Battery draining fast

^^^ As above....The battery and alternator main output are always connected.

Get a voltmeter and disconnect the battery. Test the battery voltage every hour for a few hours. It should be steady after a while; if it keeps going down, then the battery is internally shorted.

If battery test OK as above, then just pull all fuses and start disconnecting things and monitor the battery voltage as it drops. When you get to the item that is on, then the battery voltage will stop dropping.

An easier to see indicator that may be worth trying is to put a headlight in series with the battery negative lead to chassis or block; it will glow with the current draw. (You can just disconnect the left headlight and jumper to one of the 2 filaments.) Then disconnect things 'til it stops glowing.