How Many Volts Should A Car Battery Have?

how many volts does a car battery need to start?There are a lot of people who ask, how many volts should a car battery have? This inquiry is especially common in people who just got their first car, and experienced their first even encounter with their new car’s battery system.

The question is commonly asked to determine what the voltage of a fully-charged battery is supposed to be. It may also be asked when people think that their car batteries are not holding a charge, or if their car’s alternator is not transferring energy to the battery properly.

Well, the simple and short answer for it is 12.6 volts, but that is just a “surface” answer, which really does not tell you anything practical. If you test a battery using a voltmeter and find out that the battery is carrying 12.6 volts, then it means it is fully charged.

But of course, that is not the only practical voltage rating a car battery should have. It should show a typically higher voltage when given a load or when used to “crank” the engine.

It also shows different voltage levels as it discharges (and recharges) throughout its natural life cycle. When the battery is damaged, it has a different voltage as well.

There is a certain acceptable voltage range for batteries active in the automotive industry, and that is anywhere from 9.6 volts to 14.7 volts, and the voltage will vary according to time of testing and function.

However, knowing this voltage range is not enough because you as a professional driver must know the state of your battery at different times and how to test and measure its output and capacity in a given circumstance.

If you do the measurements regularly, you will have a collection of past data that will be useful in comparing the state of your battery then and now. It will be a useful tool to determine the battery’s performance over time, or how fast it has been deteriorating through its months of service.

You can also notice the effect of certain maintenance checks and procedures on your battery, if you do any. So to our original question, there is no exact answer. It all depends on the situation.

Charge Levels and Corresponding Voltages

Of course, if we expect our car to be in normal operation, there will be a “correct” answer.

If you want to see if a battery is fully-charged, then as mentioned, you should check if the battery has 12.6 volts. When it drops to 12.5 volts, it means it is at least 85 percent charged, while at 12.4 volts it means the battery is at least 65 percent charged.

Batteries at 50 percent charge have 12.3 volts, while those at 12.2 volts have at least 35 percent charge. When your battery is tested at 12.1 volts, then that means the battery needed to be recharged because it is completely drained.

Practical Voltage and Makeshift Tests

We have established that a fully-charged battery has 12.6 volts of electricity when tested idle. But this is a static value and not one under load.

If the battery is tested with a multimeter while the car engine is running, the reading should be anywhere from 13.7 to 14.7 volts.

This is a sign that the battery is doing its job— providing s steady stream of ample electricity to run the car’s electronic components (headlights, stereo, etc.) while also taking in energy from the alternator so that it does not get drained of electricity while providing power for essentials inside the car.

If you do not have a multimeter, or if one is not available at your disposal right now, but want to know if your battery is working great, then there is a simple test you can perform with your car. This test can also help determine if something is wrong with your battery and to diagnose what exactly is the problem, if any.

To perform the test, first start the car and turn on the headlights. If you see that the light is dimmer than what should be normal, then it means that the battery is trying to provide the energy that the lights need, but it ends up not being enough because it does not get help from the alternator— the alternator does not produce any charge!

The second part of the test is to try revving up the engine. If there is no change in the headlights, then you have just confirmed the theory presented in the first part of the test above.

But if the headlights do light up when you rev up the engine, it means that the alternator is providing some power, but it is still not enough energy to keep charging the battery and power the lights at the same time.

However, if the lights’ brightness is normal and it does not change brightness while the engine is revved up, then it means that the alternator and its charging system are working properly.

Now, if you think you are having problems with your battery despite performing this test with the car and battery system responding ideally, then you should take the car to an auto shop where professionals and experts in the field can take a maintenance check on the battery system.

There is also a “load test” you can perform to test if the battery is in optimal condition.

However, you will need to have a gadget that generates true load (carbon pile), and not one those handheld devices that perform their tests with a conductance algorithm.

To pass this particular test, the battery must in 15 seconds produce and maintain 9.6 volts of power at one half of its cold cranking amps rating, and in at least 70 degrees Fahrenheit of temperature.

Additional Troubleshooting Steps

One good thing to keep in mind is that batteries do not hold electrical charge the way a bottle holds water. You cannot reason that you will use half the battery’s charge today and then save some to use for much later.

A battery is not like a canteen that holds electricity in that it does not just give off power the way a typical liquid container “flows” or “leaks.” Rather, it is a box that has a meticulous combination of chemicals that are primed to react with each other when the proper load is attached to it.

Batteries will, of course, provide power to this load ideally. However, there comes a time when batteries just do not do its job as intended.

Besides the methods detailed earlier in this article, here are some additional steps you may take to try and determine what problems your battery has.

Take a Very Good Look at the State of Your Battery

One of the first things you do is inspect the battery by sight, and identify any physical deformities it may have. First, check the positive and negative terminals, and make sure they are not overrun with dust and corrosion.

Clean them if so, and then check if they are not in any way or shape broken. This is critical, because broken terminals are known to cause short circuits. Now, if a short circuit occurred before you made a check, you should see some signs of melting or burning.

Short circuits can be very dangerous, as what happens is that the battery will unload all the power it contains on one short burst. This immense amount of energy can even cause an explosion under certain circumstances.

Next, check if there are any bulges on the battery’s plastic case. If there are any, then these bulges are signs that the battery is being subject tom too much overcharging.

One must be very careful with using some fast chargers that do not have the feature of detecting whether the battery is already fully charged or not, as these chargers are frequent causes of why batteries are overcharged.

There are smart chargers that can regulate the process, but in general, slow charging is more preferable to fast charging when it comes to automobile batteries.

Also check if your battery has cracks or any tearing or openings in the cover. This is usually the cause of mishandling.

Batteries with holes and splits may still work, but obviously batteries like these cannot be used safely anymore and need to be replaced. Labeling them as “unsafe to use” will also help.

This next point is only for “flooded” or wet cell batteries that require maintenance: check the water levels. Refilling them with distilled water when the level is low will help.

This is an important point for these types of batteries, because leaving wet cells battery dry will cause sulfation to build up in the plates. Sulfation is one of the most common causes of battery failure, so it is in your best interest to take good care of your wet cell batteries.


Voltage plays an important role in a battery, and asking “How many volts should car battery have?” is a sign that a curious driver is interested in the proper workings of your car. We hope this article helped answer this question and more!