Bests & Worsts Reviews from Amazon

I've had experience with solar batteries similar to this one before, so I'll go ahead and get this out of the way early. The solar panel is not powerful enough to charge the battery in any reasonable amount of time. My old 4,000mAh batteries this replaced would take 3 days of summer sunlight to charge from dead, and this panel is no bigger so I imagine it would take an entire week to charge completely. Best bet is to see this as a battery that needs to charge from an electrical source, but also has the ability to put in some juice from the panel to make this basically a 21,000mAh battery for the day. Twin USB ports is a plus, charges my phone at 2.1 amps (tested based on time matching my quick chargers, not with a multimeter), and the added light function has been useful over the 3 months of ownership. 4 out of 5 for now because it seems to slowly drain if I don't cover the panel completely.