There are two ways to recharge a battery with a bad alternator: jump starting it with another car or using a portable battery charger. Although it is possible to recharge a battery without the alternator, the battery will probably not be powerful enough to make it far without the alternator to cycle the charge.
- Use jumper cables and a second car with a good battery. Using the jumper cables, attach the red cable to the red terminal of the stalled battery, then attach the other red cable to the red terminal of the good battery.
- Next, attach the black cable to the black terminal of the good battery, and the other black cable to a clean, unpainted metal surface under the disabled car's hood.
- Start the car with the good battery, and leave it running for 2 to 3 minutes before attempting to start the disabled car. Because the alternator is bad, you will not have much time before the battery drains again, so it is best to get to a dealership or auto parts store to have the alternator replaced.
Use a portable car battery charger
- This option is similar to jump starting the car, but it does not require another car's battery. It does require a place where the portable charger can be plugged in.
- Attach the cables the same way that you would to jump start your car, set the charge rate and keep in mind that the higher the charge rate, the higher the internal battery temperature; this can affect the life of the battery.
- Finally, plug in the charger, and turn it on to begin charging the battery.
If the battery dies due to a bad alternator, the best solution is to get a new alternator. In a properly functioning car, the alternator is the primary source of electricity to the car, and it also recharges the battery. The battery provides temporary power to start the engine and run accessories when the engine is not running, such as the lights or the radio.