FlexSolar 40W Review

The FlexSolar 40W is a highly durable, powerful, and portable mono-crystalline solar charger. It is one of the few portable panels we tested that has a DC output in addition to its two 2-amp USB-A ports and a single 2-amp USB-C port. It unfolds quickly and easily into a 49-inch long, 11-inch tall, and 0.1-inch thick, six-panel array. Folded away, this 47.25-ounce solar charger becomes just 7.5 inches long and 1 inch thick. The rugged design is thin enough to be highly portable yet strong enough to handle the abuses of daily use.

Performance Comparison

Direct Solar Charging Speed

The FlexSolar 40W performed relatively well in our direct solar charging speed test. It has a DC output, which is unique among smaller solar panels. When using this output, the solar panel performed exceptionally well. When testing the USB output charging capabilities, it also performed well, albeit not entirely as well as the DC output.

To test direct solar charging speed, we hooked up every panel to an identical 10,000 mAh battery bank and left them in direct sunlight for one hour. Afterward, we discharged each batter using a digital USB multimeter and recorded the mAh of charge each panel generated. This test was repeated three times, and we averaged the results.

On a sunny day at 5,000 feet in Colorado, the FlexSolar 40W generated 713 mAh of charge on its 10,000 mAh test battery. That's more than most other panels we tested. When we tested the DC charging capabilities of this model, also on a sunny day in Colorado at a similar elevation, the FlexSolar generated 1466 mAh of charge on a 167-watt-hour power station.

Overall, the FlexSolar 40W performed better than smaller, lower-watt panels but not as well as the highest-performing panels in direct solar charging. Its DC output charging capabilities, however, are better than any other panel with a DC output, including some 50-watt panels we've tested.

The FlexSolar 40W was about average when testing its USB device charging capabilities. If we only tested the USB charging capabilities, this panel would not have scored as highly in this metric. On the contrary, if we were only testing on DC charging capabilities, it would have scored even higher in the direct solar charging metric.

It has a total of six panels — that's a ton of surface area. It's rated at 40 watts of electricity, higher than most portable panels we tested. In our testing, it never actually put out 40 watts at once, but it still created more measurable watts than any other panel we tested. In our experience, most solar panels are rated for a wattage output that is only attainable in ideal conditions, so no panel ever puts out the watts it's rated for. The FlexSolar puts out more watts than most of the other panels we tested, whether or not it puts out the 40 watts it advertises.

Indirect Solar Charging Speed

The FlexSolar 40W performed about average in our indirect solar charging speed test. In our simulated cloudy day test, it didn't perform as strongly as it did during direct charging tests, but here again, it performed better when we used the DC charging output.

For our indirect solar charging speed test, we repeated the direct solar charging test using a white sheet suspended over the panels to simulate a cloudy day.

On another Colorado day at 5,000 feet, the FlexSolar 40W, with a white sheet suspended over it, generated 195 mAh of charge on its 10,000 mAh test battery. This isn't nearly as well as it performed during direct solar charging, but it still generated more mAh than most other small panels it was up against.

Portability

For a 40-watt panel, the FlexSolar 40W is highly portable. It folds away into a small enough size to carry in a backpack. Though it isn't the lightest panel we tested, it's light enough to load up and carry with you.

The FlexSolar 40W features a simple folding design so you can quickly unfold it and get set up. It has no velcro or other clasps to mess with while unpacking. It simply folds and unfolds into a relatively small package.

The FlexSolar 40W is far from the lightest panel, but it's not the heaviest either. At 47.25 ounces, this panel weighs less than the higher-watt panels we tested but much more than the smaller, lower-watt panels. These findings aren't surprising, but it's worth noting for those prioritizing weight.

Though it doesn't have a way to secure it when folded, it never seemed to be a problem for our testers. We packed and unpacked this panel repeatedly and never found it to be an issue that it didn't latch closed. In fact, we found that this design actually made it easier to unpack when we needed to set it up.

The solar charge controller has nothing to protect it, though. This means it has exposed USB and DC outputs. We didn't have any issues with this, but we could see this lack of protection being a long-term problem. There is nothing to prevent these connection points from accumulating the inevitable dirt and debris that comes with anything used in the outdoors.

Functionality

The FlexSolar 40W is one of the most functional portable solar chargers we tested. It features three different outputs: USB-A, USB-C, and DC. It also has carabiners and enough loops to make it possible to hang this panel just about anywhere.

No matter what kind of device you need to charge, this panel is capable. You can charge anything from large power stations and laptops to smaller USB devices with three different outputs.

Like most portable solar panels, the FlexSolar 40W has carabiner loops and comes with carabiners to hang it to charge. It doesn't have legs to angle it at the sun, but between its small size and included carabiners, it's easy to find a way to point it at the sinking sun.

Should You Buy the FlexSolar 40W?

The FlexSolar 40W is an excellent option for a high-watt output solar panel that is still relatively portable. It packs away quickly and easily and unpacks just as readily. Many panels are more portable than this one, but none are as portable and have this high of a watt output. If you're looking for a large-capacity solar panel to charge a lot of devices while remaining relatively portable, this is a great option.

What Other Portable Solar Chargers Should You Consider?