Review on 🌞 KINGSOLAR 21W Portable Solar Charger: Waterproof, Foldable Solar Panel Charger with 2 USB Ports for Camping, Cell Phone, Tablet, GPS, iPhone, iPad, Camera & More by Chris Norman

It seems to work well. I've attached a video of my battery being charged in daylight. My USB Amm/Voltmeter shows 1.64 amps at 5.2 volts. The price was right. I was skeptical of product reviews because they don't really tell any facts, just "didn't charge my phone" I would recommend buying. Don't be an idiot and expect fast charging, it's 21W. Leave it and charge the battery and then charge your mobile phone with it. Phones love constant performance.