ELECTROCHEMICAL CELL MONITORING AND BALANCING CIRCUIT WITH SELF-DIAGNOSTIC FEATURE

• US 20120139553A1
• Filed: 12/06/2011
• Published: 06/07/2012
• Est. Priority Date: 12/06/2010
• Status: Active Grant

• Current Assignee: Exergonix, Inc.
• Original Assignee: Coda Automotive, Inc.
• Inventors: Nortman, Peter Fredrick, Sufrin-Disler, Daniel A., Weicker, Phillip John, Mcgulpin, Patrick J.
• Granted Patent: US 9,568,555 B2
• Time in Patent Office: Days
• US Class Current: 324/537
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 2240/549 Current
• CPC Class Codes: B60L 2240/80 Time limits
• CPC Class Codes: B60L 58/22 Balancing the charge of battery modules
• CPC Class Codes: G01R 31/382 Arrangements for monitoring battery or accumulator variables, e.g. SoC
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• 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
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: H01M 50/569 Constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals battery terminal connectors with integrated measuring arrangements G01R31/364
• CPC Class Codes: H02J 2310/48 for electric vehicles [EV] or hybrid vehicles [HEV]
• CPC Class Codes: H02J 7/0014 Circuits for equalisation of charge between batteries
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/0069 Charging or discharging for charge maintenance, battery initiation or rejuvenation
• CPC Class Codes: H02J 9/002 in which a reserve is maintained in an energy source by disconnecting non-critical loads, e.g. maintaining a reserve of charge in a vehicle battery for starting an engine
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/92 Energy efficient charging or discharging systems for batteries, ultracapacitors, supercapacitors or double-layer capacitors specially adapted for vehicles

Abstract

A system and method for measuring a voltage of electrochemical cells of a pack. The system includes circuit elements individually associated with respective electrochemical cells of the pack and having electrical characteristics that are different such that individual electrochemical cells can be distinguished from one another. The system also includes a measurement circuit configured to measure the voltage of the electrochemical cells and to identify an electrochemical cell being measured based on an electrical characteristic of a circuit element associated with the electrochemical cell. Various self-diagnostic techniques are described, as well as techniques for measuring sense resistance, reducing sense resistance, and measuring changes in voltage of a cell over time.

Claims

1. A system for measuring a voltage of electrochemical cells of a pack, the system comprising:

circuit elements individually associated with respective electrochemical cells of the pack and having electrical characteristics that are different such that individual electrochemical cells can be distinguished from one another; and

a measurement circuit configured to measure the voltage of the electrochemical cells and to identify an electrochemical cell being measured based on an electrical characteristic of a circuit element associated with the electrochemical cell.

2. The system of claim 1, wherein the circuit elements comprise resistive elements individually associated with respective electrochemical cells, the resistive elements having different resistances.

3. The system of claim 2, wherein the measurement circuit is configured to make a first measurement of a voltage associated with the electrochemical cell when a first current is applied to the electrochemical cell and to make a second measurement associated with the electrochemical cell when a second current is applied to the electrochemical cell.

4. The system of claim 2, wherein the measurement circuit is configured to make a first measurement of a voltage associated with the electrochemical cell when a current is applied to the electrochemical cell and to make a second measurement associated with the electrochemical cell without a current applied to the electrochemical cell.

5. The system of claim 2, wherein a first resistive element is connected to a first terminal of a first electrochemical cell, and wherein the measurement circuit is configured to measure a voltage across a series combination of the first resistive element and the first electrochemical cell.

6. The system of claim 5, further comprising a current generating circuit configured to provide a current to the series combination of the first resistive element and the first electrochemical cell.

7. The system of claim 6, wherein the measurement circuit is configured to measure the voltage across the series combination of the first resistive element and the first electrochemical cell when the current generating circuit provides the current to the series combination of the first resistive element and the first electrochemical cell.

8. The system of claim 1, wherein the measurement circuit is configured to check that an electrical characteristic measured for a circuit element associated with an electrochemical cell is within an expected range of values of the electrical characteristic.

9. The system of claim 8, wherein the system is configured to use an identification of an incorrect cell or an out of range measurement to detect a fault in the measurement circuit or a balancing circuit associated with the pack.

10. The system of claim 1, wherein the electrical characteristic comprises resistance.

11. A method of monitoring an electrochemical cell of a pack comprising a plurality of electrochemical cells, the method comprising:

measuring a voltage of the electrochemical cell; and

identifying the electrochemical cell from among the plurality of electrochemical cells based on an electrical characteristic of a circuit element connected to the electrochemical cell.

12. A system for monitoring and balancing electrochemical cells of a pack, the system comprising:

a balancing circuit configured to charge or discharge a first electrochemical cell of the pack, the balancing circuit being configured to generate a current through the first electrochemical cell; and

a measurement circuit connected to the first electrochemical cell, the measurement circuit being configured to measure, based on the current, a sense resistance established by coupling the first measurement circuit to the first electrochemical cell.

13. The system of claim 12, wherein the sense resistance comprises a contact resistance established by coupling the first measurement circuit to the first electrochemical cell.

14. The system of claim 13, wherein the balancing circuit is configured to generate a wetting current through the first electrochemical cell of sufficient magnitude to wet a contact between conductors coupling the measurement circuit to the first electrochemical cell.

15. The system of claim 14, wherein the system is configured to:

determine whether the sense resistance exceeds a threshold; and

control the balancing circuit to generate the wetting current through the first electrochemical cell when the sense resistance exceeds the threshold.

16. A system for monitoring electrochemical cells of a pack, the system comprising:

a measurement circuit connected to a first electrochemical cell of the pack; and

a current generating circuit configured to generate a wetting current through the first electrochemical cell of sufficient magnitude to wet a contact between conductors coupling the measurement circuit to the first electrochemical cell.

17. The system of claim 16, wherein the system is configured to:

determine whether a sense resistance established by coupling the measurement circuit to the first electrochemical cell exceeds a threshold; and

control the balancing circuit to generate the wetting current through the first electrochemical cell when the sense resistance exceeds the threshold.

18. A method of monitoring an electrochemical cell, the method comprising:

measuring a change in voltage over a time period as the electrochemical cell charges or discharges; and

determining, based at least partially on the change in the voltage over the time period, a range of the state of charge of the electrochemical cell.

19. The method of claim 18, wherein, when the change in the voltage over the time period is higher than a threshold, the range is determined to correspond to a low state of charge or a high state of charge.

20. The method of claim 19, wherein, when the change in the voltage over the time period is lower than a threshold, the range is determined to correspond to a moderate state of charge between the low state of charge and the high state of charge.

21. The method of claim 19 further comprising identifying which of two or more possible voltage readings for the electrochemical cell is correct based upon the determined range of the state of charge for the electrochemical cell.

22. The method of claim 21, wherein the two or more possible voltage readings are produced as a result of a fault within measurement, balancing and/or selection circuitry.

23. A system for monitoring an electrochemical cell, the system comprising:

a measurement circuit configured to measure a change in voltage over a time period as the electrochemical cell charges or discharges; and

a controller configured to determine, based at least partially on the change in the voltage over the time period, a range of the state of charge of the electrochemical cell.