Range-Extending Option for Electric BMW i3: a Smart Hedge?

On Friday in Frankfurt, BMW showed working prototypes of its i3 electric runabout and i8 plug-in hybrid sports coupe. The carbon-fiber-reinforced concepts were relatively faithful to the renderings that accompanied the launch of the German automaker’s “i” subbrand in February. A new wrinkle, however, is the addition of an optional gasoline-burning range extender for the i3, an otherwise purely electric car.

As Jack Ewing noted in The Times on Friday:

In recognition that many buyers may worry about running out of juice, BMW announced Friday that the i3 would offer an optional gasoline range-extender engine. The engine will be able to generate electric power if the batteries run low, in a manner similar to the Chevrolet Volt, though the i3 will have more range on the batteries alone.

Setting aside, for a moment, the challenge of carving adequate room for a gasoline engine and its attendant pipes, hoses, baffles, wires and reservoirs, the decision by BMW to hedge its bets and acknowledge that range anxiety is real, or real enough to offer a partial remedy for would-be buyers of the i3, is significant.

The range extender, or REx, in BMW speak, is a “small, very smooth-running and quiet petrol engine” (BMW did not reveal its displacement) that feeds a generator, which in turn recharges the batteries. By contrast, the Chevrolet Volt, a series hybrid, cannot call on its gasoline engine to charge its batteries; for that it needs a plug and socket.

BMW, however, has not said how the i3’s platform would adjust to accommodate the two powertrains. In fact, the brand went to great lengths Friday to emphasize that the i3’s architecture was conceived around purely electric mobility.

It’s too early to judge if the addition of the gas engine would create an inherently compromised driving experience for the i3, but BMW engineers surely will be working to prevent that impression before the production car’s formal introduction in 2013.