Car Battery keeps Dying but Alternator is Good 2023

Vehicles are designed with several components to properly function in providing maximum satisfaction to the driver.

A simple fault with any of those components can alter the pleasure derived from the vehicle.

One of the common faults that most car owners face is when the car battery keeps dying, but the alternator is good. This problem can be so frustrating, especially when you are ignorant of the causes and how to rectify the faults.

However, whenever you experience this situation, do not panic, as sufficient information has been provided in this article to unravel the causes and how to fix the problem immediately.

Causes of Car Battery Dying when Alternator is Good

A car’s battery can die for several reasons, including; corrosion in battery terminals, loose battery cable connections, leaving dome lights or headlights on, charging problems due to a bad alternator, etc.

All the reasons that result in a car’s battery running flat, as outlined above, are common causes of battery drainage.

However, let’s focus on what could be wrong if a car’s battery keeps dying even when the alternator is good and working well. Some of the causes include the following:

Faulty battery

Batteries are manufactured and designed to live a specific lifespan before replacing them.

Also, a battery can be affected by high temperatures or extremely low temperatures from cold weather. All these factors over time can develop a fault in the battery.

If you have a faulty battery that partially charges or constantly discharges on its own, it doesn’t matter whether your car’s alternator is in perfect condition; the battery will keep dying.

The remedy will be to remove the battery and charge it fully with a battery charger or replace it.

Loose connections or battery corrosion

Batteries transmit electrical power through cable connections that link them to the designated systems of the vehicles where the power received from the battery is utilized.

That means a loose connection will alter the power transmission process.

Also, batteries can develop corrosion on their terminals over time, especially when they are not used for a long time.

The corrosions hinder the proper connection between the cables and the battery terminals; in that case, the cables cannot contact electrical power from the battery, and charging also becomes difficult.

So, it doesn’t matter whether your vehicle’s alternator is good; if you have a loose cable connection or corroded battery terminals, the vehicle’s battery cannot connect properly to charge; hence, it keeps dying.

Parasitic battery drain

Parasitic battery drain is another culprit to a vehicle’s battery dying even when the alternator is good.

Parasitic battery drain is when a vehicle’s battery runs down even when the engine is off, especially overnight when the car is not in use.

Unidentified short circuits, constantly ON interior or trunk lights that were not correctly turned OFF, etc., are some factors that result in a parasitic battery drain.

Sometimes, an ignition circuit fault may leave a car’s radio on when the vehicle is off, thereby draining the battery.

Faulty ground connection

A defective battery ground connection can result in several issues, including a connection problem between a vehicle’s starter motor and the battery.

When this occurs, there is a tendency of experiencing a poor start.

Also, a bad or faulty ground wire will hinder the proper charging of a vehicle’s battery.

So, while a vehicle’s alternator is in good shape, you may have a weak battery, which is possible because of a bad ground wire.

Not using battery over time

There is a common misconception that a car’s battery stays intact whenever the vehicle is parked and not in use.

Hence, some people believe they can park their vehicle and travel; then return after a long time to start the car and expect it to run exactly how they left it.

A car’s battery is designed to power several components, even when the car is off.

However, this process does not drain the battery to a point where it is difficult to start the engine the following morning. The battery drain when a car is off is in milliamperes.

However, when the car is left for a very long time, the drainage in milliamperes accumulates daily over the period until the battery is completely drained. So, starting a vehicle with a good alternator when the battery is completely drained is a complete waste of time.

How to Fix Car Battery Dying When Alternator is Good

Fixing a vehicle with an experience of a constantly dying battery even when the alternator is good requires that you first ascertain what may be wrong. The following remedies are directly referred to the various causes of battery drainage discussed above.

  • Remove and charge the battery fully with a battery charger or replace old batteries.
  • Tighten loose connections and clean corrosions on battery terminals and cables with a mixture of baking soda and water; then, apply it with a stiff bristle brush.
  • Get a heavy grounding cable to ground your vehicle properly.
  • Remove, inspect, recharge or replace a vehicle’s battery that has been left for a long time.

How do I test to see if my alternator is bad?

Usually, when a vehicle’s alternator is faulty, a dashboard light illuminates immediately to signal the driver about the fault in the vehicle’s charging system. Meanwhile, if you want to practically test to see if your vehicle’s alternator is bad, do the following:

  • Start the car’s engine and keep it running.
  • Disconnect the battery’s positive terminal.

After disconnecting the battery’s positive terminal, if the car goes off, the alternator is bad. If the car doesn’t go off, then your car’s alternator is still intact. So, if you have a bad alternator, ensure to fix the problem immediately before it leaves you stranded on the highway.

Related Post: How to test an alternator by disconnecting the battery


Can bad ground drain a battery?

Good ground is necessary for a vehicle’s battery to charge successfully. Besides any issues with a vehicle’s alternator or a defective wire connection between the battery and the alternator, the bad ground is also a culprit to quick battery drainage. Properly grounding a vehicle is necessary if the battery must charge appropriately. The process of grounding a vehicle requires using a heavy ground cable. To correctly connect the cable, attach one end of the ground cable to the negative terminal of the vehicle’s battery and the other end to the engine block very close to the starter motor or directly to the starter motor. When this is done, the vehicle’s battery will definitely charge correctly without glitches.

How long does it take for a bad alternator to drain a battery?

A vehicle’s battery is expected to power the vehicle properly under good working conditions. But this expectation can be disappointing due to a bad alternator. A bad alternator will alter the proper charging process of a vehicle’s battery and cause it to run dead. It doesn’t take the whole day for a defective alternator to run a car’s battery down. In most cases, a bad alternator can completely make a car’s battery go dead within 30 minutes. Sometimes, you may be lucky to discover that your vehicle’s alternator is bad after 2 hours before it totally runs the battery flat.

If you observe any symptoms of a bad alternator while driving, ensure to park the vehicle and check it out immediately; try to keep the engine running until you can contact an expert auto mechanic.

What can drain a battery if the alternator is good?

Even when a vehicle’s alternator is good, one major culprit to battery drainage is a defective diode. Diodes are expected to allow the flow of current in only one direction. This process is usually altered by a defective diode which keeps the vehicle’s charging circuit flawlessly open irrespective of whether the engine is running or not. When this occurs, the vehicle’s battery will run flat, even when it is off. This commonly occurs overnight when the car owner is asleep with the mindset that the car is in good condition. The tragedy is when the car owner tries to start the vehicle the following morning.

What is draining my car’s battery when it’s off?

Electrical glitches are the main causes of battery drainage when a vehicle is off. When a car is off, the battery still powers components like the radio, clock, and alarm system. However, these may not necessarily drain a vehicle’s battery. Electrical faults that keep the door and interior lights ON are suckers of a vehicle’s battery life. If you experience this situation, ensure to inspect the electrical components of your car to ascertain whether there are any faults that need to be rectified immediately.

Final thoughts

Your vehicle’s battery is a very vital component. A slight malfunction in the battery or its connections can hinder the proper running of your vehicle’s engine.

A lot has been unveiled about what may be wrong if a car battery keeps dying but the alternator is good, and remedies have also been provided.

If you ever experience a similar situation, don’t panic or hurry to get a new battery.

Ensure to inspect the vehicle’s battery and the connections to see what may be wrong. If it is something you can fix, go ahead.

If you aren’t sure of the problem or its remedy, kindly contact an expert auto mechanic.

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