Margin-based battery charge balancing

• US 9,728,820 B2
• Filed: 03/29/2012
• Issued: 08/08/2017
• Est. Priority Date: 03/29/2012
• Status: Active Grant

• Current Assignee: Atieva, Inc.
• Original Assignee: Atieva, Inc.
• Inventors: Risk, Gabriel, Hu, Stanley, Diamond, Steven, Chang, Samuel Yeong-Shi
• Primary Examiner(s): Berhanu, Samuel
• Assistant Examiner(s): Kebede, Tessema
• Application Number:
  US13/434,678
• Publication Number:
  US 20130257323A1
• Time in Patent Office: 1,958 Days
• Field of Search: 320118
• CPC Class Codes: B60L 2240/545 Temperature
• 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 2250/10 by alarm
• CPC Class Codes: B60L 2250/12 by confirmation, e.g. of the input
• CPC Class Codes: B60L 2250/16 by display
• CPC Class Codes: B60L 2260/44 by parameter estimation
• CPC Class Codes: B60L 3/0046 relating to electric energy storage systems, e.g. batteries or capacitors
• CPC Class Codes: B60L 3/04 Cutting off the power supply under fault conditions protective devices and circuit arrangements in general H01H; H02H
• CPC Class Codes: B60L 3/12 Recording operating variables ; Monitoring of operating variables
• CPC Class Codes: B60L 58/12 responding to state of charge [SoC]
• CPC Class Codes: B60L 58/16 responding to battery ageing, e.g. to the number of charging cycles or the state of health [SoH]
• CPC Class Codes: B60L 58/20 having different nominal voltages
• CPC Class Codes: B60L 58/22 Balancing the charge of battery modules
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 2220/20 Batteries in motive systems, e.g. vehicle, ship, plane
• 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 battery pack management system adjusts the relative state-of-charge of respective battery blocks in a battery pack to equalize (i.e., align, balance or otherwise make similar) the peak battery block voltages (i.e., maximum or “upper peak” battery block voltages when the battery pack is being charged and/or minimum or “lower peak” battery block voltages when the battery is being discharged). Upon detecting an anomalous battery block that exhibits outlier upper and lower peak voltages, the battery pack management system adjusts the relative state of charge of respective battery blocks to center their respective upper and lower peak voltages between operating limits, thus maximizing the operating margin of the battery pack as a whole.

Claims

1. A method of operation within a battery system having a plurality of battery blocks coupled in series between terminals of a battery pack, the method comprising:

measuring respective charging voltages of the battery blocks while receiving charging current via the battery pack terminals;

measuring respective discharging voltages of the battery blocks while sourcing current to a load via the battery pack terminals, wherein the measuring of the charging voltages and the discharging voltages comprises;

generating a plurality of initial estimate of state-of-charge (ESOC) values based upon open circuit voltage (OCV) corresponding to a plurality of battery blocks;

determining each offset between the initial ESOC value and an actual state-of-charge (SOC) for each battery block;

revising the ESOC value based upon each offset corresponding to each battery block; and

updating the ESOC value for each battery block based upon block tags or statistics of aggregate block voltage margins with respect to operating limits;

identifying an anomalous one of the battery blocks as having a higher charging voltage than charging voltages of others of the battery blocks and a lower discharging voltage than discharging voltages of others of the battery blocks, the charging voltage of the anomalous battery block being a first marginal voltage below an upper threshold and the discharging voltage of the anomalous battery block being a second marginal voltage above a lower threshold; and

adjusting a state of charge of the anomalous battery block to reduce a difference between the first and second marginal voltages of the anomalous battery block, wherein the adjusting is based on an estimate of the state-of-charge (ESOC) value for the anomalous battery block that is determined as part of a balancing of the plurality of battery blocks, wherein adjusting the state of charge of the anomalous battery block comprises discharging the anomalous one of the battery blocks without discharging one or more others of the battery blocks, or charging the anomalous one of the battery blocks without charging one or more of the battery blocks.

2. The method of claim 1 wherein measuring respective charging voltages of the battery blocks while receiving charging current via the battery pack terminals comprises measuring the charging voltages while receiving current from a regenerative braking system within a passenger-conveying vehicle powered at least in part by the battery pack.

3. The method of claim 1 wherein measuring respective discharging voltages of the battery blocks comprises measuring the discharging voltages while sourcing current to a load via the battery pack terminals comprises measuring the discharging voltages while sourcing current to an electric motor that provides motive power to a passenger-conveying vehicle.

6. The method of claim 1 wherein identifying the anomalous one of the battery blocks as having a higher charging voltage than others of the battery blocks comprises generating a first statistical measure representative of at least the charging voltages of the others of the battery blocks.

7. The method of claim 6 wherein the first statistical measure is a statistical mean of at least the charging voltages of the others of the battery blocks.

8. The method of claim 6 wherein identifying the anomalous one of the battery blocks as having a higher charging voltage than others of the battery blocks comprises determining that the charging voltage of the anomalous one of the battery blocks exceeds the first statistical measure.

9. The method of claim 1 wherein identifying the anomalous one of the battery blocks as having a higher charging voltage than others of the battery blocks comprises identifying the charging voltage of the anomalous battery block as a statistical outlier with respect to charging voltages of others of the battery blocks.

10. The method of claim 1 wherein measuring respective charging voltages of the battery blocks while receiving charging current via the battery pack terminals comprises measuring respective charging voltages of the battery blocks concurrently.

11. The method of claim 1 wherein discharging the anomalous battery block comprises switchably coupling the anomalous battery block to one or more balance resistors to draw current from the anomalous battery block.

4. The method of claim adjusting 1 wherein measuring respective charging voltages of the battery blocks comprises measuring respective upper peak voltages of the battery blocks and wherein measuring respective discharging voltages comprises measuring respective lower peak voltages of the battery blocks.

5. The method of claim 4 wherein adjusting the state of charge of the anomalous battery block to reduce the difference between the first and second marginal voltages comprises adjusting the state of charge of the anomalous battery block to align a midpoint between the upper and lower peak voltages of the anomalous battery block with a midpoint between the upper and lower thresholds.

12. A battery management system to control a battery system having a plurality of battery blocks coupled in series between terminals of a battery pack, the battery management system comprising:

voltage measurement circuitry to measure respective charging voltages of the battery blocks while receiving charging current via the battery pack terminals, and to measure respective discharging voltages of the battery blocks while sourcing current to a load via the battery pack terminals, wherein the measuring of the charging voltages and the discharging voltages comprises;

generating a plurality of initial estimate of state-of-charge (ESOC) values based upon open circuit voltage (OCV) corresponding to a plurality of battery blocks;

determining each offset between the initial ESOC value and an actual state-of-charge (SOC) for each battery block;

revising the ESOC value based upon each offset corresponding to each battery block; and

updating the ESOC value for each battery block based upon block tags or statistics of aggregate block voltage margins with respect to operating limits;

logic to identify an anomalous one of the battery blocks as having a higher charging voltage than charging voltages of others of the battery blocks and a lower discharging voltage than discharging voltages of others of the battery blocks, the charging voltage of the anomalous battery block being a first marginal voltage below an upper threshold and the discharging voltage of the anomalous battery block being a second marginal voltage above a lower threshold; and

charge adjusting circuitry to adjust a state of charge of the anomalous battery block to reduce a difference between the first and second marginal voltages of the anomalous battery block wherein the adjusting is based on an ESOC value for the anomalous battery block that is determined as part of a balancing of the plurality of battery blocks, wherein the state of charge of the anomalous battery block is adjusted such that the anomalous one of the battery blocks is discharged without discharging one or more others of the battery blocks, or the anomalous one of the battery blocks is charged without charging one or more of the battery blocks.

13. The battery management system of claim 12 wherein the voltage measurement circuitry to measure respective charging voltages of the battery blocks while receiving charging current via the battery pack terminals comprises circuitry to measure the charging voltages while receiving current from a regenerative braking system within a passenger-conveying vehicle motively powered at least in part by the battery pack.

14. The battery management system of claim 12 wherein the voltage measurement circuitry to measure respective discharging voltages of the battery blocks comprises circuitry to measure the discharging voltages while sourcing current to a load via the battery pack terminals comprises measuring the discharging voltages while sourcing current to an electric motor that provides motive power to a passenger-conveying vehicle.

15. The battery management system of claim 12 wherein the voltage measurement circuitry to measure respective charging voltages and respective discharging voltages of the battery blocks comprises circuitry to measure respective upper peak voltages of the battery blocks while receiving charging current and to measure respective lower peak voltages of the battery blocks while sourcing current to the load.

16. The battery management system of claim 12 wherein charge adjusting circuitry to adjust the state of charge of the anomalous battery block to reduce the difference between the first and second marginal voltages comprises circuitry to adjust the state of charge of the anomalous battery block to align a midpoint between the upper and lower peak voltages of the anomalous battery block with a midpoint between the upper and lower thresholds.

17. The battery management system of claim 12 wherein the logic to identify the anomalous one of the battery blocks as having a higher charging voltage than others of the battery blocks comprises logic to generate a first statistical measure representative of at least the charging voltages of the others of the battery blocks.

18. The battery management system of claim 17 wherein the first statistical measure is a statistical mean of at least the charging voltages of the others of the battery blocks.

19. The battery management system of claim 17 wherein the logic to identify the anomalous one of the battery blocks as having a higher charging voltage than others of the battery blocks comprises logic to determine that the charging voltage of the anomalous one of the battery blocks exceeds the first statistical measure.

20. The battery management system of claim 12 wherein the logic to identify the anomalous one of the battery blocks as having a higher charging voltage than others of the battery blocks comprises logic to identify the charging voltage of the anomalous battery block as a statistical outlier with respect to charging voltages of others of the battery blocks.

21. The battery management system of claim 12 wherein the voltage measurement circuitry to measure respective charging voltages of the battery blocks while receiving charging current via the battery pack terminals comprises circuitry to measure respective charging voltages of the battery blocks concurrently.

22. The battery management system of claim 12 wherein the charge adjusting circuitry to adjust the state of charge of the anomalous battery block comprises circuitry to discharge the anomalous battery block without discharging one or more others of the battery blocks.

23. The battery management system of claim 12 wherein the circuitry to discharge the anomalous battery block comprises circuitry for switchably coupling the anomalous battery block to one or more balance resistors to draw current from the anomalous battery block.

24. A battery management system to control a battery system having a plurality of battery blocks coupled in series between terminals of a battery pack, the battery management system comprising:

battery management means for measuring respective charging voltages of the battery blocks while receiving charging current via the battery pack terminals and for measuring respective discharging voltages of the battery blocks while sourcing current to a load via the battery pack terminals, wherein the measuring of the charging voltages and the discharging voltages comprises;

generating a plurality of initial estimate of state-of-charge (ESOC) values based upon open circuit voltage (OCV) corresponding to a plurality of battery blocks;

determining each offset between the initial ESOC value and an actual state-of-charge (SOC) for each battery block;

revising the ESOC value based upon each offset corresponding to each battery block; and

updating the ESOC value for each battery block based upon block tags or statistics of aggregate block voltage margins with respect to operating limits;

the battery management means for identifying an anomalous one of the battery blocks as having a higher charging voltage than charging voltages of others of the battery blocks and a lower discharging voltage than discharging voltages of others of the battery blocks, the charging voltage of the anomalous battery block being a first marginal voltage below an upper threshold and the discharging voltage of the anomalous battery block being a second marginal voltage above a lower threshold; and

discharge control means for adjusting a state of charge of the anomalous battery block to reduce a difference between the first and second marginal voltages of the anomalous battery block wherein the adjusting is based on an ESOC value for the anomalous battery block that is determined as part of a balancing of the plurality of battery blocks, wherein the adjusting of the state of charge of the anomalous battery block comprises discharging the anomalous one of the battery blocks without discharging one or more others of the battery blocks, or charging the anomalous one of the battery blocks without charging one or more of the battery blocks.