Embodiments of the invention provide a foam proportioning system powered by a battery, with the system including a pump, a pump motor, and a solid state contactor. The solid state contactor includes a battery terminal connected to the battery, a load terminal connected to the pump motor, and an enable switch. The enable switch selectively connects the battery terminal and the load terminal in order to form a power line carrying a current from the battery to the pump motor. A state of the enable switch is based on the current being drawn through the power line by the pump motor. The enable switch is closed in order for the solid state contactor to provide power to the pump motor when the current through the power line is between about zero amps and about 80 amps.