Lead acid state of charge estimation for auto-stop applications

• US 9,625,533 B2
• Filed: 04/15/2014
• Issued: 04/18/2017
• Est. Priority Date: 04/16/2013
• Status: Active Grant

• Current Assignee: CPS Technology Holdings, LLC
• Original Assignee: Johnson Controls Technology Company (Johnson Controls International plc)
• Inventors: Le, Daniel B., Sisk, Brian C.
• Primary Examiner(s): Tso, Edward
• Application Number:
  US14/253,720
• Publication Number:
  US 20140309911A1
• Time in Patent Office: 1,099 Days
• Field of Search: 320104, 320132, 320147, 320149, 702 63, 702 64, 702 65, 701112
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/379 for lead-acid batteries
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements

Abstract

The present disclosure describes a method that includes predicting terminal voltage of a battery module in a vehicle using a battery control module. Predicting the terminal voltage includes determining a gassing current of the battery module using a gassing current model, in which the gassing current quantifies terminal current that is not used to charge the battery module, and calculating the predicted terminal voltage based at least in part on a measurement model and the determined gassing current. The method also includes measuring terminal voltage of the battery module using a sensor communicatively coupled to the battery control module, and determining a corrected state of the battery module using the battery control module by minimizing a difference between the predicted terminal voltage and the measured terminal voltage. In other words, the corrected state of the battery (e.g., corrected state of charge) may be more accurately determined using the measurement model and the gassing current model. As such, this may provide more efficient use of energy.

Claims

1. A method, comprising:

predicting terminal voltage of a battery module in a vehicle using a battery control module, wherein predicting the terminal voltage comprises;

determining a gassing current of the battery module using a gassing current model, wherein the gassing current quantifies terminal current that is not used to charge the battery module; and

calculating the predicted terminal voltage based at least in part on a measurement model and the determined gassing current;

measuring terminal voltage of the battery module using a sensor communicatively coupled to the battery control module;

determining a corrected state of the battery module using the battery control module by minimizing error between the predicted terminal voltage and the measured terminal voltage; and

controlling operation of the vehicle using a vehicle control module based at least in part on the corrected state of the battery module, wherein the corrected state of the battery module comprises a state of charge of the battery module.

2. The method of claim 1, comprising predicting a state of the battery module using the battery control module based at least in part on a state space model, a corrected state of the battery module determined in a prior time step, and an operational parameter of the battery module determined in the prior time step, wherein the predicted terminal voltage is calculated based at least in part on the predicted state of the battery module.

3. The method of claim 2, comprising determining uncertainty of the predicted state of the battery module using the battery control module, wherein the corrected state of the battery module is determined based at least in part on the determined uncertainty of the predicted state of the battery module.

4. The method of claim 2, comprising determining a corrected uncertainty of the predicted state of the battery module, wherein the corrected uncertainty is used to determine uncertainty of a predicted state of the battery module in a subsequent time step.

5. The method of claim 1, wherein predicting the terminal voltage comprises:

measuring the terminal current using the sensor communicatively coupled to the battery control module; and

determining amount of current actually used to charge the battery module by subtracting the gassing current from the terminal current.

6. The method of claim 1, wherein the battery module is a lead-acid battery module and the gassing current model models a gassing reaction that takes place in the lead-acid battery module.

7. The method of claim 6, wherein the gassing reaction is dissociation of water into oxygen and hydrogen gas in an electrolyte of the lead-acid battery module.

8. The method of claim 1, comprising training the gassing current model by determining characteristic parameters and tuning parameters of the gassing current model offline from vehicle operation.

9. The method of claim 1, comprising determining a subsequent corrected state of the battery module based at least in part on the corrected state of the battery module.

10. A tangible, non-transitory, computer-readable medium storing a plurality of instructions executable by a processor of a battery control module in a vehicle, the instructions comprising instructions to:

predict terminal voltage of a battery module in the vehicle using the processor, wherein the instruction to predict the terminal voltage comprises instructions to;

determine a gassing current of the battery module using a gassing current model, wherein the gassing current quantifies terminal current that is not used to charge the battery module; and

calculate the predicted terminal voltage using a measurement model and the determined gassing current;

measure terminal voltage of the battery module using a sensor communicatively coupled to the battery control module;

determine a corrected state of the battery module using the processor by minimizing error between the predicted terminal voltage and the measured terminal voltage; and

communicate the corrected state of the battery module to a vehicle control module to enable the vehicle control module to control operation of the vehicle based at least in part on the corrected state of the battery module.

11. The tangible, non-transitory, computer-readable medium of claim 10, wherein the instructions comprise instructions to:

predict a state of the battery module using the processor based at least in part on a corrected state of the battery module determined in a prior time step and an operational parameter of the battery module determined in the prior time step, wherein the predicted terminal voltage is calculated based at least in part on the predicted state of the battery module; and

determine uncertainty of the predicted state of the battery module using the processor, wherein the corrected state of the battery module is determined based at least in part on the uncertainty of the predicted state of the battery module.

12. The tangible, non-transitory, computer-readable medium of claim 10, wherein the instructions to predict the terminal voltage comprise instructions to:

measure the terminal current using the sensor communicatively coupled to the battery control module; and

determine amount of current actually used to charge the battery module by subtracting the gassing current from the terminal current.

13. The tangible, non-transitory, computer-readable medium of claim 10, wherein the battery module is a lead-acid battery module and the gassing current model quantifies a gassing reaction that takes place in the lead-acid battery module.

14. A vehicle, comprising:

a battery module configured to supply electrical power to electrical systems in the vehicle;

a battery control module configured to recursively determine a corrected state of the battery module using a state space model and a measurement model that predicts an operational parameter of the battery module, wherein the measurement model comprises a gassing current model that enables the battery control module to determine amount of current that is actually used to charge the battery module; and

a vehicle control module configured to control operation of the vehicle based at least in part on the corrected state of the battery module.

15. The vehicle of claim 14, wherein the vehicle control module is configured to determine whether to disable an internal combustion engine in the vehicle when the vehicle is idling based at least in part on the corrected state of the battery module.

16. The vehicle of claim 14, wherein the vehicle control module is configured determine when to restart an internal combustion engine disabled during an auto-stop operation based at least in part on the corrected state of the battery module.

17. The vehicle of claim 14, wherein the vehicle control module is configured to determine when to charge the battery module based at least in part on the corrected state of the battery module.

18. The vehicle of claim 14, wherein the vehicle control module is configured to determine at what voltage to charge the battery module based at least in part on the corrected state of the battery module.

19. The vehicle of claim 14, wherein the corrected state of the battery module comprises a corrected state of charge of the battery module.

20. The vehicle of claim 14, wherein the gassing current model quantifies a gassing reaction that takes place in the battery module.

21. The vehicle of claim 20, wherein the battery module is a lead-acid battery module and the gassing reaction is dissociation of water into oxygen and hydrogen gas in an electrolyte of the battery module.

22. A vehicle, comprising:

a battery module configured to supply electrical power to electrical systems in the vehicle;

a battery control module configured to recursively determine a corrected state of the battery module using a state space model and a measurement model that predicts an operational parameter of the battery module, wherein the measurement model comprises a gassing current module that enables the battery control module to determine amount of current that is actually used to charge the battery module; and

an internal combustion engine configured to disable when the vehicle is stationary and to restart when propulsion is desired.

23. A method, comprising:

predicting terminal voltage of a battery module in a vehicle using a battery control module, wherein predicting the terminal voltage comprises;

determining a gassing current of the battery module using a gassing current model, wherein the gassing current quantifies terminal current that is not used to charge the battery module; and

calculating the predicted terminal voltage based at least in part on a measurement model and the determined gassing current;

measuring terminal voltage of the battery module using a sensor communicatively coupled to the battery control module;

predicting a state of the battery module using the battery control module based at least in part on a state space model, a corrected state of the battery module determined in a prior time step, and an operational parameter of the battery module determined in the prior time step, wherein the predicted terminal voltage is calculated based at least in part on the predicted state of the battery module;

periodically calibrating the state space model by fully charging the battery module; and

determining a corrected state of the battery module using the battery control module by minimizing error between the predicted terminal voltage and the measured terminal voltage.