# regenerative braking energy



## Duncan (Dec 8, 2008)

Hi Hyper

Depends on - 
driving area - city/country, hilly/flat, 
driving style - hoon/hypermiler

anything from less than 3% to more than 15%

Where are you going to be driving?
How are you going to drive?


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## tomofreno (Mar 3, 2009)

Duncan said:


> ...driving style - hoon/hypermiler...


 Hoon?? Where's that come from?
Edit: to the OP, +1 on what he said (I've been driving a car with regen for over 3 years).


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## Lauris_K (Feb 25, 2013)

Well someone said that theoretically regeneration add you about 10% of driving range, according to EVTV if I remember right.

But in real world it depends on driving conditions, I don't think there is big difference in driving style though. By that I mean if your driving course is set in more urban area, so in lower speeds, more breaking and accelerations you will get much more use out of regeneration than driving in freeways. Since in urban areas less energy is waste to cope with air force resistance so naturally more used force will be gained back.

By the way in theory regeneration is about 70-80% efficient, except low rpm range, at least we got these numbers in our system Amperbox-75 rough tests.

Hope we will make some real field tests with Marius Audi A2 in near future to see how much power is regenerating while using car in everyday use.

Laurynas


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## njloof (Nov 21, 2011)

The regen on the Prius tells you how much power you get back, which I dimly recall is in the hundreds of Wh for a typical half hour drive. To me the savings is that your brake pads last forfeeakingever.


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## Lauris_K (Feb 25, 2013)

Well Prius also have VERY complicated gearbox system, which makes it significantly less efficient compared to usual manual one, and what to say about direct drive. So I would not take its results for a conventional EV. Also anyone have any info if during regeneration Prius ICE is disconnected from gearbox, because if not, it should use hell of extra energy from regeneration, same as in every car with ICE breaking with a motor.


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## major (Apr 4, 2008)

Lauris_K said:


> Well Prius also have VERY complicated gearbox system, which makes it significantly less efficient compared to usual manual one, and what to say about direct drive. So I would not take its results for a conventional EV. Also anyone have any info if during regeneration Prius ICE is disconnected from gearbox, because if not, it should use hell of extra energy from regeneration, same as in every car with ICE breaking with a motor.


The Hybrid Synergy Drive (HSD) in the Prius is actually an efficient gearbox and really simple in mechanical operation although difficult to understand at first. It does have mode of operation where regeneration occurs without the ICE rotating but it is not actually mechanically disconnected.


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## Lauris_K (Feb 25, 2013)

Well I had no opportunity to examine HSD mechanically, but couple years ago we had real field tests where Renault Espace with ICE changed to AC motor was driven side by side with Toyota Prius (using electric motor only) at 60Kmph speed and we compared energy required to keep constant speed, Renault were more efficient. And since in theory Prius motor could not be less efficient at least significantly were showing greater energy needs to keep same speed in same conditions we assumed that higher need of energy is due to higher complexity and lower efficiency of gearbox.

P.S. Renault was driven by refurbished and rewound AC motor controlled by controller which in further development were made to Amperbox-75 controller, at the moment it was only 40KW of power.


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## IamIan (Mar 29, 2009)

HyperUniverse said:


> How much energy can you get back from a regenerative braking?
> 
> theoretical?
> ideal?
> ...


As others have said it depends a great deal the system , context , etc.


I think a few distinctions should be made / added.

Back from what?



From the Kinetic energy of the vehicle moving at the time the brakes are applied:
~99% Theoretical
~80% Ideal
~50% Practical
 
From the Potential energy coming down from the top of a hill:
~90% Theoretical
~70% Ideal
~40% Practical
 
From the amount of fuel energy spent:
~60% Theoretical
~30% Ideal
~10% Practical
 


- - - - - - 

When people talk about the regenerative braking benefit to over all MPG and overall BEV range they are referring to the 3rd type above ... which can never get as much as the other two above it.

- - - - - - - 

It is also important to keep in mind that this is only good comparison when equal amounts of energy for braking are used either friction or Regenerative ... in general ... if you don't use your brakes at all you don't gain anything by using the brakes more often with regenerative brakes... and if you would have used your friction brakes for 1% of the net energy used ... trying to do regenerative braking for more than 1% is a very different comparison.

You will sometimes see less knowledgeable people try to show regenerative braking not being a benefit at all by doing significantly more braking with regenerative braking than they did with friction brakes on the same course ... the premise of their claim is not a valid comparison ... if the same course is used ... same vehicle ... same average speed ... and the same joules of braking energy used ... regenerative braking is ALWAYS better than friction braking for total trip energy used , or MPG, etc.


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## Duncan (Dec 8, 2008)

tomofreno said:


> Hoon?? Where's that come from?
> Edit: to the OP, +1 on what he said (I've been driving a car with regen for over 3 years).


Don't you have Hoons where you are?

Don't know where the term cane from but Hoons blast about everywhere - max power then hard on the brakes


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## njloof (Nov 21, 2011)

Duncan said:


> Don't you have Hoons where you are?
> 
> Don't know where the term cane from but Hoons blast about everywhere - max power then hard on the brakes


http://en.wikipedia.org/wiki/Hoon


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## major (Apr 4, 2008)

Lauris_K said:


> Well I had no opportunity to examine HSD mechanically, but couple years ago we had real field tests where Renault Espace with ICE changed to AC motor was driven side by side with Toyota Prius (using electric motor only) at 60Kmph speed and we compared energy required to keep constant speed, Renault were more efficient. And since in theory Prius motor could not be less efficient at least significantly were showing greater energy needs to keep same speed in same conditions we assumed that higher need of energy is due to higher complexity and lower efficiency of gearbox.


Seems a pretty weak case to globally blame the HSD gearbox as inefficient. But you're welcome to state your opinion  Thanks.


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## tomofreno (Mar 3, 2009)

IamIan said:


> As others have said it depends a great deal the system , context , etc.
> 
> 
> I think a few distinctions should be made / added.
> ...


 These are a bit high, as you have to account for losses due to drive train friction, the motor and controller, as well as work done against drag and rolling resistance forces - the latter especially if braking on a long hill at higher speed. I think you are likely doing well to convert 60% of the vehicle kinetic energy to potential energy in the battery pack. These tests indicated around 50% (data logged by the Curtis controller):
http://www.diyelectriccar.com/forums/showpost.php?p=280765&postcount=14


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## evmetro (Apr 9, 2012)

Personal opinion... whatever transmission the prius is using should be questioned. These are the same guys that are installing an EV system AND an ICE system on the same vehicle, which does not add up.


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## major (Apr 4, 2008)

evmetro said:


> Personal opinion... whatever transmission the prius is using should be questioned. These are the same guys that are installing an EV system AND an ICE system on the same vehicle, which does not add up.


Here you go again  The Prius appears to "add up" well for Toyota and the millions of satisfied owners around the world. It is one of the cleanest vehicles sold in the USA. It basically forced the entire industry to reexamine their products. It accomplished electric propulsion to some degree before lithium batteries were ready for prime time. Hybrids may be just a stepping stone to the EV but the gap from the need to implementation is served very well by hybrids and the Prius is the leader.


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## evmetro (Apr 9, 2012)

You hit the nail on the head when you confirmed that the prius adds up for toyota. I was referring to science.


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## Ziggythewiz (May 16, 2010)

Hybrids fill a gap (1% for some, 90% for others) between what EVs and ICEs can do economically. We will still need hybrids 50 years from now, they just won't be called that because nearly all cars will be hybrids or pure EVs.


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## tomofreno (Mar 3, 2009)

evmetro said:


> You hit the nail on the head when you confirmed that the prius adds up for toyota. I was referring to science.


Would you please explain the science behind your opinion?


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## major (Apr 4, 2008)

Lauris_K said:


> Well Prius also have VERY complicated gearbox system, which makes it significantly less efficient compared to usual manual one, and what to say about direct drive.


Actually during regeneration the Prius HSD is essentially in direct drive to the generator. Notice the forth diagram down the page. The generator is linked to the drive axle through a single set of gears.











Ref: http://www.toyoland.com/prius/gen2.html


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## major (Apr 4, 2008)

evmetro said:


> ... whatever transmission the prius is using.....


One could argue that the HSD in a Prius is not a transmission according to a commonly accepted definition.


> a transmission is a type of gearbox that can be “shifted” to dynamically change the speed-torque ratio such as in a vehicle.


 From: http://en.wikipedia.org/wiki/Transmission_(mechanics)


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## Lauris_K (Feb 25, 2013)

I have one question about that schematics... You want to say that under normal driving condition ICE is powering wheels and generator which uses generated energy to electric motor to also drive wheels?
That does sounds somehow unrealistic, or very bad engineering solution, well from 1st point of view at least, since it is wasting already low ICE efficiency. Because if I am not mistaken then in this case part of ICE generated movement energy is converted to electric energy then electric DC energy converted to AC and after this back to movement energy, and all these steps with their own waste of energy for inefficiency or certain process. So basically what I say, it sounds close to people claims when they think that adding generator to motor or wind turbine in EV exterior will generate energy back to battery and that will add driving range (in some cases that is escalated to perpetual engine).

sorry if that was a bit off topic.


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## evmetro (Apr 9, 2012)

tomofreno said:


> Would you please explain the science behind your opinion?


Tomo, the science that I was referring to is the same science that stops wind turbines from making sense when they are installed on a car. What the prius DOES do is time collection an dispursement of braking energy which can net a small gain DURING THE RIGHT CONDITIONS. The sciece that I understand (I have 3 years of high school and no college) tells me that the lighter and more aerodynamic a car is, the more efficient it is. I suspect that this is why my 3 cylinder ICE only metro beats the prius on mpg. The other thing that my understanding of science tells me is that if you drive correctly and follow what a vaccum gauge and/or a good mpg computer with live and instant data tells you, you will get get much better economy, more than you would compared to a braking energy dispursement system. In fact, ecodriving tends to cancel the regen energy benefits. The guy driving the prius 55mph in the left lane probably has some kind of instrumentation that he is paying more attention to than the traffic mess that he is causing.


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## major (Apr 4, 2008)

evmetro said:


> The sciece that I understand (I have 3 years of high school and no college) tells me that the lighter and more aerodynamic a car is, the more efficient it is. I suspect that this is why my 3 cylinder ICE only metro beats the prius on mpg.


Just think how efficient your little metro would be with a hybrid drive in it


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## major (Apr 4, 2008)

Lauris_K said:


> I have one question about that schematics... You want to say that under normal driving condition ICE is powering wheels and generator which uses generated energy to electric motor to also drive wheels?
> That does sounds somehow unrealistic, or very bad engineering solution, well from 1st point of view at least, since it is wasting already low ICE efficiency. Because if I am not mistaken then in this case part of ICE generated movement energy is converted to electric energy then electric DC energy converted to AC and after this back to movement energy, and all these steps with their own waste of energy for inefficiency or certain process. So basically what I say, it sounds close to people claims when they think that adding generator to motor or wind turbine in EV exterior will generate energy back to battery and that will add driving range (in some cases that is escalated to perpetual engine).
> 
> sorry if that was a bit off topic.


Yep, off topic. But I think the Toyota engineers were smart enough to take advantage of all modes of operation of both electric machines and the ICE to optimize efficiency for the intended duty cycle. It is an ingenious system using the Atkinson cycle engine. Study it and you'll see they don't have to rely on perpetual whatever


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## evmetro (Apr 9, 2012)

major said:


> Just think how efficient your little metro would be with a hybrid drive in it


Major, I am retrofitting one of my metros right now with a system that beats hybrids and ICE systems hands down, and you can see the progress in the thread "the metro"in under the all conversions heading. My limited understanding of science has me doing aeromods to it, removing excess weight, and yes, capturing braking energy.... maybe even a place to stow my tin foil hat.


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## major (Apr 4, 2008)

evmetro said:


> ..I am retrofitting one of my metros right now with a system that beats hybrids and ICE systems hands down,....


Unless you need to use it to go 4 or 500 miles in a day


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## evmetro (Apr 9, 2012)

Well its not like I will be using one of those little 30 amp j plugs...


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## major (Apr 4, 2008)

I don't know why this thread has wandered off topic into the merits of hybrids. HEVs can benefit from regeneration as much as EVs. Regeneration makes use of energy which has been wasted as heat in automobile friction brakes for the 100 years or so. Having the ability to reuse a significant portion of that energy due to regeneration with EV or HEV systems is about the closest thing to free energy you guys will ever see


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## Jesse67 (May 12, 2009)

I did a test with the mini truck, I reset my Ah meter, and immediately accelerated up to about 40km/hr and then immediately slowed down using only regen, no brakes. The best I could get back was 30% of the Ah that went in to accelerate. 

Now, my energy used to accelerate is more than just the kinetic energy of the vehicle at that speed due to motor and controller efficiency and I did have to travel some distance to accelerate and decelerate which means energy was lost to air, rolling and drivetrain resistance. 

Some day I will get an accurate weight on my truck and then I can calculate the actual kinetic energy at a given speed and then measure how much I get back during a regen only deceleration. I would think around 50% is pretty close for my truck. Of course a heavier, more aerodynamic vehicle with less drivetrain drag than my 4wd mini truck would be able to recover a larger portion of it's KE as proportionately less of it's energy would be lost to drag.

Normal driving see's between 5 and 10% of my fwd Ahs returned as regen.


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## IamIan (Mar 29, 2009)

tomofreno said:


> These are a bit high, as you have to account for losses due to drive train friction, the motor and controller, as well as work done against drag and rolling resistance forces - the latter especially if braking on a long hill at higher speed. I think you are likely doing well to convert 60% of the vehicle kinetic energy to potential energy in the battery pack. These tests indicated around 50% (data logged by the Curtis controller):
> http://www.diyelectriccar.com/forums/showpost.php?p=280765&postcount=14


What do you think is too high? ... and why?
My highest practical number is 50% ... same number you listed for the Curtis log.

I agree one would be doing very well if one was able to convert / recover 60% of the vehicle's kinetic energy ... that's higher than the highest practical I gave of 50%.

Keep in mind the 'magic' that opens up when one uses terms like 'Ideal' ... and 'Theoretical'.


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## major (Apr 4, 2008)

__-_-_-__ said:


> but is it worth it?


Basically regen is free. All it takes is a bit of software and in some cases an extra sensor. So why wouldn't it be worth it? Not to mention the reduced wear on the friction brakes.

Disclaimer: Pretty much this whole discussion does not apply to systems using DC commutator motors.


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## subcooledheatpump (Mar 5, 2012)

Yeah like Major said, if you have an AC EV then it's already there, so why not. 

Also don't discount dynamic braking. Great for trucks or for driving down mountains. Brakes get hot and can fade. A properly cooled dynamic brake resistor can replace the engine compression drag in a converted car for downhill braking


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## major (Apr 4, 2008)

__-_-_-__ said:


> after some research I've found that regenerative braking gives a maximum of 10% savings.
> so it's worthless. it's much better to just buy +10% more batteries.


Regenerative braking cost nothing, weighs nothing and consumes no space. How is that worthless compared to spending another $1000, carrying another 70-80 pounds and losing a few cubic feet of space


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## tomofreno (Mar 3, 2009)

evmetro said:


> Tomo, the science that I was referring to is the same science that stops wind turbines from making sense when they are installed on a car. What the prius DOES do is time collection an dispursement of braking energy which can net a small gain DURING THE RIGHT CONDITIONS. The sciece that I understand (I have 3 years of high school and no college) tells me that the lighter and more aerodynamic a car is, the more efficient it is. I suspect that this is why my 3 cylinder ICE only metro beats the prius on mpg. The other thing that my understanding of science tells me is that if you drive correctly and follow what a vaccum gauge and/or a good mpg computer with live and instant data tells you, you will get get much better economy, more than you would compared to a braking energy dispursement system. In fact, ecodriving tends to cancel the regen energy benefits. The guy driving the prius 55mph in the left lane probably has some kind of instrumentation that he is paying more attention to than the traffic mess that he is causing.


 In addition to adding regenerative braking, the electric motor in the Prius gives an assist to the ice during acceleration so that the ice can run in a more efficient rpm and load range. Much of the added torque necessary to accelerate is supplied by the electric motor. That may well be a larger effect on mileage than regen. 

I think the guy driving his Prius at 55 mph likely has cruise control set at 55 to improve his gas mileage.


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## tomofreno (Mar 3, 2009)

IamIan said:


> What do you think is too high? ... and why?
> My highest practical number is 50% ... same number you listed for the Curtis log.
> 
> I agree one would be doing very well if one was able to convert / recover 60% of the vehicle's kinetic energy ... that's higher than the highest practical I gave of 50%.
> ...


 50 to 60% is the theoretical, because any theory that describes regen would account for all known effects such as friction, resistive losses in the circuitry, and work done against drag and rolling resistance forces. Then experiments would be done to determine how well the equations based on these matched measurements. If they matched well, then it would start to gain some credence as an accurate theory, but would still have to be corroborated by measurements by many others to be accepted as accurate, and then only for the conditions investigated. There is no magic to theory.


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## Jesse67 (May 12, 2009)

The point of a car is to get you some place, the most efficient way to get there is if you accelerate gently up to speed and don't slow down at all until you get there. If you drive like this all the time regen will have very little effect. On the other hand if you're using regen that aggressively slows you down every time you let off the accelerator you will end up recovering significant energy but your overall energy use for the trip will be higher than if you coast to slow down and only use regen when you actually need to slow down more quickly. That said, in city driving there are often times when you have to use you brakes no matter how well you anticipate traffic, so why not recover at least some of your energy?

I picked AC for a lot of reasons other than just the ability to provide regen. It is pretty cool though to watch your Ahs count back up when you're coming to a stop!


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## evmetro (Apr 9, 2012)

major said:


> Regenerative braking cost nothing, weighs nothing and consumes no space. How is that worthless compared to spending another $1000, carrying another 70-80 pounds and losing a few cubic feet of space


Major, This is why the prius does not make sense. Adding this stuff to an ICE is like adding a wind turbine.


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## evmetro (Apr 9, 2012)

tomofreno said:


> In addition to adding regenerative braking, the electric motor in the Prius gives an assist to the ice during acceleration so that the ice can run in a more efficient rpm and load range. Much of the added torque necessary to accelerate is supplied by the electric motor. That may well be a larger effect on mileage than regen.


I thought that this was the whole point of regen on an ICE...


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## Jesse67 (May 12, 2009)

evmetro said:


> Major, This is why the prius does not make sense. Adding this stuff to an ICE is like adding a wind turbine.


And yet there are more than a milion Priuses (Prii? ) driving around but I haven't seen too many wind turbine cars. The technology works, if you want to argue cost benefit that's fine but the hybrid system which uses regenerative braking in a prius is not the same as putting a wind turbine on a vehicle.


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## IamIan (Mar 29, 2009)

tomofreno said:


> 50 to 60% is the theoretical, because any theory that describes regen would account for all known effects such as friction, resistive losses in the circuitry, and work done against drag and rolling resistance forces. Then experiments would be done to determine how well the equations based on these matched measurements. If they matched well, then it would start to gain some credence as an accurate theory, but would still have to be corroborated by measurements by many others to be accepted as accurate, and then only for the conditions investigated. There is no magic to theory.


Thanks for the explanation.

I think we are not thinking of the three terms in the same way ... Theory , Ideal , and Practical ... are vastly different things.

If you think that 50 to 60% is the the upper limit for what can be achieved with ideal equipment under ideal conditions ... or even going further past ideal into just what is possible in theory ... I disagree ... those are too low... practical ... sure ... I already listed 50% as my highest practical number.

- - - - - -

I agree there is no real magic to theory ... what I was referring to is that there is a vast difference between the three types ... what is possible in theory is not remotely the same as what is possible to achieve under ideal conditions ... and what is achievable under ideal conditions is not remotely the same as what is practical.

The VAST gap between them makes for what I was referring to previously ... not real magic ... that's why I tried to make a distinction by writing it as 'magic'... sorry that wasn't descriptive enough.

I'll try to re-explain better.
- - - - - - - - - - - -- - - - 

In Theory all kinds of things are possible ... Time Travel , Worm Holes, warp drive, cold fusion , etc .... those and many other things are 100% achievable in the realm of what ... is possible in 'theory'... to fit possible in theory doesn't even have to be testable ... it only has to fit the current theory which itself has been tested... thus those crazy near 'magic' things are possible in 'theory' ... even if we can't actually do any of them , even under ideal cases.

Achievable under ideal conditions is very different from what is possible in theory ... this requires it to fit current limits of technology ... what is testable ... even if it is cherry picked 'ideal' case ... theory doesn't share this limit ... time travel and whole whole might be possible in theory ... but they are no longer currently possible in terms of when under even ideal cherry picked conditions and equipment.

What is practical is just as vastly different ... while under ideal cherry picked conditions one can convert kinetic energy to electrical energy at extremely high % efficiency ... get those levels outside of the 'ideal' is not possible ... so it is not possible to get that high as a practical number.

- - - - - - - 

An example of 'ideal' concept.

Under ideal conditions ... I have virtually no drive train losses for regen ... it is a direct drive.

Under ideal conditions I use superconductive generators at well over 98% efficiency to convert the kinetic energy to electrical ... even without superconductors the CSIRO motor reaches up to 98% efficiency... and sense this is an 'ideal' case ... I get to operate that motor under 'ideal' conditions for the conversion.

Under 'ideal' conditions there are batteries up around 98% cycle round trip energy efficiency... when the OP asks about how much you can get back , that might 'ideally' be interpreted to be the recovery or charging half of the cycle ... thus even higher efficiency than the round trip.

Want to throw in 'ideal' controller losses ... sure... we'll use the wavesculptor22 which is compatable with the CSIRO ... and under ideal conditions gets over 99% efficiency.

In an 'ideal' case ... a tiny and aerodynamically near perfect vehicle ... think better than the best solar racer ever built ... with the lowest rolling resistance possible under our ideal case.

The weather and atmospheric conditions are of course 'ideal' for our 'ideal' case.

under this 'ideal' case even with the required steps ... we are easily over 95% combined efficiency ... and the highest 'ideal' efficiency I listed was 80% ... allowing for significant other losses ... all of which I am allowed to cherry pick my 'ideal' conditions in order to get the highest % number possible ... because it is the 'ideal' case.

previously when I listed it ... I thought ~80% was being a bit conservative of what would be possible under 'ideal' case... but I went low with ~80% anyway.

- - - - - - - 

That would all change under what is 'practical' ... because practical removes the ability to cherry pick ideal best case conditions , equipment , etc... because what is practical is not what is 'ideal'.


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## major (Apr 4, 2008)

evmetro said:


> Major, This is why the prius does not make sense. Adding this stuff to an ICE is like adding a wind turbine.


Yet you add a transmission to an ICE. And probably a cranking motor, and alternator, and a muffler. All those things don't make sense to you, right?


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## evmetro (Apr 9, 2012)

major said:


> Yet you add a transmission to an ICE. And probably a cranking motor, and alternator, and a muffler. All those things don't make sense to you, right?


Major, I am not sure I follow. These parts are essential for an ICE. A pop up wind turbine and an EV drive system with regen are not essential for everyday operation of an ICE. It sounded like you saw the light for a moment on why regen on an ICE does not make sense, but I must have been mistaken.


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## major (Apr 4, 2008)

evmetro said:


> Major, I am not sure I follow. These parts are essential for an ICE. A pop up wind turbine and an EV drive system with regen are not essential for everyday operation of an ICE. It sounded like you saw the light for a moment on why regen on an ICE does not make sense, but I must have been mistaken.


The things I mentioned enhance the utility of the ICE but are not essential. In fact, the cranking motor, alternator and auxiliary battery make the ICE a hybrid to some degree. If adjusting the size of those components improves the utility of the ICE and makes it more efficient and cleaner and more cost effective for the user, what's wrong with that? Or do you believe there is a conspiracy by the brake pad industry to prevent regeneration from becoming widespread? Or perhaps the government has developed a braketooth app for smart phones which will report the number of Joules recovered from regen so that you can be taxed on the otherwise free energy? Give me a brake...pun intended


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## evmetro (Apr 9, 2012)

Major, you were the one to point out that although the amount of energy recovered from regen may be trivial, it is free on a car that is already AC drive. A prius is still an ICE that has a lot of high dollar stuff added to it that is not essential to comply with laws or for everyday operation, and it harvests the same trivial amount of energy. I don't know how much a prius traction pack costs, but I bet it adds up to more than an exaust, starter, and alternator combined. And then there is the special transmission... how much is one of these? Are these cars subsidized in any way? This is much more than increasing the size of a few minor ICE systems. After all this expense, it still gets less mpg than my ICE vehicle, it weighs more, and it is a burden to traffic flow.


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## tomofreno (Mar 3, 2009)

IamIan said:


> Thanks for the explanation.
> 
> I think we are not thinking of the three terms in the same way ... Theory , Ideal , and Practical ... are vastly different things.


 Yes we are not.



> If you think that 50 to 60% is the the upper limit for what can be achieved with ideal equipment under ideal conditions ... or even going further past ideal into just what is possible in theory ... I disagree ... those are too low... practical ... sure ... I already listed 50% as my highest practical number.


You seem to think that theory is just some conception of what might be possible. That is not the meaning of the term to scientists. Hypothesis, conjecture, speculation or in some cases just a wild ass guess come to mind as what I would consider more appropriate terms. 



> I agree there is no real magic to theory ... what I was referring to is that there is a vast difference between the three types ... what is possible in theory is not remotely the same as what is possible to achieve under ideal conditions ... and what is achievable under ideal conditions is not remotely the same as what is practical.
> 
> The VAST gap between them makes for what I was referring to previously ... not real magic ... that's why I tried to make a distinction by writing it as 'magic'... sorry that wasn't descriptive enough.


 There is not a vast difference when the term theory is used as I use it.



> In Theory all kinds of things are possible ... Time Travel , Worm Holes, warp drive, cold fusion , etc .... those and many other things are 100% achievable in the realm of what ... is possible in 'theory'... to fit possible in theory doesn't even have to be testable ... it only has to fit the current theory which itself has been tested... thus those crazy near 'magic' things are possible in 'theory' ... even if we can't actually do any of them , even under ideal cases.


This is incorrect. There is currently no theory that states that time travel is possible. There have been conjectures that maybe if a candidate formulation of equations used to describe gravity do prove to accurately describe the phenomena, then time travel might be possible. But that is mostly in the realm of speculation, not theory. There is a quote from a famous physicist, Richard Feynman where he facetiously uses the term "guess" for theory: "It doesn't matter how beautiful the guess is, or how famous the guesser is, if it doesn't agree with the data it's wrong." That is how scientists use the term theory. In order for any conjecture to attain the status of theory it has to be testable, and it has to be proven to agree with test results. It is still far from being considered well established theory at this point. There must be many more tests or experiments done by many more people and the theory must agree within experimental error with all of them. And not just repetitions of the same experiment. The more angles it is approached from, and the better it agrees with all these results, the more accepted it becomes as an accurate theory of the phenomena described by it.



> Achievable under ideal conditions is very different from what is possible in theory ... this requires it to fit current limits of technology ... what is testable ... even if it is cherry picked 'ideal' case ... theory doesn't share this limit ... time travel and whole whole might be possible in theory ... but they are no longer currently possible in terms of when under even ideal cherry picked conditions and equipment.


 You are using the term as synonomous with "under ideal conditions", that is not the way scientists generally use the term theory.



> What is practical is just as vastly different ... while under ideal cherry picked conditions one can convert kinetic energy to electrical energy at extremely high % efficiency ... get those levels outside of the 'ideal' is not possible ... so it is not possible to get that high as a practical number.


Any theory of anything has to take account of all things that effect the phenomena being described. So any theory describing the kinetic energy of a vehicle that can be converted to potential energy in batteries has to account for all things that effect that process, especially all losses which will effect the efficiency. What you are describing is the ideal case, for example if there were no losses. That is different from theory.

- - - - - - - 



> An example of 'ideal' concept.
> 
> Under ideal conditions ... I have virtually no drive train losses for regen ... it is a direct drive.
> 
> ...


I agree these are all ideal. That is completely different than any theories that would accurately describe these phenomena.

- - - - - - - 



> That would all change under what is 'practical' ... because practical removes the ability to cherry pick ideal best case conditions , equipment , etc... because what is practical is not what is 'ideal'.


Practical, as you use the term is reality. That is what theory strives to describe, some theories do so more accurately than others, some are refined over many years as understanding deepens, becoming more accurate over time. For example, Einstein's theory of general relativity is an improvement over Newton's law of gravitation since it is more widely applicable, describing a wider range of phenomena accurately, but Newton's law is still correct, and agrees with results from general relativity in local Euclidean space.

I think that is enough on this since this thread is on regenerative braking, and I don't care to debate it further anyway.


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## tomofreno (Mar 3, 2009)

evmetro said:


> I thought that this was the whole point of regen on an ICE...


Huh? What is regen on an internal combustion engine?


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## major (Apr 4, 2008)

evmetro said:


> Major, you were the one to point out that although the amount of energy recovered from regen may be trivial, it is free on a car that is already AC drive. A prius is still an ICE that has a lot of high dollar stuff added to it that is not essential to comply with laws or for everyday operation, and it harvests the same trivial amount of energy. I don't know how much a prius traction pack costs, but I bet it adds up to more than an exaust, starter, and alternator combined. And then there is the special transmission... how much is one of these? Are these cars subsidized in any way? This is much more than increasing the size of a few minor ICE systems. After all this expense, it still gets less mpg than my ICE vehicle, it weighs more, and it is a burden to traffic flow.


Yet over 3,000,000 people buy the Prius and drive it and save fuel, save carbon emission and save money and are pleased with the experience. What is the downside which upsets you? If you have a better solution, make it and sell it and put the Prius out of business  

I really fail to see how or why people are opposed to regeneration whether it be on a BEV or HEV. It is like the closest thing to free energy there is and it basically cost nothing to start with and has side benefit of reducing brake maintenance lowering the overall cost of vehicle ownership.


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## evmetro (Apr 9, 2012)

Major, I am already building a better solution with my all electric vehicle that plugs into higher power sources than the already outdated 30 amp J, and can plug into everyhome or business without any adapter. Even though the prius cannot compete with my ICE or my EV, I still cannot compete with the goverment when they are spending my money on it. 3,000,000 people may think that the prius makes sense, but I bet there are exponentially more people who believe that a pop up wind turbine or solar panels on your roof adds up. To make matters worse, they are will use my tax dollars to do it . This makes it pretty hard to compete from the private sector.


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## major (Apr 4, 2008)

evmetro said:


> Major, I am already building a better solution with my all electric vehicle that plugs into higher power sources than the already outdated 30 amp J, and can plug into everyhome or business without any adapter. Even though the prius cannot compete with my ICE or my EV, I still cannot compete with the goverment when they are spending my money on it. 3,000,000 people may think that the prius makes sense, but I bet there are exponentially more people who believe that a pop up wind turbine or solar panels on your roof adds up. To make matters worse, they are will use my tax dollars to do it . This makes it pretty hard to compete from the private sector.


None of this has anything to do with regeneration which is the topic of this thread. Take it over to chitchat to bitch about your tax dollars please.


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## trukr (Mar 17, 2013)

I don't get it. I've read the thread over again a couple times and it seems the opposing sides of the coin are on different coins.

On one side of the coin, vehicles equipped with an AC drive system only benefits from regen. It's there, it's free, and no one talks about it adding stress to the system. The only question I would have is if the sporadic inputs of energy somehow reduces cycle life.

On the other side of a different coin you are using regen to express your dislike towards hybrids.  HUH?!? Regen seems like a strange way to argue against hybrids, other than it being the topic of the thread.



evmetro said:


> Major, I am already building a better solution with my all electric vehicle that plugs into higher power sources than the already outdated 30 amp J, and can plug into everyhome or business without any adapter. Even though the prius cannot compete with my ICE or my EV, I still cannot compete with the goverment when they are spending my money on it. 3,000,000 people may think that the prius makes sense, but I bet there are exponentially more people who believe that a pop up wind turbine or solar panels on your roof adds up. To make matters worse, they are will use my tax dollars to do it . This makes it pretty hard to compete from the private sector.


How does a normal plug found at every home and business equal a higher power source? From childhood experiences, I found trying to draw more power than the rated voltage and amps to result in two ways, blown fuse/ tripped breaker, or melted plastic and burning wires. The only higher power I witnessed was the excited state of anger this caused my Dad.

I don't see how this works without preloading some type of capicitor.


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## major (Apr 4, 2008)

trukr said:


> It's there, it's free, and no one talks about it adding stress to the system. The only question I would have is if the sporadic inputs of energy somehow reduces cycle life.


What is the deal with an on-topic question 

Sure, anytime you transmit power thru a system there will be some stress. So the system with regen opposed to the same system without regen will see more stress. But my experience and from literature which I've come across and from my knowledge of theory, these additional stresses are within the design capabilities of the system and those stresses do not significantly reduce the service life of electrical or mechanical components including the battery.

Of course we will see an occasional failure during regeneration and there will be those quick to blame regeneration but it is likely that it can be better attributed to a design, build or quality fault.

I suspect your main concern is the battery. On the BEV the battery is typically sized large enough in energy that the C-rates from regeneration are within the capabilities and if that rate or duration is exceeded, a proper system will simply reduce the regen torque and force on* the friction brakes eliminating the stress problem.

On the HEV there will be a different type of battery used which can tolerate high C-rates and often times this includes active thermal management. Such batteries are designed and validated and likely warrantied to function acceptably with the frequent regen cycles.

Thanks for asking,

major

* edit: By "force on" I mean to have the operator press harder on the brake pedal to apply the friction brakes.


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## evmetro (Apr 9, 2012)

Trukr, I use and a fifty amp 220 plug in my home and shop, and a common 3 prong male recepticle to adapt to the north american power grid if need be. Two seperate plugs. One to charge faster than a 30 amp J, one to be able to charge anywhere.

Major, I can understand that you will need to avoid discussion of who is really paying for the hybrid system, but it seems relevant to how practical regen is depending on if installed on an ICE or an AC drive. The original post of the thread did not specify hybrid or ac drive, so bringing hybrids into the answer made sense to me since regen is not practical on these. In theory the prius may have its merits, but in the real world it is not practical. Until we look at the big picture including who pays for it we are only looking at it subjectively. You and I will butt heads on things till death do us part and I will still have a deep respect for your deep knowledge and sharp mind. I do agree that some of the things we dispute should have their own specific threads, but this one still seems somewhat related to the original post.


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## major (Apr 4, 2008)

evmetro said:


> .... One to charge faster than a 30 amp J,...


Still off topic but I can't resist. What is a 30 amp J? There is no 30 amp rating associated with the SAE J1772 standard.


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## njloof (Nov 21, 2011)

major said:


> Still off topic but I can't resist. What is a 30 amp J? There is no 30 amp rating associated with the SAE J1772 standard.


No, but there are plenty of 7.2kW EVSEs...


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## trukr (Mar 17, 2013)

major said:


> I suspect your main concern is the battery. On the BEV the battery is typically sized large enough in energy that the C-rates from regeneration are within the capabilities and if that rate or duration is exceeded, a proper system will simply reduce the regen torque and force on the friction brakes eliminating the stress problem.


Thanks for clearing this up for me. It's one of many questions I have that I wasn't sure where to find the answer for.

I would prefer the regen switch to resistors to continue dynamic braking. I'm not crazy about the idea of computer controlled active braking, or a screen prompt to use the brakes instead. I know it's a waste of free energy but I would think it more seemless and less confusing for the general public. I remember when ABS was first introduced, a lot of people would let off the brake completely when the pedal would start pulsating.


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## major (Apr 4, 2008)

trukr said:


> Thanks for clearing this up for me. It's one of many questions I have that I wasn't sure where to find the answer for.
> 
> I would prefer the regen switch to resistors to continue dynamic braking. I'm not crazy about the idea of computer controlled active braking, or a screen prompt to use the brakes instead. I know it's a waste of free energy but I would think it more seemless and less confusing for the general public.


Actually it was a figure of speech. The regen systems which I have installed and prefer to use have a sensor on the brake pedal. The first portion (inch or so) of pedal travel actuates a proportional signal to apply increasing negative torque (regen). If the operator needs more torque than available from regen he simply depresses the brake further and gets a blend of regen and friction brakes. If the regen approaches the battery voltage limit or other limiting factor the controller fades away the negative torque signal and the operator seamlessly applies increased foot pressure on the pedal maintaining the desired deceleration. It is completely intuitive for the operator and becomes second nature just like the first time you used power brakes (if you're old enough to remember manual brakes).

BTW, resistors are unneeded. The friction brakes on the car are designed to do the same job (waste energy as heat) so there is no need to duplicate that function with additional components.


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## IamIan (Mar 29, 2009)

tomofreno said:


> IamIan said:
> 
> 
> > I think we are not thinking of the three terms in the same way ... Theory , Ideal , and Practical
> ...


Agreed.

And if we aren't using the terminology the same ... there is little point in trying to have a discussion about it.

.... but because you seem to have misunderstood me in soo many ways ... I'll reply shortly to a few of your items you posed bellow.

If you want to go into more depth about any of the more off topic items ... open another more appropriate thread ... let me know about it and I'll be happy to move it there... otherwise this will be my last reply about any of these fringe to off topic items.



tomofreno said:


> You seem to think that theory is just some conception of what might be possible.


No.
I'm sorry you misunderstood me.

What is 'possible' is an entirely different and even broader scope than 'theory' ... because it is 'possible' that the 'theory' is wrong,inaccurate, etc.

Further discussion is off topic for this thread.



tomofreno said:


> There is not a vast difference when the term theory is used as I use it.


Yup ... You are using the term very differently.



tomofreno said:


> This is incorrect. There is currently no theory that states that time travel is possible.


Incorrect.
There are many actually.
Further discussion is off topic for this thread.



tomofreno said:


> You are using the term as synonomous with "under ideal conditions", that is not the way scientists generally use the term theory.


No I am not... sorry you misunderstood.

In that particular case you were referring to ... I was pointing out a difference between ... what being limited by 'theory' does ... vs ... what being limited by 'ideal' does.

So by the very definition of 'synonomous' that is absolutely not what I was doing.



tomofreno said:


> Any theory of anything has to take account of all things that effect the phenomena being described.


Incorrect.

If anything ... the Theory of everything ... that actually is able to account for all effected things ... has not yet been worked out ... pretty much none of the current theories about anything take account of all things that effect the phenomena being described ... instead they pick specific pieces and ignore the rest ... leaving the rest to other different theories ... which in-tern pick pieces and leave the rest of yet other theories.



tomofreno said:


> What you are describing is the ideal case, for example if there were no losses. That is different from theory.


Which is why ... I gave three different % ... what you can do in theory , is different from Ideal ... and theory or ideal are both different from practical.

These three distinctions is what the OP asked for... if you don't recognize a difference between the three ... then don't worry about those of us answering the OP for the difference between the three.



tomofreno said:


> I agree these are all ideal. That is completely different than any theories that would accurately describe these phenomena.


That aspect you replied to here ... was not about theory at all ... it was specifically written as an example of 'ideal' ... I clearly wrote that at the beginning of it... we can list a great many things different from what that was talking about ... oranges... green beans ... WiFi ... etc.



tomofreno said:


> Practical, as you use the term is reality.


Nope ... sorry you misunderstood.

Spending $1Trillion dollars to gain 0.000001 MPG on one vehicle is not practical at all ... but it would fit into the 'ideal' case ... and thus another example of the distinction between 'ideal' , and 'practical'.


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## evmetro (Apr 9, 2012)

major said:


> Still off topic but I can't resist. What is a 30 amp J? There is no 30 amp rating associated with the SAE J1772 standard.


Yea, this is pretty farr off topic and a cheap shot on my part, but I understand that the charging stations installed with MY money (federal grant money) are limited to 30 amps. I will leave further discussion of the j plug alone in this thread, since I had no business bringing that up.


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