Lithium ion battery heater systems and methods

Patent metadata

Field	Value
Publication number	US-9831534-B2
Application number	US-201414517206-A
Country	US
Kind code	B2
Filing date	Oct 17, 2014
Priority date	Oct 18, 2013
Publication date	Nov 28, 2017
Grant date	Nov 28, 2017

Abstract

A battery heater system for a battery used in cold weather operations and methods for using the battery heater system are described. Embodiments of the battery heater system may incorporate a heater switch with an indicator, a timer circuit, a controller, a voltage meter, a temperature transducer, and a heating element. In some methods of using the device, the battery powers the heating element for a fixed cycle time based on the time to discharge the battery at a cold-soaked temperature. In other methods of using the device, the battery powers the heating element for a varying cycle time as necessary to discharge the battery to a discharge cut-off voltage value. In other methods of using the device, the heating element is operated using a duty cycle that is varied based on the battery temperature.

First claim

What is claimed is:

1. A method for operating an electrical heater provided in a battery case to heat an electrochemical cell disposed in the battery case, the method comprising the steps of:
determining a power-on time period;
determining a power-off time period;
discharging the electrochemical cell through the electrical heater for the power-on time period; and
disconnecting the electrochemical cell from the electrical heater for the power-off time period,
wherein the step of determining a power-on time period further comprises:
measuring a voltage of the electrochemical cell with a voltage meter;
discharging the electrochemical cell through the electrical heater until the voltage of the electrochemical cell drops to a discharge cut-off voltage; and
measuring the time period elapsed during the step of discharging until the voltage of the electrochemical cell drops to the discharge cut-off voltage.

2. The method of claim 1 wherein the step of determining a power-off time period further comprises the steps of:
disconnecting the electrochemical cell from the electrical heater when the voltage of the electrochemical cell drops to the discharge cut-off voltage;
measuring the time period elapsed until the voltage of the electrochemical cell recovers to an open circuit voltage of the battery cell.

3. The method of claim 2 wherein the step of determining a power-on time period and the step of determining a power-off time period are executed when the temperature of the electrochemical cell is a selected temperature.

4. The method of claim 3 wherein the step of determining a power-on time period and the step of determining a power-off time period are executed on a test article of the battery.

5. The method of claim 2 wherein the step of determining a power-on time period and the step of determining a power-off time period are executed on the battery.

6. The method of claim 1 further comprising the step of sequentially repeating the steps of discharging and disconnecting until the temperature of the electrochemical cell is at or above a target temperature.

7. The method of claim 1 wherein the discharge cut-off voltage is selected to prevent damage to the electrochemical cell.

8. The method of claim 6 wherein the target temperature is greater than the melting point of an electrolyte utilized in the electrochemical cell.

9. An automated method for operating an electrical heater by a controller, the electrical heater being provided in a battery case to heat an electrochemical cell disposed in the battery case, the method comprising the steps of:
selecting a duty cycle comprising a percentage of a unit of time having an initial value;
repeatedly discharging the electrochemical cell through the electrical heater for the duty cycle percentage of each unit of time;
monitoring the temperature of the electrochemical cell;
increasing the percentage of the duty cycle to a first value when the temperature of the electrochemical cell exceeds a first threshold temperature;
increasing the percentage of the duty cycle to a second value when the temperature of the electrochemical cell exceeds a second threshold temperature, wherein the second value for the duty cycle is greater than the first value for the duty cycle; and
reducing the percentage of the duty cycle when the temperature of the electrochemical cell exceeds a final threshold temperature, wherein the second threshold temperature is greater than the first threshold temperature and less than the final threshold temperature.

10. The method of claim 9 wherein the step of reducing the percentage of the duty cycle comprises the step of reducing the percentage of the duty cycle by a first incremental value each time the temperature of the electrochemical cell increases by a second incremental value.

11. The method of claim 10 wherein the first incremental value is 10% and the second incremental value is 1 degree C.

12. The method of claim 9 wherein the second threshold temperature is equal to or greater than the melting temperature of the electrolyte in the electrochemical cell.

13. The method of claim 9 wherein the step of selecting a duty cycle comprises the steps of:
determining a power-on time period;
determining a power-off time period; and
calculating the percentage of the duty cycle as the ratio of the power-on time period to the sum of the power-on time period and the power-off time period.

14. The method of claim 13 wherein the step of determining a power-on time period comprises the steps of:
discharging the electrochemical cell through the electrical heater until the voltage of the electrochemical cell drops to a discharge cut-off voltage; and
measuring the time period elapsed during the step of discharging until the voltage of the electrochemical cell drops to the discharge cut-off voltage.

15. The method of claim 14 wherein the step of determining a power-off time period comprises the steps of:
disconnecting the electrochemical cell from the electrical heater when the voltage of the electrochemical cell drops to the discharge cut-off voltage; and
measuring the time period elapsed until the voltage of the electrochemical cell recovers to an open circuit voltage of the electrochemical cell.

16. The method of claim 14 wherein the step of determining a power-on time period and the step of determining a power-off time period are executed when the temperature of the electrochemical cell is a selected temperature.

17. The method of claim 14 wherein the step of determining a power-on time period and the step of determining a power-off time period are executed on a test article of the battery.

18. The method of claim 9 wherein the first threshold temperature or the second threshold temperature is greater than or equal to the melting point of the electrolyte in the electrochemical cell.

19. The method of claim 9 wherein the percentage of the duty cycle is selected based on the temperature of the electrochemical cell to prevent damaging the electrochemical cell.

20. An automated method for heating a battery, the method being performed by a controller, comprising:
measuring a voltage and a temperature of an electrochemical cell of the battery;
discharging the electrochemical cell through an electrical heater until the voltage of the electrochemical cell drops to a discharge cut-off voltage;
disconnecting the electrochemical cell from the electrical heater until the voltage of the electrochemical cell recovers to an open circuit voltage of the battery cell; and
repeating the steps of measuring, discharging, and disconnecting until the temperature of the electrochemical cell reaches a target temperature.

21. An automated heating method for a battery, the method being performed by a controller, comprising:
measuring a temperature of the battery;
operating a heating element according to a duty cycle to heat the battery using power from an electrochemical cell of the battery;
increasing the percentage of the duty cycle to a first value when the temperature of the electrochemical cell exceeds a first threshold temperature;
increasing the percentage of the duty cycle to a second value when the temperature of the electrochemical cell exceeds a second threshold temperature, which is greater than the first threshold temperature; and
reducing the percentage of the duty cycle when the temperature of the electrochemical cell exceeds a third threshold temperature, which is greater than the second threshold temperature.

Assignees

• Textron Innovations Inc
• Textron Innovations Inc

Inventors

• Beuning Charles Bernard
• Chang Vernon Weng-Yew

Classifications

• H01M10/657

  by electric or electromagnetic means · CPC title

• H01M10/633

  characterised by algorithms, flow charts, software details or the like · CPC title

• H01M2220/30

  Batteries in portable systems, e.g. mobile phone, laptop · CPC title

• H01M10/615

  Heating or keeping warm · CPC title

• H01M2220/20

  Batteries in motive systems, e.g. vehicle, ship, plane · CPC title