Hey guys I was wondering if you could give me some tips or advice over what just happened to me this week:

Tuesday: car starts fine in the morning, takes me to school. Around 3:30 I'm trying to head home and the car won't start. A little symbol with a car and a lock on it lights up on my dash, and the car's dinging noise make it sound like the car is low on battery. I get security to give me a boost with their boost pack and the car turns on right away and I head home. In the evening I borrow my neighbour's voltmeter and car battery charger. Measure 12.5 ish volts across the terminals. I attached the trickle charge battery charger to my car and the needle shows my battery at about 65-70% charged. I unplugged the charger at around 95 ish% before going to sleep.

Wednesday: The next morning I plug in the charger to check the battery and it goes down to about 75% again. I assumed this meant that the problem was with the battery not the alternator. I take booster cables and a charger with me, and the car still starts fine that morning. Once again in the afternoon around 4:15 the car won't start. This time it's totally dead, no lights on the dash, no sign of life. I tried boosting the car from the trunk ( I only learned today you can boost it from the front) with 2 different cars and nothing. Security brought the booster pack again, and it wouldn't start. It took significant charging time from the booster pack to get it to start, and it barely started.

Thursday: The next day I just left the car in the garage, and didn't use it. In the evening I needed to get something from the car and I noticed the key fob worked (and the headlights/ brake lights turned on), as well as when I locked it the horn went off too. The previous 2 days, when the car wouldn't start, there wasn't even enough juice to get the horn to make noise. I didn't have much time but I was puzzled.

Friday: I left the car in the garage again. Had no time to try anything.

Sat: so today I went to try the car out. I notice that the lock horn still goes off like thursday. I put the key in and the car starts easily. How does this make any sense? The car sat for less than 8 hours and died on Tues and Wednesday, but now sat for over 50 hours and starts just fine? Can anyone shed some light on this?

 

Most likely a failing battery. Sometimes the problem can be intermediate.

 

Sulfate builds up in the bottom of the battery and shorts out the lead plates. Sometimes they are fine one day and dead the next or intermitting like yours. A quick fix to get a little more time out of the battery is to bang it on a concrete floor. Be careful not to bust the case so do it on a piece of plywood. Knock it good a half dozen times to knock the sulfate down. It works well but you basically will need a battery before winter.