When it comes to marriages, the one between your car's battery and its alternator is an uneven one. Both are important components of your electrical system, but while your battery is weighted with the responsibility of starting your car, it is the alternator that largely takes over from there.
While you're out running errands in your car or idling at the drive-thru coffee shop, your alternator is keeping busy powering the electrical components of your car like its headlights and power windows, and steering. Quite the multi-tasker, it also charges your car's battery at the same time.
Alternators have their own special way of letting your know they are getting tired often by emitting a whining sound from under your hood. Another way you may find out is if the car won't start. While it may be natural to assume your battery is on its last legs, it may be the alternator not sending enough power to the battery. An easy way to check is by a jump start. If it keeps running after you remove the jumper cables, then your battery needs a charge. If it dies again soon after, it's time to replace the alternator.
