End-of-discharge control apparatus for a battery of rechargeable electrochemical cells

• US 20030235754A1
• Filed: 01/22/2003
• Published: 12/25/2003
• Est. Priority Date: 01/31/2002
• Status: Active Grant

• Current Assignee: Arts Energy Co.
• Original Assignee: Alcatel SA (Nokia Corporation)
• Inventors: Maloizel, Serge
• Granted Patent: US 7,018,731 B2
• Time in Patent Office: Days
• US Class Current: 429/61
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery assembly (E) comprises firstly a battery (B) having at least one module (1-i) constituted by at least two secondary electrochemical cells (2-j) connected in series, and secondly control apparatus comprising control means (4) for acting at the end of charging the battery (B) to determine the number of cells (1-i) that are in working condition in each module (2-j) and then for determining a threshold voltage value for each module (1-i) as a function of said number, and finally for acting at the end of discharge of the battery (B) to compare an end-of-discharge voltage measured across the terminals of each module (1-i) with the corresponding threshold voltage as previously determined so as to interrupt operation of the battery (B) when at least one measured end-of-discharge voltage (VFD-i) is less than the corresponding value determined for the threshold voltage.

Claims

1. Apparatus for controlling the end of discharge of a battery (B), the battery comprising at least one module (1-i) made up of at least two secondary electrochemical cells (2-j) connected in series, said apparatus comprising control means (4) arranged to act at the end of discharge of said battery (B) to compare an end-of-discharge voltage (VFD-i) measured across the terminals of each module (1-i) with a module threshold voltage value (TS1-i) so as to interrupt operation of said battery when at least one measured end-of-discharge voltage (VFD-i) is less than said module threshold voltage value (TS1-i), wherein said control means (4) are arranged, at the end of charging said battery (B), to determine the number of cells (1-i) that are in working condition in each module (2-j), and then to determine each module threshold voltage value (TS1-i) for use in performing said comparison as a function of said number of cells (2-j) in working condition.

2. / Apparatus according to claim 1, in which said control means (4) are arranged to determine each module threshold voltage value (TS1-i) used for performing said comparison as a function of said number of cells (2-j) in working condition and of a cell threshold voltage (TS2).

3. / Apparatus according to claim 1, including electrical measurement means (3) arranged to measure said end-of-discharge voltages (VFD-i) and end-of-charging voltages (VFC-i) across the terminals of each of said modules (1-i), and in which said control means (4) are arranged to determine said number of cells (2-j) in working condition within each of said modules (1-i) from the end-of-charging voltage (VFC-i) measured at their terminals.

4. / Apparatus according to claim 3, in which said control means (4) are arranged to determine said number of cells (2-j) in working condition within each of said modules (1-i) from the end-of-charging voltage (VFC-i) measured at their terminals and from a nominal voltage value (VG) corresponding to the end-of-charging voltage across the terminals of a cell (2-j).

5. / Apparatus according to claim 3, in which said electrical measurement means (3) are arranged to act at the end of discharge to measure said voltages (VFD-i) across the terminals of each of said modules (1-i) while said battery (B) is presenting substantially zero current.

6. / Apparatus according to claim 1, including temperature measurement means (5) arranged to determine the temperature (Ti) of each module (1-i), wherein said control means (4) are arranged to determine said number of cells (2-j) in working condition within each of said modules (1-i) from said end-of-charging voltage (VFC-i) measured at their terminals and from said nominal voltage value associated with said cell (VG) as corrected by a first correction factor which is a function of said measured temperature (Ti) of said module (1-i).

7. / Apparatus according to claim 6, in which said control means (4) are arranged to correct said impedance value (R) of a cell (2-j) of a module (1-i) by at least a third correction factor which is a function of said module temperature (Ti).

8. / Apparatus according to claim 2, including current measurement means (7, 8) arranged to determine the discharge current (I) of said battery (B), wherein said control means (4) are arranged to determine each module threshold voltage value (TS1-i) as a function of said number of cells (2-j) in working condition within said module (1-i) and of said cell threshold voltage (TS2) of said module (1-i) as corrected by a second correction factor which is a function of said discharge current (I) and of the impedance value (R) of said cell (2-j).

9. / Apparatus according to claim 8, in which said control means (4) are arranged to correct said impedance value (R) of a cell (2-j) of a module (1-i) with at least a third correction factor which is a function of said module temperature (Ti). means (4) are arranged to correct said cell threshold voltage (TS2) of a module (1-i) with at least a fourth correction factor which is a function of said module temperature (Ti).

11. / Apparatus according to claim 8, in which said control means (4) are arranged to determine said impedance value (R) of a cell (2-j) of a module (1-i) as a function firstly of a variation in the voltage (V2−

V1) across the terminals of said module over a selected time interval (t2−

t1), and of a variation in the current (I2−

I1) through said battery (B) in said time interval (t2−

t1).

12. / Apparatus according to claim 1, including a memory (9) suitable for storing said nominal values and certain nominal parameters of cells involved in each of said correction factors.

13. / Apparatus according to claim 12, in which said memory (9) is suitable for storing at least some of the determined values.

14. / Apparatus according to claim 1, including a communications interface (11) coupled with said control means (4).

15. / Apparatus according to claim 1, including a switch (6) arranged to allow or prevent current to flow through said battery (B) as a function of instructions received from said control means (4).

16. / Apparatus according to claim 1, including detector means (10) arranged to detect the presence of an external system connected to the terminals of said battery (B).

17. / Apparatus according to claim 16, in which said system is selected from a group comprising:

a battery charger; and

apparatus constituting a load.

18. / A battery assembly (E) comprising at least one battery (B) together with control apparatus according to claim 1.

19. / A battery assembly according to claim 18, in which each secondary electrochemical cell (2-j) is selected from a group comprising:

at least alkaline cells, and in particular nickel/metal hydride (Ni/MH) cells and nickel/cadmium (Ni/Cd) cells; and

lithium cells, and in particular lithium/ion (Li/ion) cells.