What Should A 12 Volt Battery Read When Fully Charged? [Easiest Way Explained] 

Hi, I'm Luis Johnson, an automobile technician, and power equipment professional. By profession, I'm a businessman and operate a car workshop. I have created this...Read more

When it comes to 12 volt batteries, there are a lot of questions that people have. One of the most common is- what should a 12 volt battery read when fully charged? This is actually a difficult question to answer because it depends on the type of battery and the charger that is being used.

However, when you fully charge a 12 volt battery, it should typically give you a reading of 12.4 to 12.8 on the voltmeter. Any reading above 12.9 will define that your battery is in super condition.

There is more to know about this fact, like how to charge a 12V battery or how to troubleshoot it, and so on, that you can find by reading further.

What Should a 12 Volt Battery Read when Fully Charged?

Like we said in the intro, a fully charged battery should give a reading of 12.4 volts to 12.8 volts on a voltmeter. Within this range, the battery will offer the best performance since it is in perfect condition.

What Should a 12 Volt Battery Read when Fully Charged

If the range is above 12.9 volts, it means there is excessive voltage on the battery, which is good in a way. It is not bad to have more “juice” on the battery than it actually requires. Why? Due to the battery’s inherent resistance, which makes it unlikely that it will fully charge. You need to apply force to insert electricity into the battery by overpowering it.

Normally, To charge a typical 12 volt battery, you must increase its voltage to at least 14 volts. Perhaps, you can take a look at these landmarks for charging a 12V battery –

  • 6 volts = Your battery is 100% charged.
  • 5 volts = Your battery is 70% charged.
  • 3 volts = Your battery is 50% charged.
  • 4 volts = Your battery is 20% charged.

Here is a more detailed picture indicating almost all the possible voltage points of a 12V battery.


To distribute electrons equally through the battery plate, you should charge an ordinary wet-cell battery above 14 volts. Once your battery is charged, leave it for a while. This will allow the electrons ample time to disperse uniformly inside the plate at 12.6 volts.

Battery States at Different Charge Levels

Now that we have shown the percentage for specific voltages, it is your right to know when the battery will perform well and when it will not. Let’s see the different states of the battery at different voltage levels –

  • At 12 volts or lower: At this voltage point, it is likely that you charged the battery only 20%. This actually means that it is not charged at all. At this time, you should start charging the battery. It won’t be long before your battery dies if you use it or keep it charged at less than 12 volts.
  • From 12.1 volts to 12.4 volts: You should charge the battery more if it stays within these voltage points. When your battery is charged from 12.1 volts to 12.4 volts, it is partly discharged. You shouldn’t keep the battery at this stage for a long time.
  • At 12.5 volts: The charge of the battery is full at this voltage point. You don’t have to charge it, but make sure it always stays at this point.
  • At 12.6 volts or higher: This is the voltage point where your battery will remain healthy. If you keep the battery charged at 12.6 volts or more, it will perform at its peak and have a longer lifespan.


When you think you have fully charged the battery, take it to a local service center for a diagnosis. You will know whether your 12V is fully charged or not. Additionally, this will point out if there is any problem with the battery or the charging system.

How Do You Know when A 12 v Battery Is Fully Charged?

It is very easy to find out whether the battery is fully charged or not. Perhaps, you may already have the answer to this question. Like we said in the part before, a completely charged battery should register at least 12.6 volts on a voltmeter.

All you need to do is connect a voltmeter to the battery after fully charging it and then see the volt reading that appears on the display. If it is 12.6 or higher, then you are all set. If that is not the case, then you need to charge the battery more and then see the result after some time.

Please note:

The voltage level for a full charge is determined by the type of vehicle as well as the battery type. Some batteries require at least 13.7 volts to be fully charged, depending on the vehicle and model.

How To Check Your Battery Charge Level And Troubleshoot Issues?

Okay! There are several ways to check the charge level of a 12V battery. You can check it with a multimeter, a voltmeter, or a watt meter. Before we go with any of these options, make sure your battery is not connected to any external appliances. So, you’d better disconnect the battery from the vehicle first.

Battery Charge Level with a Multimeter

If you are checking the battery charge level with a multimeter, then please follow these steps –

  • First, set the multimeter to read DC voltage. Make sure the scale setting is at 12 volts.
  • Connect the probes of the multimeter to the battery terminals. The positive probe should connect to the positive terminal. And negative probe to negative terminal.
  • Once you do that, a voltage reading will appear on the multimeter.
Battery Charge Level with a Multimeter

Battery Charge Level with A Voltmeter

You can also check the battery charge level using a voltmeter. This is the most common method for this. Follow the steps accordingly –

  • You may find a voltmeter in the battery box. This will make the task of checking the battery voltage level easier.
  • Simply connect the battery to a voltmeter. You need to connect the red cable from the voltmeter to the battery’s VΩ port and the black one to the common (COM) port. The red lead is meant to be connected to the positive terminal and the black lead to the negative terminal.
  • This will give a reading of the charging level in volts.
Battery Charge Level with a Voltmeter

Battery Charge Level with A Watt Meter

You can also use a watt meter to check the battery’s voltage. This method is not as straightforward as the previous methods. However, you can follow the steps to go with this method –

  • You need to connect the watt meter between the 12V battery and an appliance.
  • To check the charge level, you just need to connect the input port of the battery to the watt meter, while the other port is connected to the appliance.
  • The watt meter will display a reading as soon as you do that.
Battery Charge Level with a Watt Meter

What Should You Do If A 12 Volt Battery Isn’t Fully Charged?

The answer is simple; you need to charge it properly until it is full. Even after a lengthy charge, the situation won’t be normal if the voltage reading doesn’t go to 12.6 volts or above. Then, you may expect to have some issues either with the battery or the charging system.

There are some reasons why a 12V battery won’t fully charge. Here are some of the mentionable –

  • Loose Connections: Due to the vibration from a bumpy road or from the engine, the battery connectors may get loose. This will prevent the battery from fully charging no matter how hard you try. So, check the connections properly.
  • Damaged Wires: If the connector wires get damaged without noticing you, then it would be difficult to detect the cause of not charging. However, you may notice if the wires are burned or damaged.
  • Damaged or Old Battery: Charging issues will become common when it gets damaged or old. The lifespan of a typical 12V lead-acid battery is somewhere between 3 and 4 years. You should change the battery before this.
  • Faulty External Charger: Make sure the external charger is okay if you are using it. Check if the connections are tight enough or if you have connected them properly. Don’t forget, not all cars use the same type of charger. You should use the right charger for specific batteries. Don’t mix these things up, or your battery won’t charge fully.
  • A Bad Alternator: This might be common when you are using a 12V battery for your car. Typically, while driving, an alternator maintains the battery charge. Although the lifespan of an alternator is greater than that of a 12V lead-acid battery, it will die at some point.

If you experience dim headlights or the battery drains quickly, then you should check the alternator. Your battery won’t fully charge due to a faulty alternator. Experts advise changing alternators at least once every seven years, or after running around 80,000 miles.

Read Also: Do You Have To Replace Battery When Replacing Alternator?

Final Thoughts

So, do you understand what a fully charged 12 volt battery should read? We guess there is no more confusion regarding this question. To top it off, we also believe the trickle charging method is the greatest of all approaches. It is great not only for charging a 12V battery but also extending the battery life.

When you are getting a trickle charger, try to look for a modern one rather than an older variant. Because, the old trickle chargers are not very effective for modern vehicles anymore.

The best trickle chargers should have high-end features and designs that are necessary for optimal charging. If there is something that you have trouble understanding, please let us know in a comment.

Hi, I'm Luis Johnson, an automobile technician, and power equipment professional. By profession, I'm a businessman and operate a car workshop. I have created this site Batteryquery to help people purchase the right battery for their vehicles. The reason behind creating this site is to help my customers purchase the right car battery who often purchase the wrong one due to their lack of knowledge.

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