Battery Voltage Keeps Going Up and Down: Solved

Battery voltage keeps going up and down is a situation that can lead towards trouble so, you must try to fix it in real. The answer ranges from factors such as a bad alternator, weak battery, and battery corrosion to using an abandoned car.

Battery Voltage Keeps Going Up and Down

Read on to learn why your car battery voltage keeps fluctuating and the solutions you can try.

Why Does the Gauge of Your Battery’s Voltage Keep Going Up and Down?

The gauge of your battery’s voltage keeps going up and down because of a bad alternator, a weakened battery, and a loosened connection. Other reasons might also make the battery gauge have varying voltage levels. You might have to consult a professional mechanic to get a correct diagnosis.

– Defective Alternator

A bad alternator can keep the car battery’s voltage increasing and decreasing. The alternator is an electrical generator. Its function is to recharge the car battery and supply power to the vehicle’s electronic system.

The alternator takes mechanical power from the car’s engine and converts it into electrical energy to charge the battery. A defective or bad alternator might bring many problems to your car. Defective alternators don’t distribute adequate electrical energy in the car’s electronic system and into the battery.

Why the Gauge of Your Battery's Voltage Keeps Going Up and Down

Thus, if the alternator fails to provide enough energy to charge, the battery’s voltage will fluctuate, but you can’t conclude that the alternator is why your car’s voltage keeps going up and down. You have to confirm by checking the battery and testing to see if it’s the cause of the problem or not.

In order to test the health of your alternator, you can use either a voltmeter or an ammeter. A voltmeter is used to test the voltage output of your alternator, while the ammeter is generally used to measure the current output being generated by the alternator. In addition to these tests, you can also utilize a load test to see if your alternator will be able to perform well under a heavy load.

– Old or Weak Battery

An old or weak battery can be why your gauge keeps moving up and down. The battery controls the battery gauge reading on the dashboard. If a battery is old or in bad shape, the gauge will depict the battery’s voltage fluctuation.

A good quality battery should last four to six years, powering the car’s electronic system. However, after a long time, the battery works less because it’s getting out of order.

You can tell that a car’s battery is weak when the battery takes longer to kickstart, the headlights become dimmer, and you hear a clicking noise whenever you turn the key in the ignition. Other signs include no sound or interior lights when you start the vehicle, the vehicle backfiring, and intermittent sparks when you start the vehicle.

– Abandoned Car

An abandoned car that you start after some time often has many issues. In some cases, a battery’s voltage fluctuation while driving would be one of them.

If you leave your vehicle for a long time, the battery can die. A typical car’s electronic systems should receive and supply power daily. Without power, the battery cells become damaged, or the battery develops voltage issues.

If you’re leaving town or planning to go on vacation for a while, make sure to remove the battery from your car in order to keep it in good working condition. Alternatively, you can ask a friend or relative to take your car out for a drive once in a while.

– Corroded Battery

A corroded battery is now damaged and cannot produce enough power for the car, so the battery experiences a voltage drop while you are driving the vehicle. Observing the battery’s condition will tell you whether it has experienced corrosion or not. You can check for battery corrosion by looking at the alternator and battery wires.

To keep your car battery healthy and avoid corrosion, there are several things you can do. First, regularly charging the battery is of utmost importance. In line with this, you should avoid overcharging the battery as this is not good for its health. Lastly, always keep the terminals and connections clean and tidy.

– Loose Electrical Connections

Loose electrical connections in batteries affect the flow of electricity. If the electrical connections are loose, the battery cannot maintain its voltage. Also, if the battery doesn’t maintain the correct voltage, the gauge level will drop while driving.

Loose Electrical Connections of Car

Moreover, loose electrical connections negatively affect the car’s alternator. Any damage to the alternator will cause the gauge to fluctuate up and down.

Solutions for Why Your Battery’s Voltage Keeps Going Up and Down?

The solutions to your battery’s voltage going up and down include replacing the alternator belt and the battery. You should also test and clean the battery and check electrical connections. These remedies help the gauge record the expected voltage level while driving the car or when the engine is off.

– Replace the Alternator Belt

The alternator uses a belt called a serpentine belt. If you are inspecting the alternator in your vehicle, check this belt to see if it’s old. An alternator belt that looks too old is no longer fit for use. It would be best if you replaced it with a new one.

Also, if the serpentine belt has visible damage and is too loose to spin, you should replace it. The cost of replacing the belt ranges between $120 and $180, and a professional should do it. The alternator belt replacement restores the alternator to good working condition.

Changing the serpentine belt isn’t the only way to repair a defective alternator. You also have to test the alternator using a voltmeter. With the aid of the voltmeter, check the battery voltage when the engine is off. The battery’s voltage should be between 12.5 and 12.8 volts.

If the voltage is lower than 12.5 volts, the battery is low and needs a recharge. Charge the low battery before conducting the alternator test on the vehicle. After that, start the engine and check the voltmeter once more. If the voltage is between 13.8 and 15.3 volts, the car alternator is in good condition.

– Replace the Battery With a New One

Replacing the old battery with a new one will restore the gauge of the battery to an optimal level. It helps the battery to maintain the proper voltage. The choice of battery for your car matters a lot.

Purchasing the battery from the best places and quality manufacturers is important. Also, avoid buying the wrong battery size for the vehicle. Furthermore, regular maintenance of the battery helps you avoid damage to the battery and also helps you prevent battery acid leaking. In addition, check the battery regularly to observe any changes in the voltage level.

Fixing Battery’s Voltage Keeps Going Up and Down


On average, a car’s battery lasts about four years, but it depends on some factors, including how often you use it and how well you care for it. It can last more than four years for car owners who take good care of their batteries. Nevertheless, most battery manufacturers assure consumers a trouble-free period of about 36 months (three years).

– Test the Battery or Replace It With a New One

Take the battery to an auto mechanic shop for a voltage-checking test on the battery. The test will determine if the battery is working well or not. Also, if you plan to go out of town without using the car for some time, you should remove the battery. Removing the battery will ensure that the cells don’t become damaged.

A dead battery can be restored by jump-starting it. However, there are some batteries for which jump-starting can no longer work, so it would help if you replaced the battery with a new one. Once you get a new battery, ensure that you warm the car’s engine and check the battery gauge’s read daily.

– Keep the Battery Clean

A clean battery will not suffer corrosion. To keep the battery clean, ensure the connection between the alternator and battery is done correctly. If there is a bad connection between the battery and the alternator, the gauge level might drop while driving. The same thing applies to battery corrosion.

More so, ensure that a professional mechanic handles the battery fluctuation issues. Do not leave the issues to chance.

– Check the Connections

You should check the alternator connections to see if anything is amiss. The wires are expected to be tight and correctly connected. Also, check for any flux or corrosion around the connections.

Once you check the wires and see that the loose connections cause the gauge drops while driving, replace and reconnect the wires. Thus, you will restore the battery to its normal voltage level.

Frequently Asked Questions

– By How Much Should Your Vehicle’s Battery’s Voltage Reduce Overnight?

A car battery’s voltage should reduce by about 0.50 volts overnight. If the battery drops by more than 0.50 volts, this is your cue that the cells might not be well charged. Typically, the battery should be above 13.6 volts when running.

On the other hand, it should be at 12.6 volts when the engine is off, so the voltage can be about 12.1 volts in the morning, with the rest (0.5 volts) lost overnight.

– How Can You Restore a Dead Vehicle Battery?

You can restore a dead vehicle battery by charging it for a few hours to gain electrical energy. You can restore it by jump-starting it with another vehicle, or you can apply an overcharge to a fully charged battery using a regulated current of about 200mA for about 24 hours.

If these measures fail to work, you should consider replacing the battery.

– What Should Your Car Battery’s Voltage Be While You’re Driving?

Your car battery’s voltage should be between 13.7 and 14.7 while you’re driving. If it is higher than 14.7, the battery cells are overcharged. If the voltage is lower than 13.7, the battery cells are undercharged.

Whichever the case might be, you should visit the auto mechanic to inspect it and diagnose the problem.

Why Does My Battery Voltage Gauge Keep Going Up and Down Conclusion

Can Loose Battery Terminals Cause Fluctuating Voltage?

Can loose battery terminals cause fluctuating voltage? Yes, it is possible. When the battery terminals are loose, the connection between the battery and the electrical system can become unreliable. This can lead to fluctuations in voltage, affecting the performance of various electrical components. Regularly tightening battery terminals is crucial to maintain a stable flow of voltage and prevent potential issues.


If your battery’s gauge keeps fluctuating, there is no need to panic or worry.

Here is a quick summary of the main points discussed in the article:

  • “Why does my battery voltage keeps going up and down?” is a valid question that will help you figure out why your car’s battery experiences varying voltage levels.
  • The main reasons the voltage of your battery’s gauge keeps going up and down are a bad alternator, a weakened battery, a loosened connection, an abandoned car, and a corroded battery.
  • The solutions to this problem include replacing the alternator belt and the battery, testing the battery, keeping the battery clean, and checking electrical connections.

With all the points discussed in this guide, you should now know which components to check before repairs.

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