Overcharge protection device and methods for lithium based rechargeable batteries

Abstract

A protection circuit (100) and protection device (300) for protecting a rechargeable (lithium-based) battery cell or cells from overcharging. A voltage regulator element (110, 310) is connected in parallel with the battery cell or cells (5) and is thermally coupled to a thermal element (120, 322, 326) connected in series with the charging current supply. The voltage regulator element (110, 310) prevents overcharging of the battery (5) by shunting current away from the battery when a predetermined voltage across the battery is exceeded. Moreover, the thermal element (120, 322, 326) prevents failure of the voltage regulator element (110, 310) by open circuiting the current path when the heat dissipated by the voltage regulator element (110, 310), thermally coupled to the thermal element (120, 322, 326) causes the thermal element to enter a high resistance state. Additional protection may be provided by fuse bonds (332, 334) connecting the combination of the shunt voltage regulator 310 and the thermal elements (322, 326) to the charging current supply and to the battery (5).

Dependencies are inferred from the claim text.