Method and system for charging multi-cell lithium-based batteries

A battery charger operable to charge a power tool battery having a plurality of Lithium-based battery cells, the battery charger comprising:

• a charging circuit operable to provide a pulsed charging current to the power tool battery for at least a portion of a charging operation of the power tool battery;
• and
• a controller operable to control the pulsed charging current provided to the power tool battery based at least in part on a comparison of an individual state of charge of at least one of the plurality of battery cells to at least one state of charge threshold value,
• wherein controlling the pulsed charging current includes entering one of a defective power tool battery mode in which the pulsed charging current is interrupted and an indicator is correspondingly controlled to indicate the defective power tool battery mode, and entering a normal charge mode in which the pulsed charging current is provided to the power tool battery and the indicator is correspondingly controlled to indicate the normal charge mode, and
• wherein the defective power tool battery mode and the normal charge mode are each entered based at least on part on the comparison of the individual state of charge of the at least one of the plurality of battery cells to the at least one state of charge threshold value.