Automotive Voltage Regulator

Automotive Voltage Regulator Function

An automotive voltage regulator is an intermediary between the alternator and the battery. It regulates or maintains a constant output voltage despite variations in the input voltage, thus, the constant supply from the alternator to the battery.

The alternator usually produces more than 15 volts when the car is running and if there is no regulator the battery will be repeatedly overcharged and will be ruined in a short time. Not only the battery is ruined but the car’s fuses and electrical lines may also melt.

A normal battery could serve your car for three to four years or even more depending on how the car is used. Without the voltage regulator, your battery life will be shortened and will cause you more expenses in car maintenance.

How Current is Regulated?

A car’s normal electrical voltage should not exceed 14.5 volts when the car is revved. When the car is idle the voltage should not be lower than 12.6. The normal voltage of a battery is 12 volts.  This will supply all the lights, the fans or blowers, air-condition, dashboard, and everything including audio if there are.

If the regulator is set to charge the battery at 12 volts it will run short. In the long run, you will notice that the headlights dim. That tells you that the battery is being drained because it is being undercharged.

In that case, the regulator must be set at a higher voltage than the battery reserves and conserves.

In a brand new car, the company has set everything in place. But in a car used for many years and it had gone electrical modifications and repairs, the new owner may not know that there is a voltage related issue. It should be fixed as soon as possible for if not you will have more expenses due to battery ruin and electrical lines busting.

How does the Regulator work?

Either undercharging or overcharging are both detrimental to the car battery but the worse thing is overcharging. Never an alternator is running in a deficit current because it produces a maximum or even more than 15 volts.

This is the reason why the voltage regulator is a very important part of the electrical system in a car. It is to set the proper voltage for the battery that will work for all the electricity needed during the night and day operation of the vehicle.

The alternator should not work directly or it bypasses the battery, its function is to charge the battery and the battery will do its function for electrical supply for the car to work efficiently. But in between the regulator does its work also.

Let’s picture it in this way. Everyone owns a cellphone and you need to charge it when the battery is low. You needed a charger and the charger is plugged into the electrical outlet that supplies 110 to 220 volts. The cellphone charger is equipped with a voltage regulator inside the charger. When you charge your cellphone from a 220-volt electrical line, without the charger’s voltage regulator the cellphone battery will surely burst.

From 220 volts to 6 volts you can charge your phone safely.

This is how the voltage regulator works in a car. The alternator produces a current that is more than what the car overall operation needs and the voltage regulator controls, sets the limit of electrical current that is enough for the battery.

Automotive Voltage Regulator-battery


Symptoms of battery overcharging

1. Battery liquid dissipates-batteries maintained with liquid or water should stay in the for a long time in the level indicated on the battery. If it dissipates in an unexpected time you suspect that the battery is over overcharged.

2. Battery overheats and liquid boils-if you drive your car and you see liquid spills over the battery, even not much, that means it’s being overcharged.

3. Fuse Melts-You may be wondering why the fuses melt. Not only fuses but the wirings. The reason is that the battery is being overcharged. Because the battery has a limited load it releases whatever excess that it cannot contain.

These are some of the signs that you have to keep watch when your vehicle doesn’t have a dashboard that warns you of electrical issues. 

In need of voltage regulators, you can have your choice of brands:

Standard voltage regulator
ACDelco E650C Professional Voltage Regulator


Before you leave please leave a comment on the box below. I would like to hear your stories on automotive, your driving experiences and your wisdom that would enrich the knowledge of our readers.

Thank you and you can also watch videos related to this post:

Voltage Regulator Videos



10 thoughts on “Automotive Voltage Regulator”

  1. I have zero knowledge of voltage regulators up until this article. The way you explained what it is and how it works was fantastic for us car “dummies” to understand. This is important stuff too. I can now look at my battery for signs of over charging and what to do about it. I really enjoyed this and thank you for providing this information. 

    Best Wishes


    • Thanks, Melissa for your comment. I’m happy this simple post helped you in some aspects. Have a happy driving with a reliable battery taken cared for by the voltage regulator.

  2. Hi Jimmy,

    Thanks a lot for that guide on automotive voltage regulators. It is very informative.

    I have a Toyota that has thus far not given me any issues with the battery but I’ve always wondered if it is still optimally performing or not. I’m not sure how new it is either. 

    Your post has given me clues of what to look out for- e.g. dimming of lights, liquid spillovers, and fuse melts. I’ll be on the look out for these. I didn’t honestly have that information before, so thanks again.


    • Hi, Boniface. I would suggest that you go to a battery center and let your voltage regulator output checked. To know how old is your battery just think how long have you been using the car.

      Dimming lights tell the battery is weak, liquid spillover tells the battery cap is not tight or the battery is being overcharged, the fuse melts asks for the checking of voltage.

      Thank you for your comment.

  3. I really like this post, because I am a new car owner and I have been searching and trying to learn more to help me take care of my second hand car. And your post just gave me some great insights on the health of my car battery. I will be very careful and attentive to any sign of battery overcharging.


    • I’m happy Adyns that this post helped you and gave a sense of being attentive to any sign of battery overcharging and you being responsible to check for immediate address of the issue.

      Thanks for your interest.

  4. I remember when i was taking a course on automobiles few years ago, that was when I knew how important voltage regulators are.. The impact of voltage regulator cannot be overemphasized; it works hand in hand with the alternator (glad you’ve talk about the alternator as well); The voltage regulator makes the alternator to make more current in the electrical system of your car. The voltage regulator will also help the alternator to produce more output, when the voltage of the electrical system is low. In the electrical system the voltage regulator is responsible for putting the alternator on and as needed to maintain voltage at the proper level. The course was fun then, and still very much in my head.

    Thanks for the insight.


    • Thanks for your input, Jordan. It’s enriching when knowledgeable people share their own expertise. I do accept I should study more on the aspect you mentioned because as of this moment it’s somewhat unreliable to me. Although I thank you for that contribution.

      A very important function of a voltage regulator is to control, according to how it has been set, the current that supplies the battery.

  5. I guess it is easier to jump into a car and drive away than knowing exactly what to do when the car breaks down at some point. That is why I felt the necessity to study all these important aspect of the functions within my car.

    At least now I understand better why there are spills on my battery occasionally.

    Hmmm… never knew this is what the voltage regulator does either.

    Thanks for this educative tutorial, really very handy.


    • Yes, oftentimes people don’t mind what is happening about their car until the problem is severe. Knowing the symptoms of a problem can lessen our expenses and time.

      Thank you for reading and I’m glad you’ve been enlightened.


Leave a Comment