BMW Patent Shows Hybrid Bike

Electric boost system under development.

BMW hybrid patent drawing
BMW’s hybrid patent drawing showing a larger battery beneath the fuel tank.BMW Patent Application

Hybrids—vehicles that combine electric motors and gas engines—are fast taking over the four-wheeled market, but so far the same idea has failed to make any appreciable impact on motorcycle design.

On paper it’s a great idea. You get the instant low-speed torque and silent, emissions-free power of an electric motor while still hanging on to the advantages of a traditional internal combustion engine—notably ease of refueling and unrivaled power density. Many modern hybrid cars can run in pure battery mode for short distances at city speeds, allowing for guilt-free commuting, while reverting to powerful, long-range gas engines as soon as you get out on the highway and need to cover some serious miles.

You’d have thought bikes would be a prime target for the same benefits, but there’s one major drawback that’s stopped hybrid tech from appearing on two wheels: packaging. Whereas a car has acres of luggage space and you’ll barely notice if there are a couple of hundred pounds of battery in the trunk, motorcycle designers take pains to pare back every last inch and ounce. Another battery, an electric motor, and all the associated control systems needed to make a hybrid just don’t have a place.

But BMW is working on hybrid bikes nonetheless, and has come up with an idea that could at least partially solve the ever-present problem of where to put all the extra kit. This new patent application from the firm illustrates how it's thinking of sacrificing fuel tank space for the heavy, bulky battery, but doing it in such a way that you can reclaim it when needed. The idea is to make the lower half of the fuel tank from a flexible, rubber-like material, with the hybrid battery (labeled "15" in the drawings) fitted underneath.

New BMW hybrid patent
The second BMW patent drawing shows the flexible tank expanded without the battery in placeBMW Patent Application

The drawings make the system’s advantage clear. When you can make the most of the hybrid nature of a bike, for instance while commuting for short distances, you’d leave the battery in place, reducing the fuel capacity in the tank but gaining an electric boost. Come the weekend, when you’re loading up for a longer-distance road trip, you could ditch the battery, virtually doubling the fuel capacity at the expense of a reduced electric range. Since the rest of the hybrid system including the electric motor will remain in place, a smaller, permanent battery is expected to remain so you can still get the extra acceleration from the hybrid system, just losing the ability to run on electric power alone for any distance.

Older BMW 2wd hybrid patent
An older BMW patent application for a hub-mounted electric motor for the front wheel.BMW Patent Application

The new patent application doesn’t go into detail of the hybrid system itself, but BMW has already dropped hints about that. The firm applied for patents on a hub-mounted electric motor setup back in 2015, with the intention of mounting it on the front wheel to create a hybrid, two-wheel-drive bike. That earlier patent, titled “Motorcycle with an electrically driveable front wheel” was published in early 2017, shortly before BMW—either by coincidence or as an intentional double-bluff—released an April Fools’ Day press release about an R1200GS featuring exactly such a system.

Wunderlich X2 prototype
Wunderlich’s X2 prototype had a hybrid two-wheel-drive system using a hub-mounted electric motor.Wunderlich

In fact, a running prototype of a bike was shown in 2015 courtesy of BMW tuner Wunderlich. The firm’s X2 prototype featured a hybrid two-wheel-drive system identical to that in BMW’s two-wheel-drive patent. By combining the tried-and-tested hybrid 2WD system with the under-tank removable battery seen in the latest patent application, BMW may go a long way toward eliminating the downsides of hybrids while offering a tangible improvement over conventional bikes.