Protection systems for rechargeable elements

• Main Authors: BERNARD DALLEMAGNE, GILLES GOZLAN
• Format: Patent
• Language: English
• Published: 16.11.1999
• Edition: 6
• Subjects: CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTINGELECTRIC POWER; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER; ELECTRICITY; EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS; GENERATION; SYSTEMS FOR STORING ELECTRIC ENERGY

The present invention provides a protection system that prevents a rechargeable battery from being overcharged into a dangerous operating mode. The protection system may generally be used as a backup system in conjunction with a smart electronic circuit which, when functioning in its normal mode, protects the battery cells against being overcharged. The protection system will be activated before the battery voltage reaches a dangerous threshold value. According to one embodiment of the present invention, a rechargeable battery is coupled, in parallel, to a voltage dependent resistive element, such as a zener diode or a diac, having a threshold voltage just below the threshold operating voltage of the battery. A protection element, such as a positive temperature coefficient (PTC) device, a thermal fuse, or a bikemetallic breaker, etc. is coupled, in series, to the battery or to the parallel circuit of the battery and the voltage dependent resistive element. According to another embodiment of the invention, a rechargeable battery is coupled in series with a fuse and in parallel with a power MOSFET transistor which is preferably thermally coupled to an overcharge detection device. A protection method of the present invention is also disclosed.