A starter system for a powertrain comprises a brushless electric starter motor operatively connectable to an internal combustion engine. The starter system includes both an ultracapacitor power pack and a battery power pack. A nominal voltage of the ultracapacitor power pack is greater than that of the battery power pack. A DC-DC converter operatively connects the battery power pack and the ultracapacitor power pack and converts direct current at a first voltage level of the battery power pack to direct current at a greater second voltage level of the ultracapacitor power pack. An electronic control system is operable to control the brushless electric starter motor to start the engine using power provided from the ultracapacitor power pack, and to control the DC-DC converter to recharge the ultracapacitor power pack using power provided from the battery power pack through the DC-DC converter. A method of controlling the starter system is included.