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Car Battery Shows 13 Volts – What You Need To Know!

Car Battery Shows 13 Volts – What You Need To Know!

Fully charged car batteries usually measure at around 12.6 volts or above, with some instances of your car battery showing 13 volts. When the engine is running and functioning correctly, the car battery will fluctuate between 13.7 and 14.7 volts. If you don’t have the proper diagnostic tools or multimeters to tell you the voltage, you can perform some electrical tests yourself.

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By turning on and off the car’s headlights and dashboard lights, you can indicate whether or not the battery is functioning correctly. If the lights have normal brightness as the engine is turning over, the charging system functions typically. However, if something is discharging the system, your car battery shows 13 volts and can indicate an issue. 

Car Battery Function


When it comes to your car’s functioning, the car battery is one of the most important components. The last thing any driver wants is to be left stranded on the side of the road with a dead battery. The battery is the power of your vehicle – without it, you wouldn’t be able to drive anywhere.


The car battery provides electricity to power the electrical components within your vehicle. Without the battery power from the car’s internal battery, no electrical component will work, leaving you without lights, radio, and power windows. If your car battery shows 13 volts, there might be an issue with the electrical system. 


The chemical reaction occurs in the battery system, transforming the chemical energy into electrical energy to deliver voltage to the starter. In addition, the battery stabilizes the voltage to keep your engine running consistently and constantly. Without the battery, the car would not have the energy required to start and maintain the power to run your vehicle. 


When looking at why your car has issues and your car battery shows 13 volts, it is important to keep in mind the varying functions that each component has in your vehicle and why your car battery shows 13 volts. 


  • How long does it take to charge a battery?



When figuring out why your car battery shows 13 volts, you need to know the charging process and the charging timing. There is a pretty easy equation that can show you how long it takes to charge your car battery: (battery capacity) / (charger current) = hours. This equation can give you a base estimate for how long it will take to charge your battery to the correct level.


If the battery is fully discharged, but the car battery shows 13 volts, the first estimation for the charge time can help tell you how long it'll take to recharge the battery to almost the max capacity. If you are using a three or 4-step charger and you need to recharge your battery so that the car battery shows 13 volts, it will take almost an equal amount of time for a 3-step and 4-step charger to get to the max level. 


  • How can I tell if I need to replace my battery?



You can accidentally over-discharge your car battery beyond what it is intended to withstand, causing a 12-volt battery to go down to 3 or 4 volts, or make it misread, with the car battery showing 13 volts. Many lead batteries do not respond well to being over-discharged or overcharged, but some can recover to 8 or 9 volts without recharging. 


If there are no other issues with your battery, then it can be possible to restore the full charge if it is fixed within just a few hours of the over-discharge situation. This can prevent the “car battery showing 13 volts situation” that can harm your battery’s lifespan. 


  • Car Battery Composition


A car battery is a wet cell battery with six cells. Each battery cell contains plates that alternate between lead alloy and sponge lead, filled with a sulfuric acid solution to provide the necessary power and electricity. The battery cells are connected by straps from the positive plates of one battery cell to the neighboring cell’s negative.


Batteries usually consist of six cells in a series. Each cell provides 2.1 volts while not charging, and 2.2 volts while charging in the battery. If the battery is not charging, the entire unit makes up 12.6 volts at full charge, making up 13.2 volts while charging. The negative terminal releases electrons to the external circuit during discharge and procures an electric current, sometimes having the car show 13 volts. 

  1. 12 Volt Battery Reading as 13 Volts

If you are wondering why your car battery shows 13 volts when it shouldn’t, there is a clear explanation for this occurrence. All lead batteries are composed of 2.2-volt cells connected to achieve the necessary voltage. For example, a 6-volt battery will have three cells to reach the required six voltage. The 12 voltage will have six cells to reach the 12 volts, etc. 


The 2.2-volt battery cells are fully charged and ready to work. However, the actual resting voltage will settle after 1-2 days of being removed from the charger and lowers after being removed, coming down to about 2.1 volts instead of 2.2 volts per cell. This means that your 12-volt battery can actually read as 13.2 volts instead of 12 when it is not fully charged. 

Bad Battery Symptoms


Most drivers never want to experience their car not starting or a bad battery. If you cannot turn on your car, let alone drive it to work or school, a bad battery, alternator, or starter are often at fault. If the problem is a damaged or faulty battery, this means it is time to get a replacement – which can, unfortunately, be quite expensive.


Fortunately for you, car owners don’t have to wait until the point of no return to fix their battery issue and their car voltage reading. In the meantime, they can look for several signs that show the car battery is going bad while the car battery shows 13 volts instead of the correct number. 


  • Dashboard lights


One of the most obvious signs of a bad battery is the warning light on the car’s dashboard that can indicate to the driver and passengers something is wrong with your car. In some cars, the dashboard will show a light that appears like a battery, and in some cars, it will even say the word “CHARGE” beneath the icon.


If your car doesn't have a battery icon, the check engine light might come on. Even though this light can come on for various reasons, like a faulty mass air flow sensor or a faulty throttle position sensor, it can come on if your car battery shows 13 volts. Regardless, the dashboard light is a clear indication that you should bring your car to the mechanic to buy a new battery that shows the correct voltage reading. 


  • Old Battery


Another sign that you might be having battery and voltage issues is that you have an old battery in your car. If you have not repaired or replaced your battery in many years, and the battery is showing signs of deterioration, this is a clear indication that the battery is not withstanding the rough conditions and needs to be replaced with a new option. If it has been years since the last replacement, you might notice the car battery shows 13 volts. 


  • Slow Start


If your car is slow to start and the engine is being too slow to crank and turn over, this is a sign of a battery issue that can enhance the car’s performance issues. As you know by now, the battery is responsible for producing the power to start the car. If the power is not stored in the battery, then the car battery will show 3.12 volts, and the car will not be able to start. 


  • Big Battery Case


If you live in very cold or very warm conditions that can harm your battery or internal engine components, this can cause the battery case to swell while it is sitting idle. The result of this swelling is that the battery inside of the case will die and have the car battery show 13 volts. This one a battery issue where it is very obvious to the eye what is wrong when the car battery shows 13 volts. 


  • Strange Smell


If you notice a smell coming from under your car’s hood, this could be due to the battery leaking fluid and causing a noticeable smell. This problem requires a new battery and can affect other engine components due to the leaking liquid, like acid corroding the metal engine parts. 


It is very important that you test your car battery and electrical system regularly and during certain intervals, not just when it is too late to fix your car without a battery replacement. By figuring out why your car battery shows 13 volts, you can ensure the battery is charging at the right intervals and providing the correct amount of charge to your vehicle.