SYSTEM TO MEASURE SERIES-CONNECTED CELL VOLTAGES USING A FLYING CAPACITOR

• US 20080272791A1
• Filed: 05/04/2007
• Published: 11/06/2008
• Est. Priority Date: 05/04/2006
• Status: Active Grant

• Current Assignee: EnerDel, Inc. (Ener1, Inc.)
• Original Assignee: EnerDel, Inc. (Ener1, Inc.)
• Inventors: Hartzog, Chad
• Granted Patent: US 7,902,830 B2
• Time in Patent Office: Days
• US Class Current: 324/434
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery

Abstract

A system for measuring voltage of individual cells connected in series includes a single flying capacitor. The capacitor stores the charge of one of the cells such that an analog-to-digital converter (ADC) connected to the capacitor may process an accurate representation of the voltage of the cell being measured. A plurality of MOSFET-based switches electrically connects and disconnects the cells and the capacitor. A controller is in communication with the ADC and the switches for sequencing the switches and recording the voltage measurements of each cell.

Claims

1. A system for measuring voltage of individual cells in a plurality of cells connected in series, said system comprising:

a plurality of cell switches for electrical connection to the plurality of cells wherein each cell switch includes a first side and a second side with said first side of each cell switch electrically connectable to a positive terminal one of the cells;

a first bus electrically connected to said second side of every other cell switch;

a second bus electrically connected to said second side of each cell switch not connected to said first bus;

a first bus positive switch having a first side and a second side wherein said first side is electrically connected to said first bus;

a second bus positive switch having a first side and a second side wherein said first side is electrically connected to said second bus;

a first bus negative switch having a first side and a second side wherein said first side is electrically connected to said first bus;

a second bus negative switch having a first side and a second side wherein said first side is electrically connected to said second bus;

a capacitor for storing a charge of at least one of the cells wherein said capacitor includes a positive terminal electrically connected to said second sides of said first bus positive switch and said second bus positive switch and a negative terminal electrically connected to said second sides of said first bus negative switch and said second bus negative switch; and

an amplifier for amplifying the charge stored on said capacitor wherein said amplifier includes an inverting input electrically connected to said negative terminal of said capacitor, a non-inverting input electrically connected to said positive terminal of said capacitor, and an output.

2. A system as set forth in claim 1 further comprising a ground switch having a first side and a second side wherein said first side is electrically connected to said negative terminal of said capacitor and said second side is electrically connected to ground.

3. A system as set forth in claim 1 further comprising an analog-to-digital converter (ADC) electrically connected to said output of said amplifier for converting an analog signal supplied by said amplifier into digital data.

4. A system as set forth in claim 3 further comprising a controller in communication with said ADC for receiving the digital data from said ADC.

5. A system as set forth in claim 4 wherein said controller is in communication with said switches for controlling the operation of said switches.

6. A system as set forth in claim 4 wherein said ADC is integrated with said controller.

7. A system as set forth in claim 4 further comprising a multiplexer electrically connected between said amplifier and said ADC for allowing other analog signals to be converted by said ADC.

8. A system as set forth in claim 1 wherein each of said cell switches includes at least one transistor.

9. A system as set forth in claim 1 wherein each of said cell switches is further defined as a pair of MOSFETs wherein the sources of each MOSFET are electrically connected together and the gates of each MOSFET are electrically connected together.

10. A system as set forth in claim 1 wherein each of said bus switches includes at least one transistor.

11. A system as set forth in claim 1 wherein each of said bus switches is further defined as a pair of MOSFETs wherein the sources of each MOSFET are electrically connected together and the gates of each MOSFET are electrically connected together.

12. A system as set forth in claim 1 further comprising a controller for controlling operation of said switches.

13. A system as set forth in claim 12 further comprising a decoder electrically connected to said controller and said cell switches for receiving a signal from said controller and directing operation of said cell switches.

14. A system as set forth in claim 13 wherein said decoder includes a plurality of outputs wherein each of said outputs is electrically connected to a pair of cell switches for simultaneously controlling operation of said pair of cell switches.

15. A system for measuring voltage of individual cells in a plurality of cells connected in series, said system comprising:

a plurality of cell switches for electrical connection to the plurality of cells wherein each cell switch includes a first side and a second side with said first side of each cell switch electrically connectable to a positive terminal one of the cells;

a first bus electrically connected to said second side of every other cell switch;

a second bus electrically connected to said second side of each cell switch not connected to said first bus;

a first bus positive switch having a first side and a second side wherein said first side is electrically connected to said first bus;

a second bus positive switch having a first side and a second side wherein said first side is electrically connected to said second bus;

a first bus negative switch having a first side and a second side wherein said first side is electrically connected to said first bus;

a second bus negative switch having a first side and a second side wherein said first side is electrically connected to said second bus;

wherein each of said cell switches and said bus switches includes at least one transistor.

a capacitor for storing a charge of at least one of the cells wherein said capacitor includes a positive terminal electrically connected to said second sides of said first bus positive switch and said second bus positive switch and a negative terminal electrically connected to said second sides of said first bus negative switch and said second bus negative switch;

a ground switch having a first side and a second side wherein said first side is electrically connected to said negative terminal of said capacitor and said second side is electrically connected to ground;

an amplifier for amplifying the charge stored on said capacitor wherein said amplifier includes an inverting input electrically connected to said negative terminal of said capacitor, a non-inverting input electrically connected to said positive terminal of said capacitor, and an output;

an analog-to-digital converter (ADC) electrically connected to said output of said amplifier for converting an analog signal supplied by said amplifier into digital data; and

a controller in communication with said ADC for receiving the digital data from said ADC.