How long will a battery last with a bad alternator?

How long can a car last on just the battery? If your alternator fails when you're far from home, you can typically drive up to 200 miles on battery power alone. That's assuming your battery is in good shape and fully charged.

How does it sound when your alternator goes out?

Most of the time a bad alternator doesn't make any unusual noises at all. But if it's squealing or grinding or chattering or the belt is tight and the belt is slipping on the alternator pulley, etc, which makes the BELT squeal, then the alternator has gone bad.

January 9, 2024

Will a bad alternator drain a battery when the car is off?

Yes, a bad alternator can drain a car’s battery even when the car is turned off. The alternator is responsible for charging the battery while the engine is running. If the alternator is not functioning properly, it may not provide the necessary charge to the battery, causing it to slowly lose power over time, even when the car is not in use. This can lead to a dead battery if the issue is not addressed. If you suspect your alternator is bad, it’s important to have it inspected and replaced if necessary to prevent battery drainage and potential starting problems.

Will the battery be dead if the alternator is bad?

Yes, if the alternator is bad and not charging the battery properly, it can eventually lead to a dead battery. The alternator’s primary function is to generate electricity to charge the battery and power the vehicle’s electrical systems while the engine is running. If the alternator fails to do so, the battery will rely on its stored charge to power the car’s electrical components. Over time, as the battery’s charge depletes, it can result in a dead battery, leaving the car unable to start.

So, a bad alternator can indirectly cause a dead battery if it is not addressed, as the battery will lose its charge without being replenished by the alternator.

What is draining my car battery when its off?

If your car battery is draining when the car is turned off, there could be several reasons for this issue. Here are some common culprits:

Parasitic Draw: A parasitic draw occurs when something in your car’s electrical system continues to draw power even when the car is off. Common causes include interior lights, trunk lights, glove box lights, or aftermarket accessories that are not wired correctly.
Faulty Alternator: A bad alternator, as mentioned earlier, can lead to a dead battery as it fails to charge it properly while the engine is running.
Battery Age and Condition: Over time, car batteries degrade and lose their ability to hold a charge. If your battery is old or in poor condition, it may not retain its charge well, leading to a drain when the car is off.
Electrical Issues: Faulty wiring, corroded connections, or damaged components in the electrical system can cause unintended power drains.
Aftermarket Accessories: If you’ve installed aftermarket accessories like alarm systems, audio systems, or dash cameras, they can sometimes draw power even when the car is off if not installed or configured correctly.
Malfunctioning Components: Certain vehicle components like the radio, power seats, or power windows may have issues that cause them to draw power when the car is off.
Extreme Weather Conditions: Extremely cold or hot weather can affect battery performance, potentially leading to a discharge.

To diagnose the exact cause of your car battery drain, it’s often best to have a professional mechanic perform a battery and electrical system inspection. They can use specialized tools to measure the electrical draw and pinpoint the issue.