargerPosted in How To: Electrical on June 1, 2012
When we go camping, we like to bring the comforts of home along with us. We aren’t ashamed to admit that an ARB Fridge Freezer is a nice addition on the trail, or that we have become more reliant on our cell phone for communication and our iPad for navigation. As technology marches forward, we are finding ourselves needing more power than we are used to in order to keep our devices topped off.
Even with a traditional deep-cycle battery, starting the engine daily and wasting limited fuel to charge our rig’s battery was not uncommon, especially if we decided to be stationary for more than a couple nights. To avoid unnecessary engine start-ups in the backcountry, a dual battery system has often been a good solution, but on newer vehicles, such as the ’12 Wrangler, there isn’t enough room under the hood for a second battery. Looking for alternatives to the dual battery setup, we turned to our friends at Adventure Trailers for suggestions. The company recommended looking into PowerFilm solar panels, a product line Adventure Trailers has had great success with on its expedition trailers.
PowerFilm, a leading provider of American-made solar power to the military, has a growing resume in the self-sufficiency community due to the efficient design and robust materials used in the company’s products. While PowerFilm has a complete line of products, we were most interested in the foldable panels.
Product: PowerFilm 60W Foldable Solar Charger
Operating voltage: 15.4
Operating current (amp): 3.6
Folded dimensions (in): 9.5x11x2
Deployed dimensions (in): 43x59
Weight (lbs): 3.19
The foldable solar chargers are ultra-lightweight and extremely durable. Each charger folds in to a compact roll for storage, but can be deployed in seconds to begin harnessing the sun’s rays. The Foldable series of chargers from PowerFilm are available in 10 different sizes and power outputs. The smallest chargers can fit into a cargo pocket and are designed to recharge AA or AAA batteries, as well as USB 2.0 devices, such as a cell phone. The larger panels come in 5-, 7.5-,10-, 20-, 30-, 60-, 90-, and 120-watt outputs, and all chargers are built to US military specifications. PowerFilm also equips each panel with marine-grade connectors for reliable, weatherproof, and easy plug-and-play connections.
At the heart of the PowerFilm panels is Amorphous Silicon (A-Si) technology. According to PowerFilm, A-Si is a better-developed and proven technology that the company is able to reliably manufacture in high volumes. A-Si modules are also lighter than competing thin-film technologies and by using a polymer plastic substrate, the finished product is much more flexible, lending to its unmatched durability. When compared to copper indium gallium (di)selenide (CIGS) technology, A-Si is also less affected by temperature, which means that the PowerFilm panels don’t have to sun-soak to reach their rated power output and can produce power as soon as they are exposed to light.
Because of the A-Si technology, PowerFilm chargers perform in low light, such as early morning and late afternoon, ensuring that the panel “turns on” earlier than other technologies. This translates in to a greater period during the day that the panel can produce power. Another benefit to the PowerFilm panels are their resistance to point, or puncture, damage. However, even if point damage occurs, the charger will continue to operate effectively—with minimal loss of output.
So how do you choose the output of a panel that will meet your needs? Adventure Trailers pointed us to a simple mathematic formula of Ohms Law available on the company’s website:
Volts x Amps = Watts
Watts ÷ Amps = Volts
Watts ÷ Volts = Amps
You can use this formula to determine the draw of your accessories and once you know your power requirements, you can narrow down the panel based on the output you need. Ultimately, it comes down to balancing panel cost versus panel output, but you should always lean toward buying as much capacity as you can afford.
For our usage, we settled on the 60-watt panel and a 4.5 amp charge controller. Knowing that our fully charged Group 34/72 Optima YellowTop has 55 Amp-hours (Ah) at 12.9 volts gave us a baseline to determine how much solar we needed. When running a single battery that has the primary duty of starting the vehicle, you never want to go below 50-percent of amp capacity. For reference, a 50-percent charge on our YellowTop is 27.5 amps at 12 volts—around the minimum of what you would comfortably want to start the engine.
In extremely hot weather, our 50-quart ARB Fridge Freezer can use up to 1.6 Ah or 38.4 amps per day on average. Using the formula above shows that our 60-watt, 15.4-volt panel will put out approximately 3.89 amps per hour at 100-percent efficiency. Due to the imperfect nature of operating in the environment (clouds, solar panel position, tree coverage, sun position throughout the day, less than optimal panel placement, and so on), solar panels will average about 75-percent efficiency, which would put our panel at about 2.9 amps of output per hour. On a full sunny day in the desert Southwest, you can expect to pull around 28-30 amps for the day with the 60-watt panel. This would be enough to allow us to stay in one location for at least three days under conservative conditions, longer under ideal conditions. Under perfect conditions the 60-watt panel is capable of putting out enough power to extend a stay indefinitely. Of course all of these variables we chose are on the pessimistic side and subject to change; your experience can vary greatly. Because PowerFilm’s panels can be daisy-chained together with an accessory cable, adding more solar capacity is as easy as hooking panels together provided you don’t exceed the charge controller’s rated amp capacity.
Since it is unrealistic to think you would track the sun all day with a five-foot-long foldable panel, it is important to ensure the panel is deployed pointed at the sun. Optimal orientation to the sun depends on location. The closer you are to the equator, the less of an angle that is required. For example, at PowerFilm’s headquarters in Iowa the optimal orientation would be approximately 42 degrees, while in Arizona it may be closer to 30-35 degrees, pointing south. Just remember that the panel will work as long as the solar material is face up, even if it is just lying on the flat ground, or across the hood of your vehicle.
Going solar is easy once you decide on which components you need. We were able to do the complete install on our ’12 Wrangler in under an hour and we now have the ability to run our accessories in camp without worrying about the Jeep’s ability to start when we are ready to be on the move again. Keep reading to see how straightforward the process is to add solar charging to your rig.
Are you curious to know how many amps your devices, toys, and tools draw? Here is a short list of items that can be plugged in to a 12-volt outlet and how many amps you can expect to consume over the course of one hour (Ah).
Amps draw per
Accessory hour (Ah)
ARB Fridge Freezer (50 qt) 0.87 – 1.6
LED camp light 1.1
12V Air mattress pump 2.0
Spot lamp 2.5
12V DVD player 3.0
12V Electric blanket 5.0
12V Coffee maker 13.0
12V Hair dryer 14.0
12V Curling iron 15.0
400W Inverter (max draw) 33.3