IRONWOOD Solar Charger - Portable USB Charger and Backup Battery For Your Cell Phone - Light Weight Waterproof Dustproof Shock Resistant Outdoor With Flashlight (Green)

I've been trying to charge it by sunlight for two days and it still hasn't charged past 25% which is where it was when I started charging.It charges fine from an outlet but I wanted it for a backpacking trip I'm taking and was hoping to get a couple charges out if from sunlight.I'm not impressed.