The Design Specifications for this project are:
Must be charged from a micro USB plug.
Must deliver up to 2A.
Must be as small as possible.
Must be as cheap as possible.
Must boost the battery voltage to 5V.
Must be able to use most single celled LiIons.
Must have a charging LED.
I haven't included a battery protection circuit, as a lot of batteries come with them built it, for my drill cells, I bought a set of ten protection circuits off Ebay for a couple of pounds.