Abstract: A modular jumper cable system for connecting two batteries together. The cable system includes two cable units, one for detachable connection to one battery, the other for detachable connection to the other battery. The cable units may be connected to the batteries' terminals by easy-to-operate connectors, such as conductive eyelets. The system further includes an intermediate cable connector for joining the two cable units together. The linking connection ends of the cable units and the intermediate connector are formed of releasable connection devices that must be oriented in only one way to complete a connection. The connection devices ensure that like terminals of the batteries will be connected to one another. Difficult-to-manipulate alligator clamps are avoided in the modular jumper cable system.