I backed my car out of the garage today to check the oil and it started fine...came out a couple hours later while it was raining and tried to the start the car..when I turned the iginition all power was there but as soon as I tried to crank it all the power disappeared and the car was dead...all the lights turned dim and it did not even turn...I had the card boosted and it started, checked the alternator and was approx 14V consistent charge. I let the car run for approx 15mins but when I turned the car off same thing...any ideas? is the battery? If it is would it die slowly vs immediately? or is there anything else I can check....any help is apprecciated!