I purchased two chargers, the Duracell Instant USB and the Tekkeon mp1550. The Duracell Instant charger is a lithium battery that holds 1150Mah of power. It's very slim and light and fits in your pocket comfortably. This charger will only charge my phone (motorola droid) about half way. The Tekkeon charger is a little bit bulkier, it holds 4AA batteries and the casing is just about an inch bigger than the AA batteries and about 3/4 of an inch thick. I am using some cheap brand AA low self discharge batteries they are rated at 2300mah but I have tested them to be at about 2000 to 2100mah with a lacrosse charger. I am only getting about 1 complete charge out of a set of batteries. Is that normal? I figured if the Droid battery is 1300mah and I am using 4 2000mah batteries I should at least get 3 full complete charges shouldn't I? Anyway, unless I have a faulty tekkeon unit I think I would prefer to carry around two of the duracell chargers because they are smaller and lighter. Any thoughts, or suggestions on other portable chargers?