Abstract: A method and system for charging a rechargeable battery, such as a Lithium based battery, by applying a voltage charge signal, and monitoring a battery charging current and a varying internal resistance of the rechargeable battery and changes in open circuit voltage of the rechargeable battery. The voltage charge signal is dynamically established as a function of the varying internal resistance of the rechargeable battery during charging and the changes in open circuit voltage of the rechargeable battery. The voltage charge signal is a function of a state of charge (SOC) of the rechargeable battery.