Patent ID: 8436583

Claim:
A multiple cell battery charger comprising: a regulator for receiving a predetermined input voltage and supplying a PWM (pulse width modulated) output current at its output, wherein the pulse width is modulated as a function of the total charging current at its output; a plurality of charging circuits, each charging circuit configured to charge an individual battery cell, said plurality of charging circuits electrically coupled to each other in a parallel relationship forming a parallel circuit, said parallel circuit being electrically coupled between said output of said regulator and ground; a total current sensing resistor for measuring the total charging current applied to said plurality of charging circuits; wherein each charging circuit comprises: a pair of terminals for coupling to a battery cell; a switching device serially coupled to said pair of battery terminals for selectively connecting and disconnecting said pair of terminals from said output of said regulator; and an individual cell current sensing resistor for sensing the charging current applied to said battery cell , said individual current sensing resistor , said switching device and said pair of terminals all connected in series forming said charging circuit; said battery charger further including a microprocessor operatively coupled to said charging circuits for selectively monitoring the voltage across the pair of terminals in each charging circuit independently and selectively controlling the switching device so as to disconnect said pair of terminals in an individual charging circuit when said battery cell in that individual charging circuit reaches a predetermined voltage, said microprocessor also coupled to said total current sensing resistor for monitoring the charging current applied to said plurality of charging circuits and varying the pulse width of the output current at the output of the regulator.