Times vary in regards to how long it takes to charge a car battery. If you jump start your car and charge the battery through the process of using your alternator, it will likely take an hour (at least) to fully charge your battery. When using a battery charger, you can vary the time by lowering the amperage. The lower the amps, the longer it will take to charge the battery, but the better it will be for the overall health and life of your battery. Charging times vary from 1 to 3 hours on most normal settings and much, much longer when using a trickle charge.