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.

 

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.

 

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.

 

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

 

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

 

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/

 

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

 

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...

 

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.

 

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.

 

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

 

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.

 

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.

 

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.

 

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.

 

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.

 

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)

 

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)

Judging by the amount of speed bumps around my area, I think I would blow by batteries due to over charging!

 

Next time you drive your vehicle, feel your shocks when you stop. Unless something is wrong or you're racing off road they should barely be warm, which means very little energy to be recovered.

 

Hi. I'm going with Qer's comment on alternator inefficiencies. I had been thinking of using one instead of DC/DC converter but after running the efficiency numbers plus adding the mechanical losses, it just didn't make sense.

As for using an alternator as a regen medium and expect it to brake the car, I'm not sure the tiny belt driven alternator will be able to stop it much and one 12V battery won't be able to absorb much energy from that either to make an impact.

JR

 

Hi. I'm going with Qer's comment on alternator inefficiencies. I had been thinking of using one instead of DC/DC converter but after running the efficiency numbers plus adding the mechanical losses, it just didn't make sense.

As for using an alternator as a regen medium and expect it to brake the car, I'm not sure the tiny belt driven alternator will be able to stop it much and one 12V battery won't be able to absorb much energy from that either to make an impact.
JR

For sure a DC/DC is the way to go!

As for the alternator used for regen/braking idea...ya, a normal alternator feeding a 12 volt battery is a waste of time. . . however, a re-wired large truck alternator outputting something over pack voltage can actually brake your vehicle..

 

however, a re-wired large truck alternator outputting something over pack voltage can actually brake your vehicle..

Good point. I'm not sure the expense of buying, modifying and adapting a truck alternator is worth the ROI just to get some regen and braking. Further, a belt-driven alternator capable of stopping your car is not something you want to hang on your expensive motor shaft. And assuming the motor shaft can take the lateral forces with those two bearings so far apart, the entire momentum of the car would lean on a belt. That better be one mighty belt if there's any hope of using it as a dependable braking system. If the alternator could be coupled inline with the motor shaft, that would be a different story.

JR

 

I don't think the people who have done it had problems with bearing loads or belts, but it's also not a huge amount of power.

 

I'm wondering why the shocks have to get hot to show they are producing energy? If they are well designed and good at the job, there is no reason why they would get even warm. This doesn't mean they are not doing any work or not moving enough.

Stick a video camera under your car and take it for a short run. I think you will be amazed at how much work the suspension actually does, even on a seemingly smooth road. Maybe there is some possibilities here, but I think it would be a nightmare to set up.

On the subject of attaching an alternator to charge the aux battery...

This is something I am going to do. The alternator would be direct drive from the motor and as you all know, when an alternator is not energised, it takes virtually nothing to drive. This is why mine will only be energised when I release the accelerator.

When you work out how much energy will be taken from the aux battery during normal driving, there is no reason why at least some of it would not be replaced this way.

I'm not hoping to have a "self sufficient" aux battery and I know it will need to be charged along with my pack, but I'm sure it will not take much to top it up.

 

I'm wondering why the shocks have to get hot to show they are producing energy? If they are well designed and good at the job, there is no reason why they would get even warm. This doesn't mean they are not doing any work or not moving enough.

Actually it does. If they are absorbing any significant energy it has to show up as heat. The fact that a 2inch diameter by 1-2ft long tube of oil doesn't get warm in normal use tells you there is very little energy available.
Bose has an active electronic suspension that generates some energy to help with the active dampening but nothing extra. Unless it's a real off road vehicle I don't think you'll see anything worthwhile.

 

What long strokes? Your normal suspension travel on normal roads is less than a two inch throw. If shock absorbers don't dissipate energy as heat please tell me where that energy goes?

 

What long strokes? Your normal suspension travel on normal roads is less than a two inch throw. If shock absorbers don't dissipate energy as heat please tell me where that energy goes?

Explanation from Wikipedia
The shock absorber's duty is to absorb or dissipate energy. One design consideration, when designing or choosing a shock absorber, is where that energy will go. In most dashpots, energy is converted to heat inside the viscous fluid. In hydraulic cylinders, the hydraulic fluid will heat up, while in air cylinders, the hot air is usually exhausted to the atmosphere. In other types of dashpots, such as electromagnetic types, the dissipated energy can be stored and used later. In general terms, shock absorbers help cushion vehicles on uneven roads.

So you are correct. The energy is turned into heat. this still does not alter the fact that it is possible to exaggerate the suspension movement and use it. Just because it's not going to be easy, does not mean it's not possible.

Something else:
New Shock Absorber Harvests Energy From Bumps In The Road, Increases Fuel Economy

Senior Shakeel Avadhany and his teammates say they can produce up to a 10 percent improvement in overall vehicle fuel efficiency by using the regenerative shock absorbers.

The project came about because "we wanted to figure out where energy is being wasted in a vehicle," senior Zack Anderson explains. Some hybrid cars already do a good job of recovering the energy from braking, so the team looked elsewhere, and quickly homed in on the suspension.
They began by renting a variety of different car models, outfitting the suspension with sensors to determine the energy potential, and driving around with a laptop computer recording the sensor data. Their tests showed "a significant amount of energy" was being wasted in conventional suspension systems, Anderson says, "especially for heavy vehicles."

The full article here:
http://www.sciencedaily.com/releases/2009/02/090212181904.htm

 

I always thought it took a considerable amount of energy dissipation to absorb a pothole or bump. But if, as a prev poster commented, Bose only needs about 3 HP to keep the car suspended, it certainly won't give back much in terms of regen.

Something in the back of my mind is telling me that the dynamic forces created by a 1.5 ton vehicle is way more than what 3 HP can dish out to keep the car suspended. But I haven't looked into that at all so I'll accept it for now.

JR

 

Ok let's play with this a bit. Let's say you have a setup with a pivot point such that if the wheel travels 2 inches the shock on the other side of the pivot travels 4 inches. Yes it's traveling a longer distance, but the leverage difference means that it's producing half the force, so the net energy is exactly the same. There is no extra energy to recover.

 

Ok let's play with this a bit. Let's say you have a setup with a pivot point such that if the wheel travels 2 inches the shock on the other side of the pivot travels 4 inches. Yes it's traveling a longer distance, but the leverage difference means that it's producing half the force, so the net energy is exactly the same. There is no extra energy to recover.

Ok... Let's play if you want.

So we have a lever setup, producing 4 inches of movement, but it's only developing half the force. Half the force of what? In my mind, it's producing half the force of quarter the weight of the car.

So... If we have a 1 ton, perfectly balanced car, this is about an eighth of a ton. No energy you say? How much energy do we need to generate a bit of battery juice?

 

Did I not say half of the quarter weight of the car? Maybe I said an eighth of a ton later? Maybe I should speak slower? Maybe I'm just confusing to listen to?

What's the vector Victor?

Ok.... Silliness aside. Yes, there will be more losses than my simple explanation allows for, but I was simply making the point that there is a lot of enegy tied up in the weight of a car. Energy that could be used if someone was smart enough to figure it out and make it happen. Should it be half, quarter, eighth, tenth or 0.002%

 

You're jumping around and missing the point. I say there is little energy to be recovered, which is evidenced by the fact that in normal driving your shocks don't get very warm. You claimed that using a lever to increase the length of motion would somehow increase the potential energy that could be recovered. This is of course false and I'm trying to get you to see that.