here's a another thing to try i seen a few times
disconnect the cables from the battery put a 12 volt bulb between the pos post and cable if the bulb glows the battery case is leaking to ground
a small volt meter also works for this if no luck replace nev cable place voltmeter between the pos cable and look for a voltage draw if you have one you can find out where by pulling one fuse a time until meter shows no thing on it (pull fuse for the cd player first as it like clocks will have a small current draw
good luck
harvey41