I'll try to make a long story short. I replaced the battery in my daughter's 2008 Civic several months ago. The other day, the car was totally dead though indication that anything was going bad. The battery light has never come on at any time. I took the battery to get charged or replaced at Avance Auto Parts where I bought it and it took a charge and checked out okay. I installed the battery this morning and on my lunch hour, I drove back up to Advance for them to check my alternator etc. They said I needed a new alternator. I still had some time so I went by AutoZone and had the same procedure done for a second opinion and they said the same thing, the alternator needs to be changed. I went home and later this afternoon, I put my multimeter on the battery and it was approximately 11.4 volts. When I started the car, it was putting out 12.52 volts, so I thought okay I'll just get another alternator and install it since it doesn't seem to be charging. This evening I went out to check to make sure the car was locked and pushed the lock button and the horn was very faint as if the battery really drained itself down in about 4 hours. I went to start the car and it is dead again. I just don't understand how the battery can discharge itself that fast, regardless of the alternator need to be in replaced. The car was sitting in the driveway and went from 11.4 volts down to a dead battery, I haven't checked to see how low it was but when I took it in for charging yesterday it was only at 4 volts.

What can be causing the battery to drain so fast in just a few hours just sitting in the driveway? If the alternator is bad, is there something on the alternator that can be draining the battery, i.e a short, or ? Nothing was left on in the car this time or any other time to cause a draw on the system. Just trying to find out what else there could be wrong before I start throwing parts at this car.

Thanks for your help in any advice you can share.

 

Are there any accessories your daughter added to the car? I have a backup camera/mirror that drains the battery, if left for 3 days straight. When I know the car sits longer than that, I unplug the accessory fuse.

 

No accessories and car is 100% stock. No interior lights or anything left on. After the battery was charged, it's set in the driveway for a few hours yesterday and was dead by that evening. Can a bad alternator drain the battery just by sitting there? If not something else has got to be drawing power from it but what I don't get is how fast it's dying.

 

You'd have to try pulling fuses (by driver's side left leg) and see which is the culprit.