Hybrid too hot, hybrid too cold…
KUALA LUMPUR, Feb 24 — The ActiveHybrid 5 is not BMW’s first attempt at the electric-petrol hybrid. Preceding it are the ActiveHybrid X6, which is based on the X6 Series “sports activity coupe”, and the ActiveHybrid 7 limousine.
Despite the shared first names, the underlying technology and approach in each of the three vehicles are unique to the individual models. In a sense, this is BMW testing the waters of the hybrid segment and experimenting to see which — if any — sits best with its customers.
The first of the BMW hybrids, the ActiveHybrid X6 is the variant that is most invested in hybrid technology. Fitted with not one but two integrated electric motors that were mated to a 407bhp twin-turbocharged V8, this vehicle was built with performance in mind.
The first of its electric motors was a 91bhp/260Nm unit, which was supplemented by a smaller 86bhp/280Nm example. Owing to the ample space in the X6, BMW saw fit to use a 2.4kWh nickel metal-hydride (NiMH) battery pack rather than the more advanced lithium-ion variety.
With all three motors firing, the ActiveHybrid X6 generated 480bhp and a stump-pulling 780Nm, and was capable of going from zero to 100kph in just 5.4 seconds.
Adding to the complex arrangement of the three motors was the twin-mode continuously-variable transmission (CVT), developed in collaboration with Mercedes-Benz and GM, that provided for what was termed a dual-hybrid system.
Billed as the “most powerful hybrid vehicle ever”, it saw tepid response in the marketplace due to its perplexing product positioning. The low fuel economy offered despite the hybrid billing also did not aid its cause.
It was a vehicle built by a company that had — at the time — stubbornly refused to adopt hybrid technology and did so only when other green-tech options failed to manifest. This was also BMW trying to push the envelope when it finally did decide to go the hybrid route, though in particularly unconventional fashion.
Unsurprisingly, BMW quietly dropped the ActiveHybrid X6 from its stable at the end of 2011.
Having gone off the deep end with the ActiveHybrid X6, BMW pulled the reins hard with the ActiveHybrid 7 to produce what it termed a “mild hybrid.”
Instead of using the electric motor to boost power output, BMW’s engineers set about integrating hybrid technology as a means to supplement any gaps in the performance of the 4.4l twin-turbo V8.
The result was a relatively small motor, producing around 20bhp and 210Nm, which functioned more as an upgraded Active Start Stop system rather than an out-and-out hybrid. Its synchronous nature did, however, allow BMW to claim an up to 30 per cent improvement in fuel economy.
In unison, the electric motor and the 440bhp/650Nm eight-cylinder petrol engine will output 465bhp and 700Nm, allowing the ActiveHybrid 7 to boast of a 4.9 second 0-100kph time and a top speed of 250kph — sportscar-like performance in a hybrid luxury limousine.
Because of its output, the electric motor is unable to propel what is essentially the 750i solely on battery power; the V8 must come to life in order for the car to move forward.
Opting for the more expensive lithium-ion battery meant intrusion into the trunk and extra weight was kept to a minimum, with the 400Wh battery tipping the scales at just over 27kg.
Despite the more pragmatic approach with the ActiveHybrid 7, the added cost and complexity of the vehicle consigned it to being an elusive sight on the road.
Aiming for the middle ground between the wild approach of the ActiveHybrid X6 and the barely-there system in the ActiveHybrid 7, the new 5 Series-based model is also the first of BMW’s hybrids to utilise the straight-six motors for which the company is renowned.
Like its X6-based stable mate, the ActiveHybrid 5 is capable of running purely on battery power, but like the 7 Series version, the emphasis is more on efficiency instead of brutish power. It also lifts the lithium-ion battery technology from the ActiveHybrid 7.
The electric motor is capable of 55bhp/210Nm, while the twin-turbocharged six-cylinder 3.0l engine makes a maximum of 306bhp and 400Nm. In tandem, BMW claims they allow for 340bhp and 450Nm.
On the battery alone, the ActiveHybrid 5 can go as far as 4km before the petrol engine needs to be fired up to recharge the trunk-mounted pack.
This system will also be deployed on the upcoming ActiveHybrid 3.