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Discussion Starter #1
The 2012 S60 brochure talks about the alternator decoupling on acceleration and engaging on braking to improve fuel economy. It does not mention specific engines that might include this feature. Is this available with all engine types? I do not see any type of mechanism that could do this on my T5. Its alternator looks like a standard serpentine belt drive with no clutching that I can see.
 

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I believe an Alernator Decoupler Pulley is what disconnects the alternator from the engine upon acceleration, and it is a separate unit from the alternator and the KERS flywheel.

http://www.decouplerpulley.com/files/RotoRxbrochure.pdf

That's an aftermarket replacement option, but it kind of explains things and shows where it would be.
 

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The coupling looks like this on the T6 (the alternator is under the intake manifold):

http://i294.photobucket.com/albums/mm104/promise383/new xc60 and T6 engine close ups/S6302388.jpg

So the alternator is to the center left and it is shaft driven on it's right side.
The gearbox on the right of the alternator is driven from a gear off the crankshaft.
Further to the right of that is the belt drive and you can see the AC compressor in the
far right. The timing chains for the camshafts also are driven from the intermediate
gear box drive shaft. So it is quite different the the T5 setup.

This cutaway view shows the gears that are driven off the crank fairly well as well
as the timing chains:

http://www.sae.org/images/enewsletter/technology/070201Powertrain/03_455.jpg

Also, that rubber coupling is called out to be replaced in the service schedule (in the
owners manual). It only lists that for the T6. I forget the interval (probably around 100K miles).

Edit: I checked, the alternator rubber sleeve service replacement is at 150K miles.
 

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Discussion Starter #4
So if I understand correctly this system is completely mechanical in nature? I was expecting a type of A/C clutching mechanism on the alternator but in hindsight I guess that would probably waste more energy than it saved. Thanks for the links. That pulley does look very much like the one I see on my alternator.
 

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Discussion Starter #5 (Edited)
Still a little confused about this device. While I can understand it's fuel saving ability, by smoothing out accessory drive drag, I don't see the "Regeneration effect" with this device. In fact, it appears this device will allow the alternator to "free wheel" on drastic engine deceleration which is basically opposite from what is explained in the Volvo brochure. I think I'm still missing a piece to this puzzle.

Here's a link to a BMW ad. (Couldn't find any information on the Volvo system)
http://www.youtube.com/watch?v=WwiKllsJ-sY&feature=related

This system seems more sophisticated than a simple mechanical device. The BMW even has a gauge(imagine that) to measure the regenerative effect. I'm just not seeing anything on the T5 engine that could do this.. Given the lack of information in general on the Volvo system I'm doubting whether this system is even implemented, at least in the US.
 

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its not 100% mechanical. The alternator likely has electronics, so even though the alt. is always spinning, the system isn't charging (or reduced charging), thus avoiding extra drag losses. Since electrical system drains the battery during operation, the regeneration effect is the fact that when you are not using the accelerator pedal and/or braking, the alternator electronics engage the battery charges back up. hence the regeneration...seems like marking speak though. It does seem like just generation.

I say this because, some Hyundai's for example have a smart alternator (minus the fancy setup). http://metronews.ca/drive/41989/hyundais-smart-alternator-saves-on-fuel/

Though Volvo's setup is curious.
 

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Given the lack of information in general on the Volvo system I'm doubting whether this system is even implemented, at least in the US.
All Volvos have this feature.
 

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Discussion Starter #8
its not 100% mechanical. The alternator likely has electronics, so even though the alt. is always spinning, the system isn't charging (or reduced charging), thus avoiding extra drag losses.

Though Volvo's setup is curious.
That was my next theory. Instead of a mechanical clutch use an electronic switch to disconnect the alternator. Looking at the battery it doesn't seem substantially oversized so maybe they do some controlled charging setup like you mention.
 

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All modern alternator's have a clutch assembly, whether they use an IDP or OAP. I think these ones simply decouple when the accelerator is pressed. It's part of the pulley, as shown in the PDF linked above.

POI - Volvo is also working on the possibility of using a mechanical flywheel KERS system which actually powers the rear wheels rather than the electrical system in much the same way. This is already used in Formula 1 racing.
 

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Discussion Starter #10
All modern alternator's have a clutch assembly, whether they use an IDP or OAP. I think these ones simply decouple when the accelerator is pressed. It's part of the pulley, as shown in the PDF linked above.
I'm not questioning the use of an IDP or OAP. From what I've read, these devices decouple on belt deceleration. I don't believe they do what Volvo describes as Brake Energy Regeneration in their brochure. I'm just trying to understand the technique that Volvo has implemented.
 

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Don't read this, it's incorrect.
 

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I believe an Alernator Decoupler Pulley is what disconnects the alternator from the engine upon acceleration, and it is a separate unit from the alternator and the KERS flywheel.

http://www.decouplerpulley.com/files/RotoRxbrochure.pdf

That's an aftermarket replacement option, but it kind of explains things and shows where it would be.
Volvo has been using these pulleys for years now, my 2001 has one.....and it does not do the function you are thinking.....read that website again and you will find out its more for noise/belt vibration....

I havent found anything in writing from Volvo yet, but i am guessing that just command different charge rates via the ACM LIN bus depending on coasting/accel driving.
 

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In order to charge the battery optimally, the central electronic module (CEM) calculates output voltage from the alternator based on battery temperature. The alternator control module (ACM) (charge regulator) will then regulate output voltage based on control from the central electronic module (CEM). As the engine control module (ECM) can also control the alternator, there may be output voltages deviations, such as in different driving situations.
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This is from VIDA, I believe the last sentence is the key here...
 

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Okay, re-reading your post more carefully and taking a bit more time, I think I can better help to some degree. I apologize for being short and making it confusing before.

You don't need to look to the alternator. The alternator can be exactly the same on a car with Brake Energy Regeneration as it is on a car without it. The majority of the parasitic drag from the alternator is only created when the circuit the alternator is in is complete. In other words, if you cut power to or from the alternator, it begins to freewheel. The pulley, which is specifically an IDP in modern Volvo cars, has bearings in it which further reduce drag on the drive belt. As a result, if you cut power to the alternator, it is not really creating any drag on the engine. On the other hand, if you power up the alternator when the vehicle is slowing down, it will create drag and the Engine Braking of the vehicle is increased. As a result, the alternator is now going to aid braking and generate electricity to recharge the battery without being parasitic in any way. If the battery charge falls too low, we still want to turn on the alternator to keep the battery from dying, but otherwise we have simply told the computers in the vehicle to turn off the alternator when we are accelerating or cruising. No special equipment is needed for this component of Brake Energy Regeneration, you just need Intelligent Alternator Control programming in the car's computers which control the flow of electricity to or from the alternator.

So again, there is no special part unless you're talking about Flywheel KERS. Hybrid vehicles also have a more advanced BER system in which the electric motors which drive the wheels produce braking power by generating electricity, killing two birds with one stone whenever it's time to slow down.

PS The clutch is not reversed as I had previously thought.
 

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You are right (I know this is 2 years hence but still relevant), the voltage regulator is an Alternator Control Module since 2005 MY. With an ACM the voltage target of charging system is controlled by another control unit. On newer models with Denso engine management the ECM will control charge rate with several factors considered and one of these is least fuel consumption.. Initially after engine start, alternator will be commanded to a normal charge program for 15 or so minutes but load and engine speed can alter the time. Once the normal recharge has finished then the regenerative function commences. The charge rate is lowered to target V of 13.2-13.3 and on higher engine load charge rate is lowered to 12.8V. On coast when injectors are off the charge rate is increased to 15.3-15.5V so the operation of the alternator under highest output is effectively free as no fuel is being consumed on coastdown until engine speed falls to 1200 RPM +/-.
This variability in charge voltage is not usual in the old sense but it has been discovered that periods of high charge and then lower charge are beneficial to batteries so long as neither lasts extended times. Effectively the maintenance of battery charge can be done on extended drives with little fuel consumed using the regenerative charge concept.
The year that this feature went into effect is not known to me exactly. I have observed this up and down charge rate on extended drives it sees back as far as 2008 MY. I have a radar detector with voltage displayed and I have seen the variances in charging voltage but the association of the high charge with coast was not noted by me at first.

The one way clutch used on alternator pulleys is not part of this. That clutch is there to smooth belt drive. The crankshft has normal undamped pulsations from acceleration from cylinder firing and then deceleration from the following cylinder compression stroke. On decel the alternator pulley decouples and does not waste the kinetic energy but more importantly, this means no cyclic slack and then tensioning of the belt.
 
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