# Adding Regen to DC? Not for range...



## ewdysar (Jun 15, 2010)

I live in the foothills of SoCal and I notice that while I drive any of my ICE vehicles, auto or stick, I use downshifting to control my speed. I do this for traffic or hills. Since I am seriously considering a DC electric conversion, I would like some resistance from the drivetrain when operating under zero throttle. I would use the transmission to select the amount of drag, lower gears for more deceleration, just the same as the ICE vehicles. My intended pack voltage will probably be 156V (48 lithium cells). I know that a controller will be needed to prevent overcharging, the max regen (charging) voltage should be no higher than 168V - 170V. 

Since I typically care about efficiency, I don't want to just drag the brakes all the way downhill or approaching a traffic signal (I don't do that today in my Suburban, Fit, Insight or 914-V8). So for the sake of driveability, how can I get the conversion to feel more like a regular car? I'm not impressed with the AC systems that are available today, none seem to match the power of a WarP9 for a similar weight.

I've spent a day reading way too many threads that barely touch on the subject (please don't mention perpetual motion) and the only practical advice that I mined from all that has been the guy with the S-10 that rewound his own alternator. I was hoping that I could buy most of the components necessary to build a similar finished product. I'm not looking for a kit, just some sources for the major components. I'm also open to alternative strategies. Anybody else headed down this path before?

Thanks,
Eric


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## JRP3 (Mar 7, 2008)

Seems like a rewound alternator, or DC generator head, are about the only options. You could also stack an AC motor on top of the DC motor for extra power and built in regen, if it ran the same voltage, expensive though.


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## TX_Dj (Jul 25, 2008)

If you care more about the braking effect than the regen charging function, plug braking may be your answer. Also called dynamic braking, it's very similar in effect to regen, but instead of putting that energy back into the pack, you burn it off as heat in a resistor bank.

Not easily done with a series DC motor for the same reasons regen isn't easily done, so you'd still need some offboard generation device that can be "switch" into the mix to give you the braking effects. Then you're also carrying lots of extra weight to support that system, so your range goes down as well.

So long as your brakes can stay cool enough going down those hills so as not to fade and lose braking efficacy, I'd say just use the brakes unless you're willing to go all the way to build a proper regen system; otherwise it doesn't make sense to carry any additional weight to support the effect.


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## ewdysar (Jun 15, 2010)

So let's say I chose the rewound alternator solution. Are there ones available on the market or do I have to wind my own? Since it appears that the "high power" alternators' voltage varies with RPM, is there an off-the-shelf controller that can take the raw alternator output with fluctuating voltage and output my desired 168V? Are perm magnet alternators the only way to get to our kinds of voltages? If so, adding a clutch like Wayne's S-10 configuration seems mandatory.

Adding an A/C drive does sound like a way to get the best of both worlds, but cost was one of the factors pushing me towards D/C. I guess that if they were coordinated correctly, both motors could be smaller... Hmmm.... Still seems expensive....


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## ewdysar (Jun 15, 2010)

TX_Dj said:


> If you care more about the braking effect than the regen charging function, plug braking may be your answer. Also called dynamic braking, it's very similar in effect to regen, but instead of putting that energy back into the pack, you burn it off as heat in a resistor bank.
> 
> Not easily done with a series DC motor for the same reasons regen isn't easily done, so you'd still need some offboard generation device that can be "switch" into the mix to give you the braking effects. Then you're also carrying lots of extra weight to support that system, so your range goes down as well.
> 
> So long as your brakes can stay cool enough going down those hills so as not to fade and lose braking efficacy, I'd say just use the brakes unless you're willing to go all the way to build a proper regen system; otherwise it doesn't make sense to carry any additional weight to support the effect.


Yeah, I can see that weight is coming back into play. I beginning to think that your last paragraph may be what we're stuck with until better A/C systems become available. 

Back in the mid 1990's while I worked for Disney, a friend won Frank Wells' electric Fiero in a rideshare drawing. I helped him refresh the car and worked on a number of other EV's. At that time, I decided that for me, the FLA batteries were too big of a performance/range hit for how I expect a car to work. Fast forward to today, and I'm converting my 30' sailboat to electric with a 48V system and a TS 160Ah battery pack. With a battery pack that weighs less than half as much, a conversion is looking more viable. 

AC Propulsion was building some solid systems back in the 1990's, I would have figured that they would be more available by now. Oh well....

Eric


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## DavidDymaxion (Dec 1, 2008)

You could get a sepex DC motor and sepex controller http://www.kellycontroller.com/kdc1260324v-120v600aseparate-excited-with-regen-p-418.html . I have no personal experience with Kelly, so that is not a recommendation for or against them.

I'm doing a diy controller for my sepex motor -- regen down hills is very nice. Strong regens seem to have the side benefit of keeping the batteries balanced.


ewdysar said:


> I live in the foothills of SoCal and I notice that while I drive any of my ICE vehicles, auto or stick, I use downshifting to control my speed. I do this for traffic or hills. Since I am seriously considering a DC electric conversion, I would like some resistance from the drivetrain when operating under zero throttle. I would use the transmission to select the amount of drag, lower gears for more deceleration, just the same as the ICE vehicles. My intended pack voltage will probably be 156V (48 lithium cells). I know that a controller will be needed to prevent overcharging, the max regen (charging) voltage should be no higher than 168V - 170V.
> 
> Since I typically care about efficiency, I don't want to just drag the brakes all the way downhill or approaching a traffic signal (I don't do that today in my Suburban, Fit, Insight or 914-V8). So for the sake of driveability, how can I get the conversion to feel more like a regular car? I'm not impressed with the AC systems that are available today, none seem to match the power of a WarP9 for a similar weight.
> 
> ...


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## ewdysar (Jun 15, 2010)

DavidDymaxion said:


> You could get a sepex DC motor and sepex controller http://www.kellycontroller.com/kdc1260324v-120v600aseparate-excited-with-regen-p-418.html . I have no personal experience with Kelly, so that is not a recommendation for or against them.
> 
> I'm doing a diy controller for my sepex motor -- regen down hills is very nice. Strong regens seem to have the side benefit of keeping the batteries balanced.


So where can I find Sepex motors? Is there a system available that is of similar performance to a WarP9 with a 750A controller? All I can find is the D&D 6.7" that seems max out around 84V, or Kostov's, where the only high voltage model is the 268mm model. Are there Sepex controllers available that run to 144-156V?

Thanks,
Eric


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## JRP3 (Mar 7, 2008)

ewdysar said:


> Are there Sepex controllers available that run to 144-156V?
> 
> Thanks,
> Eric


Not that I've ever heard of. Saying "get a sepex" sounds good, until you actually try to do it.


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## toddshotrods (Feb 10, 2009)

JRP3 said:


> Not that I've ever heard of. Saying "get a sepex" sounds good, until you actually try to do it.


Then it's frustrating as h3!!.  Since I finally realized that high-power SepEx wasn't worth the hassle, I've been testing not using the engine for braking in my (5spd) Accord daily driver. It's really not that big of a deal once you get used to it. Definitely not something that's worth spending a lot of unnecessary cash to simulate. You'd get more for your money with better brakes and/or more batteries.


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## DavidDymaxion (Dec 1, 2008)

I'm not aware of any current sepex controller that goes higher than the Kelly 120 V. I think the max Curtis one is 96 V.

If you want an off-the-shelf sepex solution, it looks like you have to either go lower power, or go multiple motors (might as well go AC in that case).

That's one of the reasons I'm doing my own controller!


ewdysar said:


> So where can I find Sepex motors? Is there a system available that is of similar performance to a WarP9 with a 750A controller? All I can find is the D&D 6.7" that seems max out around 84V, or Kostov's, where the only high voltage model is the 268mm model. Are there Sepex controllers available that run to 144-156V?
> 
> Thanks,
> Eric


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## Georgia Tech (Dec 5, 2008)

If you use a Sep ex motor, frorm what I have learned, MAKE SURE it has Interpoles!!!!


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## ewdysar (Jun 15, 2010)

DavidDymaxion said:


> I'm not aware of any current sepex controller that goes higher than the Kelly 120 V. I think the max Curtis one is 96 V.
> 
> If you want an off-the-shelf sepex solution, it looks like you have to either go lower power, or go multiple motors (might as well go AC in that case).
> 
> That's one of the reasons I'm doing my own controller!


Ok, so what sepex motor are your running?

Eric


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## Georgia Tech (Dec 5, 2008)

ewdysar said:


> Ok, so what sepex motor are your running?
> 
> Eric


 
I am not running ANY motor at the moment... I have a BIG sep Ex motor just sitting in my Garage. 

I have read some SERIOUS debates and posts on here on the importance of interpoles for High voltage Sep Ex systems... It seems the consincous is that a Sep Ex system with out interpoles can be run at about 72 volts max...


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## ewdysar (Jun 15, 2010)

Georgia Tech said:


> I am not running ANY motor at the moment... I have a BIG sep Ex motor just sitting in my Garage.
> 
> I have read some SERIOUS debates and posts on here on the importance of interpoles for High voltage Sep Ex systems... It seems the consincous is that a Sep Ex system with out interpoles can be run at about 72 volts max...


 What kind of "BIG sep Ex motor"? Like I said ealier, the only Sep Ex motor specs that I've seen rated to 144V is the Kostov 268mm. I'm just trying to figure out what options actually exist...

Eric


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## DavidDymaxion (Dec 1, 2008)

I have an old Kostov 11 inch sepex. It does have interpoles. I have only run it gently so far, but by the end of the summer I should have some higher voltage and current results to report.


ewdysar said:


> Ok, so what sepex motor are your running?
> 
> Eric


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## Tesseract (Sep 27, 2008)

The Kostov SepEx motor looks to be an excellent size even for relatively heavy conversions. Too bad making a SepEx controller that can work with a variety of motors is such a P.I.T.A. ...

As for a really "Big" SepEx motor... how about this 13" GE monster which is going to be added to our dyno real soon:


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## ewdysar (Jun 15, 2010)

Tesseract said:


> The Kostov SepEx motor looks to be an excellent size even for relatively heavy conversions. Too bad making a SepEx controller that can work with a variety of motors is such a P.I.T.A. ...
> 
> As for a really "Big" SepEx motor... how about this 13" GE monster which is going to be added to our dyno real soon:


Cool, though I might have to beef up the suspension in the Metro... 

Eric


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## Georgia Tech (Dec 5, 2008)

ewdysar said:


> What kind of "BIG sep Ex motor"? Like I said ealier, the only Sep Ex motor specs that I've seen rated to 144V is the Kostov 268mm. I'm just trying to figure out what options actually exist...
> 
> Eric


 
It's one that I bought from a guy on this forum 10" motor ...I just don't have time to fool with it...It has an inverted spline shaft that I don't know what to do with. I have an 11 inch series, just out of the machine shop and a monster 13 inch like Tesseract's 13 inch except mine is the series version, his is the sepex version..

I sure wish I could figure a way to retro fit Interpoles in one of these things.....


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## Guest (Jul 6, 2010)

So a decent little sepex with interpoles and a medium weight vehicle and a kelly sepex 120 volt controller and you have a system. What's so bad about that? Sure it's not a super high voltage system but what is interesting is that if you ask Kelly Controller your needs I am sure they can build you one for higher voltage. Did you ask them? They are actually very willing to work with you. I have a software modified SepEx controller we are now going to be able to test. I am sure they will build a 144 or 156 volt controller that will power a SepEx but if you go that high of voltage you risk flashover. Advance it and you loose regen ability to the point you may damage the com even with sepex. So a nice small car like a VW should do just fine with 120 volts and regen with a decent sized 9" GE SepEx motor. You can change parameters to your controller to custom configure the software to work better with your motor. It is still possible. You can control the amount of regen too. 0 to full on. I will let you all know about our testing. Got the pan and going to mount the motor and do some tests.


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## david85 (Nov 12, 2007)

ewdysar said:


> I live in the foothills of SoCal and I notice that while I drive any of my ICE vehicles, auto or stick, I use downshifting to control my speed. I do this for traffic or hills. Since I am seriously considering a DC electric conversion, I would like some resistance from the drivetrain when operating under zero throttle. I would use the transmission to select the amount of drag, lower gears for more deceleration, just the same as the ICE vehicles. My intended pack voltage will probably be 156V (48 lithium cells). I know that a controller will be needed to prevent overcharging, the max regen (charging) voltage should be no higher than 168V - 170V.
> 
> Since I typically care about efficiency, I don't want to just drag the brakes all the way downhill or approaching a traffic signal (I don't do that today in my Suburban, Fit, Insight or 914-V8). So for the sake of driveability, how can I get the conversion to feel more like a regular car? I'm not impressed with the AC systems that are available today, none seem to match the power of a WarP9 for a similar weight.
> 
> ...


Just a suggestion, but have you considered dropping your system low enough to run a sepex or AC motor like JRP3? His Fiero has fully functioning regen setup and seems to have enough pow - well, I'll let him tell you how it runs

I do agree however that under some conditions, not having any engine brakes can be hazardous.


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## Overlander23 (Jun 15, 2009)

What about the 11" Kostov neutrally-timed, interpoled, series-wound motors?


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## EVfun (Mar 14, 2010)

Overlander23 said:


> What about the 11" Kostov neutrally-timed, interpoled, series-wound motors?


That motor can do regen. Not a lot of vehicles use such large DC motors so there are not very many series DC motor controllers designed to offer regen.


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## JRP3 (Mar 7, 2008)

david85 said:


> Just a suggestion, but have you considered dropping your system low enough to run a sepex or AC motor like JRP3? His Fiero has fully functioning regen setup and seems to have enough pow - well, I'll let him tell you how it runs


I do love my system  Just put it in second gear and go, all the way to 65 mph. Doesn't have the off the line pull of a DC series motor but it's plenty for normal driving, and there is always first gear if I want a quick shot from 0-35 mph.


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## Tesseract (Sep 27, 2008)

ewdysar said:


> I live in the foothills of SoCal and I notice that while I drive any of my ICE vehicles, auto or stick, I use downshifting to control my speed.
> ...the only practical advice that I mined from all that has been the guy with the S-10 that rewound his own alternator.
> ...


My take is that this isn't terribly practical for two reasons:

1. The average automotive alternator is ~1kW in size and about 50% efficient (typical "claw pole" design) and that power capability applies no matter what voltage you re-wind it for. This means you can develop a maximum of about 2kW of braking power with the average alternator.

2. 2kW of braking power, alone, can decelerate a 1000kg vehicle from 60mph to 0 in about 138 seconds. My guess is you would barely notice the difference between that rate of deceleration and simply coasting.


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## few2many (Jun 23, 2009)

Well, how about two Automotive alts on the rear wheels?
You could have them charge the batteries directly using maybe a diode bank, if using 12v batts.
Also, you can change the voltage output by controlling the voltage input. Build a new voltage regulator that can charge at the whole pack voltage


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## ngrimm (Oct 19, 2007)

IMHO the highest gear ratio that the alternator can use without damaging it by over spinning would be desired in order to multiply the braking force. An average ice alternator is geared at around 3:1 X 3.5 final drive ratio equals >10:1 So wouldn't 1kw of stopping force also be multiplied by 10? I realize it would be less as the vehicle speed is reduced.


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## ewdysar (Jun 15, 2010)

Tesseract said:


> My take is that this isn't terribly practical for two reasons:
> 
> 1. The average automotive alternator is ~1kW in size and about 50% efficient (typical "claw pole" design) and that power capability applies no matter what voltage you re-wind it for. This means you can develop a maximum of about 2kW of braking power with the average alternator.
> 
> 2. 2kW of braking power, alone, can decelerate a 1000kg vehicle from 60mph to 0 in about 138 seconds. My guess is you would barely notice the difference between that rate of deceleration and simply coasting.


That raises an interesting question, how much decelerative hp comes from a regular 4 cylinder engine at zero throttle? In my experience, not that much, certainly way less than our Insight in it's regen mode. Since 2 minutes sounds about right for my car to coast down from 60mph on level ground in neutral, 2kW added to the regular coasting drag may be close to what a ICE adds (subtracts?), i.e. slowing down twice as fast.

That said, after evaluating how much braking would actually be needed during my regular commute without engine decel (shifting into neutral every time I lifted my foot off the throttle), I find that I had over-estimated the amount of braking that a regular DC conversion would require. So unless the regen for driveability solution is both cheap and easy, it won't make it onto the build list.

Eric


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## Overlander23 (Jun 15, 2009)

ICE deceleration depends on what gear you're in... Certainly, you won't feel much if you're coasting down in fifth or sixth, but the engine compression braking in first and second is very noticeable. Remember, it's safer (with an ICE car) to coast down a mountain pass in a lower gear than ride the brakes in a higher gear.

It would also seem that electric regen would be able to provide a constant level of deceleration, while an ICE's compression deceleration diminishes with engine speed.


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## JRP3 (Mar 7, 2008)

EV deceleration is also gear dependent, you won't get much in 4th or 5th, another reason I do most of my driving in second. The nice thing about regen is the way you can modulate the intensity with the accelerator pedal. I can hold the pedal neutral for zero regen and coast, or I can use varying amounts of regen depending on what I need. Takes a little getting used to and some practice but I like it. Adds another dimension to driving.


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## Overlander23 (Jun 15, 2009)

Yes... I'd love for the Soliton-1 to be able to provide regen with my neutrally-timed, interpoled-Kostov (hint, hint ). As it stands I have to rely on drum brakes designed in the fifties to slow an SUV (a small SUV, granted). Or... figure out how to engineer disc brakes on... it's possible.




JRP3 said:


> Takes a little getting used to and some practice but I like it. Adds another dimension to driving.


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