Alternator?

[clickman]

If anyone can help me with suggestions for this electrical problem, that would be much appreciated.

I hadn’t driven the car for a few weeks, but put the CTEK battery tender on it a few days ago, and it went green a day or so later. I drove to work (about 100 km) on Thursday, and at the end of the day before I started the car I put the top down, which went really slowly in retrospect. I stopped once for a few minutes on the way. When I got home I turned off the engine, then tried to restart a minute later. All I got was a few clicks and weird lights in the dash. Jumper cables easily started the car. After driving it about another 10 km and shutting it off, I tried starting it again right away; no go, with same low battery symptoms.

Battery last replaced April 2011. Ignition switch replaced last summer (had trouble getting the key out). I've been having some issues with the central locking for some months now – sometimes I get the proper lock and alarm activation (2 flashes) and sometimes I get only one flash and the beep. I also just noticed that the spoiler wasn't all the way down, but manually lowering it worked.

The voltage across the battery when it was flat was 11.65. I tried the battery open-circuit voltage test from the Bentley manual and got 11.51 after leaving the lights on for about a minutes. Then I charged the battery again with the CTEK until green light, and did the test again. 13.15V dropped to 12.82.

I started the car ok, ran it for about a minute, shut it off and measured 12.90. Leaving it and coming back the next day I measured 12.93.

Today while running the engine I measured about 14V initially, but this steadily dropped until I shut the engine off at 12.5V. The voltage drop was slowed by revving higher.

I store the car for the winter, but use the CTEK maintainer.

Battery? Alternator? Voltage regulator?? Any suggestions welcome. Thanks.