How Long Will a Battery Last With a Bad Alternator?

Most of the ignition and electrical problems in a car come from the battery or the alternator. The battery relies heavily on the alternator for most of its work, and if the alternator is bad, your car may not run for long. To find out how long your car battery will last with a bad alternator, read on;

What is an alternator?

The alternator is a generator that helps convert mechanical energy into electrical energy. The alternator charges the battery, thereby helping to distribute electricity to the car, which makes it an essential part of the car. If you suspect a damaged alternator, it is best to get it checked out immediately as your car battery may not start or work for long.

Signs of a bad alternator?

Many indications show that the car alternator is not working. Here are some common signs to look out for:

  • Flickering headlights

A car’s headlights should maintain a bright light regardless of the driving speed. If the headlights flicker or become brighter with increased RPMs and dimmer with low RPMs, it can mean the alternator cannot generate enough power.

  • Indicator light

Most vehicle dashboards have a warning indicator light labeled ALT or GEN. When this indicator lights up, it may mean that the alternator has faults. This is one of the car’s early signs for a bad alternator. It’s advisable to check it out as soon as possible.

  • Unusual sound

A strange sound coming from the car can mean a lot of things. However, the alternator comprises many spinning parts, and a strange sound may mean one of the parts is malfunctioning. The sounds from a bad alternator are commonly grinding, and whining, which coupled with a continued weakened battery shows the alternator is bad.

  • Dead battery

The alternator charges the battery to replenish the energy loss in running the car. A dead battery can mean the battery is bad or the alternator is bad. You will likely have a bad alternator if jumpstarting works for your car.

  • Strange smell

Another way to detect a bad alternator is a strange smell from under the car hood. This can be due to overheating as the alternator is working too much. If you detect a smell of hot wire or electrical fire, it is probably from a bad alternator.

car alternator

How long will a battery last with a bad alternator?

A car can still work perfectly even with a bad alternator as most of the energy consumption is on the battery, but how long will the car last? A battery will not last long with a bad alternator even though many factors are involved. Some of these factors include the type of engine, how modern the car is, the type of electronics in the car, the time of day you’re driving, how charged the battery is, and the battery’s age. As all these factors are different for each car, we can’t state exactly how long the battery will last.

Can a bad alternator destroy a new battery?

There is a possibility of a bad alternator destroying a battery. The alternator charges the battery so the battery doesn’t lose power while running the car. A bad alternator can cause the battery to lose power faster than expected and cause the battery to wear out. This is a process called sulfation which occurs when the battery is not receiving enough charge.

How long will a battery last without an alternator?

We can’t estimate how long a battery will last without an alternator. However, based on the capacity and the battery’s condition, the car can last for a bit more or less than 5 – 30 minutes without an alternator. This depends on the electrical components used in the car. This shows that the car battery will not last long without an alternator.

How long will a car run with a bad alternator?

A car can run with a bad alternator, but the time it runs for may vary from car to car. However, it will not last long with a bad alternator. A few factors can determine the duration, such as the state of the battery and the model of the car, which is the main factor. 

Can you drive with a bad alternator?

Yes, you can drive with a bad alternator, but it’s unlikely you drive well and for long. As pointed out, the alternator plays an important role in the car’s performance. So, if the car has a bad alternator, it won’t take long before the car or its components stop working.

Bad alternator vs. Bad battery

The alternator and the battery depend on each other even though they serve different purposes to keep the car going. The alternator sends charges to the battery to replenish the electrical charges used while the battery helps the ignition turns on the engine and distribute current to various electrical components. Either one of them going bad can result in car failure. Here are some ways to differentiate if the alternator or the battery is the one at fault.

Signs of a bad batterySigns of a bad alternator
– Dim headlights 
– Clicking sounds when starting
– Pressing gas pedal to start
– Backfiring
– Corroded battery terminals
– Battery not holding charge
– Flickering headlights
– Whining or grinding sounds
– ALT/GEN dashboard indicator light
– Electrical failure
– The smell of burning rubber or hot wire
– Weak or dead battery

Risk of Driving with a bad alternator

Even though the car can run with a bad alternator, it has risks since the battery will have to carry most of the car’s power outage. Some of the risks involved are:

  • The car can lose power and break down since the alternator that should replenish the lost power is bad.
  • Battery drain: a bad alternator will allow the car battery to drain faster than usual, which can leave you stranded on the road. Also, a bad alternator can shorten or destroy the battery’s ability to hold a charge.
  • Fire hazard: due to the increased workload on the battery, it can cause overheating, leading to the battery catching fire.

Tips for driving longer with a bad alternator

Driving with a bad alternator is not advised, but there are ways you can drive longer if you’re far away from where you can get someone to fix your alternator. Here are a few tips to follow to drive longer:

  • Have a jumpstart booster or another car battery at hand when you want to start your car
  • When driving, limit the use of electrical components like radio, light, fan, and power window
  • Swap the car bulbs for LEDs for less electrical consumption.
  • Make sure you don’t allow your battery to die completely before another charge
  • Fully charge the battery with a trickle charger as often as possible


As seen in this article, the alternator and battery are both important and co-dependent on the car’s performance. How long a car battery will last with a bad alternator is dependent on many variables, but ultimately the car will not last long. You should always be on alert for signs of a bad alternator and have it checked out immediately, as it can cause damage to the battery in the long run and cost more to fix the alternator and the battery. This way, you can maintain wellbeing and the high performance of your car.

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