BMW’s ActiveHybrid 5 Series is the first two mode hybrid from the brand. Unlike the X6 and 7 Series Hybrids (one was a learning tool codeveloped with Mercedes Benz and GM , the other is barely a hybrid) the 5 Series Hybrid follows the typical formula of two drivetrains than can work together or separate using a battery pack to supplement engine drive. There are some key additions to this formula that makes this a uniquely BMW solution.
First, let’s look at the facts. The ActiveHyrid 5 Series marries the familiar N55 TwinPower in-line six with an in-house developed electric drive system and the excellent and equally familiar ZF sourced 8-speed auto. The system gives the car an extra 35 hp over the standard 535i 300hp and allows the car to be driven on electric power up to 37 mph for 2.5 miles.
Full gallery and video after the break.
Interestingly BMW hasn’t dialled up efficiency as much as it could have. Johann Kistler, 5 Series Product Manager, told us that BMW couldn’t forsake performance on a car like this and wanted to find the right balance between the two. Zero to sixty happens fairly quickly at 5.7 seconds. That’s nearly equivalent to a standard 535i but the 5 AH has quite a bit more weight to lug around.
The N55 is slightly detuned from its typical 300 hp output as the electric drive system develops 54 hp and makes 155 lb-ft of torque (all available from start). A quick check of the math would indicate that the N55 is making 281 hp. Clearly as much as BMW likes performance out of their hybrids they have made some concessions for greater efficiency.
The electric motor is integrated into the housing of the 8-speed automatic transmission, saving space. The connection point between the two is controlled by a separate clutch. Also somewhat trick is how the petrol engine’s cooling system also regulates the electric motor (How??)
The 54 hp and 155 lb-ft of torque is powered by a high-performance lithium-ion battery, specifically developed for the car. 96 cells and with a energy capacity of 675 Wh, the entire system is enclosed in special high-strength housing positioned directly behind the rear seats and between the rear wheels giving it optimal protection.
How long will the batteries last? I pressed Mr Kistler on this and was given a surprising answer; the life of the car. He reaffirmed my question by explaining, BMW intends to offer a full life-time warranty on the batteries. Long-term testing inside BMW has proven that the batteries will be fully functional long after the car has likely been sidelined by other issues.
Having this much electronics in the new AH5 presented some unique problems. While the car has a typical 14-volt power supply, it also has a high voltage supply with 317 volts. Both are linked by a transformer that connects the system and transfers power appropriately – be it used for driving or comfort. Additionally the air condition is also fed from the lithium-ion battery pack via the high voltage supply. This allows the aircon to be entirely operational in full electric mode or even when the car it off.
The result is about 12-13% more effeciency over the 21/31 mpg figures from the 535i. That would give the AH5 approximately 24/35 figures or 2/3 mpg higher than even the four cylinder 528i. Those are tangible results and real reasons to consider the AH5 if you’re aim is the best combination of efficiency and performance out of a medium sized luxury sedan. For comparison sake the Lexus GS hybrid is rated at 29/34 mpg and has all the performance characteristics of a vacuum cleaner.
But that doesn’t mean that the AH5 doesn’t have some exclusive technology when it comes to efficiency. In town that means allowing 100% electric use for up to 2.5 miles and up to speeds of 37 mph. But it also means that, on the highway, the AH5 can switch off the engine and fully decouple the drivetrain while coasting at speeds of up to 100 mph (160 km/h). This coasting mode combines comfortable driving with optimum utilisation of the kinetic energy already generated.
This is accomplished in ECO PRO mode which dials back throttle response and dials the efficiency up as high as possible.
While ECO PRO sounds great, it’s not the driving experience some of us would associate with BMW. From my experience in driving the car it only really made sense in town where speeds are slow and acceleration is limited.
Switching from ECO PRO to Sport and then Sport+ turns the AH5 into the car we’ve all come to know. Along with suspension and steering settings the electric motor also changes pace a bit. The extra 54 hp and 155 lb-ft helps deliver properly quick pace – almost as if the engine had an extra turbo bolted on somehow.
What about push to pass functionality? BMW doesn’t see this as fitting in with the regular 5 Series. Additionally the function would use up the stored energy and not allow the car to operate purely on electric power.
Also in the AH5‘s bag of ECO tricks is the levering of the navigation system to help with efficiency. The navigation system analyzes the driving conditions based on the route ahead and alters the make-up of power from the car. For one this allows the car to virtually see into the future and select the most efficient gears possible. But it also allows all drivetrain systems and the in-car electronics to be managed appropriately so that energy can be used as needed or stored in preparation for what lies ahead.
It sounds great but in practice it’s actually even cooler. Take for example, a hilly section of road. The computer will see what’s coming up and invest all the battery’s energy going up knowing that it’ll be able to recoup it all on the decent.
It’s exactly this kind of combining of technologies that makes the AH5 so interesting.
Despite the cool tech, the AH5 isn’t likely to sell in large numbers in Europe with BMW’s impressive range of diesels there. In fact BMW admitted to us that they see sales breaking down in thirds – a third in the US, Japan and the rest of the world. What about China? BMW will likely be launching a plugin model of the AH5 there later this year. But that plugin architecture won’t be sold in other markets. For one the long wheel base 5 Series, which the plugin will be based on, is a crucial ingredient due to the extra space in the trunk. BMW also doesn’t feel that the performance of the car will be what traditional BMW buyers (ie ones in other markets) will expect.
So why a hybrid over a diesel at all? While part of it surely is marketing, there are also some real reasons that one might choose the AH5. For one the petrol powerplant is the same N55 that is continually acclaimed on this site and others. And that means buyers of the AH5 will have a car that can rev and perform like a 535i with less emissions and lower MPG. Even if a diesel equivalent was more efficient it wouldn’t have the high revving characteristic many of us prize in our cars.
Additionally the AH5 works exceptionally well in tight urban environments where the electric motor can take on more of the duties. This is especially important in such markets as Japan.
Among many other eco features the AH5 also features BMW new start and stop system for the 8 speed automatic. The function provides surprisingly seamless operation when the vehicle is stopped in traffic.
Perhaps the most seamless thing about the ActiveHybrid 5 is how it moves from electric to petrol power. So subtle is the transition that you simply won’t notice it unless you’ve got the radio off and are paying attention.
Thankfully BMW will make sure you’re aware of the changes via a special function within the car’s 9.2-inch display that shows energy flow and recuperation. Additionally there’s a gauge next to the tachometer which shows the boost being provided by the electric motor during acceleration. Finally a display in the computer screen shows the battery’s current charge level and the power-sharing between the internal combustion engine and the electric motor.
BMW isn’t entirely subtle about the the fact at the AH5 is a hybrid. The phrase “ActiveHybrid 5” is emblazoned in no less than five places throughout the car. Additionally the AH5 features the optional “Streamline” 18” wheels and the exclusive Bluewater metallic paint as an option. There’s also a mention in the trunk where the battery pack takes up some room.
The current F10 5 Series gets around corners very effectively but perhaps with a little less satisfaction than the previous generation 5. It would seem the steering is to blame as the car has enormous grip but a lack of connection to what’s really happening underfoot. And it’s a shame because the car is so exceptional for a large sedan when it comes to driving experience.
We pressed BMW on this and because we frankly want them to figure it out. Based on their response they may yet. But don’t expect electric steering systems to magically get all the feel back anytime soon. Nor should you expect them to go away. Not only are they better for efficiency (sensing a trend?) but they also better integrate with technologies such as lane departure warning systems.
Nevertheless the AH5 performs almost faultlessly around the corners and sweepers. We just wish it had a bit more soul behind it all.
And that leads directly to the question – should you consider the AH5 if you’re looking at a 5 Series? At $61,845 (including $895 destination and handling) it’s not priced badly by any means. In fact it’s almost a bargain considering the technology involved.
That said the real answer is rather complex. For someone who wants to combine efficiency with power there’s really no better combination in BMW’s line-up. It’s a brilliant system that has no downsides other than extra weight, cost and a bit of trunk missing. Performance is inline with what you’d expect and the characteristics of the car are all 5 Series.
So why would you not buy it? If you’re looking for a 5 Series that combines light weight, performance, simplicity and value for money, I’m not entirely sure the AH5 makes sense. At $62,845 it’s almost 8k more than the standard 535i and doesn’t bring a shocking difference in efficiency.
However for those looking to find that fine line between performance and effeciency the ActiveHybrid 5 Series is a pretty compelling choice. And the key reason is that it’s still a BMW. From the sound, feel and overall performance, the AH5 brings BMW’s core brand values to the world of hybrids. Not a bad thing as it’s a world that can use some new blood.
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Author: Gabe
Source: http://www.bimmerfile.com/2012/01/31/bi ... -5-series/