Maximum Energy transfer through cell isolation and discharge

• US 20070216369A1
• Filed: 09/08/2004
• Published: 09/20/2007
• Est. Priority Date: 09/08/2003
• Status: Abandoned Application

• Current Assignee: Poweready, Inc. (Xicor, Inc.)
• Original Assignee: Intersil Corporation (Renesas Electronics Corporation)
• Inventors: Chandler, Lance
• Application Number:
  US10/937,735
• Publication Number:
  US 20070216369A1
• Time in Patent Office: Days
• US Class Current: 320/136
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery system includes a multi-cell battery pack in electrical communication with a load. The voltages of each cell are individually monitored by the microcontroller, such as with a high-impedance input terminal. Across each of the cells is a transistor-resistor combination such that by providing a voltage to the gate of each of the transistors, a short-circuit is created through the corresponding cell thereby providing an additional current drain on the cell. More specifically, by turning on the transistor, a short-circuit current (I_SQ1) is drawn from the cell through resistor (R1) to provide for the isolated discharge of the specific cell. By selectively measuring each of the cells in a multi-cell battery pack to determine if any of the cells are over-voltage, and if so, by increasing the current drain on that specific cell, the overall maximum amount of energy can be transferred to a load across the battery pack. Moreover, this selectively isolation and discharge provides a mechanism for maintaining a constant charge across all batteries in a multi-cell batter pack.

Claims

1. A method for optimizing the transfer of energy from a cell in a multi-cell battery, comprising the steps of:

beginning a discharge cycle;

measuring each cell of said multi-cell batter;

comparing measured values of all cells;

determining if one or more of the cells is more than a predetermined voltage (Vmax) greater than its companion cell voltages;

turning on the transistor associated with an over-voltage cell to place a shunt resistor across the over-voltage cell.

discharging the over-voltage cell through its corresponding transistor for a predetermined time to provide for the balancing of the cell voltages within said multi-cell battery pack;

turning off the transistor associated with the over-voltage cell thereby removing the shunt resistor from the discharge circuit;

continuing the discharge of the multi-cell battery.