Apparatus and method for balanced charging of a multiple-cell battery pack

• US 7,126,310 B1
• Filed: 04/20/2001
• Issued: 10/24/2006
• Est. Priority Date: 04/20/2001
• Status: Active Grant

• Current Assignee: Abiomed, Inc. (Johnson & Johnson)
• Original Assignee: Abiomed, Inc. (Johnson & Johnson)
• Inventors: Barron, Christopher
• Primary Examiner(s): Sparks, Donald
• Assistant Examiner(s): LUK, LAWRENCE W
• Application Number:
  US09/840,011
• Time in Patent Office: 2,013 Days
• Field of Search: 320/108, 320/164, 320/116, 320/107, 320/118, 320/132, 320/120, 320/122, 320/136, 320/121, 320/162, 607/60, 607/32, 607/33
• US Class Current: 320/108
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits

Abstract

An apparatus and method for charging a multiple-cell battery pack provides a balanced charge to each cell in a series by providing a cell charge monitor/regulator for (1) monitoring the charge (potential, for example) of each cell and, when a state is attained, defining a maximum cell charge, and (2) shunting further charge current to a next cell in the series via a shunt resistor that bridges the cell, and thereby bypasses further charging thereof, while directing shunted charge current to one or more next cells in the series as needed. Each of the cells is thereby charged to its fullest potential while the overall charging procedure is not unduly lengthened. The battery pack can be implanted as part of a life-saving system.

Claims

1. A method for balancing charge levels comprising:

using a battery pack having a plurality of cells arranged in series;

bridging around a first cell of the plurality of cells with a bypass resistor and a switch;

monitoring a charge level of one of the cells based upon an input connected across the first cell, including comparing a relative voltage potential across the first cell with respect to a reference voltage potential and wherein the step of comparing includes providing cell monitor/regulator includes a voltage divider connected across the first cell and having an output connected to a first input of the comparator, and a reference voltage source that outputs the voltage potential to a second input of the comparator;

closing the switch when the charge level of the first cell equals a maximum value so as to shunt charge current around the cell through the bypass resistor;

connecting an output of the comparator to a lead of the switch, the switch closing a path through the bridge when the comparator measures a voltage at the second input greater than a voltage at the first input;

saturating a transistor in response to an output of the comparator when the comparator measures a voltage at the second input greater than a voltage at the first input; and

locating battery pack terminals at respective opposing ends of the series of the plurality of the cells, and connecting respective opposing leads of a charging circuit to the terminals at predetermined times so as to charge the plurality of cells.

2. The method a set forth in claim 1 further comprising connecting a sense resistor in line with one of the terminals, and measuring an overall voltage across the sense resistor and regulating a maximum current delivered to the battery pack by the charging circuit in response to a measured value the overall voltage.

3. The method as set forth in claim 1 wherein the cells comprise lithium ion-type cells.

4. The method as set forth in claim 1 wherein the cells comprise at least six cells.

5. The method as set forth in claim 4 wherein the cells comprise lithium ion type cells.

6. The method as set forth in claim 1 further comprising operatively connecting the cells to a life-saving system and powering the life-saving system with the cells.

7. The method as set forth in claim 6 further comprising implanting the cells in a body and providing an external power source that transmits charging current to the cells.

8. The method as set forth in claim 7 wherein the step of providing the external power source includes transmitting energy through a skin layer of the body using induction.

9. A method for balancing charge levels comprising:

using a battery pack having a plurality of cells arranged in series;

bridging around a first cell of the plurality of cells with a bypass resistor and a switch;

monitoring a charge level of one of the cells based upon an input connected across the first cell, including comparing a relative voltage potential across the first cell with respect to a reference voltage potential and wherein the step of comparing includes providing cell monitor/regulator includes a voltage divider connected across the first cell and having an output connected to a first input of the comparator, and a reference voltage source that outputs the voltage potential to a second input of the comparator;

closing the switch when the charge level of the first cell equals a maximum value so as to shunt charge current around the cell through the bypass resistor;

connecting an output of the comparator to a lead of the switch, the switch closing a path through the bridge when the comparator measures a voltage at the second input greater than a voltage at the first input;

saturating a transistor in response to an output of the comparator when the comparator measures a voltage at the second input greater than a voltage at the first input; and

monitoring each of the cells based upon an input connected across each of the cells for measuring a charge of the each of the cells respectively, and providing a bridge around the each of the cells, the bridge including a respective bypass resistor and a respective switch and closing the respective switch when the charge of the each of the cells equals a maximum value so as to shunt charge current around the each of the cells through the respective bypass resistor.

10. A transcutaneous energy transmission (TET) system adapted for implantation in a body and for powering an implanted life-saving device comprising:

an implanted TET module for receiving energy through the skin and transmitting electricity derived from the energy to a life-saving device; and

an implanted rechargeable battery pack including a battery pack having a plurality of series-arranged cells, having a bridge connected around a first cell, including a bypass resistor in series with a switch, and a cell monitor/regulator having an input connected across the first cell for measuring a charge of the first cell, wherein the cell monitor/regulator closes the switch when a charge of the first cell equals a maximum value.

11. The TET system as set forth in claim 10 wherein the battery pack is adapted to be charged when the implanted TET module receives energy from an external TET transmitter and to discharge, so as to power the life-saving device when the implanted TET module receives one of either no energy or insufficient energy.