I can’t make specific conclusions les I make a fool of myself. I did just look at their website and the limited product description, and I must say that I have doubts about this product. Not saying that I know it wouldn’t work; just saying I’m not convinced that it would. 
You saw 0-19 V fluctuatin with a steady light source (i.e., sunlight)? Beats me why – doesn’t seem normal unless the sunlight intensity was changing accordingly during your measurement. You’re right, if its output is unregulated like that, how’s it supposed to charge a battery?
