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Alternator or Battery Issues: All You Need to Know

Most car drivers are familiar with the sinking-gut feeling they get when the car suddenly doesn’t respond when the ignition gets engaged. 

But what could prompt a car’s unresponsiveness on a random day? The issue might stem from an alternator or battery malfunction.

Call Nationwide Report’s Car Genius™ from RepairPal at 1-877-671-3040 from 9am-6pm ET, Monday through Friday. 

When Is the Alternator or Battery the Problem?

In a car, you start the engine in a three-step process. The first step is when the battery delivers an electric charge to the starter — the first turn of the key in most cars. This act starts the engine.

The second step involves activating the alternator. The last stage occurs as the alternator completes the loop by charging up the battery.

The battery and the alternator play a significant role in the engine start-up process. If you’d like to know if your car’s battery or alternator is faulty, you can jump-start the car (start it without the battery, using jump leads).

One of two things might happen: the car starts but dies shortly after, or runs only to die after you replace its own power. 

The first instance suggests the alternator isn’t charging the battery to keep the car active. The second scenario most probably points to a flat car battery.

Functions of a Car Battery

The fundamental role of a car battery — or any battery — is supplying energy to the system. Beyond that, a vehicle battery acts as a backup power source for the car’s electrical appliances, whereas an alternator is the main power source.

Typically, a car battery gives out about 600 amps for electricity. However, this value can go up to 2000 amps in heavier-duty engines. 

By design, vehicle batteries dump most of their amps during the vehicle’s starting phase because the engine needs significant energy to start. Once the engine is up and running, the battery is recharged by the alternator afterwards.

In this system, the battery might have problems when it doesn’t have enough charge to give when you start the car. Also, this structure also affects its ability to retain a charge from the alternator.

Signs of a Bad Car Battery

These are the tell-tale symptoms of a bad car battery you might want to check out:

  • The Dashboard Lights are Dim

If your car has a battery gauge on the dashboard, you might want to check it first to see if it still gives charge, even when the engine is off. 

Next, inspect the general dashboard lights: if dim, it’s likely the battery has a problem. To confirm, try turning on the lights, automatic windows or windshield wipers to see if they respond as they should.

  • Signs of Corrosion

Rusty battery leads might be the reason your car isn’t starting. 


The corroded area makes it almost impossible for the electricity to get delivered adequately. Thus, it’ll be best to check your battery to see if its leads have corrosion on them. If they do, simply use a rag to scrub the rust out, and continue using as normal.

  • Use-Past Date Exceeded

As with all automotive products, a car battery has its expiration date. Not just that, it holds less charge as it ages because the metal components inside degrade and corrode over time.

When the battery wears out, it won’t hold charges from the alternator. Here, it’s best to replace the battery.

  • The Radio Won’t Come On

Once the ignition is active — just before you start the engine — the battery should be able to power on your radio and the car’s internal and external lights. 

If that’s not happening, or you see flickering radio lights, the battery might not have enough charge in it. It could also mean the battery can’t hold enough charge.

  • The Engine Runs and Dies Immediately

Some car owners may experience their car starting and dying shortly after. While there are many reasons for that, the battery is usually one of the first culpable components for this deficiency. 

In some cars, the battery only holds enough voltage to start the engine, but not run it.

  • The Battery Case Has a Visible Bulge

If you notice that the battery unit is visibly swollen, you don’t need a clearer sign to tell you it needs a change. Swollen batteries are a result of the unit edging close to or exceeding its expiry date. 

However, if you think you haven’t used the battery for long, the problem might be traceable to the alternator overcharging the battery over time. 

This scenario will likely happen when the alternator has a faulty voltage regulator. 

Functions of an Alternator

The alternator is a miniature generator that powers the electrical appliances in the car. It plays the double duty of charging the car’s battery. Alternators have different voltage counts, with the average being 13 – 15 volts. 

The amps they deliver also vary, depending on the car. However, you can expect an estimated 200 amps in most factory setups.

Depending on your use case, you can install a more powerful alternator into the car. For instance, if you’ve installed a stronger stereo system in the vehicle, you’d need a larger alternator to handle all the extra amps drawn by the appliance and ensure the battery remains charged upon engine ignition.

Furthermore, car alternators won’t always deliver a full amperage while the car is running. 

For instance, when the engine idles or is at low RPMs, the alternator output drops to avoid wastage. 

This add-on always prioritizes the engine ignition and other electrical appliances in such cases, which means that the battery won’t be getting charged all the time.

Signs of a Failing Alternator

If you’ve checked all the signs of a faulty battery only to find that it is performing optimally, it’s time to turn to the alternator. 

Since both components work in harmony, your vehicle probably has a faulty alternator if it refuses to start with a good battery. 

How do you check for an alternator about to give out? 

Below are crucial signs:

  • The Interior Lights go Dim

When the car is running, check the interior lights to see their behavior. If you notice that they go dim gradually, the alternator is possibly giving out.

  • A Growling Noise under the Hood

If you notice some malfunctions with the car’s ignition, you might want to pay attention to the noises you hear. If there’s been a growling noise when you try to start the engine, you might have a faulty alternator.

  • The Headlights Fluctuate With the Engine

As the engine runs and the car is in motion, check the headlights to see how they function. 

Normally, they should maintain the same brightness whether the engine revs high or low. There could be a problem with the alternator if the lights glow and dim as the car accelerates or decelerates.

If this happens, the alternator isn’t keeping the battery charged as it should.

  • You Can Smell Burning Rubber or Hot Wire

If you smell burning rubber while your car’s engine is running, it may not be your tires that have caught fire. This smell might seem from an alternator about to go bust. Thus, check the alternator and its belt to confirm. 

Conduct alternator maintenance immediately once you can trace the smell to the component.

  • It Fails the Alternator Test

You don’t always have to wait for the component to fail before you know it needs changing. With the alternator, you might have to test to know how good it still is for your car. 

A typical recommendation is hooking the alternator to a negative battery cable before starting the engine. Note that such a move might not be the best for your car, as negative cables can damage its electrical system, thus exacerbating the issue.

Is it Possible to Drive a Car with a Bad Alternator or Battery?

Automobiles are an incredible work of engineering, and it’s interesting to see how they can perform with one or more of their components malfunctioning. If the vehicle has a faulty alternator, it is possible to start the engine and let it run for a while. 

However, this approach isn’t safe. Running a car with a bad alternator or battery poses significant risk to the driver and other road users. The faulty pieces can lead to significant damage in the car if you don’t replace them promptly.

What’s worse? The battery may die at an inaccessible location, leaving you stranded. If your car has power steering, a weak or faulty battery could make you lose control in motion, increasing the risk of an accident.

Don’t drive with a malfunctioning alternator or battery. If you notice any of the aforementioned tell-tale signs of issues in these car components, head to a mechanic to conduct battery or alternator car maintenance.

How to Prevent Malfunctioning Car Batteries or Alternators

Car batteries and alternators will wear down over time, but you can prevent issues from cropping up sooner through your driving habits.

If you’re an infrequent driver who only takes short trips and leaves the engine off for days, your car battery will deplete much faster. 

The remedy?

Take the vehicle out for a drive more often, or install a device that lets the battery trickle-charge while you’re away.

In view of great car maintenance, it’s best to clean the battery terminals regularly. That’ll prevent charge leaks or unwanted discharges when the engine is active. 

Also, apply “dielectric grease” on the battery’s contact points to prevent corrosion.

FAQs About the Alternator and Battery

Below are some likely questions car drivers might have about the charging components in their cars:

How Soon Can I Replace My Alternator or Battery?

While conditions may vary between vehicles, note that faulty car batteries can’t damage the alternator. 

However, a bad alternator can ruin the battery. You’d need to have both components in working order for the engine to work properly.

If the vehicle’s battery is faulty, you can change them. Luckily, they’re comparatively inexpensive to replace, costing only about $100 for the regular lead-acid types. Conversely, alternators are expensive, and can cost up to $1000 for replacement and workmanship.

However, you can repair a faulty alternator instead of replacing it with a new one. Although this route would save you some money, its success is dependent on the car type.

How Do I Check How Much My Car Battery or Alternator Puts Out?

The first thing you’d want to do is connect the battery to a voltmeter or multimeter. Connect the meter’s leads to each of the battery’s terminals and take the reading. While the engine is off, you should get a reading of about 12.6V for a healthy battery. This reading can go up to 14.4V when the engine is running.

Another step to take is to activate the lights and other electrical appliances and take another measurement. This activity gives the alternator reading, which hovers around 13.5V for a working unit. 

Furthermore, your car may have a gauge that shows readings on the battery or alternator amps. It helps to check for those, as they might give a great idea of your current battery output.

Can I Drive the Car With a Bad Alternator?

As mentioned earlier in this piece, it is possible to drive a car with a bad alternator, but that doesn’t mean you should do it. The car battery won’t get enough charge in such a setup, which can cause your engine to stall at any moment. 

Engine stalls can leave you stranded in locations you might not like, and prompt other car malfunctions that could prove expensive in the long run. 

If you need to start the car with a faulty alternator, try wiring the battery to a charger between engine starts. That way, there’s enough power to finish the process. Since this procedure can be slightly inconvenient, the best option is to have the alternator fixed as soon as possible.

Can I Take Out the Battery While the Car Is running?

It’s possible, but avoid doing so. In modern-day cars, removing the battery while the engine is running can cause voltage spikes to cover the sudden imbalance. This scenario can damage crucial electrical circuits you have in the car, like the brain box.

Can a Vehicle Alternator Charge a Non-Car Battery

You can use an alternator to charge other big batteries besides the car battery. 

Different methods exist to plug up the alternator to a house battery or third-party battery banks. The parallel method links the alternator with the starter battery and the battery pack to get it charged.

In other charging setups, there’s an external regulator for the voltage, and an amp controller.

What Goes on in an Alternator?

An alternator integrates several add-ons, such as the stator, voltage regulator, rotor and diode. 

These components connect to the car engine with an alternator belt. The belt gets spun up by the rotor and generates current.

The diode plays the role of a converter by changing the AC current the rotor generates into a more stable DC. The voltage regulator completes the task by regulating electrical output.

How Do I Know When the Starter Motor Has Given Out?

The starter motor lies between the battery and engine, feeding the engine starting power from the battery. 

If the starter motor is failing, you’d notice these signs:

  •  A flickering clicking sound upon turning the key at ignition, yet the engine doesn’t start
  • Lighted dashboard, yet the engine doesn’t start
  • An idle engine after a jump-start

Once a vehicle diagnosis points to a faulty starter from these signs, it’s best to swap it out for another one as quickly as you can.

Wrapping Up

The battery and alternator depend on one another: the former requires the latter to remain charged, and the operation is often vice-versa once the engine is on. 

So, if you notice an issue with any of the components, it’ll be best to fix them immediately and avoid further damage to the vehicle.

However, it might help if you knew the signs to look for in a faulty car battery or alternator, as we’ve highlighted in the paragraphs above. 

You can conduct battery or alternator car maintenance yourself or have a professional mechanic check it out for you.