Advocates of battery-electric and hydrogen fuel-cell cars are often at odds over which powertrain technology is the more practical solution to reducing emissions.

But French firm Symbio continues to experiment with ways to combine the two.

It fits hydrogen fuel cells as range extenders for battery-electric vehicles, primarily small delivery vans.

CHECK OUT: Hydrogen As Electric-Car Range Extender? French Tests Start Soon (Dec 2013)

At FC Expo 2017 in Tokyo, it unveiled a fuel-cell range extender for the Nissan e-NV200 electric van.

The e-NV200 is essentially a Nissan NV200 small van with the battery-electric powertrain from a Leaf.

While the standard NV200 is sold in the U.S.—and even serves as New York City's "Taxi of Tomorrow"—the e-NV200 is not available in North America despite several years of fleet testing.

Nissan e-NV200

Nissan e-NV200

But in the markets where it is available—Japan and Europe—Symbio believes its fuel-cell range extender will make things more convenient for fleet operators.

Like range-extended electric vehicles that use gasoline engines, the e-NV200 retains a lithium-ion battery pack that can be charged by plugging in, which acts as the primary energy source.

When the battery's charge is depleted, the fuel cell takes over as the source of electricity. The result is a zero-emission vehicle with a longer range than that provided solely by its battery capacity.

ALSO SEE: More Than 500 Nissan Electric Cars In Taxi Service Now (Dec 2015)

Symbio is aiming the conversion at taxi drivers, believing they will appreciate the combination of greater range, with less downtime.

A range-extended e-NV200 taxi could fill up with hydrogen at a fueling station in 3 minutes, according to Symbio, compared to 30 minutes for an 80-percent charge at a DC fast-charging station.

But that's assuming the taxi operates in an area that has sufficient hydrogen fueling infrastructure.

Nissan e-NV200

Nissan e-NV200

Nissan's home market of Japan has undertaken a program to expand such infrastructure in time for the 2020 Tokyo Olympics, but many countries currently have only a handful of public hydrogen stations, if that.

Symbio's previous fuel-cell range extender efforts included a deal with La Poste—the French postal service—to test its technology in three Renault Kangoo ZE small electric delivery vans.

MORE: Electric Ford Transit van conversion shown by Inventev at Detroit Auto Show

The U.S. Energy Department and FedEx also started a pilot program in 2014 to install similar fuel-cell range extenders in some of the delivery company's electric vans.

The Nissan e-NV200 conversion kit will start production in September 2018, Symbio says, but it is accepting pre-orders now.

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