batteries, alternators, etc

[Brian Devlin]

>Okay, finally decided to poke around the charging system since I've
>always suspected something isn't quite right.
>
>Off, car not run in several days, battery voltage is 12.5, I believe.
>
It think your battery is a bit toasted. 12.5 is ~75% charged, which
seems a bit low for only sitting a few days. Car batteries are
supposed to be operated in the 90-100% range. The rapid rise to 14
volts suggests that it won't take a full charge (sulfated).

>Kick on the accessories; rear window defogger, headlights on high,
>etc.  Engine slows down a teeny bit. Check voltages again.  Much,
>much lower; not much above battery voltage, in fact; 12.8 or 12.9 I
>think;

How much power does the alternator put out at idle? I thought it was
less than the rated capacity?
-Brian