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BMW to Offer Intelligent Alternator Control/Regenerative Braking on Non-Hybrid 5-Series

BMW will begin offering its Intelligent Alternator Control and Brake Energy Regeneration on select models of the new 2008 5-Series. Announced last year at the Paris Auto Show, the Intelligent Alternator Control (IAC) system generates electric power for a car’s on-board network exclusively in overrun and during braking. (Earlier post.)

On a conventional car, the alternator, which generates electrical power, is permanently driven via a belt from the crankshaft. The BMW system, however, limits the use of the alternator mostly to drive phases in which the engine is not required to deliver drive power—e.g., in overrun and when applying the brakes.

,Accordingly, a greater share of the fuel energy is applied to drive the car. The use of the IAC can reduce fuel consumption by approximately 3%. The supply of power to the on-board network will be provided exclusively by the battery, the alternator only being re-activated when the engine moves into overrun or if battery charge is insufficient.

The battery is charged to only about 80% of its capacity as long as the engine is propelling the car, depending on ambient conditions. A reserve charge adequate for the consumption of power while the car is at a standstill and enabling the driver to start at any time is maintained under all circumstances.

Battery charge exceeding the 80% threshold is generated only in overrun and while the driver is applying the brakes. Since the number of charge cycles increases as a function of such battery management, BMW’s Intelligent Alternator Control uses modern AGM (absorbant glass mat) batteries able to handle greater loads than conventional lead acid batteries. An AGM battery holds the acid content in micro-glass-fibre mats between the individual layers of lead, thus retaining its ability to store energy also when charged and discharged frequently and in many ongoing cycles.

In addition to the reduction in fuel consumption, the driver benefits directly from the alternator being disconnected whenever the engine is propelling the car, since this ensures more power for dynamic acceleration and superior performance—attributes BMW considers its hallmark.

The new 5 Series with the new 6-cylinder engines is also using a new on-demand electrical coolant pump that consumes significantly less power than a conventional pump and helps the engine reach its normal operating temperature earlier.

Operating on-demand, the Varioserv steering assistance pump, varying the curve ring as a function of pressure and volume flow, avoids the usual increase in drive losses as a function of higher engine speeds. And when the driver and passengers do not require the air conditioning, the a/c compressor is disconnected to reduce drag forces to a minimum.

Use of the on-demand pump can reduce fuel consumption by up to 2%.



Have gas engines been pushed to the limit ??

this seems like a lot of work and money and not giving much back.


Considering this doesn't even include taking the A/C off the driveline, 3% is not bad. I am hoping this is only phase I though, and eventually, the alternator & batter will be sized-up to accomodate an electrically driven A/C, allowing all of the A/C needs to come from this "wasted" enery that is recaptured.


Drive belts are pretty wasteful. Electric power for AC, power steering and such could help. I know the AGM batteries are good for this job, they really last. Just having the accesories off the belt and some regen would be good.


At least they have the decency to not call this a Hybrid.
Unlike GM !


The first GM basher has entered the room. I hope you are referring to their mild-hybrid full-size truck aproach. GM's BAS provides a 15% improvement with little more complexity than this setup.


BMW tech could be safely named “hybrid assessory drive vehicle”. Hopefully they will grow-up to GM mild hybrid technology, eventually.


BMW is part of the 2mode hybrid joint development effort. The others are DaimlerChrysler, and GM.


Nice to see that BMW's updates to their 5 series engines have avoided the typical route that has always been taken (increasing the hp on a continual basis) and instead focus on better fuel efficiency with the same hp output.



Thanks, I am pretty well informed on 2-mode transmission technology and consider it as major player in US vehicle market in coming couple of years. This drivetrain allows for hybrid towing!


WHEN: All this hype about this new technology and nothing about WHEN. Also, WHEN will see diesel cars in this country, they have them in Europe and the public pay the additional price just to have the economical power.

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