Method and apparatus for determining the available of energy of a lithium ion battery

• US 20050269993A1
• Filed: 06/04/2004
• Published: 12/08/2005
• Est. Priority Date: 06/04/2004
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Palanisamy, Thirumalai G., Singh, Harmohan N., Hoenig, Steven, Atehortua, Hector M.
• Granted Patent: US 7,248,022 B2
• Time in Patent Office: Days
• US Class Current: 320/149
• CPC Class Codes: G01R 31/382 Arrangements for monitoring battery or accumulator variables, e.g. SoC
• CPC Class Codes: G01R 31/387 Determining ampere-hour charge capacity or SoC

Abstract

In accordance with various embodiments, there is a method for determining the available energy of a battery. Various embodiments include the steps of applying an increasing current to the battery and measuring a response voltage of the battery when the increasing current is applied to the battery.

Claims

1. A method for determining an available energy of a battery comprising:

applying an increasing current ramp to a battery;

measuring a battery terminal voltage of the battery when the increasing current is applied to the battery and when the battery terminal voltage reaches a predetermined voltage greater than an open circuit voltage; and

determining the available amount of energy in the battery based on the applied current when the battery terminal voltage reaches the predetermined voltage greater than an open circuit voltage, wherein the available energy of the battery is proportional to the current when the battery terminal voltage reaches the predetermined voltage greater than the open circuit voltage.

2. A method for determining the available energy of a battery according to claim 1, wherein the increasing current is applied linearly.

3. A method for determining the available energy of a battery according to claim 1, wherein the battery is a lithium ion battery.

4. A method for determining the available energy of a battery according to claim 1 further comprising:

maintaining a constant voltage difference between a limit voltage and the open circuit voltage.

5. A method for determining the available energy of a battery according to claim 1 further comprising:

depolarizing the battery prior to applying the increasing current.

6. A method for determining the available energy of a battery according to claim 1, wherein the current is increased until the battery terminal voltage reaches 50 mV above the open circuit voltage.

7. A method for determining the available energy of a battery according to claim 1, wherein the battery has at least two cells and wherein the current is increased until the battery terminal voltage reaches 50 mV times the number of cells in the battery above the open circuit voltage.

8. A method for determining an available energy of a battery comprising:

applying a current ramp of a predetermined slope to a battery;

measuring a battery terminal voltage while applying the current ramp;

increasing the current ramp until the battery terminal voltage reaches a predetermined value greater than an open circuit voltage of the battery at a prevailing state-of-charge of the battery;

determining the amount of energy stored in the battery based on a current in the current ramp where the battery terminal voltage reaches the predetermined voltage greater than the open circuit voltage.

9. A method for determining the available energy of a battery according to claim 8 further comprising:

depolarizing the battery prior to a step of measuring the battery terminal voltage while applying the current ramp.

10. A method for determining the available energy of a battery according to claim 8, wherein the current is increased until the battery terminal voltage is greater than the open circuit voltage by 50 mV above the open circuit voltage.

11. A method for determining the available energy of a battery according to claim 8, wherein the battery has at least two cells and wherein the current is increased until the battery terminal voltage is greater than the open circuit voltage by 50 mV times the number of cells above the open circuit voltage.

12. A method for determining the available energy of a battery according to claim 8, wherein a basis for determining the available energy of the battery is linearly proportional to the current in the current ramp where the battery terminal voltage reaches the predetermined voltage greater than the open circuit voltage.

13. An available energy of a battery measuring apparatus comprising:

a control module comprising an analog-to-digital converter, a digital-to-analog converter, and an electronics control system;

a power supply that supplies an increasing current ramp of a predetermined slope to a battery until a voltage of the battery reaches a predetermined value greater than an open circuit voltage of the battery at a prevailing state-of-charge of the battery;

a current sensor disposed in series between the power supply and the battery to measure a current passing from the battery;

a sensor electrically connected to the battery to measure the battery terminal voltage; and

a processor that determines the available energy of the battery based on the current when the voltage to the battery reaches the predetermined voltage greater than the open circuit voltage.

14. An available energy of a battery measuring apparatus according to claim 13, wherein the predetermined value is 50 mV greater than the open circuit voltage of the battery at the prevailing state of charge of the battery.

15. An available energy of a battery measuring apparatus according to claim 13, wherein the battery has at least two cells and wherein the current is increased until the battery terminal voltage is greater than the open circuit voltage by 50 mV times the number of cells at the prevailing state of charge of the battery.

16. An available energy of a battery measuring apparatus according to claim 13 further comprising:

a battery terminal voltage sensor in series between the power supply and the battery to measure the battery terminal voltage.

17. A computer readable medium containing program code that configures a processor to perform a method for determining the available energy of a battery, said program code comprising:

program code for applying an increasing current to a battery;

program code for measuring a response voltage of the battery when the increasing current is applied to the battery;

program code for determining an available amount of energy in the battery, wherein the available amount of energy in the battery is proportional to the current applied to the battery when the voltage of the battery reaches a predetermined voltage greater than an open circuit voltage of the battery.