a parasitic drain tester measuring the parasitic battery drain of a vehicle and the high current used by the vehicle starter motor , includes a current measuring circuit and a unit . the current measuring circuit includes a capacitor smoothing the current distribution within the circuit , a first interface connected to a vehicle power source being tested and the capacitor , a second interface accommodating an outside connection for communication , a first processor connected to the second interface and the capacitor , the processor communicating with the second interface and performing analysis and calculation of the data received , and a converting unit connected to the processor , converting the signal received through the first interface from a first form to a second form in order to process the signal received . the first unit is connected to the current measuring circuit , and the first unit includes a memory storing information retrieved from the current measuring circuit through the second interface , and a second processor analyzes the information received from the current measuring circuit and providing instructions to the first processor through the second interface .