Fault-tolerant battery management system, circuits and methods

• US 8,598,840 B2
• Filed: 04/14/2011
• Issued: 12/03/2013
• Est. Priority Date: 04/15/2010
• Status: Expired due to Fees

• Current Assignee: Launchpoint Energy And Power, LLC
• Original Assignee: Launchpoint Energy And Power, LLC
• Inventors: Yount, Larry James, Blevins, Willard Ahart, Verma, Inder Jit
• Primary Examiner(s): WILLIAMS, ARUN C
• Application Number:
  US13/086,927
• Publication Number:
  US 20110254502A1
• Time in Patent Office: 964 Days
• Field of Search: 320/107
• US Class Current: 320/107
• CPC Class Codes: B60L 3/0046 relating to electric energy storage systems, e.g. batteries or capacitors
• CPC Class Codes: B60L 3/0092 with use of redundant elements for safety purposes
• CPC Class Codes: B60L 58/10 for monitoring or controlling batteries
• CPC Class Codes: B60L 58/12 responding to state of charge [SoC]
• CPC Class Codes: B60L 58/22 Balancing the charge of battery modules
• 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 10/4207 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 2010/4271 Battery management systems including electronic circuits, e.g. control of current or voltage to keep battery in healthy state, cell balancing
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A fault tolerant battery management system includes redundancy, with applications including electric vehicles. Portions of its circuitry are constituted in distinct fault domains with control, monitoring, and balancing of cells circuitry fault-effect-isolated from the circuitry associated with built-in real-time testing. Built-in tests are orchestrated in fault domains isolated from the functional circuitry being verified. These built-in tests provide test stimulus unique for each cell measurement. Cell balancing is performed in a fault tolerant manner. It takes at least two independent faults, in two mutually distinct fault domains, to negatively affect balancing capability or to interfere with a redundant circuit'"'"'s ability to operate. The built-in tests allow operation without the requirement for data cross-compare between redundant measuring electronic elements. Testing and balancing functions are interlocked through encoded enabling methodologies and transmit enables on serial buses. The circuitry is divided into mutually fault-isolated modules, each responsible for a subset of the cells.

Claims

1. A battery management system for a plurality of interconnected cells wherein cells are monitorable and balanceable independently by at least two sides of redundant circuitry, the two circuitry sides respectively constituted in distinct fault domains;

each side of circuitry being comprised of at least two mutually fault-isolated subsections, each subsection providing for the monitoring and balancing of at least two cells;

further, portions of the circuitry of a subsection of a first side, which, when activated, interfere with the ability of the opposite side'"'"'s circuitry to manage and balance a common cell, require at least two independent enables to activate;

still further, each of the at least two subsections of each of the at least two sides comprises test circuitry for subsection fault detection.

2. The battery management system of claim 1 wherein subsections are disable-able upon detection of a subsection fault.

3. The s battery management system of claim 1 additionally comprising control logic in communication with the at least two subsections of the at least two sides, the communication paths between the control logic and each side being mutually independent.

4. The battery management system of claim 1 further requiring receipt of an encoded message by the subsection circuitry in order to activate at least one of the independent enables.

5. A battery management module with at least two channels each for monitoring and balancing a cell, each channel comprising an input stimulation circuit and a cell balancing circuit;

the cell balancing circuit requiring at least two independent enables to be activated;

further, the stimulation circuits, when activated, applying a mutually unique, measurement-altering condition to each of the at least two channels.

6. The battery management module of claim 5 wherein the applied measurement-altering condition alters the measured cell voltages in mutually distinct manners.

7. The battery management module of claim 6 wherein the stimulation circuit, when activated, is such as to alter the measured cell voltages of at least two cells, respectively, in mutually distinct degrees according to predetermined rules imposed by the values of passive components.

8. The battery management module of claim 7 wherein the altering of measured cell voltages is a DC voltage effect.

9. A fault tolerant battery management system comprising:

a first set of electronic circuits and a second set of electronic circuits;

each set for redundantly monitoring and managing a common plurality of interconnected battery cells;

a controller for commanding and for collecting data from the first and second set of electronic circuits;

the first set of electronic circuits constituted in slices of circuitry, each slice associated with and responsible for monitoring and managing one or more cells;

further, any mode of the first set of electronic circuits that can interfere with the second set of electronic circuits'"'"' monitoring and management of commonly connected cells requires at least two independent enables to be activated, at least one of the enables further requiring a coded message from the controller for activation;

further, the controller, having notice of a failure in a slice of circuitry will effectively isolate that slice from interfering with its associated at least one cell.

10. The battery management system of claim 9 wherein the second set of electronics is constituted in independent slices of circuitry;

each respective slice requiring at least two independent enables to activate any mode that would interfere with the first set of electronics'"'"' ability to monitor and manage any common cells.

11. The battery management system of claim 9 wherein independent means constituted in distinct fault domains.

12. The battery management system of claim 9 further including the plurality of interconnected cells.

13. The battery management system of claim 9 wherein the controller commands the first and second sets of electronics over at least two redundant serial buses.

14. A method for balancing two series connected, adjacent cells of a battery as a pair comprising:

a) determining the two cells'"'"' respective individual balancing histories;

b) allowing paired balancing if the respective balancing histories'"'"' mutual agreement is within a first predetermined criterion;

c) taking a first predetermined action if the respective balancing histories'"'"' degree of mutual agreement is outside of the first predetermined criteria.

15. The method of paired balancing of two cells of claim 14 further comprising:

a) initiating charge extraction from the pair when their paired-voltage reaches a point effectively indicative of two times the value of one cell fully charged;

b) detecting, while charging, a deviation in the paired-voltage'"'"'s slope from that of a plurality of cells being charged in a common battery;

the deviation in slope being indicative of at least one of the paired cells entering overcharging; and

recording the voltage level at this first type of event;

c) detecting, while discharging, a deviation in the paired-voltage'"'"'s slope from that of cells being charged in a common battery;

the deviation of slope being indicative of at least one of the paired cells entering over-discharging; and

recording the voltage level at this second type of event;

d) comparing one or more voltages recorded at a first type of event to one or more voltages recorded at a second type of event;

if the difference in voltages at which overcharging tends to occur are as to the voltages at which over-discharging differ less than an amount set by a predetermined rule, take a predetermined action.

16. The method of paired balancing of claim 15 wherein the slope of voltage of a plurality of voltages in a battery is the total pack voltage.

17. The method of paired balancing of two series adjacent cells of claim 15 wherein the predetermined action of step (d) includes future charging and discharging in a limited manner, effectively reducing battery capacity.

18. The method of paired balancing of two series adjacent cells of claim 14 wherein the first predetermined action of step (c) comprises:

allowing paired balancing if the respective balancing histories mutual agreement is within a more liberal second, predetermined criteria, with a balancing upper voltage trigger value that is minus a de-rating factor;

the de-rating factor being a function of the degree of difference in the balancing histories such that greater difference in balancing histories engendering greater de-rating amounts.

19. A battery charging apparatus comprising:

a) an electrical connection for a battery cell;

b) a charge transfer circuit operationally coupled to the electrical connection, the circuit for transferring charge from, or optionally into, a connected cell;

c) a mutually distinct first and second control logic circuit each having a respective enable signal as an output, both enable signals operatively coupled to said charge transfer circuit;

the coupling of the enable signals to said charge transfer circuit such that activation of charge transfer requires both enable signals to contemporaneously be in activated states;

further, the first and second control logic circuits being substantially constituted in mutually distinct fault domains.

20. The battery charging apparatus of claim 19 wherein the enable signal of the first control logic is transitioned to a state engendering activation via a coded message receivable by the first control logic circuit.

21. The battery charging apparatus of claim 20 wherein the coded message is received over a serial bus interface.

22. The battery charging apparatus of claim 19 wherein at least a portion of the charge transferring circuit acts as a switch and is gated by at least one enable signal is comprised of electronic components that are fault-isolated from the electrical connection.

23. A battery monitor apparatus for connecting to at least two cells comprising:

a) at least one analog-to-digital converter having effectively at least two analog inputs;

b) a stimulus circuit for applying known test conditions to the analog inputs;

c) a first control circuit operatively coupled to said stimulus circuit, the control circuit constituted and arranged as to selectively enable application of the known test condition to the analog inputs;

further, at least a portion of said stimulus circuit being comprised of electronic components situated in a fault domain other than that of the analog-to-digital converter;

further,

the stimulus circuit so configured as to provide a distinct stimulus to a first of the of the at least two analog inputs as compared to the stimulus provided to a distinct second of the at least two analog inputs;

still further,

when connected to the at least two cells, the imposition of a stimulus on the inputs has no significant hindering effect on any concurrent monitoring and managing of the connected cells by a second, duplicate redundant battery monitor and management apparatus, or optionally has provisions for fail-safe isolation to achieve non-interference.

24. The battery monitor apparatus of claim 23 wherein said stimulus circuit comprises a voltage divider.

25. The battery monitor apparatus of claim 23 wherein said stimulus circuit, when activated provides a test condition that results in a DC voltage effect.

26. The battery monitor apparatus of claim 23 wherein said stimulus circuit, when activated provides a test condition that results in an AC voltage effect.

27. The battery monitor apparatus of claim 23 wherein said test condition'"'"'s degree of effect on said analog inputs is predetermined by the value of passive components.

28. The battery monitor apparatus of claim 23 wherein the test condition imposable on a first analog input of the at least two analog inputs is the summing of a known voltage.

29. The battery monitor apparatus of claim 23 wherein the characteristic of the test condition imposable on a first analog input of the at least two analog inputs is substantially the same as the characteristic of the test condition imposable on a second analog input of the at least two analog inputs and the two test conditions differing in degree only.