As a Ranger for The Dyrt, I am given product to test from time to time. For the last 2 months I've been testing out the Renogy Multi-Functional Solar Backpack.
This is a 20L backpack with a lot of compartments best suited for those needing a daily activity/commuter bag. If you're looking for a true hiking/backpacking pack with solar panels, I recommend checking out Renogy's stand-alone panels.
How does it work?
The solar panel is slightly larger than a regular piece of paper (11.3" x 9.7") and can be configured to face inward when not in use for protection from abrasions. When in use, it provides a USB port to charge from (max output 1.2A and can charge a phone in 2.5 hrs.
Here's the thing: Renogy recommends you use the set up to charge to a power-bank, rather than directly to devices and I completely agree. This is because even in the best light, directly connected to my phone I was only able to maintain my power level, not improve it. I found out the panel is pretty sensitive because in partially cloudy conditions I could hear my phone beep when it would go on/off charge. Sometimes it would beep at me a few times a minute. With a power bank, you can still charge devices but also build up reserve power so at night you can recharge your electronics.
Who should buy this bag?
Anyone who wants a comfortable day pack with lots of storage options and loves the idea you can grab free energy to recharge your devices. I use it for all my media projects as it carries all my cameras, cables, and tripods plus in compartments so they aren't knocking into each other and the weight stays distributed evenly. Just check out the amount of stuff I put in this thing! It has pockets everywhere, and includes an option to slide this through larger luggage's extendable handles, making it a great carry on bag if you need to travel by a plane. You will need a different bag for long expeditions because you need more than a 20L pack for that, plus this bag lacks chest and hip straps.
If you're in the market for a 15-20L day pack and want something that provides power, buy this. Especially if you're outside a lot. The bag is lasting very well, the panel is going strong even after I spilled beer on it (it's waterproof and obviously it was an accident as I would never waste beer), it's comfortable, and I like how versatile I can configure it for all my stuff. In some social or business settings the solar panel isn't the greatest thing to be showing off, so it's great you can hide that away. Last I checked electricity isn't coming from a magic bean field, and I love how I'm able to go greener now by getting energy for my devices from the sun.