PHEVs and EREVs, Series and Parallel Hybrids.


Working in the world of Electric Vehicles, two terms often come up: Plug-in Hybrid Electric Vehicles (PHEVs) and Extended Range Electric Vehicles (EREVs). Plug-in Hybrids (PHEVs)[1] are

“Hybrid vehicles with batteries that can be recharged by connecting a plug to an external electric power source.”[1]

Okay, simple enough. A plug-in hybrid is a plug-in vehicle. So what’s an Extended Range Electric Vehicle? Wikipedia redirects the article on EREVs[2] back to the article on PHEVs, so no luck there. One of the benefits of working at Arcimoto is access to the world class team building the Arcimoto Pulse. I was able to sit down with Nick, one of Arcimoto’s electrical gurus, and ask him a few questions about EREVs, PHEVs, and what the differences are between Series Hybrids and Parallel Hybrids. Nick used to work for the military on SR-71s and U-2 Spy planes. If he can keep combat aircraft up in the air, I figure he can refresh me on EV terminology.

Here’s the gist: PHEVs and EREVs are both plug in electric vehicles, but PHEVs derive most of their power from a gas engine. Technically, this eliminates them from being ‘pure electric vehicles.’ EREVs, on the other hand, are pure electric vehicles that utilize a small combustion generator to generate more electricity and extend the range of the vehicle beyond its battery pack.

(Credit: Sam Abuelsamid’s article on 9/10/2007, Toyota’s Irv Miller on Series vs. Parallel Hybrids [3])

What about Series Hybrid Vehicles and Parallel Hybrid Vehicles?

A good example of a Parallel Hybrid is the Toyota Prius. The Prius has both an electric motor and a gas motor. Both motors feed power through a single transmission. Parallel hybrids can be categorized depending on how balanced the different portions are at providing motive power.[4] In some cases, the combustion engine is the dominant partner (the electric motor is runs when an extra boost is needed), in others the relationship is flipped with the electric motor providing most of the power. Since the two motors are operating in parallel, this setup is known as a Parallel Hybrid Electric Vehicle.

On the other hand, a Series Hybrid Vehicle can be thought of as a linear system instead of the parallel system of the Prius[5]. A Series Hybrid Vehicle has a combustion engine that drives an electric generator instead of directly driving the wheels. Series Hybrids are also known as Extended Range Electric Vehicles. When large amounts of power are required, the motor draws electricity from both the batteries and the generator. Since the two motors are operating in series, this setup is known as a Series Hybrid Vehicle.

[1] According to Wikipedia on 10/23/09
[2] As of October 23rd, 2009
[3] Sam Abuelsamid’s article on 9/10/2007, Toyota’s Irv Miller on Series vs. Parallel Hybrid
[4] Wikipedia on Parallel Hybrids
[5] Wikipedia on Series Hybrids