# DC Motor with "DIY Regen"...



## Wiredsim (Jul 4, 2008)

I'm sure the University of Maine knows what they are doing, but wouldn't that create an additional load even when not braking? 

I think the cheapest way of doing this would be to add a heavy duty auto alternator such as: http://stores.channeladvisor.com/db-starter-alternator/items/item.aspx?itemid=333544

The only trick would be creating a mechanical system that would allow you to engage this when braking is needed and keep it from adding any load during normal operation.

Am I missing something here?


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## Qer (May 7, 2008)

Hm. That's a pretty nifty idea and also easy to retro-fit afterwards if you have a double shaft motor to begin with. If you connect the generator directly to the shaft the additional load shouldn't be noticeable but being able to do regenerative breaking will add range.

The question is of course how much extra range you'll get. Probably not very much, I'm afraid. For AC-systems I've heard numbers up to 10% extra, so probably not more than that. It's probably not worth the extra cost...


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## Rod Fitzsimmons Frey (Jun 12, 2008)

Wiredsim said:


> The only trick would be creating a mechanical system that would allow you to engage this when braking is needed and keep it from adding any load during normal operation.


Shouldn't need a mechanical system - if the alternator isn't energized then the only load you're adding is the bearing losses of the generator. Not nothing, to be sure, but not huge either.

Rod


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## Guest (Jul 4, 2008)

The extra motor for regen is not going to pose any problem what so ever when it is not under power. It is just along for the ride and yes you do get some bearing friction but that's all. With the size and weight of the vehicle in the post there would be no problem. Depending upon where you live and what kind of driving you do regen will help either alot or a little. It is best for city stop and go driving and least for long distance hwy driving. However I'd suspect that they are not just trying to gain back some extra into the batteries but more using the motor as a brake. The vehicle is very heavy and needs all the braking power it can get. For safety reasons it is a damn good idea. If that is all it's used for and to get a bit back for the batteries then it's worth the effort and expense.

Pete : )


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## Bowser330 (Jun 15, 2008)

Excellent responses thanks, all make sense..

I like what gottdi said... stop n go would benefit more..and the heavier the better...or i guess for the heavy vehicles its a double benefit, haha..

I guess it would be reccomended to have this on all of those 4000 pound s-10 conversions..


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## major (Apr 4, 2008)

Bowser330 said:


> This University EV team used a double shaft DC motor and mounted a generator to one side...
> 
> http://www.evalbum.com/837
> ?


Hey Bowser and all,

Anyone else have trouble with the claims on this album page?

400 HP
140 MPH
0 - 60 in less than 10 seconds
97 MPH in the 1/4 mile

??????????

Show me the timeslip!

Regards,

major


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## Guest (Jul 7, 2008)

400 HP: Show the Dyno Print out.
140 MPH: Show speed trap printout.
0-60 in under 10 sec. Possible. (under 10 sec means 9.9999 sec.
97 MPH in the 1/4 mile. Maybe. Time slip would be nice. 

It's just plain smart to show proof if you boast specific. I think the least possible is 400 HP with that motor and pack of batteries. 

Pete : )


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## Bottomfeeder (Jun 13, 2008)

Why would you trust a picture of the results if you don't trust the person boasting anyway? It's easy to fake numbers on a page. I don't blame them for not trying to "prove" their claims. Some people just won't be happy with the proof unless they see the car in action themselves. If you don't believe the boasting, then just don't believe it. I don't see how it matters either way.


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## Guest (Jul 7, 2008)

It matters because if it is not true then they are liars and that is bad all the way around. If you boast (which any one can do) then you need to back it up. Boasting is fine if you earned the right to boast. All we want to see is the proof. Anyone can claim anything and with all the bull going on about EV's these days you'd better be prepared to prove your claim. If you balk at proving your claim I and many others will assume its just hot air and nothing but bull. Proof is in the pudding and we want the pudding.


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## Guest (Jul 7, 2008)

If it were a company selling you an ev you'd expect proof. You would not buy with out it. These guys are testing a concept (to sell later as most eventually do) and they need to prove it. Not just in words but in real life action. You can't sell with out proof and if some dolt does buy with out the proof then they get what they paid for, highwaters!

Pete : )


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## Bottomfeeder (Jun 13, 2008)

Any production model vehicle will surely require more proof, usually through independent analysis (Car and Driver, etc). But for a one-off car made by a university club? They have little to gain from proving themselves to people on the internet. It looks like they prefer to compete in races and such. I'm sure they're willing to walk the walk for any companies which may want to develop their ideas. I just don't see why they should bother proving their stats to you and me. I mean, so what if I don't believe them?


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## Bowser330 (Jun 15, 2008)

This post was not created to discuss what is requried to prove numbers...

Lets go back to the topic and see what you two think about mounting generator to the 2nd driveshaft coming out of the motor (of a double shafted motor of course)...

Do you think it would hurt the DC motor to me "forced" to slow down?


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## Bouche (Jul 9, 2008)

Browser330 I agree, I'd also like more information on “DC Regen” possibilities from some of the other more knowledgeable guys on this forum.

I’ve read the endless post (sticky) relating to Alternators and Free Energy, and fully understand that you can’t get more out of it than you put into it. I also understand that regenerative braking is fairly easy to accomplish with AC system. What I haven’t seen covered here, and maybe I’ve missed it, is a decent discussion about DC regen.

It seems like the concept of a simple piggyback Alt/Gen that kicks-in during coasting or braking could provide some additional range (any additional range is better than none).

I have two question/comments:

1. What are the challenges of using (if possible) the controller to switch the drive DC motor to regen mode when braking.

2. What are the challenges of using a piggyback Alt/Gen driven by the DC motor drive shaft when coasting or braking? My thoughts are that mounting a 12v electromagnetic clutch to the shaft of the drive motor could work. This clutch would drive the Alt/Gen and switched on/off by activation of the brake or deactivation of the throttle creating a regenerative braking or coasting effect.


Please comment.


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## Guest (Jul 9, 2008)

Any motor can be used for regen. However the plain series motor has a problem with arching when used in regen mode and if the motor has advanced brushes then the arching problem is enhanced. If you happen to have a series motor with interpoles you can use that easier with regen (less arching) and be successful. I am using a military starter/generator with interpoles and it is a shunt wound motor. It will be used with regen on my VW. You'd be best off talking with Jim Husted. He is the motor master. Yes a good sticky on the ins and outs of series motors used with regen and the resulting issues. I have a large 11" Kostov series motor with interpoles that will work find with regen as long as I don't advance the motor too much if at all.


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## major (Apr 4, 2008)

Bouche said:


> 1. What are the challenges of using (if possible) the controller to switch the drive DC motor to regen mode when braking.
> 
> 2. What are the challenges of using a piggyback Alt/Gen driven by the DC motor drive shaft when coasting or braking? My thoughts are that mounting a 12v electromagnetic clutch to the shaft of the drive motor could work. This clutch would drive the Alt/Gen and switched on/off by activation of the brake or deactivation of the throttle creating a regenerative braking or coasting effect.
> 
> Please comment.


Hey Bouche,

1. Separately excited DC will regenerate fairly easily. Controllers are available to do this in versions below 72 or maybe 84 volts. Higher voltage off-the-shelf SepEx controllers are hard to find. You may be able to build such a thing.

Series wound DC motors are a real bitch to get to regenerate reliably. If you want to see what it takes, search out work that Otmar did. Maybe there is a link on his cafeelectric website. It was so much trouble that even he does not offer regen on his Zilla controllers. It can be done, but I doubt you would be happy with the result. I had the regen feature on my old E-Jeep, SCR controller with interpole series motor. Sometimes it would do nothing, sometimes it would lock the rears. Just not worth the trouble. I disabled it.

Brings up another point. To use DC motor for higher voltage systems on cars, often the brushes are advanced to reduce arcing. This works out pretty well. But a generator needs the brush shift in the opposite direction. So when you regen with an advanced motor, you see terrible arcing. Hence the use of interpoles in motors bound for regen or reversing applications.

2. Because all motors can regenerate, if properly excited, I always thought it was stupid to add a second electric machine for regeneration. Just figure out how to do it with the motor. But if you can't figure that out, then consider your objective. That was to increase the range, right? Well, I'd bet that by the time you add a second machine and clutch and controls, you would be better off using that weight in additional battery when it comes to increase of range.

Batteries, especially Pb-acid, don't like the high charge rates one would see from effective regeneration. Yeah, it does work, but you are limited to the rise in voltage, so have to reduce regen torque or cut it out as the battery voltage hits the limit. And the amount of energy put into the Pb-acid battery that quickly vs the amount you are able to get back out sucks. Called the round trip efficiency. All in all, if you make a lot of stops, you might see maybe 5 percent range increase. More likely just a couple of percent. Don't get your hopes up. Like I said, for range, another battery or two will do better.

With that said, I love regen. I have driven a number of regen capable EVs. They had AC drives. Regen works great. Even with Pb-acid. A whole lot better with ultracapacitors. But that's a different story.

Now back to the addition of an alternator for regen with a DC motor. Sure, go ahead and try it if you want. It will be a lot of work for little or no gain. But it is your project. I don't see the need for a clutch. An unexcited alternator should present little drag to the system. There will be additional inertia to accelerate the alternator's rotor, but you'll have that anyway if you want to use it to slow the vehicle. Other that that, the bearings and brushes in the alternator are probably less drag than the clutch would be.

And another thing. Realize that it typically takes greater power to stop the vehicle than to accelerate it. This is because stopping distance is usually less. So, if you have a motor capable of, let's say, 80 hp for acceleration, then a 10 kW alternator (which is a big one) isn't going to stop you quickly.

Anyway, go for it. Just giving you a few insights from a guy who has experience with regeneration.

major


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## Bouche (Jul 9, 2008)

Thank you Major!

Great explanation and break-down of DC regen. Just the kind of feedback I was looking for.

Good point about the separate motor for regen having the same effect as just adding a battery or two.

There seems to be a lot of hurdles to clear for not much payoff.

Bouche


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## Guest (Jul 9, 2008)

Once AC motors are as common as DC for DIY conversions then regen has limited payoff. However if you want DC regen you're best off thinking in the mode of saving brakes and extra measure of safety for stopping your lead sled. Granted changing your brakes to disk is going to be easier but having regen braking is going to save you from replacing brakes. It will help stop the heavy vehicle and if you do lots of stop and go you can get up to about 10 to 20% back from regen. All combined it is still a good thing but only do regen with a motor that can do regen. Most standard series motors are a very poor choice due to the problems mentioned in the previous posts. Get a series with interpoles and you can do regen or get a SepEx motor with interpoles and a good SepEx controller for the motor. Set it up for regen. My controller will limit the power for regen to protect the controller. Protect the controller and protect the motor. 

: )


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## Hi Torque Electric (Dec 23, 2007)

Hey all

I’m coming into this thread a bit late but I’m with Major on this, in that there’s no way they’re making 400 HP. At 160 volts they’re accounting for zero battery sag for one, and they’re math assumes 100% efficiency for all components (160X1800=288000 watts) where using the 1000 watt to HP rule (not 746 because there are losses) I’d care to guess they’re making less than 288 HP.

In fact in talking with John Wayland the other day he estimated that White Zombie’s making somewhere between 250 to 300 HP using twin 8’s, 360 volts, and a 2K Zilla. In general, I feel it’s better to be conservative when stating numbers as we (as a group) need to make sure the info being stated is as correct as possible (specially when estimating) so mis-information is not spread around.

Just my two HP worth
Jim Husted
Hi-Torque Electric


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## Bouche (Jul 9, 2008)

Hey Guys,

This is the idea I was talking about.

http://www.northrim.net/wyanders/ev/

It was just posted on the forum.

http://www.diyelectriccar.com/forums/showthread.php/interesting-dc-regen-idea-17078.html

What are the pro's and con's to this?


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