[rillip3]

I'm not a fan of regen personally, but I got to thinking about this the other day and couldn't figure out a reason why it wouldn't work.

Take your average DC series wound driven EV, but ensure it has a dual-shaft motor. One shaft goes to the transmission as usual, the other goes to an AC motor. While driving, the AC motor is not electrically connected to anything, so there's no load on it as a generator. You've got some efficiency losses due to weight and friction/heat but not much.

When breaking, connect the AC motor to a charger that charges the batteries. Now there is a load on the motor, and it should slow the DC motor. This doesn't seem that complicated to engineer, except possibly space limitations. Is there a good reason this would not work?

 

[Coulomb]

When braking, connect the AC motor to a charger that charges the batteries. Now there is a load on the motor, and it should slow the DC motor. This doesn't seem that complicated to engineer, except possibly space limitations. Is there a good reason this would not work?

None at all. The problem is that you need the extra weight and expense of a second motor, and at least a crude controller of some sort for it. You can't just connect the AC motor to the pack.

You're better off keeping the AC motor, swapping your DC controller for an AC one, and tossing the DC motor. Now you have regen, and no extra weight or space! However, the AC controller is more expensive.

In summary: the AC motor would need to be almost as big as your main DC motor. It would need a controller that is likely more expensive than your existing DC controller. All that extra cost and weight, all for between 5 and 20% extra range, less the extra losses. It just doesn't add up economically.

 

[vpoppv]

I think someone had a similar post that was intriguing. On the second shaft, you attach a regular car alternator that was "somehow" wired to the brake pedal. It could only recharge your auxiliary battery, but it seems like an interesting idea as a simpler way to improve the operation of your brakes similar to regen. Lot of hassle for little work, but intriguing.

 

[Coulomb]

On the second shaft, you attach a regular car alternator that was "somehow" wired to the brake pedal.

Yes, that's pretty easy. Arrange for the field to come on with the brake pedal, and perhaps even make it progressive (more brake, more field, hence more regen current, hence more regen torque). The alternator output can be attached directly to your 12 V battery, reducing the load on the main DC/DC and thereby extending range a little. It's even possible to rewind the alternator to work at pack voltage, and charge the pack directly.

This is a quite low cost route, but also quite low result. A large car alternator is capable of perhaps 1 kW, two if it's huge and/or you increase its power somehow. But they are not designed for efficiency, and a single kilowatt of regen is about half to one order of magnitude less than what you'd want for decent regen.

 

[anand.ssukhi]

a realy nice idea
but why not use the dc motor directly for the regen
use a sepex controller most of them come with an analog input for braking and the rest is done by the controller no extra wiring or anything required

 

[pm_dawn]

For that to work you would NOT need a specific hi-power controller.
It would only take a controller for the field of the altenator.
Then just use a rectifying bridge to output energi to the batterypack as DC. That is how car altenators work and there are people that use Truck altenators(24v) but just alter the field control and change the rectifier and use them as generators that give above 100v.

/Per

 

[DIYguy]

Yes, this works... but you can just use an electric clutch on the front of the DC motor, engage it (few different ways) to drive a rewired alternator to charge entire pack. This way, there is no load on the drive motor under normal driving. Of course it's more for braking than charging...but you do get some energy back.

Check the regen link on this page. I mounted the electric clutch on my motor...but haven't finished the other stuff yet.... pretty kewl.

http://www.waynesev.com/

 

[SimonRafferty]

Although this would work OK - it just seems a bit over complicated when it's perfectly possible to make a series wound motor behave as a generator. It just happens that most series controllers don't include regen because it makes them cheaper.

A controller for PM DC, Brushless DC or AC does not need to be any more complex to allow regen - so it's generally included as standard.

You say you are not a fan of regen braking? Why's that? I have it and use it - and think it's pretty good! It only increases my range by 15% - but that's still a 15% cost saving.

Si

 

[DIYguy]

Although this would work OK - it just seems a bit over complicated when it's perfectly possible to make a series wound motor behave as a generator. It just happens that most series controllers don't include regen because it makes them cheaper.

Si

Well, it is bit tricky... especially when most folks are running advanced brush timing for higher voltage. You would need to have variable brush timing and push it back to 0 degrees each time..... and then there is the controller issue.... yes.. I'm not sure that it is just a price issue...

 

[JRP3]

If you are going to have an AC motor in the vehicle along with your DC motor you might as well use it as an additional drive. I had the idea of using both motors together for added power and then the AC motor gives you regen. Probably not worth the cost and complexity but the low end torque of the DC motor gives you good power off the line and the longer torque curve of the AC motor gives you more torque at higher RPM's. You'd have to gear them differently so the AC motor didn't over speed the DC motor. I imagined a HPEVS AC 20 over a Warp9 as a nice combo, but you'd be limited to 120 volts.

 

[JRP3]

Although this would work OK - it just seems a bit over complicated when it's perfectly possible to make a series wound motor behave as a generator. It just happens that most series controllers don't include regen because it makes them cheaper.

As Zapi found out it also makes them blow up sometimes. Regen on an advanced timing motor doesn't work, and most series DC motors that we use are advanced.

 

[rillip3]

Thanks for the thoughts guys, I was just curious if there was some reason it wouldn't work. I can see now that it would be more complicated than just setting up an AC setup in the first place.

 

[DawidvC]

A good way to go about this can give you the best of both worlds, but be careful: Use a series motor for rear wheel drive (be careful not to overspeed the motor) and use an AC motor for the front wheels. This give you the serie-motor advantage on pulling away, as well as good regen for stopping.

Dis I mention you need a 4wheel drive chassis ?

Dawid

 

[Qer]

As Zapi found out it also makes them blow up sometimes.

Well, Kelly, LS etc has showed that it's possible to blow up a controller even without doing regen, so I wouldn't take Zapis problems as proof. Running regen on series wound motors is tricky, but quite possible. The big problem is that you need to have a very well written algoritm that can handle the exponential current increase, but if you manage to tame that beast it'll be all peachy.

Regen on an advanced timing motor doesn't work, and most series DC motors that we use are advanced.

That's, however, a much bigger problem. The motor MUST be neutrally timed, otherwise it'll blow up. Another problem is that you need a contactor to shift the field and when you count in that regen doesn't do that much of a different it isn't really worth it anymore.

So it's technically possible to do it, but practically speaking it's too cumbersome. Complicated software, expensive contactors, few that would use the feature, major risk of fuck-ups etc... That's why we gave the whole thing up.

 

[RupertWild]

Main trouble is efficiency, I've been hearing 3% which, even though I'm doing regen, a whole seperate regen pedal in fact (not unlike the electricIMP), doesn't impress me much.

 

[JRP3]

It really depends on your driving conditions. If you have long steep hills where you would otherwise have to use your brakes to hold speed or slow down you'll get a lot more from regen than if you do mostly steady state on the flat.

 

[anand.ssukhi]

i wud suggest set ur priorities fisrt among regen and torque.
if regen then go for a sepex motor/controller it wud give less torque but really gud and reliable regen
u can use gear to get the torque

and if torque then u can rely on series motor for that and use the ac motor for regen.

 

[ThWongs]

I'm in the planning process of my car at the moment and my plans always consist of an alternator driven from the main motor (hopefully directly, depending on space). The object of this excercise is to charge the aux battery only and it will be energized by releasing the throttle as opposed to pressing the brake.

The way I see it is this: If you energise while braking, the brakes are wasting some of the energy i.e. you are slowing the car (and alternator) with the brake pedal. Have you noticed while driving how many times you release the throttle without hitting the brakes? Coasting to traffic lights, downhill ect rarely need brakes. Seems to me that this is the right time for some regen...

I'm also going to keep the clutch in my car, so would have the added advantage of shifting down gears to keep the alternator spinning at a decent rate. I'm also hoping the alternator will give me a sort of "engine braking" feel. (Besides... I don't like clutchless changing. Done it tooooo many times)!

Maybe I'm wrong in some of my thinking? After all... I'm VERY new to this.

 

[Qer]

There's a few problems with that scenario.

1. You will only charge the battery when you're slowing down. That will probably not be enough to avoid it to be drained.
2. Your 12 Volt will jump between 11.something to 13.something which might cause, ehrm, undesired side effects to put it mildly.
3. An alternator is very inefficient.
4. You'll save peanuts compared to the power your motor needs to propel the car. Your motor will chew several kW and your alternator will provide some hundred Watts.
5. Running the 12 Volt on DC/DC directly from the pack might actually turn out being a win-win-situation since you won't have the additional friction from the alternator.

Generally speaking, trying to save Watts on the 12 Volt side (this includes replacing the lamps with LED etc) is not efficient. You're better off trying to decrease friction in brakes, in the gear box, by inflating the tires harder etc.

 

[few2many]

Car alternators are pretty small and light, why not throw one on both rear wheels, both front or all four wheels?
I'm still curious to see how a shock absorber with huge coils and neo magnets would work for a range extender.(wouldnt really call it regen)