Quick drive of the Passat HyMotion hydrogen fuel cell hybrid

20 November 2014

Volkswagen unveiled the Golf Sportwagen HyMotion hydrogen fuel cell hybrid research vehicle demonstrator yesterday at the Los Angeles Auto Show (earlier post). Volkswagen has also built several research vehicles based on the US version of the Passat using the same hydrogen drivetrain components as fitted in the Golf SportWagen HyMotion.

The fleet of Passat HyMotion vehicles is currently being tested on the streets of California. In addition, Volkswagen brought a pair of the hydrogen Passats to the Los Angeles Auto Show for test drives (and Audi brought a pair of its A7 Sportback h-tron hydrogen fuel cell plug-in hybrids for drives, as well.)

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Passat HyMotion in LA. Click to enlarge.

The drivetrain and MQB. The mechanical underpinnings for the Passat and Golf HyMotion cars are based on the Modular Transverse Matrix (MQB) that was developed by Volkswagen and is used throughout the Group. (Earlier post.)
The key drive components of the Golf SportWagen HyMotion were developed by Volkswagen Group Research in Germany.

The 100 kW fuel cell system (also applied in the A7) has a system power of 100 kW. The concept car has high-voltage 1.1 kWh lithium-ion battery pack (from the Jetta Hybrid), which stores the kinetic energy recovered from regenerative braking; assists in the starting phase of the fuel cell; and adds a dynamic boost to the maximum acceleration of the Golf SportWagen. The fuel cell and battery power an electric motor adapted from the e-Golf.

The drive components (motor, two-stage 1-speed transmission) of the HyMotion are in the engine compartment of the car as are the hydrogen fuel cell stack; the cooling system; a tri-port converter that regulates the voltage between the electric motor, the fuel cell and the lithium-ion battery; and the turbo compressor. The latter ensures that oxygen from the surrounding air flows into the fuel cell.

Top: Drivetrain. Middle: Fuel Cell Stack. Bottom: Under the hood of the Passat HyMotion. Click to enlarge.

The power electronics, which convert the direct current (DC) into three-phase alternating current (AC) which is used to drive the motor, are located in the center tunnel. The power electronics also integrate a DC/DC converter, which converts energy from the high-voltage battery to 12 volts to supply the 12-volt electrical system.
The high-voltage lithium-ion battery, which has its own cooling circuit, is mounted close to the trunk and rear suspension. The 12-volt battery is also mounted at the rear.

Two of the total of four carbon fiber composite hydrogen tanks are housed under the rear seat and the other two in the luggage compartment floor. The hydrogen is stored in the tanks at a pressure of 700 bar (10,150 psi).

The battery is housed above the rear suspension, and the tanks are mounted in the vehicle floor. With the packaging of the drivetrain elements, the interior offers the same amount of space as in other versions of the model.

Driving the Passat HyMotion. The Passat HyMotion is, well, basically a Passat with its roomy and comfortable cabin. Starting up is a simple matter of pushing the start button.

At start, the fuel cell has not built up enough electrical power to drive the motor by itself. The Li-ion battery steps in and supplies energy to the electric motor instead, allowing the car to move off.

The only indication (aside from the display) that the fuel cell engages is the sound of the blower. Although audible, it is low; turning on the climate control fan to the first level obscures the sound. Looked at another way, the sound of the fuel cell in operation is no more distracting that having the HVAC system running in the cabin.

Top: The Energy Flow display clearly shows the flow from and to the different powertrain elements. Middle: At start, energy will only be flowing from the battery (top, blue) to the motor. Bottom: On recharge, energy will flow from the fuel cell through the tri-port converter to the battery. Clicking on an element opens up a new screen with more detailed operating information. The number at the center is the range remaining. Click to enlarge.

At this point, the Passat is a fully electric car—but with a range of more than 300 miles. It exhibits all the benefits of electric drive: smooth and quick acceleration from a stop, quiet, and zero toxic emissions. In the stop-and-go of LA downtown rush-hour traffic, it was never jerky, and allowed us to dart into gaps with ease then pull quickly away when there was a chance.

The control software for the HyMotion is more akin to that of a combustion-engined hybrid than that of a battery-electric vehicle as it entails more balancing between primary power source (fuel cell or engine) and the secondary (Li-ion battery).

The battery is recharged either through regenerative events or via the hydrogen fuel cell.

Futures. Our quick drive of the Passat HyMotion highlighted the benefits of an all-electric zero emission vehicle (ZEV) drive applied in yet another model type, and the display of the range and tank fill stage together were extremely satisfying (long range, lots of fuel, fast refill). The same could be said, though, for a Passat equipped with very high energy density future batteries (along with a very fast DC charger).

Dr. Neußer (left) and Dr. Hackenberg (right) explaining at the fuel cell technology workshop. Click to enlarge.

As we noted in our write-up of the three Volkswagen Group hydrogen fuel cell prototypes yesterday, the Volkswagen Group isn’t yet calling either hydrogen fuel cell technology or all battery-electric vehicle technology a clear winner. In a workshop on Fuel Cell Technology presented by Dr. Ulrich Hackenberg, Member of the Board of Management for Technical Development at Audi and Dr. Heinz-Jakob Neußer, Member of the Board of Management at Volkswagen responsible for the Development Division, Dr. Hackenberg observed that:

Fuel cell technology is running in competition with long-range battery electric vehicles. We don’t know which technology will be the winner.

Dr. Neußer observed that the Group still expects an inflection point in fuel cell technology and adoption not before the year 2020, but that it was demonstrating with these concepts that the company will be ready to launch when all the other issues surrounding hydrogen adoption (production, refueling) have been addressed.

Volkswagen Group is also investing very heavily in battery development, and as a company is aggressively developing and introducing variants of battery-powered drivetrains (for example, the e-up!, e-Golf and Golf GTE from Volkswagen, with a Passat plug-in hybrid announced; the Cayenne and Panamera E-Hybrids and the 918 Spyder for Porsche; the Audi A3 e-tron, with a plug-in hybrid R8 and a pure electric R8 E-tron in the works, to name a few). Prof. Dr. Martin Winterkorn, Chairman of the Board of Management of Volkswagen recently said that he sees “great potential” in solid-state batteries, which possibly could boost EV range to as much as 700 km (435 miles), representing a volumetric energy density of about 1,000 Wh/l. (Earlier post.)

And Dr. Neußer earlier this year projected that the Volkswagen group by 2015-16 will boost battery energy density from the current 25-28 Ah to 36-37 Ah, providing a range of around 300 km (186 miles). Dr. Neußer also said that the company is working on the next step to around 60 Ah, which will be achieved with a “completely new” chemistry, and will come at the beginning of the next decade. This could provide range on the orders of 500-600 km (310-373 miles), he suggested. (Earlier post.)

But, getting back to Dr. Hackenberg’s comment, they don’t know for sure.

With is modular strategy (MQB for transverse application, MLB for longitudinal applications, etc.), Volkswagen is strategically positioning itself to be able to provide whatever advanced low- or zero-emission drivetrain is demanded (or required) in its high-volume vehicles. The MQB-based Golf, for example, could have gasoline engine (TSI), diesel engine (TDI), battery-electric drive (e-Golf), natural gas, plug-in hybrid (GTE) and hydrogen fuel cell (HyMotion) versions produced “bumper-to-bumper” on the assembly line.

Electrified drive systems in the MQB. Click to enlarge.