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Here’s how long a battery will last with a bad alternator

Your car’s Alternator is essential for supplying power to electronic components in your vehicle, but how long will the battery last if the alternator is bad?

Your battery will last for around 25 miles or 30 minutes with a bad alternator. However, how long you can drive with a bad alternator will vary depending on how much charge your battery has left. To avoid any issues, you should fix or replace your alternator as soon as it starts malfunctioning.

After extensively researching automotive repairs, I’ve gathered enough information to determine how long a battery will last with a Bad Alternator. In this article, we’ll be taking a closer look at how your car’s alternator affects your battery performance, and what you need to do when this component requires maintenance.

What’s an Alternator?

While most people assume their car battery single-handedly powers all of their vehicle’s electronic components, the alternator actually deserves a lot of credit. Your car’s alternator is responsible for converting mechanical energy into electronic energy.

By doing so, your car can generate power when the engine is turned on. This lowers your dependency on your car battery for electricity, and it enables you to drive without having to recharge your battery.

Using an alternating current, the alternator works with your battery to ensure that all electronic components are fully functional. That is why car batteries can often die quickly if you leave the key in the ignition without turning on the engine.

How Long Can You Drive With a Bad Alternator?

The amount of ground you can cover with a bad alternator will vary depending on the charge of your battery and the condition of the alternator. 

In general, you should not drive more than 25 miles with a bad alternator. This should give you about 30 minutes of driving time before your car dies on you. Continuing to drive further than this will most likely result in you needing to be towed.

If you know that the alternator is bad, you should avoid driving your car until you get it fixed, given that a poorly charged battery may only give you 5 minutes of driving time. With that said, if you need to drive your car with a bad alternator, only use it to drive to the nearest mechanic, given that your vehicle will not make it much further. 

How Long Can a Fully Charged Battery Last Without an Alternator?

When your alternator goes bad, it can behave unpredictably and potentially drain your battery. If the alternator is totally ruined, your battery may actually perform better without it. 

If you are driving your car with a fully charged battery and the alternator is removed, you can expect to drive upwards of 1 to 2 hours before your car quits on you. In the best-case scenario, some drivers have successfully driven 100 to 200 miles with a fully charged battery and no alternator.

How Does a Bad Alternator Affect the Battery?

Driving with a bad alternator can result in unpredictable driving performance and it can have adverse effects on the health of your battery. 

The bottom line is that you should avoid driving with a bad alternator at all costs, and you should get the part fixed or replaced as soon as possible.

Insufficient Battery Power

When an alternator goes bad, it may fail to deliver adequate power to your battery. Insufficient power delivery from your alternator can result in your car dying while you are driving.

Overcharged Battery

Too much power is not good for your battery. A bad alternator can easily overcharge your battery, causing it to heat up. 

This will lower your battery life significantly and it can potentially fry the entire battery in just a few hours.

Damaged Electrical Components

A bad alternator can cause permanent damage to your battery, as well as the rest of the electronic components in your car.

Unstable currents can potentially pass through your vehicle, which could permanently destroy anything hooked up to your vehicle’s electrical system. 

How to Test if an Alternator is Bad?

Before you start taking apart your car to install a new alternator, you should check to make sure that it’s actually malfunctioning. 

Try using one of the following methods to test if your car’s alternator has gone bad.

Method 1: Headlight Test

You can test your alternator by using your headlights. Simply turn on your vehicle and engage your high beams to start. 

You will need either a second person to confirm the condition of the headlights or a mirror to see the reflection. With your high beams on, press on the gas (while in Park) and look at your headlights for any signs of flickering.

If the headlights flicker when you step on the gas, your alternator is bad.

Method 2: Battery Test

To perform a battery test on your alternator, turn on your car’s engine and pop open the hood. You need to disconnect the negative cable from the battery and wait to see how the vehicle responds. 

If the car stutters, stalls, or shuts itself off, it’s safe to say your alternator is bad.

How Much Does it Cost to Fix or Replace a Bad Alternator?

If the issue with your alternator is with one of its components such as the bearings, fixing it will be very realistic and affordable. Although the cost of labor for fixing a bad alternator can vary, you can expect to pay around $100 for the total costs.

With that said, fixing a bad alternator is not always an option. If the alternator has irreversible wear and tear, you will need to replace it. 

The cost to replace a bad alternator is usually between $350 to $550. A quality alternator will cost you roughly $250 to $300 just for the component, and you will likely need to pay $100 to $200 for labor. 

Key Takeaways 

  • Your battery will last for around 25 miles or 30 minutes with a bad alternator. 
  • The distance you can drive with a bad alternator will vary depending on how much charge your battery has left. 
  • To avoid any issues, you should fix or replace your alternator as soon as it starts malfunctioning.
  • You can perform a battery or headlight test to confirm if your alternator has gone bad.

This post first appeared on Driven Wheels — Canada's Automotive Authority, please read the originial post: here

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Here’s how long a battery will last with a bad alternator


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