How Many Volts Is A Semi Truck Battery?

Every vehicle uses a battery, and semi trucks are no different. But have you ever wondered how many volts is a semi truck battery?

Most semi-trucks use a 12-volt battery, just like cars or other vehicles. But that is only for North American trucks. Trucks that are driven throughout Europe or manufactured there normally use a 24-volt system.

The question seems kind of innocent, but we assure you there is more to it than meets the eye. So, we welcome you to read the article, where we have tried to explain this matter thoroughly.

How Many Volts Is A Semi Truck Battery?

Like all vehicles, semi-trucks also need a battery to power all their electrical components. But not all the semi-trucks use the same volt batteries in the same fashion.

The difference lies in the region. 

US-manufactured Semi Trucks

The semi trucks that were manufactured in the US use 3×12-volt batteries in a parallel connection. The main output of that comes to 12 v.

If you connect three 12-volt batteries with each other, how is the output only 12 v? Well, this is where it gets interesting. To understand this, you must know what happens when you connect batteries in parallel

When you connect multiple batteries in parallel, the battery voltage remains the same, but the capacity increases. This means even if the voltage stays the same, the amperes per hour increase

For example, US semi trucks use three 12-volt batteries in parallel. If each battery has 80 amperes, the system will produce 12 volts and 240 Ah. That ampere count was an approximation; usually different 12-volt batteries have different amps.

US-manufactured Semi Trucks

Source: power-sonic

The connection is pretty simple. As you can see from the diagram, all the positive terminals are connected together at a single point. Similarly, all the negative terminals are also connected to another point, in parallel.

Since all the terminals use the same nodes, the voltage remains the same. But the output current is the sum of all the individual batteries. That’s because the current flows through all three batteries. 

The benefits of using a higher-amp battery are that it will improve the vehicle’s running time and last longer on a single charge. Also, the chances of your motor overheating become low.

For EU-manufactured Semi Trucks

The batteries that European semi-trucks use have different connections than those in US trucks.

EU trucks use four 6V batteries in a series connection, which produces an output of 24 volts. When batteries are connected in series, the voltage output increases, but the ampere output stays the same. 

For EU-manufactured Semi Trucks

      Source: power-sonic

In the series connection, one battery’s negative terminal is connected to another’s positive. So, the output voltage is multiplied across all the batteries. But there is only one way for the current to flow, so the current stays the same.

But there are some EU truck models that use four 6V batteries in a series-parallel connection, which amplifies both the voltage and amperage. 

How Many Volts Is A Semi Truck Battery

      Source: atbatt

In this circuit, four 6V and 225 Ah batteries are connected in a series-parallel connection that produces the output of 12V and 450 Ah. This connection doubles the output of both voltage and ampere. So, it’s also possible to connect four 12-volt batteries to get 24-volt output.

A series-parallel connection is a bit more complicated than a regular series or parallel connection. All four batteries are connected to each other in both series and parallel. That’s why both the current and voltage output are doubled. 

One last thing: the number of batteries is not constant for both of these regions. Depending on the manufacturer, a semi-truck can use up to eight-cell batteries.    

Why Right Voltage is Crucial For A Semi Truck?

In a semi-truck battery, voltage serves as the power supply. That means it sends current to the truck’s system, which powers all the electrical components.

There could be two scenarios here, either you use less voltage or more than the required amount. 

Suppose you use a 12V battery in a system that requires 24V. In that case, the electrical components will not even turn on, as they are not getting enough current input.

If you do the opposite and use a 24 V battery in a 12 V system, the devices will be overpowered and eventually damaged.

So, you must use the exact voltage the system requires. Otherwise, you will either damage them or they will not work at all.

What Else Matters Besides Voltage?

So, in a battery, getting the correct voltage is important. Besides that, there are a couple of other things that matter.

Cold Cranking Amps

Cold cranking amps, or CCA, indicate the number of amps the battery can deliver without being completely discharged. CCA is measured at freezing temperatures for 30 seconds. 

Since it measures the workability of a battery, the more CCA your battery has, the better it will perform. 

To measure the CCA, a new battery is put in a cold environment, usually 0 degrees Fahrenheit. Then the discharge load is measured in amperes. This is measured for 30 seconds, maintaining a terminal voltage of 1.20 volts per cell. 

The test is performed in a cold environment to test its ability to perform in worse conditions. So, a battery with 900 CCA can deliver 900 amps in 30 seconds at 0 degrees Fahrenheit. 

Reserve Capacity

Another important battery attribute is the reserve capacity, or RC. Reserve capacity indicates how long a battery can maintain a 25-amp load before completely discharging. It is usually measured in minutes.

A 25-amp load is drawn from a fully charged battery at room temperature until the voltage drops to 10.5 volts. That’s how RC is measured. The amount of time it can sustain the load is the battery’s reserve capacity.

So, if a battery’s RC is 190, that means it can sustain a 25-amp load for 190 minutes. The more reserve capacity a battery has, the better the battery will work.  

There are also other small factors that matter when choosing the best battery for your vehicle.

Which Batteries Does the Best Semi Truck Brands Use

After a brief discussion about batteries, let’s take a look at what type of battery the biggest truck manufacturers use. We will be comparing their voltage, amps per hour, cold-cranking amps, and reserve capacities.

BrandVoltageAmpere (Ah)CCARC
Western Star12v801150205

As you can see from the chart, the top 5 brands of semi truck batteries use 12 volts. However, other specifications are kind of varied, but still not by a long shot. 


How many volts is a commercial battery?

Commercial batteries are usually 3.6 volts if they are lithium-ion batteries. The voltage of LFP (lithium iron phosphate) batteries is 3.2 volts. NiCd batteries have a working voltage of 1.2 and lead-acid batteries have 2.1 volts.

Can a diesel truck run without a battery?

Yes, a diesel truck can run without a battery. That is because their primary source of power is not electricity but diesel. So, they can run very well without batteries.

What is the battery voltage in Freightliner Cascadia?

The Freightliner Cascadia uses a 12-volt battery. The battery also has 80 Ah, 950 cold cranking amperes, 1160 cranking amperes, and a reserve capacity of 190 minutes.

What should my truck voltage be?

Your truck’s voltage should be 12.6 with the engine off, which is called the resting voltage. When the truck is running, the voltage might rise, but it should still be between 13.5 and 14.8. The voltage level increases while driving because it gets charged by the alternator.


To answer your question, “How many volts is a semi truck battery” we have analyzed the batteries of semi-trucks. Usually, most of them use 12 volts, but some also use 24 volts, especially in the European region.

Voltage is an important specification of a battery, but it’s one of many. There are also other things to consider, such as amperage, CCA, and RC.

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