It could be a short.............a short means a circuit that should be dead, or off, is receiving current and is considered OPEN or ON. When you turn off your ignition, this SHOULD kill all your electrical systems meaning all the circuits are dead. If you have a wire that has rubbed off the insulation and is now contacting metal, this circuit is now drawing electric from your battery even though the ignition is off. Shorts are very hard to track down becasue you have to test all the cicuits until you find a reading on a circuit that should be dead. One way to stop the drain is to buy a battery disconnect and install it on your vehicle. When you turn it off it totally disconnects the battery from your system........no current can possibly get drained from your battery. BUT...you have to flip the battery disconnect when you want to start you rcar and then when you stop, you will once again have to disconnect. So it is a fix, but until you get the short tracked down, it might buy you some time.