Control device and method for discharging a rechargeable battery

Patent metadata

Field	Value
Publication number	US-11322967-B2
Application number	US-201616070918-A
Country	US
Kind code	B2
Filing date	Jan 29, 2016
Priority date	Jan 29, 2016
Publication date	May 3, 2022
Grant date	May 3, 2022

Abstract

A control device for controlling discharging of a rechargeable battery, the control device being configured to: determine the voltage of the battery during discharging of the battery, stop discharging, when the determined voltage falls below a first predetermined lower voltage limit, determine the voltage of the battery after stopping discharging, determine the voltage difference between the first predetermined lower voltage limit and the determined voltage of the battery after stopping discharging, and continue discharging, when the determined voltage difference exceeds a predetermined threshold. A corresponding method controls discharging of a rechargeable battery.

First claim

The invention claimed is:

1. A control device for controlling discharging of a rechargeable battery, the control device being configured to:
monitor:
a discharging device configured to discharge the battery;
a voltage sensor configured to measure a voltage of the battery, including during discharge of the battery;
a temperature sensor configured to determine a temperature of the battery; and
a state of charge sensor configured to measure a state of charge of the battery;

determine a state of charge of the battery based on the measurement of the state of charge sensor;
set a first predetermined lower voltage limit based on the state of charge and a degradation of the battery, such that the first predetermined lower voltage limit is set lower as the state of charge is higher, and lower as the degradation is lower;
cause the discharging device to start discharging the battery, after determining the first predetermined lower voltage limit;
determine a first voltage of the battery based on the measurement of the voltage sensor;
cause the discharging device to stop discharging, when the first voltage falls below the first predetermined lower voltage limit;
determine a second voltage of the battery based on the measurement of the voltage sensor after the discharging device stops discharging;
determine a voltage difference between the first predetermined lower voltage limit and the second voltage; and
cause the discharging device to continue discharging, when the determined voltage difference exceeds a predetermined threshold.

2. The control device according to claim 1 , further configured to, when the determined voltage difference exceeds the predetermined threshold:
replace the first predetermined lower voltage limit with a second predetermined lower voltage limit smaller than the first predetermined lower voltage limit;
cause the discharging device to restart discharging of the battery;
determine a third voltage of the battery based on the measurement of the voltage sensor during the restarted discharging of the battery; and
when the third voltage falls below the second predetermined lower voltage limit or a lower limit of a predetermined allowed state of charge range of the battery is reached, determine that the battery is fully discharged and reset the predetermined threshold.

3. The control device according to claim 1 , further configured to:
when the determined voltage difference does not exceed the predetermined threshold, determine that the battery is fully discharged and reset the predetermined threshold.

4. The control device according to claim 1 , further configured to determine the degradation of the battery based on a temperature / frequency distribution of the battery and a predetermined degradation rate of the battery.

5. The control device according to claim 1 , wherein
the determination of the degradation of the battery is based on the Arrhenius equation.

6. The control device according to claim 4 , further configured to determine the temperature/frequency distribution of the battery based on recording, for each temperature of the battery, how much time the battery had this temperature during its lifetime.

7. The control device according to claim 1 , further comprising:
the voltage sensor.

8. The control device according to claim 1 , further comprising:
the temperature sensor.

9. A battery pack comprising:
the control device according to claim 1 ; and
the battery.

10. A battery discharging system comprising:
the control device according to claim 1 ;
the battery; and
the discharging device.

11. A vehicle comprising:
an electric motor; and
the battery pack according to claim 9 .

12. A vehicle comprising:
an electric motor;
the control device according to claim 1 ; and
the battery.

13. A method of controlling discharging of a rechargeable battery, comprising the steps of:
providing a control device configured to monitor: a discharge device, a voltage sensor, a temperature sensor, and a state of charge sensor; and
using the control device:
determining a state of charge of the battery based on the measurement of the state of charge sensor;
setting a first predetermined lower voltage limit based on the state of charge and a degradation of the battery, such that the first predetermined lower voltage limit is set lower as the state of charge is higher, and lower as the degradation is lower;
causing the discharging device to start discharging the battery, after determining the first predetermined lower voltage limit;
determining a first voltage of the battery during discharging of the battery based on an output of the voltage sensor;
causing the discharging device to stop discharging, when the first voltage falls below the first predetermined lower voltage limit;
determining a second voltage of the battery after stopping discharging based on the output of the voltage sensor;
determining a voltage difference between the first predetermined lower voltage limit and the second voltage; and
causing the discharging device to continue discharging, when the determined voltage difference exceeds a predetermined threshold.

14. The method according to claim 13 , further comprising, using the control device, when the determined voltage difference exceeds the predetermined threshold:
replacing the first predetermined lower voltage limit by a second predetermined lower voltage limit smaller than the first predetermined lower voltage limit;
causing the discharging device to restart discharging of the battery;
determining a third voltage of the battery during discharging of the battery; and
when the third voltage falls below the second predetermined lower voltage limit or a lower limit of a predetermined allowed state of charge range of the battery is reached, determining that the battery is fully discharged and resetting the predetermined threshold.

15. The method according to claim 13 , further comprising:
when the determined voltage difference does not exceed the predetermined threshold, determining that the battery is fully discharged and resetting the predetermined threshold.

16. The method according to claim 13 , wherein the degradation of the battery is determined based on a temperature / frequency distribution of the battery and a predetermined degradation rate of the battery.

17. The method according to claim 13 , wherein the determination of the degradation of the battery is based on the Arrhenius equation.

18. The method according to claim 16 , wherein the temperature/frequency distribution of the battery is determined based on recording, for each temperature of the battery, how much time the battery had this temperature during its lifetime.

19. A control device for controlling discharging of a rechargeable battery, the control device being configured to:
determine a state of charge of the battery based on the measurement of a state of charge sensor;
set a first predetermined lower voltage limit based on the state of charge and a degradation of the battery, such that the first predetermined lower voltage limit is set lower as the state of charge is higher, and lower as the degradation is lower;
cause a discharging device to start discharging the battery, after determining the first predetermined lower voltage limit;
determine a first voltage of the battery during discharging of the battery;
stop discharging, when the determined voltage falls below the first predetermined lower voltage limit;
determine a second voltage of the battery after stopping discha

Assignees

• Toyota Motor Europe

Inventors

• Komiyama Keita
• Katoh Yuki

Classifications

• H02J7/825

  Detection of fully charged condition · CPC title

• H02J7/63

  against overdischarge · CPC title

• H02J7/61

  against overcharge · CPC title

• H02J7/663

  using battery or load disconnect circuits (H02J9/002 takes precedence) · CPC title

• H02J7/96

  in response to battery voltage · CPC title