When your car won't start due to a dead or weak battery you may need to jump start it. Using a set of battery jumper cables that are clearly marked positive and negative need to be attached to you vehicles battery accordingly. Attach the other end of the cables to a good working vehicle. It is a good idea to turn off the radio, lights, and fan. Start the vehicle with the good battery and let it run for several minutes. This may take up to 15 minutes to allow the dead battery time to charge. Once you have both vehicles running, go straight to a battery testing facility and get it checked out and replace it if needed.