I like the specifications of the Anker charger, but the only detractors are it's durability. Until I find something better, I'm an advocate of
Suntactics. Yes, more expensive, but by far the best performer and most robust charger I've every used. Waterproof is important; many times those afternoon thunderstorms can drench a charger in minutes (which as happened to me) and a little care of drying it out completely and they are back to working just fine. These are simple, yet very effective charges with the "smart-charging" capability, important for devices affected by changes to the charging current (like when cloud cover distrust the charging temporarily).
Unless you're getting a very expensive 40-60 watt panel, I would opt for a smaller charger battery in the range of 5000-6000 mAh. Any larger than that, and you'll be charging all day...heat and electronics don't mix, so that is a big consideration. I do make sure my cords are long enough to put the electronic device or battery charger out of direct sunlight.
I found a discontinued two-bay Eneloop (USB) charger that does well with the rechargeable AA and AAA batteries. The GOAL Zero battery bay/charger is neat in theory, but not nearly as efficient as a designed charging unit...get a charger just for batteries and a separate battery for electronic devices...just my opinion as you lose a lot of efficiency trying to charge AA batteries and then use them as a charging battery pack. I'll use them around the house for emergencies when I have a butt-load of low-discharge NiMH batteries, but not for outdoors.
Pay close attention to output. The Suntatics 14W charger is rated for 5V (about the max for portable chargers) at 2800 mA. If optimum conditions (usually not the case though), that's pretty fast charging. With any charger, the type of solar cells is important. Some more technically competent portable power gurus will chime in soon to offer some excellent suggestions.
So, I just through my phone (Galaxy S7) outside in the waning sunlight for 35 minutes with the Suntactics 8W solar charger. It was at 55% and 35 minutes later, it charged to 72%. That's pretty solid and most of these portable solar charges are best at "opportunity" charging like when you take a break or you have a few hours in the morning or evening before/after the trail.
ROCK6