I hooked up a jumper cable to a good car, started the good car and let it idle for 5 minutes. I turned off the good car, and tried starting the dead car. The engine on the dead car cranks, the radiator fans spins for a second, but I can't get the car to start. The dead car has a 1-month old Duralast battery, and all was well a few days ago until I mistakenly left the ignition in the "ON" position for about 2 hours. Should I try jumpstarting again, but this time let the good car idle for 10+ minutes? Or, do I need a new battery? Thanks for the help!