Patent ID: 7825629
Filing Date: 2010-11-02
Classification: H02J

Abstract:
1. A system for charging a secondary battery comprising a plurality of battery cells connected in a series string, said series string comprising a first battery cell connected to a load and an N th battery cell connected to a ground, and a cell junction formed at a connection between each respective pair of adjacent battery cells, said system comprising: a plurality of charging sources comprising exactly (N+2)/2 charging sources when N is an even number or (N+1)/2 charging sources when N is an odd number, each of the plurality of charging sources having a first state and a second state, wherein in the first state, the charging source provides a charging current and in the second state, the charging source does not provide a charging current, said plurality of charging sources further comprising: a plurality of shunt regulators, wherein a respective shunt regulator is connected in parallel across each battery cell connected between the first battery cell and the N a controller connected to each of the plurality of charging sources and each of the plurality of shunt regulators, said controller comprising circuitry to selectively operate each of the plurality of charging sources in the first state or the second state, and each of the plurality of shunt regulators in the first state or the second state to provide charging current to each battery cell having a voltage less than the predetermined voltage and to avoid providing charging current to each battery cell having a voltage equal to or greater than the predetermined voltage, wherein the controller is configured to allow only one charging source to be switched on at a time.