After several incidents where my battery would go dead for no reason, even after taking it to the dealer I decided to replace it with a Sears DieHard Platinum battery. Car starts faster now and the battery problems are gone. One thing I did notice was the bose stereo sounds louder with more bass. Is that typical or am I imagining things. I had my Galaxy S3 streaming to it and it was very loud and volume was only half way.

 

I bought the Duralast Gold Top Battery. Can't say I have any complaints with it yet. Starts fast, idk about the Radio and Music Quality though..

 

I thought when the engine is running, the battery is only used if alternator isn't supplying enough power.

 

As I understand it the alternator has only one job, to charge the battery. The Alternator produces AC current while the battery excepts only DC current. This AC to DC conversion is done though a couple of stators on the alternator and the DC current is then transfered to the battery by way of a voltage regulator. All the 12 volt current the car uses comes from the battery.

 

Just to keep things in perspective, while driving the alternator needs to supply enough power to keep the car running and to recharge the battery to recover from its starting task. If the alternator does not keep up with the power requirements of running the car you will have a dead battery and car soon. One of the advantages of the alternator over a generator is that the brushes on the alternator only power the field, while on a generator, all the power was going thru the brushes.