I know a lot of people buy expensive batteries, but I buy Duralast from AutoZone because they have a lifetime warranty. If the battery ever goes dead, you bring it back to AutoZone and they will test it. If their test shows it's bad they will replace it for free - no questions asked.
And no I don't have any connection to AutoZone or anything either. I just know from experience. Ihave heardWalMart may have the same deal on some of their batteries as well.

 

I have a duralast as the main battery and the second battery is a yellow top, so yeah, im not too concerned about my car not starting due to a dead battery ^_^

 

The question is how in the world do you leave yourkey in the car man? A friend of mine did that at school. His started though. I don't know how the world he did it but it happened.