Bluestreak

I drive around 20 miles to go to school every day. On Thursday around noon, I parked the car at school and it gave no indications of any problems. During class break around 2pm, I went out to the hatchback to get something and it popped from the remote control just fine (battery has power). Around 4pm, I went outside to put it back - the hatchback still popped open just fine (so... battery still has power). When I went to leave the school around 6:30pm, the car was deader than a freakin' doornail. No trunk pop, no door lock solenoids, not even a beep from the door chime with the key in the ignition.

I got out my DMM and the battery had 4.2 volts on it. Thankfully, it's an Optima Yellow... using a buddy's diesel truck, we got the car started up after letting it idle on the dead batt for a few minutes.

It made the 25 mile drive home just fine, but the alternator was showing pretty low voltage. I assumed that was because the battery was so completely dead.

I have a MicroVAT tester, and I ran an alternator test as soon as I got home. Due to the low voltage output, the alternator failed the test. So I let the battery charge over night. After the battery charged up, I ran a battery test, and it came up okay - believe it or not, that darn battery recovered all the way to a full 13.1v. I ran an alternator test the next day, too, and it passed with just over 14.0v charging. The car started right up.

I checked resistance in the BATT cables, I checked the alternator output wire, I checked wires, fuses, light bulbs... any switch that might have hung up... I am completely effing stumped. Even though it starts up fine and checks out okay, I'm afraid to drive the car for fear of it crapping out on me.

What the hell could have caused a fully charged, less than 2-year old Optima Yellow to discharge in six hours? I mean, in the past I've accidentally left the cooling fans running on low overnight and had the battery start up the engine the next morning.

Bear in mind this car is kept in a climate controlled garage attached to a Battery Tender. And I usually don't trust automatic battery chargers, so I check the battery voltage with a DMM pretty regularly (almost daily). It's almost always on maintenance charge, floating b/w 13.0-13.1 volts. I keep all my batteries like this, and I've had a Yellow Top last as long as eight years.

I think I'm going to be brave and take the car out tonight, then leave it off the charger and see what happens.

I'm hoping that by describing this, someone will know exactly what it is... but I'm guessing that's a long shot!

Any ideas what happened here? TIA...

MAROBOY_TRAV

Did you receive any feedback about this thread? I'm having the same exact problem.. Batt checks out fine.. So does the alt..