During a recent visit to BMW’s normally top-secret electric powertrain development center in Munich, we had the chance to take a closer look at the company’s next-generation e-power unit, known internally as the HEAT. It didn’t look particularly radical or exciting, yet this family of modular powertrain units will be at the heart of the company’s dramatic expansion plans for electrification throughout the models spun from its forthcoming fifth-generation architecture.
While the company’s previous electrical drivetrains have had their components spread around the cars they are fitted to, the HEAT unites the motor, a single-speed gearbox, and the power electronics necessary to run them into a single casing, creating an entirely modular unit that can be installed into a car in the same space that could, alternatively, house an internal-combustion engine. It’s a key component in BMW’s plan to build future models that can be offered as EVs, hybrids, or internal-combustion vehicles, adjusting the mix to meet market demands of the moment.
While the HEAT name is currently just a working title, the company’s electrification engineers have been trying to find a designation that could turn it into an official acronym. “It’s a Highly Integrated Electrical Drivetrain,” Ilka Horstmeir, the company’s head of electric powertrain production, told us. The acronym “doesn’t quite work, but it’s close enough to have inspired the name.”
The HEAT uses a water-cooled, high-speed, externally excited synchronous motor built to BMW’s own design. The company regards the technology as being important enough to be developed and built internally. The motor uses a new type of stator with thick copper “hairpins” instead of the more normal wire windings. This is claimed to both simplify production and make the motor more efficient. HEAT units will come with a variety of outputs, ranging from around 134 to more than 400 horsepower. Since they’re modular, different units will be easily integrated into different cars, so the same HEAT module used in an entry-level BMW 2-series EV could also provide the electrical assistance in a mid-spec 5-series plug-in hybrid. “The idea is to make it plug and play,” said Stefan Juraschek, BMW’s head of electric drivetrain development. We were shown the 268-hp unit that we believe will power the iX3, and it is indeed impressively compact.
We also got the chance to see some of the company’s work on battery design. Although it uses external suppliers to produce cells, BMW has a workshop in Munich capable of making very limited numbers of its own battery packs for prototype applications. BMW still predicts an ultimate shift to solid-state batteries and is working with Colorado-based Solid Power to that end. However, the automaker said, lithium-ion technology continues to develop at a sufficient pace that the transition to the more temperamental and heat-sensitive solid-state cells probably won’t be made before 2026. In the meantime, the company projects that lithium-ion will see a 145 percent improvement from today on energy density and an 85 percent reduction in manufacturing cost per kilowatt-hour.
While electric powertrains tend to lack the emotional response engendered by combustion engines, BMW is determined to develop them to the same standards.