The car battery is not charging even though the alternator is good

An alternator’s main function is to generate electricity from the vehicle’s components and charge its battery. The alternator produces this energy through the conversion of mechanical energy.

When starting the vehicle, the battery energy alone won’t be enough to run the engine if the alternator is not available or defaulted.

Therefore, it is the alternator’s role to charge the battery and keep the battery recharged and alternate the electrical current through the car’s many components and keep them powered.

However, sometimes the car battery fails to charge even when the alternator is in good condition. When the car battery doesn’t charge, there will not be enough power in the ignition system, and therefore the car engine won’t start.

Why doesn’t the car battery charge even if the alternator is good?

Having a battery that won’t charge can be a frustrating experience, and most probably, the first thought would be replacing it. But understanding why the battery won’t charge will be of great help as it can save you a lot of costs.

If you experience problems with battery charging even when the alternator is in good condition, then there might be problems with the wiring system, the ECU, and maybe the battery is damaged or too old.

Possible causes why the car battery won’t charge

The following are some of the reasons why the battery might not charge even with a good alternator.

1. Wiring problems

There are various car parts that aid in power production for the alternator. It only takes one wire to be disconnected or cut for power to halt being generated.

Due to this, the alternator cannot charge the battery until the wire is replaced or repaired. The engine vibration can cause loose battery connections.

A damaged or loosened battery cable can minimize the electrical contact between the battery and the alternator. Moreover, other wiring problems can lead to the charging system’s electrical problems, like an ungrounded neutral.

2. There is a consumer that drains your battery

A flat battery is often caused by headlights forgotten on, but sometimes other sources can discharge the battery especially if the car’s off. Because of this, the battery won’t be charging as required. You need to find the culprit and remove it.

Car components like Bluetooth kits and interior lighting need to be shut down when the engine goes off. However, if these parts do not correctly shut down, they can drain the car battery.

Some car components need a live power connection to retain particular settings and can produce an abnormal draw on the battery and lead to battery failure.

3. Too old or damaged battery

The Vehicle’s lead-acid battery often lasts for about three to four years. So when the battery is damaged or too old, it bloats and develops cracks leading to the battery’s acid or even rusting.

Old car batteries are also affected by sulfation, whereby the battery cells’ internal plates get damaged. While it can be reversed at early stages, all lead-acid batteries are subject to sulfation.

4. Damaged alternator belt

The alternator belt drives the car’s alternator. The belt is responsible for allowing the alternator’s speed to be in line with the engine’s. The belt can be damaged or become loose and slip off the alternator pulley in some cases.

5. Computer error defaulted ECU.

Most cars have a central computer system that operates and manages the car’s parts and components. Moreover, the ECU also manages the alternator, implying that the alternator might not be functioning well if it is defected, hence preventing it from charging. The ECU errors often come with symptoms like the Check Engine light turning on or engine stalling.

6. External battery charger issues

When using an external battery charger, it is important to ensure it is properly connected by ensuring that the positive lead goes to the positive terminal and the negative lead to the negative.

Some batteries might require specific chargers for charging, so the battery charger might not be the right one. Therefore if any mix-up happens, the battery won’t be properly charged.

Symptoms that tell the driver that the battery is discharging fast

It is always inconvenient to start a car with a dead battery. However, this can be avoided because a discharging battery can always give warning signs to make the driver aware and avoid frustrations.

Here are the symptoms of a discharging battery a driver can note.

  • Dim headlights
  • A clicking sound when turning the key
  • Slow engine crank
  • Dashboard warning light illuminated
  • loose battery terminals
  • Backfiring
  • A need to press the gas pedal to start the vehicle
  • Overheating battery
  • Noises under the hood

Solutions for a discharging battery with a working alternator

Battery charging problems are obvious but somehow challenging to determine the root cause. The first step to take after experiencing the failure is to inspect the whole electrical system.

There are various solutions to discharging batteries, but the easy solution is taking the car to a mechanic who will identify the root cause of the problem and make necessary amendments.

Other solutions include

  • Removing or stopping unwanted consumers
  • Fixing the wiring problems
  • Replacing the battery
  • Repairing or fixing the ECU
  • Repair and replacement costs

Replacing a damaged car battery can cost about $70 to $700 depending on battery type, car technology, type of car, and the mechanic you visit.

How do I know if my alternator is not charging my battery?

Here are the signs to know that your alternator isn’t charging the battery.

  • Dead battery, overly bright or dim lights
  • Malfunctioning or slow accessories
  • The smell of burning wires
  • Dashboard battery warning light

Is there a fuse between the alternator and battery?

Yes, in most cases, there is always a high amperage fusible link or fuse between the battery and the alternator’s battery; or terminal.


Sometimes the car batteries can fail to charge even with a good alternator. While this comes with several frustrations, it is unavoidable.

The common causes of a discharging battery with a good alternator include wiring problems, damaged battery, battery power drain, computer error, and external battery charger issues.

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