Direct Solar Charging Test
An important part of a solar panel is its capability to convert sunlight into energy effectively. Completely sunny days are often uncommon outdoors, but they serve as the ideal benchmark for assessing the actual efficiency of a solar panel. To determine which model performed the best, we conducted tests under similar conditions, taking meticulous notes and comparing the results for each test.When dealing with solar power, we discovered, through trial and error, that the sun, wind, and clouds are constant environmental factors that we needed to find ways to overcome. This is the beauty of solar power; it establishes a direct link between our modern electronic devices and the natural world. In order to obtain consistent data in our pursuit to find the optimal solar model, we had to limit our testing period to ensure that all models were examined under the same conditions. We found that a specific time on a sunny day in late April met our requirements. We positioned each model under peak daylight when the skies were clear and devoid of clouds in Lake Tahoe. From 12:10 pm to 1:50 pm, with temperatures in the high 50s, we measured the amount of charge each device provided to a 5mAh battery pack. Subsequently, we compared the charges among the models and determined which panels were the most effective at converting sunlight into energy.
By establishing stable conditions and utilizing a battery pack charger, we obtained consistent test results for the solar chargers.
In our highly advanced outdoor test lab, we measure the Outad 7W’s output to the external battery during our “race to charge” test.
Credit: Jane Jackson
Indirect Solar Charging Test
One of the most common complaints from users is how small, portable models perform on days that are less than “bluebird”. If you spend a significant amount of time outdoors, you are well aware that finding a flawless blue-sky day is quite elusive in many locations. It is highly likely that clouds will pass through the sky for a portion, if not the entire day. Consequently, a solar panel that only functions optimally under ideal conditions may not be the most ideal choice. To determine which models performed best under suboptimal conditions, we devised a test that assessed their ability to recover a charge after being shaded. Various scenarios could lead to a panel not receiving direct sunlight for its entire charging period, such as clouds passing overhead, the panel tilting or falling over in the wind, or some other object casting a shadow over it while left unattended for a few hours.Testing charge interruption recovery with the 10W-15W panels using a human-shaped cloud simulator.
Credit: Jane Jackson
We wanted to ensure our bases were covered so we conducted a test resembling our direct sunlight test. On a sunny early May day, we laid out each of the models under optimal daylight conditions with clear skies and no clouds in Lake Tahoe. For one and a half hours during the middle of the day, we measured the charging capacity of each device using a 5mAh battery pack. The difference this time was that we fully shaded the panels by placing a sheet 4 feet above the models, and then partially shaded them by covering only half of the panel with a sheet. We compared the charging performance of the models and examined the conversion rates of sunlight to energy. Some models were unable to continue charging the battery after the interruptions, while others continued to deliver charge even with portions of the cells covered and even managed to charge the battery pack a few percentage points more once they returned to direct sunlight after being shaded. Typically, the smaller wattage models performed worse than their larger wattage counterparts.
Multiple Device Charging
An important feature of any solar charger is its ability to power more than one device simultaneously. In most cases, when one device loses power, the others follow suit. Therefore, it is crucial for these solar panels to be capable of charging multiple devices at once. This category applies to models with a capacity of 10W or higher. The smaller options simply lack the capability to charge two devices simultaneously, as a significant amount of the output power is lost due to inefficiencies.
The extensive length of cord that comes with the Goal Zero Nomad 14.
Credit: Jane Jackson
For this test, we placed the models under direct sunlight and connected two 5mAh batteries to assess their charging capabilities. We then compared the amounts of charge between the different brands. From this test, we discovered that having two devices plugged in simultaneously significantly reduces efficiency. This is due to the wiring of the panel, with the first USB port receiving considerably more power than the second one. Since all the models have relatively low wattage, it is advisable to have one or two external batteries to charge from, rather than relying solely on the panel for all your charging needs. The extra canvas panel adds unnecessary weight and excess material to the X-Dragon. Additionally, the flap tends to flap or blow over the panel in windy conditions.
Credit: Jane Jackson
Some of the reviewed devices had more than two USB ports, although we did not test beyond the two ports. Charging more than two devices simultaneously can result in a significant power drain, which may not be an issue for some of the models. However, to establish a consistent metric across the board, we focused on testing with two ports.
Portability
The degree to which a solar panel can be transported has a significant impact on its usability. Mass carries significant weight in our evaluations; pun intended. After all, the primary purpose of a portable solar panel is to be easily movable. In this category, we assessed the weight of each panel, measured its size when folded and unfolded, taking into account all the necessary accessories, and based our ratings on the assumption of an average person’s backpack. A model that weighs less than one pound and is highly compact suits most outdoor activities, such as hiking, backpacking, biking, and climbing. If it exceeds one and a half pounds, it should be capable of robustly charging multiple devices, including laptops, and may not be the most convenient choice for a self-supported journey. When boating, setting up a basecamp, or traveling in a van, weight becomes less critical. Consider this when examining the ratings. Generally, larger solar panels performed poorly, while smaller battery packs generally obtained higher scores.The Anker 21W is nearly as compact as its two-panel counterpart, the Anker 15W. From this perspective, it is challenging to distinguish between the two, highlighting the sleekness of the Anker 21W.
Credit: Jane Jackson
Take into account that the weight will increase if you need to bring multiple charging cables and/or a case. The weights provided in our specifications indicate the total weight of the reviewed setup. Keep in mind that many panels function optimally when charged at home and utilize sunlight to maintain charge during off-grid trips.
