Abstract: Disclosed are a method, processor and device for charging of multi-celled battery pack (101) is disclosed to determine if one or more cells (A, B, C and D) is malfunctioning. The battery pack has a voltage (114) and includes a discharge FET (104) which when open prevents discharge of the battery pack and which when closed allows discharge. The method includes establishing a predetermined rapid charge error threshold, applying a rapid charge current the battery pack (304), determining whether the discharge FET is open (308), determining whether the voltage of the battery pack exceeds the rapid charge error threshold (306) and disabling charging when the voltage exceeds the rapid charge error threshold and the discharge FET is open (310).

Abstract: A battery charging circuit having two levels of safety protection is provided. The circuit is said to have “two levels” of safety because if any one component fails (either as a short circuit or as an open circuit) the remainder of the charging circuit ensures that a rechargeable battery coupled to the circuit will not be overcharged. The circuit includes both hardware and firmware protection components, with a microprocessor providing the firmware protection. Overvoltage protection, voltage regulation and current regulation are provided, along with a microprocessor capable of sensing a plurality of voltages across the circuit. The overvoltage protection, voltage regulator and current regulator each include safety actuation points. In parallel, the microprocessor may isolate a rechargeable battery from the cell if voltage and current minimums and maximums are exceeded.