A control-module implemented method for controlling a powertrain system comprising an internal combustion engine, at least one electric machine, a high-voltage battery and an electro-mechanical transmission operative to transmit torque to a driveline includes monitoring a state of charge (SOC) of a high-voltage battery configured to provide stored electrical power to a first electric machine, a second electric machine and at least one auxiliary load. A trickle-charging event is enabled only when the SOC of the high-voltage battery is less than a first SOC threshold. The trickle-charging event activates the first clutch coupled to a first planetary gear set. The trickle-charging event further coordinates a torque capacity of the activated first clutch and a charging set of torque commands between the engine, the first electric machine and the second electric machine to establish a net zero output torque condition.