In the space between conventional combustion engine vehicles and those requiring a plug, there’s a niche occupied by ‘full hybrids’. Like most cars they have an engine, but they also have an electric motor, and are designed to alternate between the two seamlessly. There’s no cable-based charging involved as full hybrids use the engine and regenerative braking to charge the battery, and when not using both power sources simultaneously the car itself chooses when to slide into electric mode rather than the driver.
It’s a compromise, but full hybrids are usually around 20% more efficient than their combustion-engined counterparts, so there’s some justification for their existence.
The original full hybrid was 1997’s Toyota Prius, and since then their popularity has risen dramatically, to the point where most manufacturers now offer some kind of hybrid model in their range. Sometimes at all costs, which results in cars like the BMW ActiveHybrid 7--a hybrid of monstrous proportions.
A grand, and slightly confused, gesture
‘ActiveHybrid’ is BMW’s effort in the full hybrid sphere, and it’s a waypoint en route to the hotly anticipated BMW i models that will signal the full electrification of the company’s drivetrains. The leviathan seen here is the ActiveHybrid 7, which is probably the most un-hybrid hybrid you could ever imagine. This one’s actually the second-generation car, which substitutes the 2011 model’s V8 for six-cylinder engine, improving the overall package substantially.
Nevertheless, backed up by some cold hard facts, there are a couple of reasons why this car shouldn’t exist, but equally there are one or two why it does.
Fuel economy presents the first conundrum. As the name suggests, the ActiveHybrid 7 should merely sip fuel relative to its non-electrified two-and-a-half-tonne siblings, shouldn’t it?
Not so. Combined economy is a respectable 41.5mpg, but the 730d is roughly 20% more efficient, returning 50.4mpg. It’s the same story with emissions, as although the ActiveHybrid 7 emits just 158g/km carbon dioxide (which, incidentally, is on par with a Fiat 500 Abarth), the 730d trumps it again with emissions of just 148g/km. In this instance, then, the hybrid is neither the cleanest (in terms of carbon dioxide) nor the most efficient model in the range. Strange.
So perhaps BMW should have attached the 40kW electric motor to the diesel drivetrain in the 730d, then. Not only would they then have beaten Peugeot to selling the world’s first diesel-electric hybrid, but by throwing an efficient oil-burning engine into the mix instead of a thirsty straight-six the result would be the best of both worlds.
A reasonable suggestion, certainly, but unrealistic because a significant reason for the ActiveHybrid 7’s very existence is to appeal to vast diesel-skeptic American market, and the chance of prospective 7 Series buyers over there opting for a diesel is, in all seriousness, zero. So whilst BMW can expect to offload quite a few ActiveHybrid 7s in the US, in the diesel-worshipping UK they’re resigned to selling but a handful.
The reality is that BMW, despite their trail-blazing i3 and i8 electric cars, feel to the need to offer something, anything even, overtly ecological in the production lineup. They’re not the only ones either, with Mercedes soon to release a hybrid S-Class and Jaguar hard at work to bring a plug-in hybrid XJ to market at some point in the next 18 months. With ActiveHybrid they can showcase some very clever efficiency-boosting technology, too, and also apply the same drivetrain to the 3 and 5 Series.
Electric mode is magnificent but fleeting
Above 40mph the ActiveHybrid 7’s twinturbo three-litre engine is a permanent fixture, but feather the throttle and it’s possible to squeeze nearly two-and-a-half miles range from the small lithium-ion battery that sits in the boot. Now that’s not exactly far, and can’t hope to compensate for the 30-or-so miles per gallon that the petrol engine alone manages, but so beguiling is the 7 in all-electric mode that you could almost forgive it its various shortcomings.
In electric mode the 7 is turkey with all the trimmings but no calories. On London’s dark and awkwardly narrow thoroughfares it becomes a wraith; a lurking dark mass that sneaks up on pedestrians in utter silence. It’s unique and something to savor, and as an experience is a million miles away from more ‘typical’ EVs, which lack the same physique and presence. Something like a McLaren P1 is going to feel otherworldly to drive when powered by electricity alone.
The 7 is frustratingly eager to deploy six-cylinder power, however, and without any way of selecting electric mode, anything more than a passing glance at the throttle is enough to trigger ignition. The result if that even if you have enough charge for the full two-mile range, as indicated by an onboard graphic, making that range a reality is a real challenge.
The zero emissions experience is short lived, then, and leaves you wondering if fifthteen rather than two miles range would really push the technological envelope too far?
ECO PRO Mode
When you exceed 40mph or run out charge BMW’s ECO PRO mode – one of five selectable driving setups – kicks in to boost efficiency under normal circumstances.
Most significantly, throttle response is dampened to limit unnecessary acceleration, and at speeds between 30mph and 100mph the engine decouples from the rest of drivetrain when coasting. The result is that the engine can shut down and revs drop to zero, effectively turning the 7, once again, into a zero emissions vehicle until further throttle input calls the engine smoothly back into action. Whilst coasting, and indeed at any opportunity, the 7 is also harvesting charge from its regenerative brakes.
We’re glad it exists
BMW’s carbon dioxide emissions claim for the ActiveHybrid 7 of 158g/km means very little. It’s either emitting an average of around 180g/km in normal combustion mode or 0g/km in electric mode. Since maximum electric range is less than three miles, this means that for the most part the 7 isn’t a very green at all.
That cars of the 7’s size and stature, which can be driven under electric power alone, exist on the open market, however, is quite special. The electric range of full hybrids is only going to increase, after all, and it's clear that the buying public still need a hydrocarbon-burning safety net.
All that's needed now is a socket and the BMW 7 Series Plug-in Hybrid will be a huge success. Perhaps.
Engine: 3.0-litre 6-cyl petrol engine + electric motor Combined power: 349bhp CO2: 158g/km Economy: 41.5mpg combined Electric range: 2.4 miles 0-62mph: 5.7 Top Speed: 155mph Price: £69,140
Photography Mark Raybone
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