Battery management system and driving method thereof

• US 7,684,942 B2
• Filed: 09/06/2007
• Issued: 03/23/2010
• Est. Priority Date: 11/01/2006
• Status: Active Grant

• Current Assignee: Samsung SDI Company Limited
• Original Assignee: Samsung SDI Company Limited
• Inventors: Choi, Soo-Seok, Park, Ho-Young, Lee, Young-Jo, Kim, Beom-Gyu, Seo, Se-Wook, Lim, Gye-Jong, Yun, Han-Seok, Tae, Yong-Jun
• Primary Examiner(s): Raymond; Edward
• Application Number:
  US11/851,032
• Publication Number:
  US 20080103709A1
• Time in Patent Office: 929 Days
• Field of Search: 702/63, 702/64, 702182-185, 702/188
• US Class Current: 702/63
• CPC Class Codes: G01R 31/006 on road vehicles, e.g. automobiles or trucks testing of ignition installations peculiar to internal combustion engines F02P17/00
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: H01M 10/486 for measuring temperature
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery management system and a driving method thereof includes a sensing unit and a micro control unit (MCU). The sensing unit measures a battery temperature and a battery current. The MCU receives the battery temperature and current, detects battery internal resistance corresponding to an estimated state of charge (SOC) and the battery temperature when the estimated SOC is included within an SOC area corresponding to the transmitted battery temperature, and estimates a battery state of health (SOH) by using the battery internal resistance. In the SOC area, a variation of the battery internal resistance is minimized.

Claims

1. A battery management system to manage a battery, comprising:

a sensing unit to measure a battery temperature and a battery current; and

a main control unit (MCU) to estimate a state of charge (SOC) based on the battery current;

to calculate a battery internal resistance corresponding to the estimated (SOC) and the battery temperatures, only when the estimated SOC is determined to be within an SOC area; and

to estimate a battery state of health (SOH) using the battery internal resistance.

2. The battery management system of claim 1, wherein the SOC area corresponds to an SOC range of from 40% to 60%.

3. The battery management system of claim 2, wherein the MCU uses:

$I=\frac{\mathrm{Vocv}-\mathrm{Vcutoff}}{\mathrm{Rb}}$

to calculate a maximum discharge current of the battery;

uses P=I×

Vcutoff to calculate a battery power value; and

uses the calculated maximum discharge current and the battery power value to estimate the battery SOH,

wherein I denotes the maximum discharge current, Vocv denotes an open circuit voltage of the battery in a key-on state, Vcutoff denotes a permissible low battery voltage, Rb denotes the battery internal resistance, and P denotes the battery power value.

4. The battery management system of claim 3, wherein:

the MCU determines that the battery SOH is included within a normal range, when a ratio of the battery power value P to a fresh battery power value is greater than a first threshold value; and

determines that the battery is depleted when the ratio of the battery power value P to the fresh battery power value is lower than the first threshold value.

5. The battery management system of claim 4, wherein:

the MCU determines that the battery SOH is included within the normal range, when a ratio of the battery power value P to a previous battery power value is greater than a second threshold value; and

determines that the battery is depleted, when the ratio of the battery power value P to the previous battery power value is lower than the second threshold value.

6. A driving method of a battery management system which manages a battery, the driving method comprising:

determining whether an estimated state of charge (SOC) of the battery is included within an SOC area corresponding to a temperature of the battery;

calculating a battery internal resistance corresponding to the estimated SOC and the battery temperature, only when the estimated SOC is determined to be within the SOC area; and

determining a battery state of health (SOH) based on the battery internal resistance.

7. The driving method of claim 6, wherein the SOC area corresponds to an SOC range of from 40% to 60%.

8. The driving method of claim 7, wherein the determining of the battery SOH comprises:

calculating a maximum discharge current of the battery by using;

$I=\frac{\mathrm{Vocv}-\mathrm{Vcutoff}}{\mathrm{Rb}};<br><br>$

 

and

calculating a battery power value by using;

P=I×

Vcutoff,

wherein I denotes the maximum discharge current, Vocv denotes an open circuit voltage of the battery in a key-on state, Vcutoff denotes a permissible low battery voltage, Rb denotes the battery internal resistance, and P denotes the battery power value.

9. The driving method of claim 6, wherein the determining of the battery SOH comprises:

determining that the battery SOH is included within a normal range, when a ratio of a battery power value to a fresh battery power value is greater than a first threshold value; and

determining that the battery is depleted, when the ratio of the battery power value to the fresh battery power value is lower than the first threshold value.

10. The driving method of claim 6, wherein the determining of the battery SOH comprises:

determining that the battery SOH is included within a normal range when a ratio of a battery power value to a previous battery power value is greater than a second threshold value; and

determining that the battery is depleted when the ratio of the battery power value to the previous battery power value is lower than the second threshold value.

11. A battery management system to manage a battery, comprising:

a sensing unit to measure a battery current; and

a main control unit (MCU) to estimate a state of charge (SOC) of the battery, based on the battery current, and to calculate an internal resistance of the battery, only when the estimated SOC is within an SOC range of 40% and 60%.

12. The battery management system of claim 11, wherein the sensing unit further measures a temperature of the battery.

13. The battery management system of claim 12, wherein the MCU calculates the battery internal resistance matching the estimated SOC for the battery temperature to a battery internal resistance.

14. The battery management system of claim 13, wherein the MCU calculates a maximum discharge current of the battery using:

$I=\frac{\mathrm{Vocv}-\mathrm{Vcutoff}}{\mathrm{Rb}},$

calculates a battery power value using;

P=I×

Vcutoff, and

uses the maximum discharge current and the battery power value to estimate a battery state of health (SOH),

wherein I denotes the maximum discharge current, Vocv denotes an open circuit voltage of the battery in a key-on state, Vcutoff denotes a permissible low battery voltage, Rb denotes the battery internal resistance, and P denotes the battery power value.

15. The battery management system of claim 14, wherein:

the MCU determines that the battery SOH is included within a normal range, when a ratio of the battery power value P to a fresh battery power value is greater than a first threshold value; and

determines that the battery is depleted, when the ratio of the battery power value P to the fresh battery power value is lower than the first threshold value.

16. The battery management system of claim 14, wherein:

the MCU determines that the battery SOH is included within the normal range, when a ratio of the battery power value P to a previous battery power value is greater than a second threshold value; and

determines that the battery is depleted, when the ratio of the battery power value P to the previous battery power value is lower than the second threshold value.

17. A driving method of a battery management system which manages a battery, the driving method comprising:

measuring a current of the battery;

estimating a state of charge (SOC) of the battery, based on the current; and

calculating an internal resistance of the battery according to the estimated SOC and a temperature of the battery, only when the estimated SOC is within an SOC range.