DOROEO40W Portable Solar Panels with USB QC3.0(Support Fast Charging), 18V DC Output Port, Waterproof Solar Panels Charger, Foldable Solar Panel for Power Bank, Laptop,Cell Phone, Camping, Hiking

It is compact as a hand bag when folded, but it is really large when unfolded, then the panels could absorb more solar energy.It is pretty cool to charge my phone with sunshine when we camping at the river side!

Item info says 21V DC output. Received product and label says 15.5V DC output Plug in on unit says 18V above DC port. I need 21V 4.0A to charge my battery power pack. Disappointed

The DOROEO 40W Portable Solar Bank is an easy to carry and store power source for QC 3.0 USB devices. Charging power is provided at a USB Type A port. The eight 5-1/4 X 6-3/8 cells differ from the product photos in that they have no visible silver cathode grid.The built-in charge controller circuitry affects only the Type A port, and apparently limits voltage to 5 V (despite the QC 3.0 specification of up to 20 V). Under partly cloudy sky, I was able to get a maximum charge current of about 3.5 A, or about 20 W into a QC 3.0 power bank. Although I could not get the QC 3.0 system to switch to a higher voltage, it might be possible under full sunlight.The auxiliary DC port accepts a 5.5 x 12 mm coaxial plug, providing up to 2.2 A at 21 V according to the product info page (the 9 - 18 V specification appears to be incorrect, as open-circuit voltage measured up to 22 V). To safely use this output for battery charging requires a separately supplied MPPT solar charging controller, which I scavenged from another system. As shown in the photo, I was able to obtain 1.627 A at 13.4 V (21.4 W) charging a 100 Ah LiFePo4 battery under a hazy sky. I have little doubt that under ideal full-sun conditions, the specified 40 W output should be obtainable, although maintaining a 100 Ah battery at full charge would still be impractical (at least 33 hours of full sunlight for full recharge at 3 A). For smaller batteries, such as 7 Ah gel cells, full recharge time is a more reasonable 3 hours in full sun.While the DOROEO fabric is specified as waterproof, I would not want to use it in the rain, as the fabric would appear to be absorbent and could be difficult to dry. For best product life, I plan to use the solar bank when I can attend to it, folding it away at night and during foul weather.

This 40W panel folds to a nice compact size that makes it especially convenient for travel and at the same time provided good flexible charging options and performance when compared to several other 40W panels I have including conventional panels. Shown here it did an excellent job charging a LifePO4 12v battery and a power station. There are 2 areas where I have to deduct a star. What you get here is a bare panel with no instructions no accessories. If you have cables and connectors like that which came with a power station you may be all right but otherwise you will need to scrounge up what ever you will need. For mounting options the panel only has 4 grommets and no stand or built in props so you will have to improvise propping it up in some manner. This is made more difficult due to the fact the panels are not full width but 2 smaller panels set side by side. This does not make it any more compact when folded but creates a seam across the center of the panel width wise that collapses the panel when you try to prop it up. This makes optimizing angle to sun challenging as the top and bottom halves will end up at different angles as seen in the photo.

The 40w panel with full sun should be able to output what it's rated for, but it doesn't charge that fast from the USB. It has compatibility with QC for Android phones, and it did indicate fast charging on my Samsung devices, but it was still fairly slow (like the lowest tier of fast charging from an older wall plug). Don't expect to run anything directly.If you were on a camping trip with clear skies and used it to recharge a medium sized power bank (10-20k mah) though it should work well and be able to get a good charge during the daylight hours. At least enough that you can then use that stored power for some led lights or flashlights all night, maybe run a small tent fan, or recharge 2 phones to full. It would also be important to bring a stand or learn to make something in the field with rope/sticks to get the best angles.For faster charging though, you'll want to skip the USB output altogether and use a more serious power bank/solar generator or controller and use the other port that fits.My favorite thing about this panel though is that for casual use it should work fine out of the box and it folds up pretty compact to fit into a normal backpack. Or you can drape it down and let it charge as you walk/hike if the situation makes sense, but don't expect a ton of output with all the movement, I imagine the constant variation wouldn't be good for some batteries either.