Method of Controlling a State-of-Charge (SOC) of a Vehicle Battery

• US 20120200257A1
• Filed: 02/04/2011
• Published: 08/09/2012
• Est. Priority Date: 02/04/2011
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Schwarz, Jonathan R., Smith, Gregory E., Hanna, Ian L., Frisch, Damon R.
• Granted Patent: US 8,937,452 B2
• Time in Patent Office: Days
• US Class Current: 320/109
• CPC Class Codes: H01M 10/42 Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells H01M10/60 takes precedence
• CPC Class Codes: H01M 10/486 for measuring temperature
• CPC Class Codes: H01M 2200/10 Temperature sensitive devices
• 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

Abstract

A system and method for controlling a state-of-charge (SOC) of a vehicle battery, such as a high-voltage battery used by a hybrid electric vehicle (HEV) for vehicle propulsion, so that the SOC is maintained within a desired SOC range that is temperature-dependent. In an exemplary embodiment, the system and method use a battery temperature prediction to determine a desired SOC range, and then control the amount of charge on the vehicle battery such that the SOC is maintained within the desired SOC range. As the battery temperature prediction goes lower (i.e., as it gets colder), the desired SOC range may need to be adjusted or shifted upwards in order to account for increased internal battery resistance and to ensure that the vehicle battery has enough power to start the vehicle. Similarly, as the battery temperature prediction goes higher (i.e., as it gets warmer), the desired SOC range may need to be adjusted or shifted downwards in order to reduce degradation effects and improve battery. The exemplary system and method control the SOC of the vehicle battery and may seek to optimize a number of different parameters, including battery life, battery performance and/or vehicle fuel economy.

Claims

1. A method of controlling a state-of-charge (SOC) of a vehicle battery, comprising the steps of:

(a) generating a battery temperature prediction for the vehicle battery;

(b) using the battery temperature prediction to determine a desired SOC range for the vehicle battery that includes an upper SOC limit, a lower SOC limit, or both, wherein the desired SOC range is at least somewhat temperature dependent; and

(c) controlling the amount of charge on the vehicle battery so that the SOC of the vehicle battery is generally maintained within the desired SOC range.

2. The method of claim 1, wherein step (a) further comprises generating the battery temperature prediction by receiving an actual outside temperature from a first sensor and an actual battery temperature from a second sensor, and setting the battery temperature prediction to the lower of the actual outside temperature and the actual battery temperature.

3. The method of claim 1, wherein step (a) further comprises generating the battery temperature prediction by using at least one piece of historical data selected from the group consisting of:

past outside temperatures or past battery temperatures.

4. The method of claim 1, wherein step (a) further comprises generating the battery temperature prediction by receiving a forecasted outside temperature from a telematics that receives it from a weather-related service.

5. The method of claim 1, wherein step (b) further comprises comparing the battery temperature prediction to a first temperature threshold, if the battery temperature prediction is greater than the first temperature threshold then using a first SOC region to determine the desired SOC range, and if the battery temperature prediction is less than the first temperature threshold then using a second SOC region to determine the desired SOC range.

6. The method of claim 5, wherein the first SOC region has an upper SOC limit and a lower SOC limit that are generally constant over a temperature range, and the first SOC region generally has upper and lower SOC limits that are lower than those of the second SOC region.

7. The method of claim 5, wherein the second SOC region is a transition region and has an upper SOC limit and a lower SOC limit that generally vary over a temperature range, and the second SOC region generally has upper and lower SOC limits that are higher than those of the first SOC region.

8. The method of claim 5, wherein the first temperature threshold is between −

15°

C. and −

25°

C., inclusive.

9. The method of claim 5, wherein step (b) further comprises comparing the battery temperature prediction to a second temperature threshold, if the battery temperature prediction is greater than the second temperature threshold then using the second SOC region to determine the desired SOC range, and if the battery temperature prediction is less than the second temperature threshold then using a third SOC region to determine the desired SOC range.

10. The method of claim 9, wherein the third SOC region has an upper SOC limit and a lower SOC limit that are generally constant over a temperature range, and the third SOC region generally has upper and lower SOC limits that are higher than those of the first and second SOC regions.

11. The method of claim 9, wherein the third SOC region has an upper SOC limit that generally varies over a temperature range, and a lower SOC limit that is generally constant over a temperature range.

12. The method of claim 9, wherein the second temperature threshold is between −

20°

C. and −

30°

C., inclusive.

13. The method of claim 1, wherein step (b) further comprises using the battery temperature prediction to select between a plurality of SOC regions, wherein at least one of the SOC regions includes an upper SOC limit or a lower SOC limit that varies according to temperature.

14. A method of controlling a state-of-charge (SOC) of a vehicle battery, comprising the steps of:

(a) determining a battery temperature for the vehicle battery;

(b) comparing the battery temperature to a temperature threshold;

(c) if the battery temperature is less than the temperature threshold, then adjusting a desired SOC range for the vehicle battery by increasing an upper SOC limit, a lower SOC limit, or both; and

(d) controlling the amount of charge on the vehicle battery so that the SOC of the vehicle battery is generally maintained within the desired SOC range.

15. The method of claim 14, wherein step (a) further comprises determining a battery temperature for the vehicle battery by generating a battery temperature prediction.

16. The method of claim 14, wherein the desired SOC range is in a transition region and has an upper SOC limit and a lower SOC limit that generally vary over a temperature range.

17. The method of claim 14, further comprising the step of:

comparing the battery temperature to a second temperature threshold, if the battery temperature is greater than the second temperature threshold then using a second SOC region to determine the desired SOC range, and if the battery temperature is less than the second temperature threshold then using a third SOC region to determine the desired SOC range.

18. The method of claim 14, wherein step (c) further comprises using the battery temperature to select between a plurality of SOC regions, wherein at least one of the SOC regions includes an upper SOC limit or a lower SOC limit that varies according to temperature.

19. A battery control system for use in a vehicle, comprising:

a high-voltage vehicle battery;

a battery control module;

at least one temperature sensor being coupled to the battery control module and providing the battery control module with a battery temperature reading; and

a battery charging device, a battery discharging device, or both being coupled to the battery control module and being capable of influencing a state-of-charge (SOC) of the vehicle battery;

wherein the battery control module determines a desired SOC range based at least partially on the battery temperature reading, and the battery control module controls the battery charging device, the battery discharging device, or both such that the vehicle battery is generally maintained within the desired SOC range.