Location and Climate
First, it’s important to evaluate where you’ll be using the charger. Not surprisingly, solar panels need direct sunlight. Without direct sunlight, the panel will turn on and off as it collects and doesn’t collect power.
Hiking on the East Coast typically means you’ll be in and out of direct sunlight throughout the day. Jennifer “Sprinkles” Kelley is a backpacking guide who has hiked the Appalachian Trail (AT), Long Trail, Benton MacKaye Trail, and half of the Finger Lakes Trail. She’s also completed the Great Smoky Mountains 900 miles, and documents her adventures online.
“For the section I hiked on the PCT, the solar charger was invaluable.”
Throughout her adventures, she has attempted to use a solar charger a number of times. On the AT, Kelley sent her charging system home after the first 30 miles when she realized the tree cover wouldn’t allow for enough direct sunlight.
In 2013, Kelley worked at the AT Lodge in Millinocket, Maine—the closest town to Mount Katahdin and where most AT thru-hikers start or finish their journeys.
“Solar chargers were the number one item I took out of packs during pack shakedowns. Hikers refused to believe that the AT is called the green tunnel for a reason,” Kelley tells Digital Trends. “Often, when we picked hikers back up at Jo-Mary Road (approximately 50 miles south on the trail), hikers would then mail home the chargers.”
Now she guides backpacking trips in the Great Smoky Mountains National Park, and she still has trouble convincing people to leave their solar chargers at home.
“I’ll tell people to leave behind the charger and they’ll sneak it back into their packs,” Kelley says. “On the last morning of a trip, I ask: ‘tell me two things you brought with you that you’ll never bring backpacking again.’ People always admit to bringing the chargers.”
Charlotte “Bear Claw” Miller is an Eastern Mountain Sports employee who has hiked 1,000 miles on both the AT and the Pacific Crest Trail (PCT). She carried a Goal Zero Nomad ($100) solar charging system on both trails.
“On the AT, I started at Springer Mountain on April 5, which was before the leaves had come out in Georgia. It worked spectacularly for the first few weeks and I was happy with my purchase. I always had a full charge for my electronics,” Miller relays to Digital Trends. “Then the spring hit, and the sun was obstructed for much of the day by foliage.”
Once the leaves returned to the trees, Miller’s system would charge a bit when she was hiking in open locations or when she left it in the sun during breaks, which usually only resulted in a 20 percent charge. On the other hand, hikes on the West Coast often are more exposed, increasing the chances of direct sunlight.
“For the section I hiked on the PCT, the solar charger was invaluable. Considering 600 of the nearly 1,000 miles hiked was through the southern California desert, where you are praying for an escape from the constant beating of the sun, a solar charger was perfect,” Miller says. “Every day, I had a full charge for my phone, as well as enough charge to supplement power for my hiking partner.”
Proper panel placement
When hiking in exposed areas, it’s important to remember that the panel needs direct sunlight, so proper placement of the panel is key.
“You can use the power in the battery pack anytime.”
“Make sure you angle the panel on your backpack in the best place,” says Lisa Janssen, public relations manager for Goal Zero. “The best way to position your panel is to stay conscious of the position of sun and panel. Move the panel top of your backpack if sun’s overhead so it can hit as much of the panel as possible.”
To help position the panels, some gear companies make backpacks with solar panels built in, while some solar panel companies make panels that include lashing points and carabiners to help hikers properly place the device.
Other companies began installing intelligent features into panels to help hikers put their panel in the best possible position. Goal Zero has an LED solar intensity indicator that tells you the strength of the input. BioLite tackles the same problem with a sundial system on its SolarPanel 5+ ($80); you position the panel so that the shadow lines up in the middle of the target – it’s exceptionally simple and effective.
The importance of saving your energy
But even on the PCT, which is known for being more open, Miller still experienced problems with sun exposure in certain sections.
“Once we were out of the desert section, we entered the high Sierras. Through this section, a large portion of hiking is done above the tree line, but you also go through dense pine forests without much direct sunlight,” Miller says. “It was during these times I was glad I had an energy storage system instead of a direct charge.”
Storage systems allow a panel to save energy gained during the day to use when direct sunlight isn’t available. Many companies offer backup power devices that are built into the panel, though they do add weight.
“If the device has an integrated battery, you can go in and out of sun, and use that power to charge battery pack,” Janssen says. “You can use the power in the battery pack anytime.”
How to Choose a Solar Panel
Once you’ve determined whether a solar charger is a viable option for your specific trip, it’s important to understand some of the technical aspects of solar panels. Take a look at the gear that will need to be charged, as that dictates the amount of power you’ll need.
Wattage
The amount of power a panel will collect in one hour is measured in watts, which is an important spec to consider according to what you need to charge.
“In sunny conditions, a 7-watt panel can charge as quickly as if you plugged it into a wall.”
“If you want portable and you’re only using it to charge a phone, you need 7 watts or more. Bigger panels mean more power per square inch, which gives better odds that you’ll be charging,” Janssen says. “In sunny conditions, a 7-watt panel can charge as quickly as if you plugged it into a wall.”
However, watts are determined in a lab setting, in which a raw panel is put in a sun chamber to determine the number of watts it delivers. When the panel is covered with protective layers and actually used in the elements, the number of watts it delivers is actually much less.
“If you start adding layers of protection, such as glass or plastic, it will decrease efficiency. Panels work better in colder weather, so you’ll lose efficiency in warmer weather,” Janssen says. “You get about half of that wattage in real life: 7 watts gets anywhere from 3.5 watts to 5 watts.”
Panel Material
It’s also important to determine the type of panel needed. They come in two types: CIGS and monocrystalline. Monocrystalline panels are more typical panels; they usually are rectangular and fold up when not in use. CIGS panels are flexible and can be rolled up. While they take up less space, they are less efficient in regard to conversion power, meaning it will take more square footage of solar panel to get 7 watts, according to Janssen.
Output Power
The USB output is another factor that needs to be considered, and can be found in the specs from the manufacturer. Janssen recommends hikers get a panel that is 1 amp output or higher, as the higher the output, the faster the panel will charge devices.
Also, make sure to buy a panel with an automatic restart feature. Many phones, including those by Apple, are particular about their power source. Ever noticed the “charging not supported with this accessory” message? This message is produced when the flow of power fluctuates. If you’re relying on power from the sun, which is likely to fluctuate, the device being charged may reject that power due to inconsistent solar conditions.
Some companies, such as EnerPlex, create panels with automatic restarts that occur every few minutes, like the Kickr IV ($100). Others, like Goal Zero, created an intelligent restart feature, which monitors the power going into devices to adjust the power if needed and alert the user is charging stopped.
Many factors go into determining whether a solar panel is right for your trips, as well as choosing the best panel for you. Before you hit the trails, it’s important to keep in mind the location of your adventure, placement of the panel, wattage produced, charging power and whether the system has a storage component.
