Battery Draining Overnight?

Hello, I have a question for you all. First off, I have a 2015 Chevy Spark, 1.2L engine, Automatic Transmission, A/C, 72,620 miles on it. There is something draining the car battery down overnight. I can charge the battery up with my battery charger, hook up the battery cables and the car will start right up. If I leave the battery cables hooked up over night, the next morning, there is not enough juice in the battery left to start the car. But if I take the battery cables off the battery for overnight, and then in the morning put the battery cables back on the battery, the car will start right up. I have left the battery cables off of the battery for as long as two(2) weeks before hooking them back up to the battery and the car will start right up. Any ideal what could be causing this? The battery is only six(6) months old. Thank You for any ideals that might help me get this fixed.