Abstract: The present invention is related to a set of safety jumper cables for use with placing one battery parallel with another battery in order to increase the amount of electrical energy available. The apparatus includes a pair of cable conductors having at each end thereof disengageable connectors for coupling with the terminals of the primary and secondary batteries. A contactor is coupled in series with one of the cable conductors for selectively enabling the flow of electrical power therethrough. Various comparators are included for comparing the battery voltage polarities on either side of the contactor and enabling the contactor only when the polarities are the same. A first manual switch is provided for initially energizing and closing the contactor. Various other comparators are provided for preventing the closure of the contactor when the voltage of one of the batteries does not exceed a predetermined minimum and when the voltage across both batteries is substantially the same.