Why does my battery keep draining

Cavalier battery Drain overnight: make sure your battery is fully charge first and the car turns on and off. then remove the fuse BATT 1 in the engine compartment wait until the next day put the fuse back on and see if the car turns on or check to see if the battery is Drained (dead). if the car turns on the problem is not the battery or the alternator. BCM needs re-programing or replaced. i bypassed the system on my car and solved it. and did not need to replace the BCM. not recommended procedure, try at your own risk i removed the Batt1 fuse. took a wire directly from the batt1 fuse box that has no power side and ran a wire to the inside fuse box, i removed the heater fuse to the heater with a test light check for the side that has no electricity( the no power side of the heater fuse), i connected the wire there and then installed the heater fuse. (the heater fuse holds the wire in place.). know i turn on the car Ignition the BATT 1 area get electricty car runs and charges with no problem. i turn the car off waited until next day the car turn on and no battery drain