Patent ID: 8519670

Claim:
A system for balancing charge within a battery pack comprising: a plurality of cells connected in series, wherein the plurality of cells comprise a first portion of cells and a second portion of cells; a capacitor; a processor operable between: (1) a first mode, wherein the processor selects a combination of donor and receiver cells from the first portion of cells, the combination comprising equal numbers of donor cells and receiver cells; and (2) a second mode, wherein the processor selects a combination of donor and receiver cells from the first portion of cells, the combination comprising more donor cells than receiver cells; a plurality of switches transiently coupling the plurality of cells to the capacitor, the plurality of switches operable between: a first configuration, wherein the switches simultaneously electrically connect the capacitor to the donor cells of the combination of the first or second modes; and a second configuration, wherein the switches simultaneously electrically connect the capacitor to the receiver cells of the combination of the first or second modes; a second capacitor; wherein the processor is further operable between: (1) a third mode, wherein the processor selects a second combination of donor cells and receiver cells from the second portion of cells, the second combination comprising an equal number of donor cells and receiver cells; and (2) a fourth mode, wherein the processor selects a second combination of donor cells and receiver cells from the second portion of cells, the second combination comprising more donor cells than receiver cells; a second plurality of switches transiently coupling the second portion of cells to the second capacitor, the second plurality of switches operable between: a first configuration, wherein the switches simultaneously electrically connect the second capacitor to the donor cells of the second combination of the third or fourth modes; and a second configuration, wherein the switches simultaneously electrically connect the second capacitor to the receiver cells of the second combination of the third or fourth modes; wherein charge is transferred between the first and second portions of the plurality of cells.