Beyond The Batteries: How Electric Trucks Work

Electric Trucks
Electric commercial trucks are here, and they continue to rack up real-world miles. But have you ever stopped to think about what’s going on inside of one when it’s on the road? Let’s take a look.

Understanding electric semi trucks isn’t about examining every nut, bolt, wire and battery cell. It’s about looking at the big picture: how the major components of the truck work together to provide optimal efficiency, safety, durability and productivity. That’s the key to understanding the literal power inside – and grasping just how powerful and world-changing these vehicles can be.


Let’s start with the big picture. Here’s an overview of what happens inside the Freightliner eCascadia, from power-on to acceleration to braking.

  1. When the driver partially turns the key, ions and electrons from the high-voltage batteries are made available to power the truck.
  2. Once the driver fully turns the key (as if “cranking” the truck), the high-voltage system sends energy to the powertrain.
  3. Upon being pressed, the accelerator sends a software signal to the inverter, a switch that rapidly opens and closes to convert a direct current (DC) signal into alternating current (AC).
  4. AC power energizes the electric motor and creates torque. Rotational energy is fed into the electric powertrain, which causes the wheels to turn and the vehicle to accelerate.
  5. In addition to standard braking, the truck can be stopped via brake recuperation, also known as regenerative braking in passenger EVs. This allows the batteries to recharge. Energy travels from the e-motors to the inverter and all the way back to the batteries.

Despite the major design differences between battery-powered trucks and diesel vehicles, the driving experience remains largely the same– just with less noise, smoother acceleration, more torque and plenty of other benefits that we’ll explore below.



Another similarity between battery-powered trucks and diesel rigs is their reliance on software. Both types of trucks use software to coordinate all the internal components and systems. The main difference is simply the kinds of components they’re managing.

In the eCascadia, one of the most central software-related parts is the electric common powertrain controller (eCPC), also called the powertrain controller. Let’s say you depress the accelerator about halfway – or 50%. The powertrain controller receives this request to accelerate and immediately checks with other components to determine if giving 50% torque to the e-motor is both safe and efficient for the system.

Of course, the powertrain controller isn’t designed to arbitrarily limit power or torque. It’s engineered to work with a wide range of truck parts to intelligently maximize them – while also being as efficient as possible.


When it comes to batteries, a lot of drivers might just think of the one under the hood of a diesel truck. But in an electric truck, there are several batteries throughout the vehicle. There are also two distinct types:

The battery management system: A key to intelligent power

On their own, batteries are just huge stores of power. However, when controlled by the right software, they’re incredibly smart. In the eCascadia, each battery is optimized via a battery monitoring system (BMS). The BMS is a controller that uses specialized software to keep tabs on what’s happening inside each battery and help them operate efficiently.

Thermal management: Keeping batteries happy

The BMS pays attention to charge and temperature within each battery cell, so it can ensure that all systems run safely and efficiently. For example, if one battery gets too warm, the BMS calls on the truck’s thermal management system to quickly reduce the battery’s temperature via liquid cooling. In cold environments, the BMS can use the same system to keep batteries warm and performing their best.


Designed for durability with fewer moving parts

Battery-powered trucks also have fewer parts – especially moving parts – which can help minimize maintenance in the long run. And it’s not just the e-motor. In the eCascadia, a 2-speed transmission replaces the need for a more complex 12-speed transmission that one might find in a diesel truck. In short, Freightliner electric trucks are engineered with simplicity and durability in mind.


For electric trucks, energy is a two-way street. Not only can the batteries and inverter power the e-motor, which ultimately drives the e-axle and wheels. The entire system can work in reverse. The driver can quickly initiate a process called brake recuperation. Brake recuperation allows the e-motor to convert mechanical motion back into electrical charge that can be stored in the batteries. In a world where efficiency matters, brake recuperation isn’t just smart. It’s the future.


There’s a lot more to discover. Check out our eM2 and eCascadia to see how electric truck technology is racking up miles in the real world.