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      03-03-2008, 06:21 PM   #1
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Regenerative Braking in the USA?

Does anyone know if the new M3 still has regenerative braking? and if so if it is going to make it into US cars?

Hopefully it isnt a repost but i havent heard any mention of it in a long time

oops didnt realize i didn't post in the General M3 forum...could the mods move it to the appropriate forum?
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      03-03-2008, 07:47 PM   #2
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Recent trunk/batter photo comparisons between Euro and NA cars indicate a high probability that BER (Brake Energy Regeneration) comes on NA cars. BER requires a special battery (AGM - Absorbent Glass Mat) and both versions appear to have this battery. However, this feature is not mentioned in brochures.

You can find this discussion and picture on the forum more effectively by using google to serach. Try this google link, look at the search syntax and check the very first hit, reading from the begining of the thread.

As a point of clarification: do note that this system does not literally use braking energy nor the cars brakes to capture energy this electrical system simply (effectively) disconnects the cars alternator when accelerating - that's it.
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      03-03-2008, 08:01 PM   #3
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Recent trunk/batter photo comparisons between Euro and NA cars indicate a high probability that BER (Brake Energy Regeneration) comes on NA cars. BER requires a special battery (AGM - Absorbent Glass Mat) and both versions appear to have this battery. However, this feature is not mentioned in brochures.

You can find this discussion and picture on the forum more effectively by using google to serach. Try this google link, look at the search syntax and check the very first hit, reading from the begining of the thread.

As a point of clarification: do note that this system does not literally use braking energy nor the cars brakes to capture energy this electrical system simply (effectively) disconnects the cars alternator when accelerating - that's it.
Good summary. Perhaps on the 8th we can get some clarification.
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      03-03-2008, 08:38 PM   #4
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Recent trunk/batter photo comparisons between Euro and NA cars indicate a high probability that BER (Brake Energy Regeneration) comes on NA cars. BER requires a special battery (AGM - Absorbent Glass Mat) and both versions appear to have this battery. However, this feature is not mentioned in brochures.
The problem with the M3 at Detroit is that there is no reason to believe that car was a fully US spec vehicle. Indeed we've seen many examples of cars since then that don't have US spec seats and/or reflectors (not to mention constant confusion about the 18" wheels). Additionally you can adopt AGM without implementing BER and it might make sense to use the same battery everywhere. AGM charge considerations are different from normal batteries, so using the same battery would allow the use of the same battery charger/management module as well. I'm not sure we will know for sure on the 8th - I suspect the acid test will be what TIS says.
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      03-03-2008, 08:55 PM   #5
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i was under the impression that brake regeneration was something more...the standard 3 series does the alternator trick...while it was mentioned that the M would have "regenerative braking" so i assumed that meant something more complex than that
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      03-03-2008, 09:02 PM   #6
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Quote:
Originally Posted by abuzzl23p View Post
i was under the impression that brake regeneration was something more...the standard 3 series does the alternator trick...while it was mentioned that the M would have "regenerative braking" so i assumed that meant something more complex than that

I would chalk it up as almost pure marketing.

To really benefit from the power that is generated from braking, you need batteries that can take a charge quickly but since even Lithium Ion is slow to take charges, you need huge capacitors.

The system might give enough power from braking to compensate from the lack of charging from the alternator disconnect from acceleration.

Hybrid Performance Cars .... Fear it....they will wreck any pure performance car with compromises.
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      03-03-2008, 09:10 PM   #7
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Hybrid Performance Cars .... Fear it....they will wreck any pure performance car with compromises.
That's pure and silly conjecture
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      03-03-2008, 09:33 PM   #8
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That's pure and silly conjecture

BS. You want fuel economy, you pay with less power or heavy batteries.
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      03-03-2008, 09:39 PM   #9
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Hybrid Performance Cars .... Fear it....they will wreck any pure performance car with compromises.
That's not a good statement, T Bone.

"BMW's term" Regen Braking disconnects the alternator under load so more power may be put down to the road instead of powering accesories and the like.
That hardly qualifies as wrecking pure performance. It is actually quite the opposite.
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      03-03-2008, 09:49 PM   #10
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Quote:
Originally Posted by Epacy View Post
That's not a good statement, T Bone.

"BMW's term" Regen Braking disconnects the alternator under load so more power may be put down to the road instead of powering accesories and the like.
That hardly qualifies as wrecking pure performance. It is actually quite the opposite.

You need to pay the piper.... I took photos of the batteries of the M3 (as you know) and of the 1 series. There is no way we need batteries that heavy.

You gain slightly for disconnecting the alternator under acceleration (and using electric water pumps and stuff like that) but you paid with bigger and heavier batteries.

Extrapolate this further.... Hybrid batteries weigh alot and coupled with a weak motor and there is no driving pleasure. In a performance car, you buy power and performance.


BTW, I spent $5212 on fuel on my AMEX alone in 2007.... But I had a lot of smiles in 2007 driving.
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      03-03-2008, 10:17 PM   #11
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Originally Posted by T Bone View Post
You need to pay the piper.... I took photos of the batteries of the M3 (as you know) and of the 1 series. There is no way we need batteries that heavy.

You gain slightly for disconnecting the alternator under acceleration (and using electric water pumps and stuff like that) but you paid with bigger and heavier batteries.

Extrapolate this further.... Hybrid batteries weigh alot and coupled with a weak motor and there is no driving pleasure. In a performance car, you buy power and performance.


BTW, I spent $5212 on fuel on my AMEX alone in 2007.... But I had a lot of smiles in 2007 driving.
I would have to further research the weight difference between the two. Do you have figures?
Also, how do you know the gain is only minimal by disconnecting the alternator. Do you have data?
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      03-03-2008, 10:37 PM   #12
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Quote:
Originally Posted by Epacy View Post
I would have to further research the weight difference between the two. Do you have figures?
Also, how do you know the gain is only minimal by disconnecting the alternator. Do you have data?

No because I didn't manage the engineers on this project. No one will know the compromises the team made.

All products are compromises. When I hear the dreaded Hybrid word, it rings alarm bells marketing compromises were made. I cannot give you the quantum but rest assured they were made.

For disconnecting the alternator, people think this is new? When were clutched alternators introduced?
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      03-03-2008, 10:41 PM   #13
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No because I didn't manage the engineers on this project. No one will know the compromises the team made.

All products are compromises. When I hear the dreaded Hybrid word, it rings alarm bells marketing compromises were made. I cannot give you the quantum but rest assured they were made.

For disconnecting the alternator, people think this is new? When were clutched alternators introduced?
Who said it was new?

I was asking you for facts, that is all.
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      03-03-2008, 10:49 PM   #14
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Quote:
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Who said it was new?

I was asking you for facts, that is all.

You are asking for facts that will NEVER be known by anyone outside the BMW design team. Who knows what the weight of the alternative battery would be or how much power a regular alternative draws on load.

You don't need perfect data to know which way something swings.

Imagine a car with no airbags and a Lithium Ion battery that doesn't work in the cold? Or how about a narrower / shorter car with no storage? These are unpallatable compromises.

When we head down the Hybrid path, we are trading off power and weight for fuel economy, emissions, handling.
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      03-03-2008, 11:03 PM   #15
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Originally Posted by Epacy View Post
I would have to further research the weight difference between the two. Do you have figures?
Also, how do you know the gain is only minimal by disconnecting the alternator. Do you have data?
I'll answer it - there's very little difference, although AGMs are definitely a little heavier. However, they are virtually guaranteed not to outgas, rupture or explode and as a result there are gains in other areas of the vehicle such as trays, vent tubes, alternator size and weight, etc. AGMs are essentially the same as “maintenance-free” batteries but instead of letting the acid just slop around it is held in place between the plates with glass mats, i.e. fiberglass. The fiberglass weighs next to nothing, but the plates are sometimes packed closer together leading to more weight.

Batteries in BMWs are simply big and heavy no matter what kind they are. This is driven by the cold crank current required of the starter and the plethora of electrical gadgets (navi, heated seats, defrosters, high speed injectors, high compute power DMEs, etc). A modern car can easily top 3KW if all the stuff is turned on.

There's also more power being used for performance too. Now we have to have somebody operate our clutches for us. Other applications begging for more power are individual solenoid driven engine valves (instead of cam shafts and VANOS), pre-heated cats, electronic braking, per-wheel controllable torque, direct injection, blah blah blah. Like it or not big-ass batteries are here to stay.

The S65B40 outputs 313KW. If we assume the electrical stuff is pulling 1KW this means that the alternator steals about 0.3% of the available WOT engine power. If the AGM battery were to add 10lbs (and it doesn't) then the car would be 0.27% heavier than it would otherwise be. If you disconnect the alternator you are ahead of the game at WOT. However, most people will not drive WOT all the time and engine output will be lower, let's say 50KW, and a 1KW load would steal 2% of the available power. Here disconnecting the alternator yields even better returns
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      03-03-2008, 11:14 PM   #16
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I'll answer it - there's very little difference, although AGMs are definitely a little heavier. However, they are virtually guaranteed not to outgas, rupture or explode and as a result there are gains in other areas of the vehicle such as trays, vent tubes, alternator size and weight, etc. AGMs are essentially the same as “maintenance-free” batteries but instead of letting the acid just slop around it is held in place between the plates with glass mats, i.e. fiberglass. The fiberglass weighs next to nothing, but the plates are sometimes packed closer together leading to more weight.

Batteries in BMWs are simply big and heavy no matter what kind they are. This is driven by the cold crank current required of the starter and the plethora of electrical gadgets (navi, heated seats, defrosters, high speed injectors, high compute power DMEs, etc). A modern car can easily top 3KW if all the stuff is turned on.

There's also more power being used for performance too. Now we have to have somebody operate our clutches for us. Other applications begging for more power are individual solenoid driven engine valves (instead of cam shafts and VANOS), pre-heated cats, electronic braking, per-wheel controllable torque, direct injection, blah blah blah. Like it or not big-ass batteries are here to stay.

The S65B40 outputs 313KW. If we assume the electrical stuff is pulling 1KW this means that the alternator steals about 0.3% of the available WOT engine power. If the AGM battery were to add 10lbs (and it doesn't) then the car would be 0.27% heavier than it would otherwise be. If you disconnect the alternator you are ahead of the game at WOT. However, most people will not drive WOT all the time and engine output will be lower, let's say 50KW, and a 1KW load would steal 2% of the available power. Here disconnecting the alternator yields even better returns
Very nice (and I mean it).....

But at risk of not seeing the forest for the trees..... How much better fuel economy would you get with these measures by your estimation? Also starting with the electric water pump, what is the extra load on the electrical system?
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      03-03-2008, 11:25 PM   #17
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You are asking for facts that will NEVER be known by anyone outside the BMW design team. Who knows what the weight of the alternative battery would be or how much power a regular alternative draws on load.
Then it was sort bold for you to make such a claim, don't you think?

Quote:
You don't need perfect data to know which way something swings.
Actually you do these days. Getting the most performance out of a modern car is all about the game of fractional percentages

Quote:
Imagine a car with no airbags and a Lithium Ion battery that doesn't work in the cold? Or how about a narrower / shorter car with no storage? These are unpallatable compromises.
You have somehow leaped to the conclusion that all of these things are unavoidable facts of life. They aren't. I've yet to see anyone say that a Tesla is a severely compromised Elise (other than range). The X6 hybrid will be an impressive machine and will not feel compromised compared to the "standard" version. The GM SUVs with the new GM/Daimler/BMW hybrid tranny are actually BETTER than the normal versions (other than cost). I'll go so far as to say that improved performance with hybrid technology is more likely to happen than the odds that DCT takes over the world.

Quote:
When we head down the Hybrid path, we are trading off power and weight for fuel economy, emissions, handling.
Again, not necessarily true. Electric motors offer gobs of torque at zero rpm, and the ability to place exactly the ideal amount of torque at each wheel independently, not to mention electronically braking one wheel while powering another to cause the car to pivot anywhere the computer wants it to go
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      03-03-2008, 11:27 PM   #18
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The alternator disconnects under load not WOT.

BMW battery weights can be determined. They are not some closely held secret.
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      03-03-2008, 11:30 PM   #19
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Very nice (and I mean it).....

But at risk of not seeing the forest for the trees..... How much better fuel economy would you get with these measures by your estimation? Also starting with the electric water pump, what is the extra load on the electrical system?
It's very small. As I said in another post here this is a game of fractional percentages. Each technology gains very little, but cumulatively they all add up. BER is a yawner on it own, but when you throw in all the other stuff, the total gain is significant. This is why BMW speaks of "Efficient Dynamics" (the total package deal) and won't spend much time speaking of "BER"
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      03-03-2008, 11:33 PM   #20
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Quote:
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Then it was sort bold for you to make such a claim, don't you think?



Actually you do these days. Getting the most performance out of a modern car is all about the game of fractional percentages



You have somehow leaped to the conclusion that all of these things are unavoidable facts of life. They aren't. I've yet to see anyone say that a Tesla is a severely compromised Elise (other than range). The X6 hybrid will be an impressive machine and will not feel compromised compared to the "standard" version. The GM SUVs with the new GM/Daimler/BMW hybrid tranny are actually BETTER than the normal versions (other than cost). I'll go so far as to say that improved performance with hybrid technology is more likely to happen than the odds that DCT takes over the world.



Again, not necessarily true. Electric motors offer gobs of torque at zero rpm, and the ability to place exactly the ideal amount of torque at each wheel independently, not to mention electronically braking one wheel while powering another to cause the car to pivot anywhere the computer wants it to go

Let's debate this further. The problems I see with Hybrid and regenerative technologies is the lack of quick charge batteries and hence the need for big capacitors that don't exist yet oh and the need for lightweight battery that works well in the cold.

Perhaps my statement was a bit harsh but these technologies don't have an apparent solution. Tesla would be great if Lithium ION technologies were good for cars and their working environments and it would be good if the batteries could take advantage in a meaningful way the kinetic energy in the system.

The other examples you cited, the penalty is weight for the 200-300 pound batteries.

If I can get power for free, I will take it but I think we are a decade away from seeing a 3000 pound Hybrid performance car.
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      03-03-2008, 11:34 PM   #21
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The alternator disconnects under load not WOT.
Precisely. There is actually more to be gained relatively speaking if the alternator is disconnected for even small engine outputs
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      03-03-2008, 11:35 PM   #22
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Precisely. There is actually more to be gained relatively speaking if the alternator is disconnected for even small engine outputs
I know, I was correcting your statement.

sshhh, don't tell T Bone the M3 he is looking at is a hybrid...
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