How To Know The Normal Voltage For Alternator

To answer the question “How many volts should an alternator put out?”, we will notice that the normal voltage for alternator should maintain between 13.5 and 15.0 volts of power. 

A normal alternator will help you charge the battery and provide power to all electrical devices on the vehicle.

If your radio, headlights, and electrical connections are turned off, you’d better check the alternator. Is it running normally? 

In this article, you will find more details. Scroll down!

Working Principle Of Alternator

normal voltage for alternator
Working Principle Of Alternator

There are many methods of generating an electric current. In the normal alternators voltage, people use coils and magnets to generate current in the coils.

The electromotive force generated on the coil is greater when:

  • The more turns of the wire
  • The stronger the magnet
  • The rotation speed of the magnet is faster

The flux through the coil will increase when the magnet gets closer to the coil. At the same time, when the coil is moved away, the magnetic flux through the coil will decrease.

That’s what we have based on the theory of fundamental physics. In practice is applied:

  • Electromagnets replace permanent magnets. Initially, starting the car will draw electricity from the battery’s performance.
  • Having an extra steel core will increase the magnetic flux through the coil.
  • Generate a magnetic flux loop that changes flux continuously.

The Symptoms Of A Bad Alternator

how many volts should a alternator put out
What Is The Telltable Sign Of A Bad Alternator

The Lights That Are Too Dark Or Too Bright

When the car alternator voltage has trouble, the battery load is not fully charged, and the vehicle’s electric equipment is also affected.

The light system on the car will be weak, dimmer than usual, too bright, or have a phenomenon of flickering lights at dawn.

The radio, sound system, and entertainment system are all weak. The sound is not clear when you press the accelerator pedal.

Battery Is Dead

Sometimes, a dead battery has achieved the end of its lifespan after several years of use, or you may have accidentally left your lighting on all night.

On the other hand, a bad battery might indicate that your alternator is suffering trouble.

A badly running alternator will not recharge the battery while the engine is operating, which causes the surface charge to drop more quickly than usual.

Starting the vehicle is one way to approach to see if the issue is related to the battery or Asian alternator. If you begin driving and it still works, the battery might need to be replaced as soon as possible.

However, if you start your autonomous vehicle and it immediately stalls, you can understand that your alternator output is not producing enough electricity to the battery or your alternator diode failure.

Problem To Start Or Stop Frequently

The engine is difficult to burst, or defective starters can come from a variety of reasons, including weather, battery, exhausted fuel, etc.

Moreover, there is another reason derived from the alternator load.

The battery is powered by the alternator. When the vehicle components face a hard-to-start occurrence, indicating that the amount of power in the battery is insufficient.

If the cause is not from the battery, it is definitely from the alternator, which is the battery’s power source.

The Methods To Realize The Normal Voltage For Alternator

good alternator voltage
HowTo Realize The Normal Voltage For Alternator

Examining The Alternator Monitor

Any competent and complete alternator testing procedure must consist of an amperage output measurement. A volt or amp gauge will calculate the alternator power circuit for you.

Run the engine speeds at 2.000 revolutions per minute (rpm) for checks and switch on the blowers fan for the heater, headlamps, or other accessories that put pressure on the alternator internal, and monitor the dash voltmeter gauge to see if it drops volts or amps.

As a principle, if the voltmeter reads greater when the engine is operating than when it is not, you may make a certain claim that the alternator is a charging system.

Listening To the Alternator While The Machine Is Operating

While the machine is running, try to focus on the alternator power ratings. If the bearings have a problem, the front of your vehicle application will make a small noise.

This sound becomes louder when there are a large number of electrical accessories used at the same time.

Plug The Radio On And Crank The Engine

Through the radio, you can detect the problem with the alternator by turning on the radio and pressing the gas hard.

If the sound of the radio playing at the AM frequency is fuzzy, the reason may be caused by the bad alternator readings.

Testing The Alternator For Free In An Auto-Parts Retailer

If you suspect that the alternator function is having a problem, you may take your car to a parts store to check it, and the appropriate solution can be found.

This is the most common method used by automobile owners to check the alternator temperature. You should replace it if the alternator tests badly or is too old.


What Is The Typical Charging Voltage?

A typical alternator charging voltage is between 2.15V/cell and 2.35V/cell.

Because these alternator voltages are lower than the exhausted gas and cannot destroy the electrolyte, they may be adapted to fully charged batteries without overcharging or damaging them.

When we check closely, we can see that the automobile battery voltage is normally between 13.7 and 14.7 volts while it is running.

If you switch off the engine, the battery voltage must be 12.6 volts or above. This is known as the “resting voltage” phenomenon.

If you don’t have a multimeter, you may test the battery voltage by starting the engine and turning on the headlights.

Is 11.9 Volt Sufficient Able To Start A Car?

In an urgent situation, you must alter the battery or take Jump Starter to run the engine. As a result, the least voltage output to start the automobile is 11.8V.

Sometimes, you might be able to run at 10.8V. According to good alternator voltage regulation, we don’t advise you to use that solution.

How Much Power Does An Alternator Generate At Idle?

An automotive alternator generates from 13.8 volts to 14.3 volts at idle without turning the alternator lights or equipment on.

A completely charged battery should have a voltage from alternator reading of more than 12.6 volts. Moreover, the actual output voltage will normally be 1-½ to 2 volts greater than the battery voltage.


It’s better to double-check the normal voltage for alternator if your car starts slowly or won’t start as these are the two main possible causes.

In addition to using a voltmeter to check an alternator issue, you can also use a multimeter to check for accurate results.

Remember to use gloves to protect your hands from hazardous chemicals like battery acid. 

The car owner can check the alternator repair by himself or bring it to the maintenance center for an alternator testing method and professional visual inspection.

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