How does Nissan’s E-Power system work?



Back in December 2016 we drove the Nissan Note E-Power, a car that walked a strange new path between petrol and electric power.

E-Power was then in its infancy, so we spoke to Nissan engineers who explained how it works and why it’s so efficient. The technology has proven to be a winner in the real-world in one key way: Not long after its launch, the Note E-Power became Japan’s single best-selling car. Here’s a version of a story that ran all the way back in CarBuyer 254.

YOKOHAMA, JAPAN — The problem: Combustion engine cars are pollutive, at least at the tailpipe, and noisy. The solution: Use electric power, which is clean and quiet.

Another problem: There’s nowhere to charge your Electric Vehicle, and it takes bloody long to do it. The solution: Put a charger in the car.

That approach — giving an EV its own built-in charger — is the main idea behind the Nissan Note E-Power, the compact, five-door hatch you see here. It’s propelled by an 80kW electric motor that drives the front wheels, hauling the car along smartly, more or less silently. 

Japan’s number two carmaker began selling it at home in October 2016, and a month later drivers there happily took Note: it became the best-selling car in the nation.

BE LEAF IT OR NOT
Think of the Note E-Power as an EV like Nissan’s own Leaf. The best-selling electric car in history, the Leaf has basically given Nissan a rich seam of know-how to mine, resulting in the Note E-Power’s creation.

Nissan importer Tan Chong launched the second-generation Leaf (below) in Singapore this year.

Unlike most EVs, the Note has a tiny battery. Its lithium-ion power pack lives under the front seats, and is just 1.5kWh in capacity. In comparison, the Leaf’s battery is 20 times bigger.

No surprise, then, that on pure battery power, the Note E-Power can only travel a couple of km. That is, until the on-board charger kicks in.

That’s the sole purpose of a 1.2-litre petrol engine that lives under the bonnet. It sleeps for much of the time, and only wakes up when the E-Power’s small battery needs a top-up. It’s not connected to the car’s wheels in any way, so it could never directly drive the car. Instead, it just spins a generator.

That makes the Note E-Power a new breed of hybrid. Normally a hybrid has an engine with a small motor to give it a boost, and they work together to propel the car. But here the electric motor does the work and the carbon-farting engine only gives it energy.

Why put a petrol engine in a car just so it can charge a small battery to feed the motor that actually propels the whole contraption? Turns out the extra steps are totally worth it.

“In Japanese driving conditions, this system is very useful,” says Naoki Nakada, the brains behind E-Power and before that, the Leaf’s EV hardware.

In start-stop traffic electric drive is way more efficient than a petrol engine, he explains. Engines are inefficient when they’re revved up and down, and tend to do their best at constant speeds. That’s one reason you get better mileage on the highway than in the city.

The E-Power system assigns those tasks accordingly — the motor does the work and shrugs off the demands of start-stop traffic, while the engine buzzes along at a steady, efficient rpm whenever the battery needs juice — so it’s surprisingly efficient.

Japanese government fuel economy tests say the Note E-Power averages 34km per litre of petrol — 29.8 percent further than a Note with a plain supercharged 1.2-litre engine.

That still falls short of the 37km/L achieved by a Toyota Prius C, but Nakada says the instant torque of electric drive makes the Note E-Power a more fun car to drive. “I really want people to experience motor drive,” Nakada says. One of those people was me. 

A WILD EV APPEARED!
After a quick spin in a Leaf for reference, CarBuyer was let loose on two laps of a private test track in a Note E-power. The immediate impression? It feels exactly like an electric car.

Like in the typical battery-powered car, when you switch it on the dashboard lights up but there’s no sound from under the bonnet. When you take off it’s spookily silent, like ghosts are pushing the car. Strong ghosts, too. The acceleration response is instantaneous, thanks to a huge dollop of torque that the motor makes available. 

The Note E-Power is so quiet, in fact, that Nissan says if you measure the cabin sound levels you’ll find it’s as quiet as most luxury cars.

But that’s only until the generator bursts to life, at which point there’s a sudden, jarring contrast between the silence of electric drive and the now-crude thrum of a petrol engine. The 1.2-litre engine wakes up seemingly randomly, too, so it does take getting used to: one moment you’re wafting along in a car that’s as hushed as a Mercedes S-Class, and suddenly an engine has crashed the party.

It’s particularly noisy when you give it full acceleration, say, when speeding up to join expressway traffic. In that situation the motor demands more juice than the battery can provide, says Nakada, so the engine revs up to supply the needed flow of electrons.

This bears repeating, though: the Note E-Power is an electric car first, hybrid car second. Though it has an engine, what powers it is electricity. You could get a Ferrari V8 to juice up the motor, and the Nissan wouldn’t go any faster than it does now.

On the other hand, even if the E-Note has an electric motor for legs, it has a petrol engine for a heart. Empty the 45-litre tank, and the Nissan grinds to a halt.

So is it an EV, a petrol-powered car, or ultimately a hybrid of the two?

From Nissan’s point of view, it’s more Nissan Leaf than Toyota Prius. Daniele Schillaci (pictured below), the global head of marketing for Nissan, reckons that it could take 10 years for EVs to become as cheap as normal cars to manufacture, so E-Power is meant to bridge the gap by offering the driving characteristics of an electric car, but none of the main drawbacks.

Batteries are heavy and expensive at the moment, too, so this arrangement allows costs to be kept down — in Japan, the Note E-Power retails for 13 percent more than a similar-spec Note 1.2 DIG-S.

The relatively low cost hurdle and packaging convenience mean the E-Power drivetrain will likely spread across the Nissan range.

When I point at a Nissan Serena and ask if the E-Power system would fit into it, Nakada’s only answer is a coy smile.

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Leow Julen
Leow Ju-Len is a lot older than he behaves. He's been writing about cars for 25 years. Someday he might do it coherently. Ju-Len believes in world peace and V8s, but not necessarily in that order.