What Does a Car’s Low Voltage Battery Mean? Top 4 Causes

The car’s battery is one of the most important parts of the car that everyone should be familiar with. It is used to power the lights, ignition, and other accessories in the car.

A battery can have a lifespan of up to five years but you have to take good care of it for it to serve you longer.

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In this article, you’ll learn more about a car’s low voltage battery.

What does a car’s low voltage battery mean?

A fully charged battery should read over 12.6 volts. When the engine is running, this measurement should be 13.7 to 14.7 volts. A low voltage battery reads 12.45 volts or less, which means it needs to be recharged. In cases of continually low charging, you may need a replacement of a new battery. It may also mean that the alternator is failing to charge the battery properly.

Related: How to Test an Alternator Without a Multimeter? Top 6 Easy Ways

Terminal VoltageCharging StatusDescription
> 12.6 voltsBattery is charged > 60%Normal vehicle status
12.0 – 12.45 voltsBattery is partly charged 25% – 60%Abnormal vehicle status
< 12.0 voltsBattery is not charged < 25%Sulphate risk
What does a car’s low voltage battery mean?

If you don’t have a multimeter to tell you the voltage of your battery, you can conduct an electrical system test by turning on the headlights and starting the car.

What causes a battery to have low voltage?

There are several causes why your car’s battery may be weak or low. A weak battery is sometimes caused by a faulty alternator or a parasitic drain on the system.

A low battery voltage can also be caused by faulty connections to the battery. Loose or corroded connections may induce intermittent electrical issues, which functions at random intervals.

1. Faulty Alternator

Car batteries need to be charged to serve you longer. This is only possible if the alternator of your car is working properly and producing enough voltage and amperage to charge the battery.

An alternator is a device that transforms mechanical energy into electrical energy. It comprises a rotor, stator, regulator (or voltage regulator), and an internal rectifier.

It produces an alternating current that is then provided to your car’s battery for charging.

The drive belt, sometimes called an alternator belt, fan belt, or accessory drive belt is a rubber or fabric belt that engages the crankshaft and drives it through the accessories. 

If your serpentine belt breaks, becomes frayed or gets clogged, the electrical components won’t be able to spin at their optimal rate, which will result in a loss of power to the system.

Related: How to Test an Alternator Without a Multimeter? Top 6 Easy Ways

2. Corroded or Loose Connections

Connections lead to power from the battery to the vehicle’s electrical system which includes the starter, ignition coil(s), fuse box(es), and dashboard electrical components. If you have this problem then it may lead to a low voltage battery.

Corroded or loose connections may induce intermittent electrical issues, which functions at random intervals.

3. Faulty Voltage Regulator

A volatile voltage regulator is sometimes a result of faulty alternator connections or shorted electric circuits within the regulator itself, and it creates an uncontrolled charging sequence that usually ends with battery damage.

A weak or bad battery can also cause problems with your vehicle’s voltage regulator.

4. Faulty Battery

A low voltage battery requires a recharge if you want to use it in your car again or you need to change its replacement entirely if the other reasons no longer apply for this case persists. 

You’ll know if you have a dead battery when there is nothing left in your lights and they start dimming when you turn on your car.

You should always have replacement batteries ready in case the battery of your vehicle dies out completely. Visit a local auto parts dealer to purchase a replacement battery.

At what voltage is a 12-volt battery considered dead?

This is called the “open-cell” or “resting” voltage of the battery. Resting fully charged 12-volt batteries are around 12.8-12.9 volts, and flat dead ones are at 12.0 volts, so 12.4 volts on a resting battery means it’s about 50% charged.

According to BatteryStuff.com, A healthy 12-volt motorcycle battery should maintain a range from 9.5 – 10.5 volts under the load for a good 30 seconds straight.

How to measure a 12-volt battery?

There are different ways to check for low voltage battery. One way is to use a multimeter with the testing probes attached to your ground post and positive post, respectively, on the battery.

A voltmeter is the most dependable technique to tell if a battery is still holding its charge. If your voltmeter shows no reading or a reading lower than 12.4 volts, your battery is considered low. 

If the voltmeter shows 12.4 volts or more, the battery is in good working order and the problem lies elsewhere.

Low voltage on car battery?

Low voltage battery is in between 11.8-12 Volt. The low voltage battery means you should prepare for a new battery replacement if you need to use the car for a long drive. 

A low voltage also needs a recharge by itself before it is safe to run. It can still start a car but it will suffer from issues (headlights, horn, fuel gauge) and eventually be unable to start the vehicle.

Discharge battery

The discharged battery shows a voltage of less than 11.8 Volt. Mostly, you cant start the car with a fully discharged battery. You may recharge it but it needs to be replaced soon. 

A fully discharged battery can take a short time to recharge and you should use the car at once for safety reason

Batteries should not be left in a discharged state for long periods. Also, do not take your battery for storing or change the voltage settings on it as this may cause irreversible damage to your car’s electrical components and create permanent damage to the battery.

How to fix low voltage car battery

There are several ways to charge a low voltage on a car battery. A good approach is to use a battery charger with an automatic float mode to maintain the charge when it’s fully charged already.

A low voltage can be aid by jump start it from another car and letting it stay in the starting mode for half a minute at least. That should firm up the voltage enough so that you can drive the car to a nearby shop for a battery replacement.

Battery chargers come in all shapes and sizes, but it’s important to choose one that is properly suited for the needs of your 12-volt system as well as your vehicle itself.

Universal types will work on anything from motorcycles to personal watercraft. 

There are also dual-purpose chargers that can perform both functions, but these are limited to certain battery types and sizes.

If the battery is in a car located indoors, then bring it outside and hook the charger up to it.

If there isn’t room to work on your vehicle, you might need one of the smaller portable chargers.

Learning how to use portable chargers is key on how to fix low voltage car batteries.


In conclusion, the best way to tell if you have low voltage on a car battery is by using a voltmeter. If the voltage reads 12.4 volts or higher, then it means that the battery has enough energy to run the car and you can continue driving without jumping into a tow truck. 

On the other hand, if your voltmeter reads lower than 12.4 volts, your battery is low and should be changed or replaced as soon as possible because a battery with low voltage can’t provide enough power needed to run the car properly.

Did you find this article helpful? Do you have any questions? Leave a comment below!

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