Why Is Your Car Battery Voltage Too High? – Ask The Expert

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It’s the heart of your car and one problem relating to it can prevent you from going anywhere.

It’s your car’s battery. As with any human organ, this is a part you can’t simply leave until it stops functioning.

Checking it and maintaining it will ensure it lasts you as long as possible and the rest of your engine won’t be damaged by its malfunctioning.

Maintenance can even prolong its life cycle. But what if you notice a problem? If your car battery voltage is too high you need to tend to it directly. And we will show you how.

Is high voltage a big problem?

Why is this an important part of your vehicle maintenance? Is too much power in a car really a bad thing? It is if you want your car to last long.

The reason the power is regulated is that too much of it will cause risks:

  • The voltage will become dangerously high
  • The battery can overcharge which will leave it useless
  • Engine components that aren’t designed to handle the pressure, temperature or power will be damaged
  • The alternator isn’t designed to handle excessive power and eventually, it will burn out

This can happen without you knowing. Your first clue may be when your car cuts out or doesn’t want to start anymore. This is why regular maintenance is essential.

General Guidelines – What To Check For

How do you know if your battery is giving problems?

These days maintenance is fast and easy. You don’t even have to visit a professional mechanic. An ordinary volt meter or power probe can be used to test your battery. Simply make sure the battery wasn’t charged recently so you get accurate readings.

12V batteries. Your reading should be anything between 10V and 12.9V. An ideal reading is between 12.4V and 12.7V. Some experts say a reading above 12.6V is better. As soon as your engine is switched on it should increase to 13.7—14.7V.

If it reads below 10V, your battery is going to die very soon. When it rises above 12.9V—while your car isn’t switched on—you have a problem. This can turn into a hazard for you or your car, so you need to find the problem and repair it.

No, it’s not necessarily your battery. Many engine parts connect to the battery and the source of the problem can be there.

what to check

Reasons why voltage peaks

Loose connections

A simple problem of loose wires and connections can cause your battery voltage to fluctuate. You may think it is flat, charge it and afterward, voltage can go as high as 15V or 16V.

Here are a few connections to check:

  • The starter solenoid
  • Corrosion on all wires leading to and from the alternator and battery

If you have tools and skills, you can repair these yourself or ask a professional to play it safe

Alternator problems

Inside your alternator is a voltage regulator. This part manages your battery’s voltage. If it malfunctions you experience fluctuating voltage readings.

Luckily you don’t have to replace either the battery or the entire alternator. Alternators can be repaired. There is a quick solution and most professionals can repair the unit while you wait.

The starter

Since your starter has a direct connection to your alternator, you may want to check this part too. Even if your connections are sound, the part itself may be damaged. If it’s already showing signs of wear and tear, it’s best to replace it.

Your car’s starter impacts the battery. A problem in the starter can lead to problems in the other parts leading to the battery’s working, such as the alternator.

Do you struggle turning your key in the starter unit? Remember that continuous use of damaged or substandard parts can create huge problems in your engine over time. The moment you realize a part gives problems it’s wise to repair or replace it.

The battery itself

Firstly, realize the hazard of working on a battery; a car’s battery has the capacity to cause you harm. Safety procedures are of the essence.

You can test a battery in its normal condition, without the car being switched on. You’ve found the source of the problem if your readings are outside these guidelines:

  • Minimum 12.4V
  • Maximum 12.9V

There’s little chance of repairing a battery and adding liquid won’t necessarily help. In this case, you’ll have to purchase a new one. Does a hopeless feeling come over you when your car shows signs of trouble? ​

If it’s your battery there are only a few parts you can check for the source of the problem.

Choosing A Car Battery

Another reason why you’re experiencing high voltages might be because you lack a reliable car battery. Furthermore, these inconveniences might signify wearing out, and it is time to replace your old car battery. Therefore, read through the guide below that highlights the important factors to consider when choosing a healthy battery;


Car batteries have various group sizes and getting one that fits correctly in its tray is important. The right group size is clearly stated in the battery section of the car’s manual. However, if you have no aces to the manual, here is a quick reference guide to assist you in picking the correct size. This guide will help you avoid getting an incorrect size battery that is a waste of money and might cause damage to the car.

  • Size 75: Most General Motors cars
  • Size 65: Large-bodied Ford, Lincoln, and Mercury cars
  • Size 35: Recent Honda, Nissan, and Toyota cars
  • Size 34: Most Chrysler cars
  • Size 34/78: Some Chrysler and General Motors cars


Various battery brands are available in the market, but only a few are reliable. Experts recommend that you source your vehicle battery from the specified manufacturer in the manual. However, if you find that too expensive, choosing an alternative that meets the specified specifications and is from a trusted brand is best.

Manufacturing Date

The best way to determine if you’re getting a new car battery is to check the manufacturing date. A printed code is available on the battery consisting of a two-character code. The letter shows the manufacturing months, and the number indicates the year. Pro tip: avoid buying a battery within the past six months after the manufacturing date.

Reverse Capacity

This rating shows how long the battery can run the vehicle if the charging system fails. The best way to determine this ratio is to determine the time taken for the fully charged battery to get discharged down to 10.5 volts. In addition, this ratio helps you determine how long the headlines can be on and still get the car to start without the help of a jump start. Statistics show the average ratio is 1½ hours, but some batteries go up to 2 hours.

Battery life

You can conduct various tests to determine a battery’s life, and the best option is to discharge and recharge it until it registers a voltage drop to unsatisfactory levels. Getting one with a long life is essential since you can rely on it to provide sufficient energy for short and long trips.


Now you know where to look and you can take the necessary action… When did you last check yours?