Patent ID: 7928691

Claim:
A charging system for charging a rechargeable battery connected to a load, comprising: N battery cells coupled in series forming a series string, wherein said series string comprises: a first battery cell coupled to the load, and an N th battery cell coupled to a ground of the load; a plurality of isolated charging sources, each isolated charging source being coupled to a power source and coupled in parallel to one of the battery cells of said series string, wherein each isolated charging source is configured to operate in one of a first state and a second state, wherein when operating in said first state the isolated charging source provides charging current to said respective battery cell, and when operating in said second state, the isolated charging source does not provide charging current to said respective battery cell; a plurality of positive paths coupled to said series string and said isolated charging sources; and a plurality of negative paths coupled to said series string and said isolated charging sources, wherein each of the isolated charging sources are coupled in parallel to one of the respective battery cells via a respective positive path of the plurality of positive paths and a respective negative path of the plurality of negative paths, and wherein a ground of the power source is isolated from the ground of the load.