Protective device for secondary batteries

• US 5,853,908 A
• Filed: 10/29/1997
• Issued: 12/29/1998
• Est. Priority Date: 10/29/1996
• Status: Expired due to Term

• Current Assignee: NEC Energy Devices, Ltd. (Envision Group /TX/)
• Original Assignee: Nippon MOLI Energy Corporation
• Inventors: Okutoh, Tadashi
• Primary Examiner(s): Skapars, Anthony
• Application Number:
  US08/960,376
• Time in Patent Office: 426 Days
• Field of Search: 429/61, 429/62, 429/90, 429/91, 429/7, 320/150, 320/152, 320/154
• US Class Current: 429/7
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• 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 10/42 Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells H01M10/60 takes precedence
• CPC Class Codes: H01M 2200/103 Fuse
• 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

The invention provides a protective device for batteries having a high energy density such as lithium ion batteries. The protective device includes a current conduction cutoff means having a current-conducting circuit comprising a voltage-detecting means for detecting the voltage of at least one battery being charged, a heat-generating resistance for starting the conduction of a current when the detected voltage exceeds a preset voltage, and a temperature fuse thermally coupled to the heat-generating resistance. When a state where battery voltage is higher than a preset value continues, a charging circuit for the battery is cut off by the temperature fuse and current output from the battery is disabled. The protective device further includes a battery-discharging means actuated upon detection of the fusing-down of the temperature fuse, so that the battery is disabled, and then placed in a dischargeable state.

Claims

1. A protective device for secondary batteries using a non-aqueous electrolyte, which includes a current-conducting circuit comprising a voltage-detecting means for detecting voltages of a plurality of batteries during charging, a heat-generating resistance which conducts a current when one of detected voltages is higher than a preset voltage, and a temperature fuse thermally coupled to said heat-generating resistance, so that when a state where the detected battery voltage is higher than a preset value continues longer than a preset time, said temperature fuse is fused down to cut off a charging circuit for said batteries and an output circuit from said batteries, and further includes a battery-discharging means actuated upon detection of the fusing-down of said temperature fuse to place said battery in a dischargeable state.

2. The protective device of claim 1, wherein said temperature fuse is located in the vicinity of said secondary batteries, and is fused down at a temperature lower than the highest temperature at which a separator forming a part of each secondary battery is usable.

3. The protective device of claim 1 or 2, which further includes a cutoff means actuated when the voltage detected by said voltage-detecting means drops to a final discharge voltage, thereby cutting off conduction of a current to protect said batteries against overcharging.

4. The protective device of claim 3, which further includes a means for detecting a voltage drop during conduction of a current in said cutoff means, so that when a detected voltage exceeds said preset voltage, the conduction of the current is cut off by said cutoff means to protect said batteries against an overcurrent.