We drive the BMW ActiveE battery electric: Bavarian (electric) motor (car) works

February 2, 2012 | By | Reply More
2012 BMW ActiveE

2012 BMW ActiveE

It’s disconcerting, really. It’s the Twenty-first Century and all that, and there should be no doubt that if anyone can do it, BMW can. But to push the pedal down and have the BMW ActiveE move under battery electric propulsion almost silently out of the driveway and onto to the street is, well, it’s, um, not what one traditionally thinks of when thinking BMW.

But like we said, why not? The BMW ActiveE is the second step of BMW’s development of a full battery-electric car. The first was the Mini E, a conversion of the basic Mini to battery power. The Mini E was leased by X customers for BMW to gain real life experience of using an electric car in day-to-day operation.

BMW ActiveE instrument panel

The BMW ActiveE instrument panel loses the tachometer and gains a gauge to monitor electric motor operation.

As the second stage, the BMW ActiveE is more sophisticated than the Mini E and—not surprisingly—more like a BMW. It too is a conversion of an existing model, in this case a BMW 1-Series coupe. The gasoline powertrain is replaced by a lithium-ion battery pack mounted under the hood, down the center of the car in the erstwhile driveshaft tunnel and in the rear where the gasoline tank would otherwise be.

The actual motor of the BMW ActiveE is mounted in the rear, driving the rear wheels, integrated into a modified rear axle support along with the power electronics. The electric drivetrain exclusive of batteries has a total weight of only around 200 lbs. That said, it’s the batteries where the weight is in an electric car.

Maximum power output of the electric drive system in the BMW ActiveE is 170 horsepower with a maximum torque rating of 184 lb-ft. Max torque is available from a standstill—that’s the way electric motors work—and it’s available across a wide load range. BMW claims the ActiveE accelerates from 0 to 60 mph in under nine seconds, well short of thrilling. Because of the high at-rest torque number, the low speed maximum acceleration, after a bit of lag when stomping on the accelerator, feels strong, but the ActiveE feels relatively punchless above 60 mph. BMW electronically limits top speed to around 90 mph.

The BMW ActiveE iDrive system monitors electric vehicle operation

The BMW ActiveE iDrive system monitors electric vehicle operation while allowing infotainment and navigation systems visible.

The sounds of the BMW ActiveE are electric vehicle typical. It’s totally quiet at stop, of course, since there’s no motor running. But as the ActiveE moves out from rest, there’s a faint electric motor/gear whine rising in pitch with increased speed. The expected gear shift never comes, of course, as it would with a conventional gasoline engine and transmission. It doesn’t happen. The pitch simply rises until it goes to dog whistle pitch. At that point the greatest vehicle sound is road noise.

Range is the constant, indeed the biggest concern of electric car operators, so not surprisingly the BMW ActiveE has regenerative braking to recapture some of that energy expended in acceleration with the electric motor is “turned into a generator” when the accelerator pedal is lifted. The ActiveE’s regenerative braking is tuned to be less aggressive as the Mini E. Lifting the accelerator pedal on the Mini E was like slamming on the brakes, and one had to maintain speed by continuously and obsessively manipulating the accelerator.

On the other hand, the BMW ActiveE is similar in that lifting will slow the car enough that normal driving can be done with the right pedal alone. The driver only needs to use the brake pedal for hard braking.

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Category: Car Reviews

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