Current leakage detection in high voltage battery pack

• US 20040004481A1
• Filed: 05/28/2003
• Published: 01/08/2004
• Est. Priority Date: 05/28/2002
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Jin, Jizeng
• Granted Patent: US 6,998,819 B2
• Time in Patent Office: Days
• US Class Current: 324/444
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 6/42 Grouping of primary cells into batteries H01M6/40 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A method of detecting leakage currents in a high voltage battery pack system reduces detection error caused by fluctuations in battery pack voltage during the detection process. The voltages of the individual modules forming the battery pack are separately and simultaneously measured during each measurement of leakage current on the high and low sides of the leakage point. Measurements of individual module voltages are combined with the simultaneous current leakage measurements to calculate leak resistance.

Claims

1. A method of detecting a current leakage path in a high voltage battery pack having a plurality of serially connected battery modules, comprising:

(A) connecting a first set of said modules into a first circuit containing a voltage measurement resistor;

(B) connecting a second set of said modules into a second circuit containing said measurement resistor;

(C) while said first set of modules is connected in said first circuit, simultaneously determining the voltage of each of the modules, and a first current flowing through said first circuit, and measuring a first voltage across said measurement resistor;

(D) while said second set of modules is connected in said second circuit, simultaneously determining the voltage of each of the modules, and a second current flowing through said second circuit, and measuring a second voltage across said measurement resistor; and

,

(E) determining a leakage path resistance associated with said leakage path using the first and second currents, the determined voltages of the second set of modules, and the first and second measured voltages.

2. The method of claim 1, wherein steps (C) and (D) are respectively performed at first and second points in time.

3. The method of claim 1, wherein step (E) includes preparing a pair of lookup tables providing comparative data including the leakage resistance at each of a plurality of connection points to said modules representing potential current leakage paths.

4. The method of claim 3, wherein step (E) includes determining the connection point at which the leakage resistance is the same value in each of the tables.

5. The method of claim 3, wherein:

one of said lookup tables includes, for each of said connection points, a calculated leakage resistance R_L and an associated voltage representing the sum of the voltages of the first set of modules,

the other of said lookup tables includes, for each of said connection points, a calculated leakage resistance R_L and an associated voltage representing the sum of the voltages of the second set of modules.

6. The method of claim 1, including the step of calculating the voltages V₁(t_low) and V₂(t_high) respectively across the first and second sets of modules while steps (C) and (D) are performed, according to the following formulas:

V₁(t_low)=k×

V_p(t_low) V₂(t_high)=(1−

k)×

V_p(t_high)

where, V_p is the total battery pack voltage, and k is a calculated value relating changes in V_p to changes in the voltage of each of the modules.

7. A method of determining the leakage resistance R_L of a connection between a first and second sets of series connected battery modules, V_mx−

V_mn and V_m1−

V_mx respectively, forming a high voltage, rechargeable battery pack, comprising;

(A) switching said first set of modules V_mx−

V_mn into a first circuit containing a voltage measurement resistor;

(B) switching said second set of modules V_m1−

V_mx into a second circuit containing said measurement resistor;

(C) while said first set of modules V_mx−

V_mn is connected in said first circuit, determining the voltage V₁ produced by said first set of modules V_mx−

V_mn, the current I₁ flowing through said first circuit, and the voltage V_a2d1, across said measurement resistor;

(D) while said second set of modules V_m1−

V_mx is connected in said second circuit, simultaneously determining the voltage V₂ produced by said second set of modules V_m1−

V_mx, the current I₂ flowing through said second circuit, and the voltage V_a2d2 across said measurement resistor;

(E) compensating for any changes in the voltages of modules V_mx−

V_mn, V_m1−

V_mx occurring between steps (C) and (D); and

,

(E) determining said leakage path resistance R_L using the determined currents I_1, I_2, voltages V₁, V₂ and measured voltages V_a2d1 and V_a2d2.

8. The method of claim 7, wherein the voltages V₁ and V₂ are determined, using the following formulas:

V₁(t_low)=k×

V_p(t_low) V₂(t_high)=(1−

k)×

V_p(t_high)

where V_p is the voltage of said battery pack, and

k is a calculated value relating changes in the voltage V_p of said battery pack to changes in the voltage of each of said modules.

9. The method of claim 8, wherein steps (C) and (D) each include measuring the voltage V_p of said battery pack.

10. The method of claim 7, wherein:

step (C) includes simultaneously determining the voltage of each of the modules V_m1−

V_mx, and

Step (D) includes simultaneously determining the voltage of each of the modules V_m1−

V_mx.

11. The method of claim 7, wherein steps (C) and (D) are respectively performed at first and second points in time.

12. The method of claim 7, wherein step (E) includes preparing a pair of lookup tables providing comparative data including the leakage resistance at each of a plurality of connection points to said modules representing potential current leakage paths.

13. The method of claim 12, wherein step (E) includes determining the connection point at which the leakage resistance is the same value in each of the tables.

14. The method of claim 12, wherein:

one of said lookup tables includes, for each of said connection points, a calculated leakage resistance R_L and an associated voltage representing the sum of the voltages of modules V_mx−

V_mn,

the other of said lookup tables includes, for each of said connection points, a calculated leakage resistance R_L and an associated voltage representing the sum of the voltages of modules V_m1−

V_mx.