First make sure that all the connections according to the diagrams in the instruction manual are correct. Pick up the cable coming from the POSITIVE (+) battery terminal. Place the supplied charging resistor between the end of this cable and the positive terminal of the capacitor. The capacitor will begin charging. Charging generally takes 5 to 60 seconds. During charging, the voltage shown in the 3 digit display will rise rapidly, then slow as it approaches the voltage of your vehicle’s battery. When fully charged, the display voltage will stop rising. If you have a voltmeter, you can first measure the voltage of your car battery. Then you will know with accuracy that the capacitor is fully charged. CAUTION!! During charging, the resistor will become hot. This is normal, but exercise caution during the charging process. After charging is complete, remove the resistor from the incoming positive cable, and IMEDIATELY connect it to the positive terminal of the capacitor.