This is very good for the price I paid about £12. But it does have its faults. It takes ages to charge and never seems to reach full charge and I have tried for 24 hours with a 2amp iPad charger. Also it seems to get stuck on and won't turn off.
But apart from that brilliant. Proved very useful on a recent trip to Dorset when I need to use my iPhone as a Sat-Nav and it kept my iPhone charger through the whole journey over 3 hours. It still had plenty of power left and would last about 6-7 hours.
I leave it on my window cill to keep it topped which works great.