EV Hybrids Can Still Benefit the EV Market

EV sales have been on a steady growth trajectory in recent years, spanning a range of technologies where electric motors augment or replace internal combustion engines (ICEs). These electric motors include hybrid EV (HEV), plug-in hybrid EV (PHEV), battery EV (BEV), fuel cell, and series hybrid EV (SHEV) powertrains. Nissan is one of the leading proponents of SHEVs with its e-Power system expanding beyond its home market in Japan. While SHEVs offer some intriguing possibilities for optimizing the ICE component, it’s not clear that they offer a real benefit.  

No Single Answer

There is no single solution that best meets every use case. Over time, most light duty vehicles are expected to converge on BEV over the next 15 to 20 years. Getting there will require dramatic increases in production of battery materials and cells and eventual recycling. It will also require substantial decreases in cost and improvements in energy density. That process is starting, but it will take time.

In the meantime, HEVs, PHEVs, and SHEVs are gaining traction in the marketplace. While the Toyota Prius was the leading model in the HEV market, Toyota now offers HEVs in most of its models and the RAV4 SUV has become its best seller in recent years. The RAV4 HEV accounts for half of the model's sales in Europe and one-quarter of sales in the US. As with most hybrid systems, Toyota’s architecture combines an ICE and an electric motor and blends the torque so that either or both can power the driven wheels based on demand and available battery charge. 

Decoupling the ICE

An SHEV, such as e-Power, uses the ICE only to drive a generator, which maintains the charge in the battery. An electric motor is used exclusively to drive the wheels using that energy and provides regenerative braking. Nissan wasn’t the first to use this method. The original Chevrolet Volt concept in 2007 used the same approach but with a larger battery that could be charged from a plug to provide 40 miles of range before the ICE or generator activated. 

Nissan takes a different approach with e-Power. Starting in 2017 with the Japan-market Note hatchback, e-Power equipped vehicles use a small battery of about 1.5-kWh, the same size used in most HEVs. Nissan e-Power vehicles have electric-only drive but no plug. Only the ICE or generator and braking charges the battery. It’s an EV that still has to go to gas stations. Since the ICE is only driving the generator and doesn’t have to respond to transient acceleration demands, it can be optimized for steady state operation. The timing of when it runs can also be managed to keep noise to a minimum. 

The relatively small batteries used in both parallel and series HEVs make them much more affordable to purchase than all but some of the entry level Chinese BEVs. They also don’t need to be plugged in, so drivers that don’t have ready access to charging may find them more appealing until more public infrastructure is deployed.  

The new generation Nissan Qashqai (sold in North America as Rogue Sport) is the first model outside of Japan to offer e-Power and it is expected to get about 44 mpg. This number is respectable for a compact crossover utility vehicle but not notably better than competing parallel HEVs, such as the Toyota RAV4 or Hyundai Motor Company Tucson. SHEVs may drive similarly to a BEV, but from a functional perspective, they are comparable to the HEVs that have been on the road for more than 2 decades. If this approach helps reduce emissions and energy consumption, then these vehicles can provide real benefits to society.