Video of the BMW regenerative braking system
One of the sources of increased fuel consumption in modern cars is the parasitic loss caused by the drag of having to turn ever larger alternators to provide electrical power to all the assorted accessories and features. The alternator is typically belt driven by the engine and runs continuously, providing juice to charge the battery and drive radios, lights, computers, etc.
For 2008 BMW is introducing what they call Brake Energy Regeneration on the 5-Series. The new system uses a larger than normal battery, and an electronically controlled alternator. The alternator is disengaged from the engine during normal cruise and acceleration and activates during vehicle deceleration. This adds to the engine drag braking, and the car's kinetic energy is effectively transformed into electrical energy which replenishes the battery, which now provides the accessory power.
When the battery level gets too low, the system reverts to normal charging mode. Until BMW introduces some hybrids in the next couple of years this provides a stop gap that gives an extra efficiency boost. WorldCarFans has an animated video that shows the flow of energy around the car in various operational modes.
[Source: WorldCarFans]
Reader Comments (Page 1 of 1)
shanky garg 9:44AM (2/27/2009)
this is nice video..
also good effort to reduce the power consumption..& increase the efficiency...
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Doug 7:19PM (3/13/2007)
That was a very annoying video. First half made me dizzy and contained very little info. Did the video mean to suggest that at a stop light, the car turns off the engine and restarts it when you press the gas?
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1985 Gripen 9:45PM (3/13/2007)
I'm kind of confused. Is red energy "bad" and green energy "good" in this video?
I understand that theoretically the load of the alternator on a car is a drain on energy, but how much in terms of real miles-per-gallon will be gained by this system? Seems overly-complex to me and as you know as a machine's complexity increases its potential for failure does too.
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Chris M 1:30AM (3/14/2007)
It's BMWs version of a "belt alternator starter", but unlike the GM 36 volt version, runs on a standard large 12 volt battery.
Not gonna be much benefit, but at least they are trying.
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Mirko 6:12AM (3/14/2007)
Actually the new 5 series is around 15% more efficient than the old ones. The regenerative braking is not the only change - they also introduced direc injection for the gas engines, electric steering instead of hydraulic, active aerodynamic tweaks (such as flaps behind the radiator grille!), coolant pumps that only run when needed...
All that is standard, in every model across the line. Not in a fancy "green" model. The 520d gets 40 mpg now.
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Sir Nigel 1:05PM (3/14/2007)
If it's being introduced on the 5-series, why does the video show a 3-series?
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Will 10:15AM (3/16/2007)
Worse. Video. Ever.
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