There are many challenges associated with high-voltage Li-ion battery-stack management in all-electric or hybrid automotive applications. Charge and discharge cycles must be monitored and controlled, and the battery stack, which often delivers voltages of several hundred volts, has to be isolated for safety concerns. In particular, this paper will examine the requirements for Li-ion cell monitoring, and review the architecture and components used in the cell-monitoring subsystem, digital-communications subsystem, and isolation interface.