Not so good.
I bought one of these beasties a while back. So when there was glorious sunshine during April what happened?
Well to put it bluntly nothing. The system is not even powerful enough to keep a Nokia 3210 topped up on just solar power alone. After a full days charging in the sunshine it barely had enough power to boost the battery up by one mark on the scale.
As a portable charger its brilliant. Small and can keep things powered up for a while, but for solar power. Nil points. Needs something a bit beefier.
Incidently I stuck my volt meter on one of the solar units when in full sunshine. Approx voltage 4.1v. Thats fine. But current was at about 2mA which is absolutely hideous.