Nekteck 21W Solar Charger(5V/3A Max) with 2 USB Port, IPX4 Waterproof Portable and Foldable Hiking Camping Gear SunPower USB Solar Panel Compatible with iPhone, iPad, Samsung Galaxy, and More

I purchased this skeptical that it would perform well or provide good functionality for the price. I was pleasantly surprised that the packaging and form is perfect for backpacking, and the panel charges adequately. On a partially overcast Colorado day, it would not charge my iphone X directly since it did not generate enough voltage for charging. However, it did charge -- at reduced capacity -- my Anker battery pack (16000 mAh) at 4.95 volts and 2000 mAh output (approx 10 W-hours output). On a sunny Colorado day, it charges both devices at 5 volts and 3800 mAh, or 19w-h ... closer to rated capacity of 21 W, and pretty close to theoretical maximum.For the 1 pound weight, I think this is a great option for backpacking long distances where you do not have access to external power to charge the battery pack. Like me, you can charge your battery pack on lower output days and then use the battery pack to charge the phone or other devices requiring more consistent output. If you use this directly on your pack, it will disconnect from charging periodically in shade or wrong sun angle and your phone will keep beeping to let you know. You avoid this problem by charging a battery pack that is then used to charge a phone.From a dead battery back, this panel with full sunlight (pointing panel to sun throughout the day) charged the 16000 mAh Anker portable battery in a little over 8 hours. Since I don't plan on staying in a campsite for 8 hours, I suspect I can get at least half that capacity tied to a pack which hiking. I found that orientation (tilted toward sun versus pointing straight in air) did not significantly affect output by more than 20%. Since I don't use more than 5,000 mAh per day between my iphoneX and Garmin Explorer GPS unit, this solar panel should sustain my power needs unless I am in a shaded forest or inclement weather.The functionality of the velcro with the folding panels makes for a good size to hang from a pack, and also to fold up and put in the pack when not in use. The compartment on one end containing 2 USB connectors is the right size to hold a 16000 mAh Anker battery pack (and keep it shaded from sun while charging). The two provided small carabiners and grommets on the end facilitate hanging it for charging. I added 550 cord to the carabiners to make it more useful for hanging from limbs or other objects beside my pack straps.I have seen it repeal water from the panels; however, would recommend that you protect the compartment with the USB connectors from getting wet. Seems they would not respond well to this. If you kept this last compartment dry, I am fairly certain the panels themselves could get a little wet without damage.

This is a very good product.. IF you know how to use it.. by using it, i dont mean "plug it into your iphone and expect 0% to 100% in couple hours".. you MUST buy a usb power meter tester! this is the only way you will test your charging rate! and make sure charge rate increases after a cloud passes.. yea you can plug it in to your iphone and it will show charging, but when the cloud passes, you must look into your usb power meter if the charging rate increases again, if it does not, this product is useless for you but you cant blame it.. i use a EasyAcc 26,000 mah battery pack with it, the Solar Charger has 2 outputs that you can connect to a EasyAcc battery pack into its both inputs.. so; with this battery pack; if a cloud passes, obviously the charge rate decreases to about .15amps depending on weather conditions.. charge rate should automatically increase after a cloud passes and the sun shine is out.. my iPhone 6s doesn't do that, when the sun is out i get .95amps, thats very good, as soon as a cloud passes, i get .15ish amps, then it stays like that for the rest of the day till i manually unplug and plug the iPhone 6s in it.. the EasyAcc automatically allows charge rate to increase after a cloud passes..I thought i had figured it out.. its fun to see the charge rate as you are charging your "anything" using the sun.. but it is not comfortable to plug the USB Power Meter Tester into the back of the panels, hold it at the same time and watch the charge rate.. I bought USB extension cables to plug them into the Solar Charger and than plug the USB Power Meter.. BIG MISTAKE!!! the cables only allow .46amps MAX, they slow down the charge current.. make sure your cables are good, mine aren't.. but when i plug the USB Power Meter directly into the Solar Charger, i get .96amps into my iPhone 6s (10am sunlight in New York).. test it out before you use it.. all cables, phones, battery packs are different.. research, research and again, the EasyAcc 26,000mah power bank works amazing with this unit, and so as the RavPower 26,800 mah I got.. its only down hill is that its got only 1 input to charge the device, not 2 inputs like the EasyAcc.. I also have a Mophie 12,000 mah battery pack, this one will charge as the sun is looking at it, but once the clouds block the sun, the charge current drops, and will stay like that very low till the night.. RavPower and EasyAcc automatically increase charge current as the sun begins to shine..Just because you see a charging icon on your iphone does not mean you are charging it at a good rate.. same for battery packs.. test your stuff and this Solar Device is for you!Kinda sucks that no one warns about this issue, i learned the hard way..I could of not known this product and gave a 1 star review? many negative reviews are by the people who don't know how to use this product and did not test it.. giving this a 1 star when its a good product that id give 10 stars if i could!