Battery pack containing a circuit breaker

#This application is based on application No. 101363 filed in Japan on Mar. 30, 2001, the content of which incorporated hereinto by reference.

#This invention relates to a battery pack containing a circuit breaker which cuts-off current flow if excessive current flows through the batteries or if battery temperature rises abnormally.

#A battery pack containing a circuit breaker protects the batteries by cutting-off the current when excessive current flows through the batteries or when battery temperature rises abnormally. There are two types of circuit breakers. There are circuit breakers which switch on and off via movable contacts, and there are circuit breakers which abruptly change electrical resistance with temperature such as PTC devices. A movable contact circuit breaker contains a bimetal element which heats as a result of current flow. The bimetal element is heated by current flow induced Joule-heating and switches the movable contact from the on to off position to cut-off current flow. A PTC device abruptly increases its electrical resistance when temperature rises to almost eliminate current flow.

#The battery packs shown in FIGS. 2 and 3 contain batteries 1, 31, a printed circuit board 3, 33, and a circuit breaker 4, 34 inside a case 2, 32. The batteries 1, 31 are rechargeable batteries such as lithium ion rechargeable batteries, nickel hydrogen batteries, nickel cadmium batteries, or polymer batteries. The battery pack of the figures contains thin outline batteries. Circular cylindrical batteries may also be used. Further, the battery pack contains one or a plurality of batteries inside the case.

#The printed circuit board 3, 33 is disposed at a battery 1, 31 end region. The printed circuit board 33 has battery 31 protection circuit components 36 mounted on it. The battery 31 protection circuit, comprising protection circuit components 36 mounted on the printed circuit board 33, prevents battery 31 overcharge or over discharge to prevent battery 31 degradation. The protection circuit is provided with a circuit to detect remaining battery capacity and voltage, and a switching device that is switched on or off by that circuit. The protection circuit switches the switching device off to cut off battery 31 current if the battery 31 goes into an overcharge or over discharge condition.

#In the battery packs of the figures, the printed circuit board 3, 33 is disposed facing battery 1, 31 surfaces. The printed circuit board 3, 33 is disposed in a fixed position that establishes a gap 8, 38 between the batteries 1, 31 and the printed circuit board 3, 33 for mounting the circuit breaker 4, 34. The circuit breaker 4, 34 is mounted in this gap 8, 38 to put the surface of the circuit breaker 4, 34 casing in close proximity to the battery 1, 31 surfaces. In the battery pack of FIG. 2, the printed circuit board 3, 33 is connected to the batteries 1, 31 via leads 5, 35. In the battery packs of the figures, insulating spacers 22, 322 are provided to prevent leads from touching the batteries 1, 31 or the surface of the printed circuit board 3, 33.