I use imuto units bought on Amazon. I've been laid up after ankle surgery, and have been using my gadgets more than usual. Extension cords to plugs became a PITA. I first bought the 2000mAh unit, but it would charge the S8 only 3x. So, bought the 3000mAh unit, which, of course, has more capacity. Now, the wife will use these when she goes camping. Don't know how these compare to others, but work for me.