Electrifying ‘The Ultimate Driving Machine’

February 1, 2019

Which premium vehicle OEM currently offers the broadest range of plug-in vehicles? That would be BMW, with 12 production hybrids and battery EVs including new-for-2019 PHEV variants of the 3-Series sedan and X5. With many more in the pipeline and the company’s fifth-generation electric drive system in development for 2020, Automotive Engineering Editor Lindsay Brooke sat down recently with Stefan Jurascheck, BMW VP Development for Electric Powertrains, to discuss details of “the ultimate electrified driving machine.” Jurascheck, an electrical engineer, is a 32-year BMW veteran.

BMW’s next-gen electric drive architecture is due to launch in 2020. What can you tell us?

Development is in-house; we’ve done this since we started the i3 and i8 programs. We learned a lot from these pioneering electric cars. When we started development on them and also on our PHEVs, it was very difficult to find suppliers who could fill our wide range of technical requirements — including electric motor scalability, the need for front- and rear- axle drivetrains, and so on. You can cover the one-off development costs if you make a modular ‘kit’ out of it. To do that you must decide on the set of exterior dimensions, internal ratios, and power electronics. That’s very important. Because if the OEM doesn’t have full control over the power electronics, you’re forced into greater complexity in terms of hardware and software, including updates.

We have only one power electronics package. Its highly integrated box fits a range of our powertrains from 100 kW up to 350 kW. The box might be a little bit larger than optimum size, but we can use it on every vehicle and electric axle. We used a very flexible, build-to-print approach; we know the precise price points. Our development of this box is driving our expertise in our electric motors and also for our engine development.

What components constitute the hardware e-module?

The electric motor, transmission and power electronics are engineered into a single integrated e-drive unit. It’s very compact. The DC/DC charger will also be integrated. The unit is designed to be scalable, enabling it to fit many vehicle applications and power requirements. It will allow us to incorporate new battery types flexibly, according to vehicle requirements. Also, our new electric machines will be free of rare-earth metals.

And, this new series-production electric drivetrain is developed by the same people in my department who are responsible for the Formula E BMW electric racing drivetrain we launched in 2018. They are pushing the envelope to see what can be achieved in 3-5 years in this area. The racing system uses a silicon-carbide inverter, but the two systems are running with the exact same software! This year we had a test campaign, trying to identify issues under extreme loads and conditions on the racetrack. Combining the racing and series software developments has increased the speed of our series-production development.

What’s the production plan?

We’ll do production of the electric powertrain in-house as well, in scales up to 500,000 units per year. It will give us a lot of experience in this field. Our flexible production can build motors from 100 kW to 350 kW, all on one line.

How about 48-volt hybrids?

In the next five years we’ll have significant applications of 48-V in our cars. We’re doing 48-volt model by model but we need the right ‘stepping in’ point to introduce it — for instance, when we update an engine or a gearbox, we’ll also try to do an update of the voltage system.

When do you expect the cost per kilowatt-hour of EVs to finally intersect the cost of, say, that of a typical 3-Series powertrain?

It depends on what you expect for vehicle range. If you expect a 250- 300-km range, then we are not far away — maybe 2024-25. But we have demand for longer ranges and higher capacity batteries, beyond 100 kW·h. Cell price is definitely driving EV cost because of the raw material.