Yes, there is always something drawing power in you car but it should be negligible (a very small spark) I was assuming that the op did not have a dc ammeter and wanted a diy suggestion. If he had an ammeter, as I do, we could compare readings. A load tester would tell him if the battery is weak. Purposely leaving the headlights on for 30 mins would help him without cost. If the car won't start after 20 mins with light on, get a new one. From a forum its hard to know what level of competence someone has