What Should a 12 Volt Battery Read When Fully Charged?

What Should a 12 Volt Battery Read When Fully Charged

The battery can be said to be a car’s lifeline, without which the car won’t start. Commonly used in cars is the 12-volt battery, this is because it can be recharged using the alternator.

It is important to know when the battery is low and full, so, what should a 12 volt battery read when fully charged?

When a 12-volt battery is fully charged,  it should read between 12.6 and 12.8 volts.

What is a 12 Volt Battery?

12-volt batteries are batteries used mostly in cars, boats, and specific electronic applications. The 12-volt battery can take whatever form; it can be big or small, light or heavy. A major determinant of the battery size is the amp hours it is designed to produce and its use.

The 12-volt battery works with current only to start the car after which it can be recharged on the go using an alternator. The alternator ensures the battery doesn’t run out of power.

We have the rechargeable 12-volt battery and the non-rechargeable which is known as the ‘alkaline battery. For electronics that are in use all the time, it is better to use a rechargeable battery.

Can You Charge a 12 Volt Battery?

Yes, a 12-volt battery can be charged. However, the possibility of charging a 12-volt battery depends on whether you are using a rechargeable battery or non-rechargeable. Only rechargeable batteries can be charged and recharged.

To charge the battery when in the car you will need an alternator, you can as well use a battery charger. To effectively charge the battery with a battery charger, you must limit the charging current to the battery.

What Should a 12 Volt Battery Read When Fully Charged?

A fully charged battery will read something between 12.6 volts and 12.8 volts. Although the battery is 12 volts you can never get one that will be 12 exactly.

If the battery still reads 12.4 and 12.8 you have nothing to worry about, it simply means the battery is in good shape.

Anything lower or higher than this indicates that the battery is either too low and needs to be recharged or high which means there’s excess voltage. To reduce the excess voltage, you can turn on the vehicle’s high beam to drain out excess voltage.

When the battery is lower than 12.2 volts, you should consider charging at a slower rate (trickle charging). Charging at a slower rate reduces the chances of applying too much amperage which can result in excess heat or explosions.

What Voltage is Too Low for a 12 Volt Battery?

A 12.0 volt and below is considered to be too low for a 12-volt battery.

When a battery is reading 12.0 or below it is said to be flat or fully discharged with no power remaining on it. At this point, the battery should be recharged without delay, it shouldn’t be left for long in this state.

Once a battery has been left in a discharged state for a long period, the lifespan will be affected. If this keeps reoccurring with the battery, you can as well start preparing to get a replacement.

If a battery continually gets to a point of reading 12.0 volts or below, you should know there’s a problem somewhere that needs to be checked and fixed.

A lot of things can contribute to a battery getting to this stage of flat-out discharge, it could be a result of an underlying problem with the battery or charging system. In order to be sure, you can have it checked out at the auto shop.

How Do I Know My Battery is Fully Charged?

One easy way of knowing if your battery is fully charged is by using a ‘Voltmeter’. The voltmeter helps to measure the electrical difference between two points of an electric circuit.

In order to get an accurate reading, the test should be done close to 12 hours after the vehicle has been turned off. 12 hours after the vehicle is off is enough time for excess and surface charge to reduce.

To test with the voltmeter, you will need to first remove the battery’s positive terminal and clean it where necessary.

Then you can proceed to attach the positive to positive and negative to negative i.e. voltmeter positive lead to the battery’s positive terminal and negative voltmeter lead to the battery’s negative terminal.

Now, you can check and get an accurate battery reading. If the battery is fully charged you should have a reading of about 12.6 to 12.8 volts.

How Do I Know if My 12 Volt Battery is Dead?

If the battery dies, your car will not work or start. To know if your 12-volt battery is dead you should watch out for tell signs because there will always be signs showing that your battery is about to die or completely dead.

Some of such signs are as follows;

The Vehicle Not Starting

One way to know if your 12-volt battery is dead is if your car isn’t starting. The battery is needed for the car to start and it also powers some other accessories in the car, so, if the battery is dead there is definitely no way of getting the car to run. So, if your car is not starting you may want to take a look at the battery.

The Voltmeter Reading Lower

If you are in doubt of whether your car battery is dead or not, using the voltmeter is a good way to clear such doubt.

If the voltmeter is reading 12.0 volts and lower then the battery is completely discharged and died. You should immediately find a way to recharge the battery and get the car back on track.

The Check Engine Light is on

The check engine light is always a telling sign when something is wrong in the car. When your 12-volt battery is dead, the check engine light will be on.

Engine Starting and Going Off Immediately

A dead battery will not make the car start and if it does start, it will most likely go off immediately. This is because the battery does not have enough power to get the engine running.

No or Dim Headlight

Most times when the battery is dead, it may have just enough power left to make the headlight come on but not to power the vehicle. In order cases, the headlight won’t come on at all.


A 12-volt battery should be recharged immediately you realize it is dead, failure to do this will reduce the battery’s lifespan and can over time cause it to discharge quicker than it should.