Systems and methods of powering circuits with near end-of-life batteries

A circuit providing electrical power to drive a solenoid-actuated valve from a battery, comprising:

• a capacitor in electrical communication with the solenoid;
• an electrically controlled switch having at least a first state and a second state;
• an inductor receiving electrical energy from the battery when the switch is in the first state, and releasing energy into the capacitor via a diode when the switch is in the second state;
• a first control unit configured to controllably change the switch between its first and second states to controllably charge the capacitor to a voltage of about 15-40 volts DC with electrical energy from the battery, the first control unit controlling the switch to draw about 15 mA to about 100 mA from the battery while charging the capacitor;
• and
• a second control unit configured to controllably release energy stored in the capacitor to the solenoid to change the valve state.