# The regen thread



## unclematt (May 11, 2008)

Hi All,

I was trying to search the site for info on regenerative braking, but mostly found threads where it was mentioned only in passing. So I thought it might be a good idea to have a thread just for "regen" questions and answers. I have plenty of the former, and not as many of the latter as I would like.

Here are a few questions:

In General

1. Do PM motors or AC motors do better when it comes to serving as both the power motor and the regen generator? 

2. Which is more efficient at recovering energy from braking, PM or AC?

3. What are the "off the shelf" system components that are available that incorporate regen and what features do they have to offer?

More Specifically

I have an idea about using an XR3 riley kit car in a "through the road" hybrid design. This car is designed to use a small diesel IC engine to power the front wheels, with a battery powered electric motor powering the single rear wheel. When the battery becomes depleted, I would like to have the front IC motor powerful enough to both drive the vehicle normally and "pull" the electric drive rear wheel to turn the drive motor in regen mode to recharge the battery while driving. What motor design/system would be the best for attempting this setup?


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## Guest (Aug 24, 2009)

1. Yes
2. Actually it is more a design of the controller and what type of battery pack you have. 
3. Most AC motor/controller combo's have built in regen.
4. PM motors with regen controllers will work too but be careful with input amps through the controller and into the battery pack. Easy to blast a battery with hundreds of amps. Easy to smoke a controller with too much input regen. 
5. Some DC motors will work with regen if you have a sepex motor or a series with interpoles. Series DC are not useful for regen unless it has interpoles. 

Actually if you go to EVDL you can get loads of information if you spend the time to hunt the archives. 

There are very few high voltage regen controllers for PM or Series or Sepex motors. I'd go as far to say all AC Motor/Controllers provide regen. 

Pete


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## unclematt (May 11, 2008)

Thanks for your response gottdi, do you have any input about the last question I asked? I have never heard of a system that has the IC and electric motors on different drive wheels and able to regen "through the road" while driving, and not just while braking, have you? I would assume the amount of recharge current demanded from the electric motor while driving would be much lower than that produced during braking, and as close as possible to the ideal recharge rate for your particular battery design and configuration. I am also sure some measure of efficiency would be lost due to tire slippage between the front and rear wheels during recharge, but hopefully that would be minimal. This system would remove the need for a seperate generator attached to the IC engine as is normal with most series hybrids.

If anyone knows of such a system in existence, please post it.


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## major (Apr 4, 2008)

unclematt said:


> Thanks for your response gottdi, do you have any input about the last question I asked? I have never heard of a system that has the IC and electric motors on different drive wheels and able to regen "through the road" while driving, and not just while braking, have you? I would assume the amount of recharge current demanded from the electric motor while driving would be much lower than that produced during braking, and as close as possible to the ideal recharge rate for your particular battery design and configuration. I am also sure some measure of efficiency would be lost due to tire slippage between the front and rear wheels during recharge, but hopefully that would be minimal. This system would remove the need for a seperate generator attached to the IC engine as is a normal with most series hybrids.
> 
> If anyone knows of such a system in existence, please post it.


Hi uncle,

What you're talking about is a road coupled parallel hybrid. The concept isn't new, but not too many, if any, around. Basically no different than an in-line parallel hybrid, except the electric machine is on the other axle.

Regeneration is the term typically used for energy recovery during braking, either in slowing the vehicle or maintaining speed downhill. Steady speed, on the level, use of an electric motor in a hybrid to "make" electricity, is simple generation.



> 3. What are the "off the shelf" system components that are available that incorporate regen and what features do they have to offer?


To my knowledge, all the available AC (including BLDC) systems can do regeneration and have the required features. And I would imagine these will do generation easily.

Regards,

major


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## RE Farmer (Aug 8, 2009)

Yes, you would have some slippage, and consequently additional tire wear, on both the front and rear tires. Additionally, you'd be burning oil to make electricity which negates one of the main reasons for going electric in the first place.

My main reason for wanting regen is to save brake wear then putting a little energy back in my paltry batt pack.


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## unclematt (May 11, 2008)

RE Farmer said:


> Yes, you would have some slippage, and consequently additional tire wear, on both the front and rear tires. Additionally, you'd be burning oil to make electricity which negates one of the main reasons for going electric in the first place.
> 
> My main reason for wanting regen is to save brake wear then putting a little energy back in my paltry batt pack.


No, I would be burning biodiesel, but thanks for your concern. And if you don't have solar cells on your house, don't buy all of your electricity from renewable sources, or have some other form of renewable energy on your property, you are very likely using COAL to charge your batteries in your electric car.

I do agree, however, that in most ev's the best use for regen is in recapturing energy from the braking process. I was just curious if anyone had any info on them. As usual, Major came through with some interesting stuff. The only draw back I can see to a through-the-road parallel hybrid is not being able to run the IC motor at its most efficient RPM unless you have a computer controlled CVT.


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## dimitri (May 16, 2008)

Have you considered replacing all the weight of ICE and its surrounding components ( cooling, exhaust, transmission, etc. ) with equal weight of additional LiFePo4 batteries? I bet it will increase your range such that you will never need range extensions and you still get to keep braking regen.


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## major (Apr 4, 2008)

unclematt said:


> The only draw back I can see to a through-the-road parallel hybrid is not being able to run the IC motor at its most efficient RPM unless you have a computer controlled CVT.


Hey uncle,

The primary drawback to the road coupled hybrid is the need for 2 drive trains (transmissions, differentials, etc). Running the ICE at particular speeds and loads is the same as an in-line parallel system. This is all part of the hybrid architecture and control strategy. Actually I think it could do just as well on a road coupled design. But unless you have other reasons to power both axles, you will be at a disadvantage.

You always have the debate of series vs parallel hybrids. For cars running highway speeds or long constant speed travel, the parallel system with the engine driving the wheels seems like the winner. Less energy conversions. Cars engaged primarily in stop and go traffic, the series hybrid looks good. Makes you wonder how these PHEVs are really going to do when people drive them 2 or 300 miles on the highway. They are series hybrids, mechanical (ICE) to electric, and then electric to mechanical (propulsion) conversions. It seems unlikely they will be as efficient as an ICE driving the wheels.

Regards,

major


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## Woodsmith (Jun 5, 2008)

dimitri said:


> Have you considered replacing all the weight of ICE and its surrounding components ( cooling, exhaust, transmission, etc. ) with equal weight of additional LiFePo4 batteries? I bet it will increase your range such that you will never need range extensions and you still get to keep braking regen.


That's the method I am using in my conversion to remove the need for adding regen. Also I don't think regen would give me much back on my commute anyway so I am keeping my system simple.

However, as things change and I understand the methods behind regen then that might change.


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## unclematt (May 11, 2008)

dimitri said:


> Have you considered replacing all the weight of ICE and its surrounding components ( cooling, exhaust, transmission, etc. ) with equal weight of additional LiFePo4 batteries? I bet it will increase your range such that you will never need range extensions and you still get to keep braking regen.


Thing is the battery technology is not such that I could afford going all battery with a vehicle like this. I live in Durango, CO, far from any major metro areas. I need hundreds of miles of range for this vehicle to be practical, and that much battery pack A) wouldn't fit in the XR3 and B) would cost an arm and a leg to buy.

THE ICE engine I am considering is very small and does not require a lot of room or add a lot of weight to the XR3. If you are not familiar with the XR3, it was designed from the ground up this way.


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## unclematt (May 11, 2008)

major said:


> Hey uncle,
> 
> The primary drawback to the road coupled hybrid is the need for 2 drive trains (transmissions, differentials, etc). Running the ICE at particular speeds and loads is the same as an in-line parallel system. This is all part of the hybrid architecture and control strategy. Actually I think it could do just as well on a road coupled design. But unless you have other reasons to power both axles, you will be at a disadvantage.
> 
> ...


Hey Major,
I only considered this parallel (through-the-road) design because the XR3 would lend itself so readily to the concept. It has only 1 rear wheel, which vastly reduces the weight associated with a car having a parallel setup like I am suggesting for the XR3. It is also extremely light, and has a VW bug tranny as part of its original design, so the tranny is already there to use. If I was converting a Honda Ridgeline to EV, I would never consider a parallel system due to the concerns you already mentioned. I would, however, consider giving a large vehicle like that a series hybrid system, because you would have so much room for components and batteries.


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## dimitri (May 16, 2008)

I guess it all comes down to your typical driving distances and how much of it you want electric vs. gas. This will be deciding factor in sizing the battery.

For a small light car like this I would recommend HPG AC30/31/50 kit. It's designed for such cars and has regen. There is a thread about it in motor forum.

You said ICE is small, but how much power does it generate? It would have to generate enough to drive and regen at the same time.

Here is the bug with AC30 kit http://www.evalbum.com/2865 for your reference.


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## ga2500ev (Apr 20, 2008)

major said:


> Hey uncle,
> 
> The primary drawback to the road coupled hybrid is the need for 2 drive trains (transmissions, differentials, etc). Running the ICE at particular speeds and loads is the same as an in-line parallel system. This is all part of the hybrid architecture and control strategy. Actually I think it could do just as well on a road coupled design. But unless you have other reasons to power both axles, you will be at a disadvantage.
> 
> ...


One thing to consider with the series hybrid though is the fact that you can optimize the ICE engine because it doesn't have to have a wide RPM or power band like the ICE engine directly attached to a vehicle. It can be tuned for optimal efficiency. Also it doesn't have to have the same peak power demands as a traditional ICE.

ga2500ev


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## unclematt (May 11, 2008)

dimitri said:


> I guess it all comes down to your typical driving distances and how much of it you want electric vs. gas. This will be deciding factor in sizing the battery.
> 
> For a small light car like this I would recommend HPG AC30/31/50 kit. It's designed for such cars and has regen. There is a thread about it in motor forum.
> 
> ...


 Hi dimitri,
Please refer to the XR3 info on riley's website here for info on the ICE for the XR3.

However, I don't intend for this thread to be just about my little XR3 project, but also as a way for people to learn about regen in general from a theoretical and practical point of view. Please post any info you wish to share on regen, but make sure you stipulate which motor/battery/controller you are referring to when/if you do.


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## Guest (Aug 24, 2009)

You might do better getting a TDI and run bio or vegie oil.


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## major (Apr 4, 2008)

ga2500ev said:


> One thing to consider with the series hybrid though is the fact that you can optimize the ICE engine.....


Yeah ga,

That's the standard argument. With the thermal efficiency limits of the ICE, I don't see how a series hybrid will overcome the additional losses going thru the electrical system at 65 mph constant travel for 3 or 4 hours. But wait a few years and we'll see how the Chevy Volt does on those long interstate trips. But we diverge from the thread topic.

Regards,

major


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## dreamer (Feb 28, 2009)

unclematt said:


> Hey Major,
> I only considered this parallel (through-the-road) design because the XR3 would lend itself so readily to the concept. It has only 1 rear wheel, which vastly reduces the weight associated with a car having a parallel setup like I am suggesting for the XR3. It is also extremely light, and has a VW bug tranny as part of its original design, so the tranny is already there to use. If I was converting a Honda Ridgeline to EV, I would never consider a parallel system due to the concerns you already mentioned. I would, however, consider giving a large vehicle like that a series hybrid system, because you would have so much room for components and batteries.


I've also looked at the XR3, and if I wasn't so leery of building the body from scratch out of foam and fiberglass, it seems like a great option. I think using the HPG AC15 motor and Curtis 1236 controller would be a great option to provide regen/gen for the XR3.

As far as avoiding the need for two drivetrains in a parallel hybrid like the Ridgeline, I would consider looking for a pancake style motor to mount directly on the front of the engine. That way, it could add HP to what the engine is producing, thereby decreasing the fuel used around town, and absorb energy by putting it in regen mode while driving on the highway, increasing fuel use to charge the batteries in anticipation of more city driving.


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## unclematt (May 11, 2008)

dreamer said:


> I've also looked at the XR3, and if I wasn't so leery of building the body from scratch out of foam and fiberglass, it seems like a great option. I think using the HPG AC15 motor and Curtis 1236 controller would be a great option to provide regen/gen for the XR3.
> 
> As far as avoiding the need for two drivetrains in a parallel hybrid like the Ridgeline, I would consider looking for a pancake style motor to mount directly on the front of the engine. That way, it could add HP to what the engine is producing, thereby decreasing the fuel used around town, and absorb energy by putting it in regen mode while driving on the highway, increasing fuel use to charge the batteries in anticipation of more city driving.


I only brought up the Ridgeline as an example of where I thought a series hybrid setup would be very practical. It is not on my drawing board at the moment, unless you have a free donor truck to give me for the project and $60K in development funding. 

I asked the question about a "through the road" parallel design before I had considered the fact that you can no longer run the ICE at its optimim RPM for maximum efficiency if it is connected to the road. I take it off the table.

I would appreciate it if those of you with a little more knowledge of regen would expound on it at length when you get a chance. For AC, DC, and brushless and brushed. Have a drink, relax, and then tell all. I even noticed another thread posted today that was asking about how regen occurred with regard to the IGBT bridge, so there is definitely interest in this subject.


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## major (Apr 4, 2008)

unclematt said:


> I would appreciate it if those of you with a little more knowledge of regen would expound on it at length when you get a chance.


Hi uncle,

http://www.diyelectriccar.com/forums/showthread.php?t=8848 

What else would you like to know?

BTW, that page starts out with this:



> *What is regenerative braking?*
> *Regenerative braking is a way of slowing a vehicle down where some or all of the vehicle's kinetic energy is saved rather than being wasted as heat. Electrically this is achieved through the use of a generator (often the traction motor with the terminals reversed) and energy storage devices such as batteries or capacitors. This generator is usually an AC or permanent magnet DC motor.*


I have highlighted in blue a statement I disagree with. In nearly all cases, AC or DC, the motor's terminals are not reversed to regenerate.

Regards,

major


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## unclematt (May 11, 2008)

major said:


> Hi uncle,
> 
> http://www.diyelectriccar.com/forums/showthread.php?t=8848
> 
> ...


 Thanks Major, I hadn't noticed that thread was already in existence. If an admin wants to delete this thread, they should go for it.


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## major (Apr 4, 2008)

unclematt said:


> Thanks Major, I hadn't noticed that thread was already in existence. If an admin wants to delete this thread, they should go for it.


I don't like that idea. My 4 posts would disappear. And this thread may help others find what you missed.

Keep it.

major


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## major (Apr 4, 2008)

unclematt said:


> Thanks Major, I hadn't noticed that thread was already in existence.


Hey uncle,

I see from your post http://www.diyelectriccar.com/forums/showpost.php?p=136661&postcount=62 
that you are still having trouble with the generator concept, whether it be regen or generation. So maybe this will help.

EV motors could be of the 80 kW rating, right? So, go to a catalog and find an industrial motor rated at 80 kW. How much does it weigh? A ton, right? What's the difference? Design and duty cycle. The EV motors run at higher speed and have different cooling methods. They also have different duty cycles. Peak power rated perhaps vs continuous. And design life for 1000's of hours opposed to 10s of thousands of hours.

It is much the same for generators. Find a commercial 60 Hz, 80 kW generator and it weighs a ton. But a purpose designed generator could be about the same size as the EV motor. In fact, no reason the EV motor can't be used for the generator.

Any motor will work as a generator, and any generator as a motor, if properly excited. Electric dynamos are bidirectional energy converters.

Regards,

major


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## unclematt (May 11, 2008)

major said:


> Hey uncle,
> 
> I see from your post http://www.diyelectriccar.com/forums/showpost.php?p=136661&postcount=62
> that you are still having trouble with the generator concept, whether it be regen or generation. So maybe this will help.
> ...


 Thanks for your comments major, but the point I was making in the thread you linked to was that if _someone_ is doing it, then it should be able to be replicated by others. If the Volt will actually be able to extend its range with an onboard generator, why not other cars, and even DIYers? Your comments about design/weight/cooling centering around duty cycle is accurate, all I am saying is then why can't members of this forum design a functional on-board series hybrid generator? The ICE part is fairly straightforward with what is offered on the market, and more than one choice could be made there, but the generator head is the hang up due to excessive weight and lack of output on many off the shelf generator head models.

Has anyone had any experience with aviation APU generator heads? Please refer to the series hybrid generator thread to see photos that TJ posted towards the end. He and I are simply trying to determine if they could fill the roll in the generator head department. I would also be open to engineering a lightweight motor to serve as a generator as major talked about.


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## tj4fa (May 25, 2008)

The APU generator heads I have shown in the link below will put out 30Kw and 25Kw 120/208VAC 3ph 400hz @ 6000 rpm and only weigh 80 lbs or so.

http://s117.photobucket.com/albums/o42/jaynethecat/Range%20Extender%20Stuff/

But I would imagine you would want something rewound for higher voltages at lower rpms to spin off the drivetrain since it appears you would have to cross the charging threshold to get some charge back into the battery pack (i.e. if the pack is at 150V you would need something putting in >150V to start to put a charge back in).


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