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 Cell phone solar USB charger - the Foursun 21W, dual USB ports

This 3 panel unit, with a velcro sealable pouch for cables, when folded, is about the size and weight of an iPad or large Kindle Fire. It weighs just under a pound, and costs about $35 on Amazon. The unit has no built-in battery (which is more efficient for charging a phone when the sun is out, than first charging a battery, and then charging your phone from the battery). But it can also easily charge a rechargeable USB battery pack, phone or iPad, directly and efficiently. The charger has no cables, only 2 USB ports, one with USB-A, and one with USB-C. You can use both simultaneously. 

While the size of the 10W units is more appealing, often comprising of a single, lighter weight single panel, the output of those would barely keep up with having a phone on, and could take over 12 hours of being in the sun to fully charge a phone, depending on amount of light, and specific phone or device, so the multi-panel 21W made more sense for me. 

To do the math for charging times, the best site I have found is the Jackery website. They also sell solar panel cell phone chargers, of varying sizes, and also models with integrated batteries.

While I have only used this unit once, placing it on the deck in late afternoon direct sunlight, I was able to charge my Pixel 6a from 10% to 25% in 1 hour. This is about what I expected. I also have iPhones and an iPad, and expect similar results from those, but using USB-A or USB-C to Lightning port cables. 

Other than the extra weight going in my backpack, the only downside I see to this unit, is the build quality is not impressive. If I were expecting to use this outdoors regularly or attached to the backside of a backpack for many hours at a time, I would consider investing in a higher quality unit. The cloth and materials of this unit seem lightweight.