Dead battery- what could it be?

[MikeMcMo]

Okay, new information for anybody still following…

I'm pretty sure I'm on the trail of what drained the battery so quickly.

I used a friend's charger and topped off the battery, and I just put it in this afternoon. I immediately heard a clicking sound like a relay going on and off every two or three seconds.

Sitting in the driver's seat, it sounded like it was coming from the passenger door. I go around to the passenger side and it sounds like it's coming from the space under the dash above the passenger footwell, but I couldn't get in there to see any more because of the way it was parked in the garage, and then I ran out of time. Are there some relays up there?

Any idea what my next troubleshooting move should be? Thanks once again!