Car won't hold a charge - sound like the battery?

[JoeFromPA]

Hi all,

About 2 weeks ago my boxster, after sitting in the garage undriven for 3-5 days and having no problems beforehand, wouldn't crank and showed the signs of a very low battery:

1. Windows didn't go up down upon opening a door or, if they did, very slowly.
2. Lots of rapid clicking happened upon turning the key
3. Dash lights dimmed substantially when trying to start

The car has about a 2-3 year old interstate battery in it, but the battery has seen alot of full drains during it's lifetime. I trickle charged it back to life and it started up and drove fine. Drove it 32 miles to work, started up fine at the end of the day (no unusual effort), then 32 miles back home.

Garaged it for 3 days....wouldn't crank again. Trickle charge'd it. Started up fine. Drove it around onSaturday for about 20 miles with 3-4 stops in there. Each time, it started back up fine. No unusual effort.

Sunday morning (about 16 hours since last start) - wouldn't turn over.

Trickle charge'd it till this morning, added distilled water into the battery (it drank probably 8-12 ounces of distilled water without ever over-flowing). Drove it to work, where it's now sitting outside.

Now to me, this sounds like a clear case of a battery going dead. However, I'm just wondering if there is anything unusual that could be simply draining the battery when its sitting still for more than 10 hours in a row?

Thanks all,

Joe