Check the battery cells for water first ( If possible some batteries are sealed ). Once you have a good level in each cell then you can hook up a charger than that is the route I would take. To insure you do not hurt the car you can disconnect the battery from the car B-4 charging but you do not need to. Look for a charged battery voltage above 13 and below 14.5 before testing again. If you can measure the voltage of the battery when the starting the car you will probably see the voltage drop below 9.5. If you are starting with 12.6 this means the battery is not holding the proper charge to start you're car. 90% of the time this will be the problem. New battery is needed. Good luck, John