Is A Truck Battery 6V Or 12V? (How To Tell)

There are two types of automotive batteries commonly found in truck applications, a 6-volt battery and a 12-volt battery. Many people who need to replace the battery on their truck might wonder if they have 6 volts or 12 and how they can tell that. 

Full sized trucks (as well as most other vehicles) will have 12V batteries that they use however it is simple to figure out what size battery you have by simply counting the number of cells or reading the label on the battery itself. 

Each battery cell will be for approximately 2 volts which means if you have 6 cells then you have a 12V battery in that vehicle. If the battery that you have only has three cells then you currently have a 6V battery and not a 12V in your truck. 

Batteries that have become damaged or worn out will typically not hold as many volts which is why as your truck battery ages your truck will become slower and slower to start before eventually not starting at all. If you have a battery with 6 cells but your voltmeter is only showing 6V then your truck battery needs to be replaced. 

6V Vehicle Batteries

6-volt batteries are often found in older cars, trucks and motorcycles – vehicles with large electrical systems and without catalytic converters. The principles behind a 6-volt battery are similar to that of a 12-volt battery, but there are some differences. The plates inside each cell in a 12-volt battery are 6.4 inches long. However, the plates inside a 6-volt battery are only 1 and 3/16 inches long.

The lack of plates and the size of the plates leads to a lower energy density, which means each battery will only hold a fraction of the amount of energy that it could if there were twice as many cells (go figure right). 

To get around the size issue, most 6-volt batteries are used in systems that use external electrical controls to prevent the battery from being discharged too far. These batteries are referred to as sealed lead acid (SLA) batteries or gel batteries, because they’re filled with a special type of gel that will not mix with water. However, it is advisable to avoid using certain types of “hard” or “gel” cells in vehicles with auxiliary power units and other high-current applications.

12V Batteries

The term “12-volt” is a bit of a misnomer, as automotive batteries are rated at 12.8 volts. The .8 is due to the fact that there is an electrical load when a battery is fully charged, which is why there are two ratings for battery capacity – one at full charge and one when the battery is discharged. The higher voltage of 12-volt batteries offers a larger current and greater cranking power than 6-volt batteries for obvious reasons. However, they’re also more expensive which is why some people will try to get away with a cheaper 6V battery instead of buying the right one for their truck. 

Though they can be found in older cars, 12-volt batteries are most commonly used in newer vehicles that have airbags and other electrical equipment. In addition, they’re found in trucks that use auxiliary power units. For all the differences between 6-volt and 12-volt batteries, they’re both part of the same family of batteries and share many common features.

How to know if a truck battery is 6V or 12V

The easiest way to tell a 6V battery from a 12V battery is by looking at the number of cells on the battery. If you have 3 cells then you will have a 6V battery. If you have 6 cells then you will have a 12V one. 

The thickness of a 6-volt battery plate is also less than that of a 12-volt battery plate, which is thicker from adding an extra strip of material. The thickness of plates varies among manufacturers, so it may not always be possible to tell them apart just by looking at them. The positive terminal on 6 and 12 volt batteries are also different sizes.

This is by design in order to prevent a 12-volt battery from being used in a car that has a 6-volt system. In addition, the terminals are usually mounted at different places on each type of battery. (although this isn’t always the case) This makes it impossible to mate the two types of batteries together and still mount them securely on the vehicle’s frame. Many 6-volt batteries have two tabs for mounting while 12-volt batteries have three or four tabs, so it’s important to check your documentation for mounting instructions before installing a battery, so you can verify that you have the right type of battery for your vehicle.

These differences allow for different battery loads and higher capacities in 12-volt batteries. This also means that you can’t use a 12-volt battery in a 6-volt system because the thicker plates will burn out the electrical system of your vehicle. 12 volt batteries are available with capacities ranging from 20 to 240 Amp hours, while 6 volt can be purchased with anywhere from 15 to 100 Amp Hour ratings on average.

Being a sealed lead acid (SLA) battery, they need to have their terminals covered or insulated when the car is being stored or not in use.

Can you replace a 6V battery with a 12V battery? 

It’s not a good idea to try and replace a 6-volt battery with one of a larger size, as this will not work properly and will start to fry the electronics in the vehicle. It’s also important to realize that you may not have any electrical connection points for mounting. In some vehicles, you can’t even use the same battery terminals because they are too far apart on the vehicle frame. Only a 12-volt battery is big enough to fit inside your car and allow you to connect it up.

In most cases, you will be better off replacing your existing 6V battery with one of the same size and type (in other words, use your vehicle’s connection points and mounting system). You should not ever replace your existing 6V battery with a 12V to give it more power just as you shouldn’t try to replace a 12V battery with a 6V one to try and save some money. 

What’s better, a 6V or 12V battery? 

The best answer to this question is that it depends on how you want your car to run. If you’re looking for an all-around power supply, then the 12-volt system would be a better choice because it gives more power while being easier on your vehicle in terms of accessories and charging systems.

If you’re using your car for light work such as commuting, there is no need to invest in an expensive battery for a 12-volt system; if your car doesn’t already have a 12V battery. Again, you want to always replace the battery in your car or truck with the same size battery to prevent any issues unless you are in the process of upgrading or rewiring your vehicle for whatever reason. 

How to wire a 12V battery to a car/truck? 

A 12V battery should be connected to your car or truck by simply attaching the positive and negative wires to the correct terminals. Most experts recommend connecting the positive terminal first but in most scenarios it really doesn’t matter what order you connect the wires to the battery in. 

One thing that you will want to be sure of is that the battery terminals and connectors are free of corrosion or dirt/debris. If you do have some corrosion on the wires or connectors that can easily be removed by using some baking soda in water. 

Once the battery connectors and terminals are clean and free of debris/corrosion you can connect the battery and your vehicle should start up without any issue. 

At what voltage will a car not start? 

When your battery is too weak to turn the starter, it will be pretty easy to tell since your car won’t start. If you know your battery is getting old and you are wondering if it is about to be too dead to start your car or truck then testing the voltage is a good idea. However, even if you test the voltage you still have to know what the lowest voltage is that a battery will still start your car. 

In most situations and with most vehicles if your battery is below 11-11.5V it is unlikely to start. However that can vary based on the size of your motor, electrical uses of your vehicle, and even the weather conditions! 

There are a ton of variables that go into how many volts are needed to start your vehicle and although you would think that a 12V battery would be at 12V when fully charged that actually isn’t true. A 12V battery that is brand new and fully charged will be somewhere between 13.8-14V and not actually at 12V. If your car battery is at 12V then it is actually almost needed to be replaced which is super surprising to most people. 

Since the volts needed to start your car can vary so much, what most people do is simply keep starting their car/truck with an old battery until it won’t start anymore. Although it can be inconvenient to have your vehicle not start at a random time, you can often get multiple months of starting out of a battery even after it shows signs of not holding a charge as good (starting the car gets slower, etc.). 

How long is a car/truck battery good for? 

Batteries are rated in terms of their ability to hold a charge. The rule of thumb is that the average lifespan for an automobile battery is 3-5 years but some people have them last longer if they are in a warm climate or don’t use the vehicle as often. 

For example, I bought a new car in January of 2014 and didn’t have to replace the battery until 2020 so it lasted me a little over 6 years. 

I do live in a warm climate though which means the car has virtually never had to start on a sub-zero morning which allowed the battery to last a little longer. It was also my family’s secondary car so it wasn’t used (or started) as often. 

If you only have one car or have extreme temperature swings in the different seasons (like many places in the Midwest) then your battery will likely need to be replaced a little bit more often than those people who live in places where the temps stay a little more stable year around. 

Differences between 6V battery and 12V battery

Although I covered a few of the differences between a 6V battery and 12V battery a little bit earlier in this article I did want to go a little bit more in depth on that. Since 12V batteries are most often used in cars, trucks, SUVs, etc. then you won’t really need to know this info if you just have a car. However, 6V batteries are often used in small motorcycles, bikes, toys, etc. and a lot of people want to know what the differences are. 

1. The top of the battery is entirely different:

A 6V battery discharge terminal has 2-3M (metal) or without metal (plastic), and a 12V battery discharge terminal has 4M (metal) or without metal (plastic).

2. The 6V battery is normally used for smaller applications such as motorized scooters, small motorcycles, etc., while a 12V battery is widely used by virtually all larger moteried vehicles including cars, trucks, SUVs, larger motorcycles, and even riding lawn mowers. 

3. The location of the positive and negative poles is also different: the 6V battery is on the left and right sides (which are not symmetrically located), while the 12V battery is in one line.

4. The size of the battery shell is also different: 6V battery has a smaller diameter than that of 12V battery, but it is often longer than that of 12V battery.

5. The thickness of the terminal plate on each pole is different: the positive plate for 6V batteries is thicker than that for 12V batteries, while on the negative plate, they are equal thicknesses.

6. The battery charger for a 6V battery is more practical than the 12V battery because it can charge two batteries, while the 12V charger is only able to charge a single one.

7. The distance between both plates of the positive pole and negative pole of the 6V battery is longer than that of the 12V battery, which provides better insulation.

8. The location of the positive pole for 6V batteries is different from that for 12V batteries: 6-cell / 90 degrees and 7-cell / 90 degrees, while 12-cell / 180 degrees.

9. The current of the 6V battery is higher than that of the 12V battery.

10. The voltage of a 6V battery is lower than that of a 12V battery: 12V = 11.4 ~ 13.2V, 7-cell / 10A; 3-cell / 30A, however, 6-cell / 30A.

11. The discharge time of 6V batteries is shorter than that of 12v batteries: 50 minutes for a 5-hour rotation.

12. The 6V car battery has a smaller discharge current than that of 12V car battery, which means that in parallel connection, the working voltage is low and the working time is short;

13. 12V car batteries have a discharge time of 35 to 40 minutes with 1.5A power consumption;

14. The current for 6V car batteries is 0.8-1A with a discharge time of 20 to 30 minutes;

15. The price for 6V car batteries is lower than that for 12V car batteries due to its relatively small capacity.