unsolved battery mystery

[95mitsubishi]

dsm experts please help! I have a 96 mitsubishi eclipse gst and yesterday afternoon i tried to start my car but nothing happened. My battery was totally drained. I check my lights and nothing was left on. How did my battery drain? I couldnt even turn on my lights or even my hazard lights. the battery was totally drained. this is the second time this has happened to me, the last time was about 5 months ago. any ideas?

[Blackboost]

Check your alternator. I think it's faulty...

[Redsand187]

It's probably the alt, it could be a parasitic drain, too. Who long did you drive your car before you left it? How long did you leave it for?

[jankovig]

measure the voltage accross batery when your car is not running. it should read around 12V. now start your car and read the voltage again. this time it should read between 13-14V. if it looks like the voltage didn't change or changed very little (i.e 0.5V) than it's time to change your alternator.

[X-Pride]

Check your Alternator.

[alanseijas]

Disconnect your negative battery cable. Take a regular test light, and put it in between the connection of the battery, and the car's negative cable. Make sure EVERYTHING is turned off, and the doors are shut. See if the light lights more than a TINY glow. If it does, and I bet it will, you have a DRAW. A draw will drain your battery when your car is at rest, and you must locate the source of this draw. Pull out each fuse 1 by 1 until the test light goes almost dark. Make sure the domelight is not lit, because that will show as a draw too, of course.
Once you have found th fuse that is guilty of drawing, look in your manual to see everything that that fuse is responsible for, and eliminate them 1 by 1.

If your alternater shows more than 13.2 volts at idle, it is probably fine.