Abstract: A battery charging apparatus, computer system and method provide current from a single power line to charge either a first battery or multiple batteries in an independent mode or a simultaneous mode. The apparatus includes an AC-to-DC adapter, the power line, and a battery charging control system that measures the charge of the individual batteries and compares the measured charge. If the charging system detects a difference in charge between the batteries, the lowest or the lower charged batteries are charged until the charging system detects no difference in charge, and then resumes simultaneous charging. The battery charging control system also includes a comparator circuit that determines whether to enable charging in the independent mode or the simultaneous mode based on input from a user or input from a computer system. The computer system includes a processor, a memory, a bus, a power line, and a battery charging apparatus coupled to the power line.