Great stuff to mess around with, absolutely, so long as you temper your expectations of what it can do. 1.8 watts is not a lot to work with; but a dripping tap will still fill a bathtub. From what I've seen, NiMHs would be more likely to take that trickle charge. The LiOns I've fiddled around with (unprotected 18650s) need a stronger power source to charge, at least 10W of raw output from a panel. But I can't speak for the lithium polymer phone batteries. Let us know how it works out.