A hybrid powertrain system includes a method for managing electrical charging of a DC power source, which includes determining an initial charge-sustaining SOC setpoint and an initial charge-termination SOC setpoint. The DC power source is dynamically monitored. An adjustment to a charge-sustaining SOC setpoint is determined based upon the ambient temperature, the device temperature and the SOC of the DC power source, and an updated charge-sustaining SOC setpoint is determined based upon the adjustment to the charge-sustaining SOC setpoint and the initial charge-sustaining SOC setpoint. An electric energy equalization factor α is determined, and an updated charge termination SOC setpoint can be determined based upon the electric energy equalization factor α, the updated charge-sustaining SOC setpoint and the initial charge-sustaining SOC setpoint. Charging of the DC power source is controlled based upon the updated charge-termination SOC setpoint.