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Just to clarify, there exists no such thing as a good solar charger for $50. The one in your picture is a novelty. A panel that size would take several weeks to juice up that phone. That's assuming strong Summer sunlight.
Now, do you want a cheap novelty or do you want solar that really works? If the second, expect to spend ~$100-$300. I recommend a minimum of 5 watts to charge a smartphone in a useful amount of time. I have two folding three panel arrays, 20 watt and 30 watt respectively.
Under most conditions only the folding arrays will charge it at fullspeed or at all for most of the year. During the Summer, my 5 watt solar backpack charges it fine. As a rule you want huge overkill in terms of the panel output because they list the maximum under ideal conditions so you'll only really ever get a fraction of that.
Also, give up on ever charging anything more substantial than a single 18650 or a smartphone. Just give up on that. I can charge my tablet but an entire day of Summer sun only replenished about 30% of the battery. If you want to be able to charge something you'll use every day it should have a battery no larger than 3000mah.
The advantage, once you've sunk enough money into a really big, powerful folding array is that it doesn't run out. You can stay out innawoods for decades and still have power. But do you really plan to do that? Or are you looking at weekend camping/hiking trips of a few days at most?
If the latter, just buy a 6-cell18650 powerbank. That will be more power than you can realistically use in that time unless you're a doofus who brings his fucking laptop camping with him.
