Over-voltage secondary battery protector and system using same

An over-voltage protection device for protecting a secondary battery comprising a casing, at least first, second and third terminals at least partially contained in said casing, said third terminal having a fixed electrical contact mounted thereon, a piezoelectric actuator cantilever mounted in said casing, having first and second electrodes, and a movable electrically conductive member contained in said casing, having a movable electrical contact mounted thereon, said movable contact being positioned to be able to make and break contact with said fixed contact in response to movement by said piezoelectric actuator, said first and second electrodes of the piezoelectric actuator being electrically connected to the first and second terminals respectively, whereby, when a voltage above a predetermined level is impressed to the first and second terminals, the piezoelectric actuator is capable of movement to thereby cause said movable member to move so that the movable contact will move out of or into engagement with the stationary contact.

An over-voltage protection device comprising a casing, at least first, second and third terminals, a piezoelectric actuator and a snap acting bimetal element contained in said casing, said piezoelectric actuator having first and second electrodes electrically connected to said first and second terminals respectively, said bimetal element being positioned between said piezoelectric actuator and said third terminal, a first end of the bimetal member being fixed to said third terminal and a second end being in engagement with said piezoelectric actuator, said piezoelectric actuator cantilever mounted in said casing with its distal end capable of being displaced in response to a voltage above a predetermined level being impressed between the first and second terminals so as to be able to cause the second end of said bimetal element to snap out of engagement with the piezoelectric actuator, said snap acting bimetal element also being capable of snapping out of engagement with said piezoelectric actuator upon over-temperature and over-current conditions.