Just disconnect the battery overnight then recconect in the morning, if it is ok you obviously have a drain/short.
Next day disconnect the alternator, main lead overnight with battery connected, if it is ok you have a buggered alternator with LEAKY DIODES.
The alternator is ALWAYS connected to the battery and does NOT go through a fuse or relay, so will always drain if at fault, as they can be, EVEN when they charge perfectly.
tabetha