Overdischarge preventing circuit apparatus for a nonawueous electrolyte secondary battery, overdischarge preventing circuit apparatus for a battery pack, secondary battery overdischarge preventing method and overdischarge preventing method for a battery pack

• US 7,253,588 B2
• Filed: 08/29/2003
• Issued: 08/07/2007
• Est. Priority Date: 08/30/2002
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kishi, Takashi, Satoh, Yuji, Kanda, Motoya
• Primary Examiner(s): Tso; Edward H.
• Application Number:
  US10/650,769
• Publication Number:
  US 20050237686A1
• Time in Patent Office: 1,439 Days
• Field of Search: 320/134, 320/136, 320/150, 320/153
• US Class Current: 320/136
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• CPC Class Codes: H01M 10/443 in response to temperature
• CPC Class Codes: H01M 10/486 for measuring temperature
• CPC Class Codes: H01M 50/103 prismatic or rectangular H01M50/109, H01M50/11 take precedence
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

An overdischarge preventing circuit apparatus according to this invention is an overdischarge preventing circuit apparatus for a nonaqueous electrolyte secondary battery, including a discharge control mechanism which controls discharge of the nonaqueous electrolyte secondary battery when a surface temperature of the nonaqueous electrolyte secondary battery exceeds a discharge control temperature T₁ (° C.) represented by
T₁=T₀+QA   (1)
where T₀ is an ambient temperature (° C.), Q is 8 (° C./C), and A is a discharge rate (C).

Claims

1. An overdischarge preventing circuit apparatus for a nonaqueous electrolyte secondary battery, comprising:

a discharge control mechanism which controls discharge of the nonaqueous electrolyte secondary battery when a surface temperature of the nonaqueous electrolyte secondary battery exceeds a discharge control temperature T₁ (°

C.) represented by

T₁=T₀+QA 

 

(1)

where T₀ is an ambient temperature in a range of 0 to 60°

C., Q is 8 (°

C./C), and A is a discharge rate (C) of the nonaqueous electrolyte secondary battery in a case where a current required for discharging a nominal capacity of the nonaqueous electrolyte secondary battery in one hour is 1C, and is within a range of 4C to 7C.

2. An apparatus according to claim 1, wherein the discharge control temperature T₁ (°

C.) is not more than a melting point of a separator of the nonaqueous electrolyte secondary battery.

3. An apparatus according to claim 1, wherein the discharge control temperature T₁ (°

C.) is not more than 120°

C.

4. An apparatus according to claim 1, further comprising a temperature detecting mechanism which measures the surface temperature of the nonaqueous electrolyte secondary battery.

5. An apparatus according to claim 4, wherein the temperature detecting mechanism comprises at least one of a thermocouple and a thermistor.

6. An apparatus according to claim 1, wherein the discharge control mechanism comprises a temperature comparator which compares the surface temperature with the discharge control temperature T₁, and a discharge control/discharge stop circuit which performs discharge stop and discharge control on the basis of an output from the temperature comparator.

7. An overdischarge preventing circuit apparatus for a battery pack including a battery in which units each obtained by connecting nonaqueous electrolyte single cells in parallel are connected in series, comprising:

a discharge control mechanism which, when a surface temperature of the battery exceeds a discharge control temperature T₁ (°

C.) represented by equation (1) below, stops discharge of the battery pack if a voltage of the battery is not more than a discharge stop voltage V_a (V) represented by equation (2) below or a voltage of the single cell is less than 3 V, and lowers a discharge rate of the battery pack if the voltage of the battery is higher than the discharge stop voltage V_a (V) and the voltage of the single cell is not less than 3 V;

T₁=T₀+QA 

 

(1)

where T₀ is an ambient temperature (°

C.), Q is 8 (°

C./C), and A is a discharge rate (C); and

V_a=n×

3 (V) 

 

(2)

where n is the number of series-connected units in the battery.

8. An apparatus according to claim 7, wherein the ambient temperature T₀ is 0°

C. to 60°

C.

9. An apparatus according to claim 7, wherein the discharge rate A is 4C to 7C.

10. An apparatus according to claim 7, wherein the discharge control temperature T₁ (°

C.) is not more than a melting point of a separator of the nonaqueous electrolyte single cell.

11. An apparatus according to claim 7, wherein the discharge control temperature T₁ (°

C.) is not more than 120°

C.

12. An apparatus according to claim 7, further comprising a temperature detecting mechanism which measures the surface temperature of the battery.

13. An apparatus according to claim 12, wherein the temperature detecting mechanism comprises at least one of a thermocouple provided on a surface of the single cell and a thermistor electrically connected to the single cell.

14. An apparatus according to claim 7, wherein the discharge control mechanism comprises a temperature comparator which compares the surface temperature with the discharge control temperature T₁, a voltage comparator which compares the voltage of the battery with the discharge stop voltage V_a and the voltage of the single cell with 3 V, and a discharge control/discharge stop circuit which performs discharge stop and discharge control on the basis of outputs from the temperature comparator and voltage comparator.

15. A secondary battery overdischarge preventing method comprising controlling discharge of a nonaqueous electrolyte secondary battery when a surface temperature of the nonaqueous electrolyte secondary battery exceeds a discharge control temperature T₁ (°

C.) represented by

T₁=T₀+QA 

 

(1)

where T₀ is an ambient temperature (°

C.), Q is 8 (°

C./C), and A is a discharge rate (C) of the nonaqueous electrolyte secondary battery in a case where a current required for discharging a nominal capacity of the nonaqueous electrolyte secondary battery in one hour is 1C, and is within a range of 4C to 7C.

16. A method according to claim 15, wherein the discharge control is performed by stopping discharge or lowering a discharge current.

17. The method according to claim 15, wherein the discharge control temperature T₁ (°

C.) is not more than a melting point of a separator of the nonaqueous electrolyte secondary battery.

18. A method according to claim 15, wherein the discharge control temperature T₁ (°

C.) is not more than 120°

C.

19. An overdischarge preventing method for a battery pack including a battery in which units each obtained by connecting nonaqueous electrolyte single cells in parallel are connected in series, comprising:

when a surface temperature of the battery exceeds a discharge control temperature T₁ (°

C.) represented by equation (1) below, stopping discharge of the battery pack if a voltage of the battery is not more than a discharge stop voltage V_a (V) represented by equation (2) below or a voltage of the single cell is less than 3 V, and lowering a discharge rate of the battery pack if the voltage of the battery is higher than the discharge stop voltage V_a (V) and the voltage of the single cell is not less than 3 V;

T₁=T₀+QA 

 

(1)

where T₀ is an ambient temperature (°

C.), Q is 8 (°

C./C), and A is a discharge rate (C); and

V_a=n×

3 (V) 

 

(2)

where n is the number of series-connected units in the battery.