Charged with Excitement

It’s clear that cars with electric drives won’t go into mass production overnight – vehicles with combustion engines will continue to dominate our roads in the coming 20 years. But all experts agree: the electric car will shape the future. For a long time now, the Volkswagen Group has been working on a drivetrain strategy that will take the Company and its customers into the future step by step.
The electric car will shape the future. (photo)

It’s already possible today to get a taste of the future of motoring: you can hear a pin drop when you turn the Golf twinDRIVE’s ignition key. The car moves off without a jolt and only a slight hum.

As a hybrid, this prototype has both a conventional combustion engine as well as an electric one. More precisely, there are actually two other electric engines working in the twinDRIVE – in the rear wheel hubs. According to project manager Dr. Lars Hofmann, the car can actually “really drive electrically”, and not just short distances “but 30 to a maximum of 50 kilometers with a full power output of 60 to 70 kW” which is also good for consumption and environmental data: “Our prototype consumes two and a half liters of diesel and eight kilowatt-hours of electricity for 100 or so kilometers. This equates to CO2 emissions of around 94 grams per kilometer”, explains Hofmann. This means that the hybrid vehicle significantly undercuts the future EU emission limit of 120 grams per kilometer. With its environmentally friendly technology, the twinDRIVE can reach a top speed of 170 kph on the motorway, thus demonstrating its sporting prowess.

But the twinDRIVE is no conventional hybrid car. Hofmann describes the special feature: “Normally it’s the electric engine that supplements the combustion engine, but it’s the other way round with the twinDRIVE: the diesel engine fills the gaps left by the electric engine.” The electric engine ensures an emission-free and silent drive in town. If necessary, the economical diesel engine charges the lithium ion battery and provides the power for longer journeys. In addition, the twinDRIVE is a “plug-in hybrid”. This means that it can be charged using any conventional 220-volt electrical outlet.

“I believe that starting with plug-in hybrid vehicles and then building on this to develop purely electric cars is the right approach.” Dr. Martin Pehnt, Heidelberg Institute for Energy and Environmental Research (quotation)

“The twinDRIVE is one of our answers to the question of how to reduce both the fuel consumption of our vehicles and CO2 emissions”, explains Hanno Jelden. As head of Drivetrain Electronics at Volkswagen, he is responsible for all hybrid and electric engine developments. This is not the first time that Jelden has been involved with e-mobility: the Group offered its first electric vehicles in the nineties with the “Golf III Citystromer” and the “Audi duo” and supervised fleet trials: “Battery technology has now advanced to the point where we can seriously think about and work on electric cars.”

“We are working on materials that do not spontaneously combust and do not trigger any unwanted chemical reactions.” Dr. Matthias Ullrich, Head of Battery Systems Development (quotation)

Experts don’t doubt that lithium ion batteries, rather than today’s nickel-metal hydride ones, are the future. Lithium ion cells are used in their millions in laptops and mobile phones. The battery manufacturers’ development engineers now face the challenge of massively increasing the battery’s energy content at the same time as significantly cutting production costs. This is because car batteries have to last much longer than mobile phone batteries – at least ten to 15 years. Such high-capacity batteries do not yet exist for the automotive industry.

Dr. Matthias Ullrich, head of Volkswagen Group’s Battery Systems Development, explains the challenges facing the battery generation of tomorrow: “Costs for a single battery cell today are around €1,000 per kWh. Our goal is to cut these costs in the medium term to €500, and to €200 in the long term.” A further key problem is that the chemical processes involved in charging and discharging generate heat in the battery, without which the process could not take place. If the temperature in the battery reaches the region of 140°C – for example because of overcharging or mechanical damage – the cell’s membrane will melt like a plastic bag on a hotplate. This releases all of the energy in one fell swoop. As well as increasing the battery’s lifetime and reducing costs, the Volkswagen Group is also working with various partners on a 100 percent safe storage battery. This is because fires can result from the high energy density in the small space inside lithium ion batteries. “We are working on materials that do not spontaneously combust and do not trigger any unwanted chemical reactions. In addition, we are focusing on improving battery production processes in order to eliminate defects”, explains Ullrich.

Share of hybrid and electric vehicles in Europe (graphics)

Ullrich talks about the “magic triangle of lifetime, cost and safety” for lithium ion batteries. The market launch of electric cars depends on how quickly these problems can be solved. This is why the Volkswagen Group is working together with Japanese electronics group Sanyo, which is developing a battery system for both the Touareg Hybrid and the Golf twinDRIVE to Volkswagen’s specifications as a first step. In addition, Volkswagen has entered into a long-term cooperation with electronics group Toshiba for electronics modules and electric traction components. In cooperation with the University of Münster’s Institute of Physical Chemistry, Volkswagen is also studying battery cells and electrode materials for lithium ion batteries. Battery expert Matthias Ullrich explains the aim of this cooperation: “By the end of the next decade, it may be possible to double the range of lithium ion batteries to 200 kilometers. However, we need new technologies in order to reach 400 kilometers.”

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