A modular heavy load battery test system is provided. The system includes a heavy load module and a battery tester. The heavy load module includes a housing, first and second lengths of high-resistivity, large-gauge wire arranged on respective upper and lower surfaces of a heat-resistant support plate, a switch and at least one cooling fan. The battery tester includes a housing, a microcontroller and a set of battery charging wires. The microcontroller selects the configuration of the first and second wires and provides the control signal to the heavy load module, while the switch selectively connects the first and second wires to the battery tester based upon the control signal.