# Generators Discussion. Including Regen. Braking



## mattW (Sep 14, 2007)

Q1. The statement is reasonably accurate except i would add that the motor is simply in reverse polarity, not actually running in the opposite direction, so basically you are swapping the red and the black wires to the motor. The major difference between a motor and a generator (generally speaking) is whether energy is coming in or out. NB there are some exceptions eg. DC series motors which have no permanent magnets.

Q2. Sure you could wire up an alternator to the drive shaft, to switch on electrically when the brakes were applied, to charge your accessory battery (that was a very long sentence ). But it is a lot of work for a minimal gain.

Q3. A simple motor works by the idea that when current passes through a wire in a magnetic field a force is applied to the wire perpendicular to the current making the wire move (or more likely several loops of wire turn). Luckily the reverse is true, A wire moving through a magnetic field will apply a force on the electrons in the wire making current flow (in the opposite direction to the above situation). It gets a bit more complicated explaining AC and DC but if you hook the same motor/generator up to batteries and allow the current to flow one way you will get it as a motor and if you want to slow down you can allow the current to flow back into the batteries to charge them (the motor will be running in the same direction but the current won't be).

Q4. Generators just transfer mechanical energy (motion) into electrical energy, if you are generating power you are slowing down or drawing more power from the motor so while regen braking is possible, perpetual power generation while coasting is not. You could use small permanent magnet DC motors, car alternators or AC motors with inverters for your regen but it is a pretty complicated thing for a DIY project and gives a pretty small energy return for the time/effort/space.

Hope that helps!


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## WCRiot (Nov 25, 2007)

mattW said:


> Q4. Generators just transfer mechanical energy (motion) into electrical energy, if you are generating power you are slowing down or drawing more power from the motor so while regen braking is possible, perpetual power generation while coasting is not. You could use small permanent magnet DC motors, car alternators or AC motors with inverters for your regen but it is a pretty complicated thing for a DIY project and gives a pretty small energy return for the time/effort/space.
> 
> Hope that helps!


In regards to the quoted question. What would make a better generator? the dc motor?
car alternator?
or ac motor?

How can i find more info on this?
I want to know if spinning the generator faster would generate more power or spinning a motor that is larger "more drag".

How can i identify a permanent magnetic dc motor? I have some small dc motors that are used for hobby stuff. Basically would power a handheld fan or soemthing along those lines. I want to test and see how much power i can store from these applied to a go kart wheel under braking.


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## mattW (Sep 14, 2007)

If you use an AC motor you will need an inverter, an alternator is made to charge 12V batteries so i would guess it would be the most suitable but rather small in output and effect (you could perhaps look for larger vehicle ones?). I'm not sure how you work out what voltage and current from a DC motor, allo i know is that without a regulator the voltage will increase with RPM which is why i think the alternator is your best bet. I'm just making the best guesses i can here from my very general high school physics. Hope someone smarter can chime in!


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## CPLTECH (Sep 14, 2007)

“Q4: Is there a small generator that could be added to each wheel to activate under braking only? Let's even ignore the generator acting ONLY during breaking and find a generator that can be used to generate power at any time.”

Let me try to explain to those who never had the joy of driving a car with the “old style” carburetor vs. the computer controlled type that maintains a given RPM at idle no matter what the electrical load. If just idling and the headlights (~5A x 12V=60W x 2 lamps=120Watt load or just 1 amp of a 120V EV system) were activated, the big block V8 engine WOULD slow down. So the mechanic had to set the idle adjustment screw high enough that the motor would not stall at high electrical loads. I had the privilege of experiencing those old days and knowing that a generator slows down/gets HARD to turn as loads increase. If my EV needs 100A or more to push it down the road and a big V8 bogs down with an equivalent of a 1A load, can you see that using a generator on an EV is senseless unless used only for braking. IF a generator spins freely & provides all the amps needed, why does my local utility burn so much coal? It takes a lot of POWER to make electricity.

“How can I identify a permanent magnetic dc motor? I have some small dc motors that are used for hobby stuff.”

When you turn the shaft of a perm magnet motor, it is not smooth. The rotor wants to stop where it is attracted to a magnet. Therefore it does not want to stay where put & will settle either before or after that spot. A few AC motors have PM’s, too.


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## WCRiot (Nov 25, 2007)

CPLTECH said:


> “Q4: Is there a small generator that could be added to each wheel to activate under braking only? Let's even ignore the generator acting ONLY during breaking and find a generator that can be used to generate power at any time.”
> 
> Let me try to explain to those who never had the joy of driving a car with the “old style” carburetor vs. the computer controlled type that maintains a given RPM at idle no matter what the electrical load. If just idling and the headlights (~5A x 12V=60W x 2 lamps=120Watt load or just 1 amp of a 120V EV system) were activated, the big block V8 engine WOULD slow down. So the mechanic had to set the idle adjustment screw high enough that the motor would not stall at high electrical loads. I had the privilege of experiencing those old days and knowing that a generator slows down/gets HARD to turn as loads increase. If my EV needs 100A or more to push it down the road and a big V8 bogs down with an equivalent of a 1A load, can you see that using a generator on an EV is senseless unless used only for braking. IF a generator spins freely & provides all the amps needed, why does my local utility burn so much coal? It takes a lot of POWER to make electricity.
> 
> ...


DAMN, my last post was lost.

I want to have my generator ONLY engage when the brake pedal is pushed. I am not trying to have a generator constantly run while the vehicle is being driven.

CPLTECH: You said that as rpm increase the voltage produced by the generator is increased, correct?

I dont want to charge an entire 120V system. I only want to charge a set of capacitors to intially hold the charge until the brakes are released. Then to either use this energy to charge a seperate battery which would be powering the accessories on an EV or to be used my the E itself to commense acceleration.


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## CPLTECH (Sep 14, 2007)

_“__CPLTECH: You said that as rpm increase the voltage produced by the generator is increased, correct?

I don’t want to charge an entire 120V system. I only want to charge a set of capacitors to initially hold the charge until the brakes are released. Then to either use this energy to charge a separate battery which would be powering the accessories on an EV or to be used my the E itself to commence acceleration.”_

I didn’t say it, but generators need a certain RPM for rated voltage/amperage, from the specs I’ve seen. Have not researched that aspect. And on the cars that had amp gauges instead of idiot lights, the more RPM’s, the higher the needle would climb.
*NorthernTool* dot com has had generator heads (attach to your motor) in 120 & 240V versions. No need to limit yourself to a car type (Ex: 100A x 12V = 1.2KW)

I know everyone wants all the bells & whistles, but for me, I want cheap transportation and possible immunity from long gas lines (remember Arab embargo of 70’s?). But from what the experiences of others tell me is that regen is nice but as a rule does not pay for itself, LA batts are cheap but heavy, solar charging at 20KWH a 30 mi trip is not an option for me, etc. What I am trying to say is: Keep It Simple. You will be the mechanic when it breaks. From my prospective, get it on the road, make minor mods, have fun at the least expense. Don’t try to re-invent the wheel. If you don’t, your EV will exceed the ownership cost of a new ICE.

Sorry for the rant, but my experience has been just 3K miles in 9 months in a heavy 94S10, 120V, 9” Advanced motor. I keep close track of expenses. So far, charging runs $0.07 per mile. IF I can get 22K miles out of the US 145 batts, add another $0.10 per mile. If not careful, the vehicle is no longer saving some $$$ (green).


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## Twilly (Jan 22, 2008)

WCRiot said:


> DAMN, my last post was lost.
> 
> I want to have my generator ONLY engage when the brake pedal is pushed. I am not trying to have a generator constantly run while the vehicle is being driven.
> 
> ...



You need a load on the generator to produse drag, more load = more drag.... Caps will charge up in about a second, then your load is gone... You would need to charge the pack to get enough load to do any good... also, your drag would be less at the beginning of the trip and more at the end of your trip based on the pack voltage (ie amount of charge needed)


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## WCRiot (Nov 25, 2007)

Twilly said:


> You need a load on the generator to produse drag, more load = more drag.... Caps will charge up in about a second, then your load is gone... You would need to charge the pack to get enough load to do any good... also, your drag would be less at the beginning of the trip and more at the end of your trip based on the pack voltage (ie amount of charge needed)


Maybe I am not being clear as to what i am trying to do. Ill make a half @$$ed drawing to demonstrate the item i am referring to. The drag I am referring to will be because of a mechanical device which produces the drag. the drag will always be there even if the capacitors are charged.

Im just exploring the concept, but I will have a realistic demo pretty soon.


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## Testit and u shall know (Jan 27, 2008)

www.theverylastpageoftheinternet.com/ 6) Electromatic Motor Car.
200> miles per charge in 1976.


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## WCRiot (Nov 25, 2007)

Testit and u shall know said:


> www.theverylastpageoftheinternet.com/ 6) Electromatic Motor Car.
> 200> miles per charge in 1976.


I dont see anything on here about an EV. just a poor webpage


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## Testit and u shall know (Jan 27, 2008)

The range between charging as far as I know is around 200 to 500 miles.


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## Coley (Jul 26, 2007)

Testit and u shall know said:


> www.theverylastpageoftheinternet.com/ 6) Electromatic Motor Car.
> 200> miles per charge in 1976.



Ha ha ha that article is good for a laugh and written by a school kid.
Yawn


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## Testit and u shall know (Jan 27, 2008)

It's quite ironic that the sceptics have already made their minds up that the impossibilities far out way the possibilities.
It sounds like when they wake up in the morning they have very little to look forward to apart from making fun of the very inventors who invented the technology in their EV's. If you settle for limited milage then you'll always fall short.

Coley
When you run out of power in your EV you can always wave down that school kid who drives the EV with unlimited milage to tow you back home.
Yawn, you can have a little nap while he tows you back home for your recharge.


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## mjones (Jan 19, 2008)

I'm uplate reading and having thoughts/ideas on this subject. I know there are lots of the PM treadmill motors out there on the market that folks are trying to sell as wind generators. They don't work well because the rated rpm is too high to acheive from a wind turbine. They will however produce over 50v when spun fast enough as they are rated from 90v-120v. If one of these were coupled to the drive axle, assuming FWD, and sped up via a belt/pulley, just rolling would generate electricity. The output could be diode coupled to the batteries so that current would only flow into the battery when it reached .7v greater than the battery voltage. A relay, setup to "hold" that would be activated by the brake light switch would make the final connection and maintain that connection until max float was reached. A simple zener diode overvoltage relay circuit could remove current to the first relay and drop it out thus eliminating overcharge. If you tapped the brake when descending a hill it would begin generating, as you slowed down the output of the PM Motor would decrease to the point that the 1st realy would drop out. It would only apply drag/load when braking or after setting it "ON" with the brake and coasting. It wouldn't stop the car and probably wouldn't do much to charge the batteries though it might make up some of the losses for the lights/accessories. This could also be done with a car alternator instead of a PM Motor but that would only charge a single 12v battery.

Other sources for PM Motors - Electric weedeaters and edgers which can be picked up at yard sales and thrift stores for a few $s.


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