# Alternators As Range Extenders



## deanbo (Jun 7, 2010)

Could a high output alternator help extend the range of an EV by putting some charge back into the batteries while driving? Or could it be used to help supply some of the power needed to run the motor instead?


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## Qer (May 7, 2008)

deanbo said:


> Could a high output alternator help extend the range of an EV by putting some charge back into the batteries while driving? Or could it be used to help supply some of the power needed to run the motor instead?


No and no.

http://en.wikipedia.org/wiki/Perpetual_motion


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## Gavin1977 (Sep 2, 2008)

If you are going to use an engine to drive the alternator, then yes it will extend the range. It is also known as a series hybrid. Whether its worth it or not is a different question.

If you're thinking of driving it off your electric motor, then as Qer said.


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## Sunking (Aug 10, 2009)

Gavin1977 said:


> If you are going to use an engine to drive the alternator, then yes it will extend the range. It is also known as a series hybrid. Whether its worth it or not is a different question.
> 
> If you're thinking of driving it off your electric motor, then as Qer said.


Ditto. Can be done with an auxiliary ICE, but if driving it from the electric motor drive train would result in less range. Otherwise you are talking about perpetual motion machine having greater then unity gain. 

By the way I can sell you a book that will instruct you to run your car off water. It cost $99 and will pay for itself in a week and you will never have to buy gasoline again.


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## TX_Dj (Jul 25, 2008)

No such thing as a free ride.

If you take an alternator that is 85% efficient, you would expend more than 25% more energy than what you get out of it just to turn it.

http://en.wikipedia.org/wiki/Conservation_of_energy


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## deanbo (Jun 7, 2010)

Gavin1977 said:


> If you are going to use an engine to drive the alternator, then yes it will extend the range. It is also known as a series hybrid. Whether its worth it or not is a different question.
> 
> If you're thinking of driving it off your electric motor, then as Qer said.


Thanks for that. I'm not talking about having more energy than what I had to start with which I think is what perpetual energy is all about? What I am talking about is using the alternator to provide some of the power at the same time as the batteries once the motor starts turning. I thought this might lessen the load (not eliminate the load) on the batteries themselves increasing the range of the vehicle.


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## sjc (Oct 28, 2008)

deanbo said:


> Thanks for that. I'm not talking about having more energy than what I had to start with which I think is what perpetual energy is all about? What I am talking about is using the alternator to provide some of the power at the same time as the batteries once the motor starts turning. I thought this might lessen the load (not eliminate the load) on the batteries themselves increasing the range of the vehicle.


What would turn the alternator?


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## deanbo (Jun 7, 2010)

sjc said:


> What would turn the alternator?


The electric motor.


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## Sunking (Aug 10, 2009)

deanbo if you do this it will shorten your run time no ifs. ands. or buts. You are talking about perpetual motion, or above unity gain. No power generation is greater than 100%.


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## deanbo (Jun 7, 2010)

Sunking said:


> deanbo if you do this it will shorten your run time no ifs. ands. or buts. You are talking about perpetual motion, or above unity gain. No power generation is greater than 100%.


I thought you might be able to split the amount of power needed between the batteries and the alternator. Batteries will still deplete.


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## bigdawg7299 (Jun 8, 2010)

I think what everyone is trying to say is that the alternator is going to consume more energy than it produces which will lead to a reduced range. You could probably put a small ice on it and it would help, although I don't know how much.


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## TigerNut (Dec 18, 2009)

deanbo said:


> I thought you might be able to split the amount of power needed between the batteries and the alternator. Batteries will still deplete.


But you have to put mechanical power into the alternator in order for it to put out electrical power. It might seem like the alternator would present very little load to the motor when you spin it by hand, but that's because it's not generating any power in that situation. Connect your alternator to a 12v lightbulb and then see how hard you have to work to light that bulb up...

To present an example with numbers, let's say that the motor and the alternator are both 95 percent efficient - this is an optimistic number, by the way. So if you put in 100 watts of electrical power to the motor, it will generate 95 watts of mechanical power, while putting 100 watts of mechanical work into the alternator will generate 95 watts of electrical power.
Now say you're driving and it requires 9500 watts of mechanical power to maintain speed. The motor consumes 10000 watts of electrical power, which it draws from the battery. Now you add the range extender alternator, which will deliver (say) 1900 watts of electrical power to the motor and thereby take that much load off the battery... except that the alternator requires 2000 watts of mechanical power (from the motor) to generate the electricity. So now the total motor load is 11500 watts, mechanical, so it will require 12105 electrical watts of input. The alternator was delivering 1900 watts, so the battery has to supply 10205 watts, which is more than what you started with before the alternator entered the picture.

The only time that an alternator can give even a tiny bit of range boost, is if it's somehow driven by a means that is independent of the power being provided by the motor. One example is for regenerative braking, if the motor itself is incapable of being configured for it. Basically, the motor provides the drive, and the alternator provides the braking, and if you try to do both at the same time, you generate a lot of heat and don't go anywhere fast.


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## deanbo (Jun 7, 2010)

> But you have to put mechanical power into the alternator in order for it to put out electrical power. It might seem like the alternator would present very little load to the motor when you spin it by hand, but that's because it's not generating any power in that situation. Connect your alternator to a 12v lightbulb and then see how hard you have to work to light that bulb up...
> 
> To present an example with numbers, let's say that the motor and the alternator are both 95 percent efficient - this is an optimistic number, by the way. So if you put in 100 watts of electrical power to the motor, it will generate 95 watts of mechanical power, while putting 100 watts of mechanical work into the alternator will generate 95 watts of electrical power.
> Now say you're driving and it requires 9500 watts of mechanical power to maintain speed. The motor consumes 10000 watts of electrical power, which it draws from the battery. Now you add the range extender alternator, which will deliver (say) 1900 watts of electrical power to the motor and thereby take that much load off the battery... except that the alternator requires 2000 watts of mechanical power (from the motor) to generate the electricity. So now the total motor load is 11500 watts, mechanical, so it will require 12105 electrical watts of input. The alternator was delivering 1900 watts, so the battery has to supply 10205 watts, which is more than what you started with before the alternator entered the picture.The only time that an alternator can give even a tiny bit of range boost, is if it's somehow driven by a means that is independent of the power being provided by the motor. One example is for regenerative braking, if the motor itself is incapable of being configured for it. Basically, the motor provides the drive, and the alternator provides the braking, and if you try to do both at the same time, you generate a lot of heat and don't go anywhere fast.


I was under the impression that the alternator would not place that much load on the engine hence not that much more load on the batteries. I will try and explain my logic. Following your example of 95% efficiency and my theory of 100 watts of battery power being enough to drive both the engine and the alternator at the same time this would lead to 180 watts of power. Not 200% in which to my mind represents 100% efficiency or perpetual energy(?) if that assumption is correct. 

This leads me to believe that you need another 20 watts of power from somewhere, that somewhere being the batteries. So if we add that 20 watts to the original 100 watts (because we do not have 100% efficiency) we still have a gain in energy but we are still depleting the batteries at a slower rate. For to not to deplete the batteries both devices (alternator and battery) would need to run at 100% efficiency and the alternator place no load on the motor whatsoever? 

But does the alternator really place that much load on the engine. I am thinking of the alternator in terms of an amplifier. Does not an amplifier increase the amount of power than originally went in? Hope my logic makes sense.


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## Jamie43 (Dec 13, 2008)

What if you use an electric clutch off an AC pump attached to the shaft of the motor to turn the alternator. Then have your brake light switch pass current to activate the clutch to turn the alternator when you apply the brakes. So every time you apply the brakes you should be able to get some charging current. Will that work?

Greg


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## Sunking (Aug 10, 2009)

deanbo said:


> Hope my logic makes sense.


No it is illogical. There is no free ride.


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## Coley (Jul 26, 2007)

NOPE, anything you add to the load of the motor or the batteries will shorten your trip.

We get asked this all the time when we have our cars on display.

You can't add a fan driven alternator, or anything that will lengthen range EXCEPT better batteries OR AN ice running a generator. 

Which then makes it NOT an EV, but a Hybrid.......

Your theory is oft presented and always get the same answer....NO...

It is like my wheelbarrow theory.

Hop into a wheelbarrow, lift the handles and see how fast you can scoot down the driveway......


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## deanbo (Jun 7, 2010)

Coley said:


> NOPE, anything you add to the load of the motor or the batteries will shorten your trip.
> 
> We get asked this all the time when we have our cars on display.
> 
> ...


Sit further down the wheelbarrow? Does an alternator consume more power than it produces? I read that it takes about one horsepower to generate 25 amps in a car alternator. 400 amps would equal eight horsepower. Not sure how many hp it would take to run a 400 amp alternator at 144 volts but thats an output of 77 horsepower. Any ideas on how much horsepower such an alternator would require from the engine? I'm betting it's less than 77...


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## Duncan (Dec 8, 2008)

Hi Deanbo

If it takes 1 hp (750watts) to produce 25 amps at 12 volts 12 X 25 = 300 watts

400 amps is 16 times as much as 25 amps, multiplied by 12 (12 volts to 144v) 

16 x 12 = 192 Hp

So to get 77 Hp out of the alternator you will need to put 192 Hp into it

Sounds a bit inefficient to me!

To answer your question
_*Does an alternator consume more power than it produces?*_

YES, YES, ALWAYS!!


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## speedboats (Jan 10, 2009)

deanbo said:


> Sit further down the wheelbarrow? Does an alternator consume more power than it produces? I read that it takes about one horsepower to generate 25 amps in a car alternator. 400 amps would equal eight horsepower. Not sure how many hp it would take to run a 400 amp alternator at 144 volts but thats an output of 77 horsepower. Any ideas on how much horsepower such an alternator would require from the engine? I'm betting it's less than 77...


From your example 12V @ 25amps = 1hp
Therefore 144V @ 25 amps = 12hp
Therefore 144V @ 400amps = 192hp!

144V @ 400A = 57.6kW
192hp = 141.12kW

So from your own example you have proven that the alternator will require more power input than it will generate as output. Infact you have a 59.2% loss!!!


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## Gavin1977 (Sep 2, 2008)

May i suggest you go and read this thread.
http://www.diyelectriccar.com/forum...-free-energy-perpetual-motion-over-13449.html
If you still have questions after that, then by all means post them.


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## deanbo (Jun 7, 2010)

It takes a lot of inertia(?) to make a car move, and a lot less inertia than that to drive an alternator. Once the electric engine is rotating the amount of inertia required to rotate the alternator would be bugger all. At least in my theory as an alternator is much lighter than an electric motor therefore it requires much less energy to turn it. 

Therefore when the driver takes his foot off the accelerator the inertia created by the motor still keeps the alternator turning over even though there is no power coming from the batteries. This is not "free energy" just plain logic. 

This is just one reason why I can't understand why you cannot get enough energy from an alternator to slow down the depletion of the batteries. All that inertia and you can't create some sort of gain from it? I tend to think of it as inertia driving the alternator not electricity. Electricity drives the electric motor not the alternator. 

I have no doubt adding an alternator would increase the load (slightly?) on the electric motor but I think some of you are forgetting that inertia is also being created as a by product as the car starts to move. I think some of that inertia can be captured by way of the alternator! Or is that the way of the darkside?


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## speedboats (Jan 10, 2009)

One the vehicle has inertia, or momentum, it only requires very little power to maintain velocity (I use velocity as it has direction), hence power drain from the batteries lowers accordingly. Once power is removed from the alternator (either to be stored in the battery or consumed by the motor such as you suggest) then the alternator has to work hard to replace that power. If work is being done then power is required. As was stated before, to make 57.6kW in your example will require 141kW of input. So if your vehicle required 20kW of energy to maintain it's velocity, and you wanted to produce your stated 57.6kW for storage from your alternator, then you will need to use 161kW to achieve your goal. So you've taken a nominal required input of 20kW and turned it into 103.4kW (161kW - 57.6kW = 103.4kW)

Sorry, but it doesn't work, if it did energy companies would have cars driving all-over the place to store power to put onto the grid.

Try this experiment. Take 1 alternator, spin it up to any rpm with something like a drill, then time how long it takes to come to a stop. then do the same thing with the alternator hooked up to a light bulb (12V), and time how long it takes to come to a stop. When spinning at the same rpm, both setup's have the same inertia. The one hooked to the light will stop significantly faster every time. Now imagine that 12V bulb was a 144V bulb? Perhaps now you get the idea?

Remember the old dynamo (spelling?) lights for your push bike. They always required more energy to cycle the bike, that was why they had the hinge arrangment so you could dis-engage them once they were un-neccessary (ie, day time)


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## dtbaker (Jan 5, 2008)

deanbo said:


> ... I can't understand why you cannot get enough energy from an alternator to slow down the depletion of the batteries.


Just physics... if the alternator is doing work to generate electricity, it takes (slightly more) work for somewhere to spin it. In steady state it would just add to the amount of work required from your motor, and you'd have mechanical losses, giving a net loss larger than the amount of electricity generated.

Alternators/generators CAN be used to extend range if applied only during braking... when you were going to convert some of your energy to heat and throw it away out the brakes. But, this takes either an AC motor, or some pretty complex wiring to regulate how much current/voltage gets dumped into batteries so things don't burn up.

This is indeed a key technology point for EVs... but it hasn't been solved yet in part because its hard to capture the energy from a 'braking event' as fast as it is produced with current battery/charging technology. Best shot may be routing braking regen power to an ultra-capactor, but they are still too big, heavy, and expensive to make it worth sticking into a car.


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## TigerNut (Dec 18, 2009)

Jamie43 said:


> What if you use an electric clutch off an AC pump attached to the shaft of the motor to turn the alternator. Then have your brake light switch pass current to activate the clutch to turn the alternator when you apply the brakes. So every time you apply the brakes you should be able to get some charging current. Will that work?
> 
> Greg


That would work. It can be even easier than that... the idling load (zero field torque input) of an alternator is pretty low, so you can just turn on the field current when you want to brake, and leave it off otherwise. No clutches required.


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## dtbaker (Jan 5, 2008)

TigerNut said:


> That would work. It can be even easier than that... the idling load (zero field torque input) of an alternator is pretty low, so you can just turn on the field current when you want to brake, and leave it off otherwise. No clutches required.



it might work, but is it WORTH it?!

lets say you have an 80amp alternator (at 12v), and a step-up transformer that bumps that up to your pack charging voltage... assume 120v just for this example. Thats a max of 8amps, less mechanical and transformer losses for the duration of a 'braking event' which lasts about 15 seconds. Not a lot of amp-hr going back into the pack.... and the added weight and complexity of the alternator, switching, transformer, and someway to prevent OVERcharging, etc, etc.

If you did nothing but stop and go deliveries, like a mailman.... maybe.


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## TigerNut (Dec 18, 2009)

dtbaker said:


> it might work, but is it WORTH it?!
> 
> If you did nothing but stop and go deliveries, like a mailman.... maybe.


He didn't ask about how much energy you might recover in this way and at least he wasn't trying to use the alternator while driving under power.

As you say, regen only recovers the inertia energy of the vehicle, and on any extended trip that amount of energy is minuscule compared to the energy used to overcome air resistance and tire friction.

What is the inertia energy in a vehicle? Let's look at that:
1000kg vehicle, 31.6 m/s (that's about 70 MPH). E = 1/2 mv^2 so we have 500 kJ of inertial energy. If you're using 10 kW to move the car at a steady speed, then you use up 500 kJ in 50 seconds. Accelerating from rest would use much more power and your 500 kJ would be gone in 10 seconds or less.


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## Jamie43 (Dec 13, 2008)

TigerNut said:


> That would work. It can be even easier than that... the idling load (zero field torque input) of an alternator is pretty low, so you can just turn on the field current when you want to brake, and leave it off otherwise. No clutches required.


Then perhaps turning on the field current in the alternator via the throttle instead of brake switch would work better. You could then take advantage of built up inertia of the vehicle and drive motor to generate current during all periods of coasting. This should help to delay the use of brakes and help to reduce brake pad wear. It seems a shame to waste all of the energy in the form of friction using the brakes.

Greg


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## Qer (May 7, 2008)

TigerNut said:


> What is the inertia energy in a vehicle? Let's look at that:
> 1000kg vehicle, 31.6 m/s (that's about 70 MPH). E = 1/2 mv^2 so we have 500 kJ of inertial energy. If you're using 10 kW to move the car at a steady speed, then you use up 500 kJ in 50 seconds. Accelerating from rest would use much more power and your 500 kJ would be gone in 10 seconds or less.


Except that you won't even get back a fraction of that. Some wild numbers out of a hat gives that you'll lose 15% in the transmission, 10% in the motor, 5% in the controller and 10% in the charging of the batteries, which gives 0.85*0.9*0.95*0.9=65% of the energy, or 325kJ.

Now you want to accelerate the car again and that means a new set of losses, so your 325 kJ now results in 210 kJ energy to propel the car and your 10 seconds has dropped to around 4. And I think I'm an optimist and it'll be even worse in real life. It will definitely be catastrophically bad if you use lead acid-batteries since the peukert effect will punish you twice...


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## kek_63 (Apr 20, 2008)

Jamie43 said:


> Then perhaps turning on the field current in the alternator via the throttle instead of brake switch would work better. You could then take advantage of built up inertia of the vehicle and drive motor to generate current during all periods of coasting. This should help to delay the use of brakes and help to reduce brake pad wear. It seems a shame to waste all of the energy in the form of friction using the brakes.
> 
> Greg


Except that then "coasting" becomes "braking"

Keith


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## Jamie43 (Dec 13, 2008)

kek_63 said:


> Except that then "coasting" becomes "braking"
> 
> Keith


I was thinking you could have a "Null Zone" in your throttle position. A small distance of travel where you are neither sending current to your drive motor or to your alternator. When you need to slow down just raise the throttle to send current to the alternator.

Greg


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## TX_Dj (Jul 25, 2008)

Lets break this down another way...

You have batteries, lets say they are 80% efficient at delivering the power that was put into them.

You have a motor controller, lets say it's 80% efficient at delivering power from the batteries to the motor.

You have a motor, lets say it's 80% efficient at delivering power from the controler as mechanical work.

You have an alternator, lets say it's 80% efficient at converting mechanical work into electricity.

You have a charge controller, let's say it's 80% efficient at converting the alternator output current back into battery charge.

Now, you have 1kW of energy you're tapping from the battery, back into the battery by the proposed mechanism:

1000W * 0.8 * 0.8 * 0.8 *0.8 * 0.8 = 327.68W, or 672.32W wasted in conversion.

You burned 2/3 more energy than you reclaimed from the system.

There is no such thing as 100% efficiency, and there's sure as hell no such thing as >100% efficiency.

You can break the law, but you can't break the laws of physics.

I applaud your eagerness to come up with the next greatest technology in EVs, but this is not it.

This thread is about perpetual motion, and should be merged to the overunity thread, and will be if this discussion continues within this thread.


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## Joey (Oct 12, 2007)

deanbo said:


> But does the alternator really place that much load on the engine. I am thinking of the alternator in terms of an amplifier. Does not an amplifier increase the amount of power than originally went in? Hope my logic makes sense.


An alternator is not an amplifier. An alternator converts mechanical energy to electrical energy. It does so with less than 100% efficiency. Every energy conversion process is less than 100% efficient.

An amplfier taps an external source of energy to "amplify" the input. Once you consider all sources of energy into and out of a system, you will find that the energy out is always less than energy in.

In your set up, you have the following cycle: batteries power the motor (chemical to electrical to mechanical conversion), motor powers the alternator (mechanical to electrical conversion), alternator charges the batteries (electrical to chemical conversion),...

Each conversion is less than 100% efficient. You lose energy at each conversion. Adding the alternator adds an additional energy conversion step in the process, which results in lower efficiency of the system.

Regen will capture the energy that would otherwise be lost to friction in the brakes, but as others have pointed out, you need to know how much energy you capture, (given conversion efficiencies) to know if it is worth the trouble, given cost, weight, and added system complexity.


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## Joey (Oct 12, 2007)

TX_Dj said:


> This thread is about perpetual motion, and should be merged to the overunity thread, and will be if this discussion continues within this thread.


 Sorry, I started writing my post before I saw yours.


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## Sunking (Aug 10, 2009)

deanbo said:


> Does an alternator consume more power than it produces?


Well of course it does, that is the point everyone is trying to make. You are claiming a perpetual motion machine. A machine with higher than unity gain or greater than 100% efficiency. Read, study and understand the Second Law of Thermal Dynamics


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## deanbo (Jun 7, 2010)

I am not claiming something for nothing, what I am referring to is converting the cars inertia into electricity via the alternator to part power the motor. The power produced by the alternator is fed back to the engine not the batteries. Think of it this way. You turn you car on and drive it to the speed of 100 kph on a flat road. You switch off the power from the batteries but the car keeps moving forward and gradually slows down. 

Even though the power coming from the batteries has been switched off the alternator is still producing electricity. Obviously this is not enough electricity on it's own to accelerate the car, but it would reduce the amount of power now needed from the batteries to keep the car going. This proves my point simply because the alternator is producing power with no power coming from the batteries. 

What the alternator is doing is converting inertia into electricity. In other words the batteries still provide some of the power, inertia provides the rest. Batteries still deplete but over a longer period of time.

This does not equate to perpetual energy as the amount of being power produced by the alternator with the batteries switched off is still not enough to accelerate the car but the car will travel further before it stops because there is still power being created by the alternator that can feed directly into the engine.

Now I can see many of you stating 95% efficiency and all that, but what you have not included is the inertia that is also being created and is also a force that can be converted into electricity. And in a vehicle that is travelling at 100 kph weighing approximately 1000 kgs there is plenty of it waiting to be utilized.

Also and obviously inertia is something that cannot be created from nothing, but as the inertia builds and because of the alternator less and less of this power needs to come from the batteries.

No doubt the inertia being created will not convert into 100% electricity, but it would certainly help reduce the load on the batteries, not eliminate it.


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## TigerNut (Dec 18, 2009)

deanbo said:


> I am not claiming something for nothing, what I am referring to is converting the cars inertia into electricity via the alternator to part power the motor.


We understand that. But we've worked through the numbers and showed you that first, there's not as much energy there as you think, and second, the motor has to restore the car's inertia, which takes more power than you got from the alternator in the first place. So it's a losing proposition.


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## TigerNut (Dec 18, 2009)

deanbo said:


> This does not equate to perpetual energy as the amount of being power produced by the alternator now is still not enough to accelerate the car but it does require less power from the battery now as there are now two sources of electricity. Inertia and the batteries.
> 
> Now I can see many of you stating 95% efficiency and all that, but what you have forgotten is inertia is also a force that can be converted into electricity. And in a vehicle that is travelling at 100 kph weighing approximately 1000 kgs there is plenty of it waiting to be utilized.


No, as I showed you earlier, using ALL the inertial energy in a car traveling at 100 to 110 km/h, would supply enough power to move the car at a steady speed (with an improbably low power consumption) for less than a minute. Extracting all that energy would bring the car to a dead stop.
As others have noted, the efficiency of any single component in the system ranges from a low of around 80 percent to a maximum of about 95 percent. And there are many steps in your power-recycling scheme.


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## deanbo (Jun 7, 2010)

If you read my above post you will see that the alternator can provide some of the power to the motor without assistance from the battery.


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## TigerNut (Dec 18, 2009)

deanbo said:


> Also and obviously inertia is something that cannot be created from nothing, but as the inertia builds and because of the alternator less and less of this power needs to come from the batteries.
> 
> No doubt the inertia being created will not convert into 100% electricity, but it would certainly help reduce the load on the batteries, not eliminate it.


Where does the inertia come from? It comes from the motor. Which is powered by the alternator and the batteries in your scheme. But the alternator is powered by the inertia... etc. Since that's a circular loop, and you agree that perpetual motion is not possible, the only source of energy left is the battery. Adding an alternator just adds a place where energy gets converted to heat and is lost to the system.


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## deanbo (Jun 7, 2010)

TigerNut said:


> Where does the inertia come from? It comes from the motor.


It can also come from gravity and gravity does not need to be created because it already exists, free of charge. Downhill would be an even better example. If you parked the car at the top of a steep hill, disconnected the batteries and let the handbrake off, the alternator would create more and more electricity as the car accelerates. But there is no power coming from the batteries. 

This proves my point that the alternator can provide some of the electricity (not all) required to power the car without draining the batteries. Also, unless I am mistaken, you cannot have inertia without gravity as everything would be weightless? This leads me to believe that inertia and gravity are two very similar things.


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## TigerNut (Dec 18, 2009)

deanbo said:


> It can also come from the car moving forward. Downhill would be an even better example or perhaps gravity would be a better word.


That's a different ballgame. About five posts ago you were on level ground, where you need the motor to keep you moving at a steady speed.
Using an alternator to provide regenerative braking (or to keep a steady speed on downhills) can be done, but the amount of energy recovered is pretty small, and possibly not worth it given the extra complexity and weight of the system.
As far as operation on level ground is concerned, it will *NOT* give you any extra range. If you ever do build such a system and set your alternator up so that it can provide a substantial charge to the battery (or even so that it can partially power the motor) you'll find it's like throwing an anchor over the side of your car.


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## deanbo (Jun 7, 2010)

At the risk of not letting this thread die a natural death I now think the difference that I am referring to is that of kinetic and potential energy. If an EV (or any other car) could only being run with potential energy alone (battery power) then wouldn't the amount of power been drawn from the batteries remain the same when cruising as well as accelerating? 

This leads me to believe that kinetic energy is coming into play somewhere and this is what reduces the load on the batteries when cruising. It is this same force that I am talking about trying to take further advantage of.

To clarify this further, I am not suggesting getting more power out than what I put in, rather sourcing some of the power required from somehere else without placing additional load on the battery. That source of course being kinetic energy. I have no doubt you would get less electricity out than the amount of kinetic energy you put in, but once the car gains motion kinetic energy starts to drive the alternator, and less and less of the battery.


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## Anaerin (Feb 4, 2009)

deanbo said:


> Also, unless I am mistaken, you cannot have inertia without gravity as everything would be weightless? This leads me to believe that inertia and gravity are two very similar things.


On this point, you are mistaken. Take, for example, the Apollo missions (And watch the movie Apollo 13). When they were in transit from Earth to the moon, they were not burning their engines at all. They fired their engines to break free of Earth's orbit and start the journey, and when they were pointed in the right direction and at the right speed, they shut the engines off. As there is (essentially) no gravity in space once you have broken orbit, it was their inertia that was keeping them moving. And as space is a vacuum, there was nothing slowing them down (no wind or rolling resistance).

You are mixing up two of Newton's laws.

*Newton's Law of Gravity*: Objects are attracted to each other with a force equal to the product of both object's mass, divided by the _square_ of the distance between them (essentially). So, (Mass of A x Mass of B)/Distance²

*Newton's Laws of Motion* (Part 1): Objects in motion will stay in motion while all forces on it are equal.

Bear in mind that while it is convenient to think so, Mass is not equal to Weight. An object of mass 10Kg still has that mass whether it is on Earth, on the Moon, or in the depths of deepest space. However, in the case of Earth, the object will be exerting a force of 100 Newtons on the ground (or whatever else is holding it up), on the moon it will be exerting a force of 17 Newtons on the moon's surface (as the moon's gravity is only 17% that of Earth), and in space it will be exerting a force of 0 Newtons on whatever it is resting against. But even in space it will take the same amount of force to accelerate that 10Kg object as it does on Earth.


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## TigerNut (Dec 18, 2009)

deanbo said:


> Also, unless I am mistaken, you cannot have inertia without gravity as everything would be weightless? This leads me to believe that inertia and gravity are two very similar things.


Inertia and gravity are both related to the mass of an object but they are very different properties, especially where angular motion (i.e. rotation) is concerned. Two objects can have the same mass (and therefore the same gravitational effect on another object) but have drastically different amounts of rotational inertia, depending on whether the mass is concentrated near the center or near the outside perimeter of the object.
Objects have the same inertia regardless of where they are in the universe.


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## Joey (Oct 12, 2007)

deanbo said:


> I am not claiming something for nothing, what I am referring to is converting the cars inertia into electricity via the alternator to part power the motor. The power produced by the alternator is fed back to the engine not the batteries. Think of it this way. You turn you car on and drive it to the speed of 100 kph on a flat road. You switch off the power from the batteries but the car keeps moving forward and gradually slows down.
> 
> Even though the power coming from the batteries has been switched off the alternator is still producing electricity. Obviously this is not enough electricity on it's own to accelerate the car, but it would reduce the amount of power now needed from the batteries to keep the car going. This proves my point simply because the alternator is producing power with no power coming from the batteries.
> 
> ...


Think about it. The alternator is going to waste some energy as heat, because there are no 100% efficient alternators. There is no other energy going into the system, so the alternator represents a net energy loss to the system. So there is less glide distance compared to no alternator. 

You really seem to under estimate the mount of energy the alternator removes from the system. It cannot be offset fully by the electricty it generates. If you still don't believe everyone, by all means set up an experiment and try it out for yourself.


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## deanbo (Jun 7, 2010)

Joey said:


> Think about it. The alternator is going to waste some energy as heat, because there are no 100% efficient alternators. There is no other energy going into the system, so the alternator represents a net energy loss to the system. So there is less glide distance compared to no alternator.
> 
> You really seem to under estimate the mount of energy the alternator removes from the system. It cannot be offset fully by the electricty it generates. If you still don't believe everyone, by all means set up an experiment and try it out for yourself.


Electricity is now being generated that previously would not have existed as the car is now moving under is own power (kinetic energy) not power from the batteries. Think of a vehicle heading downhill with the batteries but not alternator disconnected. All for a small tax on the glide distance of the vehicle and no tax on the battery system.


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## Anaerin (Feb 4, 2009)

deanbo said:


> Electricity is now being generated that previously would not have existed. All for a small tax on the glide distance of the vehicle and no tax on the battery system.


That "Small tax" is actually a huge tax. The more power you attempt to pull out of an alternator, the harder it is to turn, which would mean you would need to put more power in to keep it turning.

Take two small motors and connect them back-to-back with some diodes (little 3v ones would do fine). The second motor will act as a generator as it is being driven. Use a battery to energize the system and get it spinning, then remove the battery and see how long it keeps going. The amount of time will be measured in milliseconds, at best. And that is a no-load best case scenario. What you are proposing would be less efficient than letting the vehicle freewheel to "extend the range", as that too would have no battery power used, and would also have no drag incurred by trying to drive a generator.

You are trying to increase the glide distance of the vehicle by taxing the glide distance of the vehicle. It doesn't matter if you are going uphill, downhill, or on the straight and level, that just won't work.


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## deanbo (Jun 7, 2010)

Is there then a form of generator that doesn't make a huge amount of more resistance the faster it spins?


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## Anaerin (Feb 4, 2009)

deanbo said:


> Is there then a form of generator that doesn't make as much resistance the faster it spins?


No. Such a device would be in direct contradiction to the laws of thermodynamics.


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## Qer (May 7, 2008)

deanbo said:


> To put it another way, is there are way to stop the resistance been generated by alternator from rising as quickly? I'm assuming it's not just a case of better bearings for the alternator shaft...


Not in this universe, no.

As long as the alternator is unloaded, it will spin easily but as soon as you put a load on it, you don't only spin the alternator but also the load attached to it (so to speak). The load will work more or less as a brake and thus make it harder to spin the alternator, simply because the energy provided to the load must come from somewhere.

You can't break the laws of physics.


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## Gavin1977 (Sep 2, 2008)

deanbo said:


> To put it another way, is there are way to stop the resistance been generated by alternator from rising as quickly? I'm assuming it's not just a case of better bearings for the alternator shaft...


Yes. Reduce the electrical load on it. It still wont allow you to break the laws of thermodynamics though.


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## deanbo (Jun 7, 2010)

Qer said:


> Not in this universe, no.
> 
> As long as the alternator is unloaded, it will spin easily but as soon as you put a load on it, you don't only spin the alternator but also the load attached to it (so to speak). The load will work more or less as a brake and thus make it harder to spin the alternator, simply because the energy provided to the load must come from somewhere.
> 
> You can't break the laws of physics.


Understood. But I still tend to think of the alternator being partly "outside the loop" and that you would get some of the energy back from the energy the batteries put in to the motor originally as the car is moving now.

To put it another way is it not possible to convert some kinetic energy to electrical power without eliminating all the kinetic energy created by the car once the car is moving?


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## Duncan (Dec 8, 2008)

Hi Deanbo

Let us look at this in a different way

Let us think of the vehicles "Kinetic Energy" as a bucket of water
The batteries pour power into the motor which accelerates the car to your cruising speed
(Fills the bucket)
With no drag or wind resistance the bucket stays full 
Unfortunately there is drag from the tires and aerodynamic drag
So the bucket slowly empties

After a short time the batteries and motor need to top it up, the most efficient running is with the batteries and motor keeping the bucket at a constant level (speed)

If we take some of the water from the bucket to power our alternator the bucket empties faster, this means that the batteries and motor need to replace more water

Now comes the big problem the water taken by the alternator only charges the batteries enough to "buy" about half the water that was taken

By drawing water which has to be replaced you get substantially less range

Now if you have to use the brakes that is like pouring the water away - that water can be used for re-charging
This is called re-generative braking

In stop start traffic that is very useful - on the highway less so

A few useful terms
Inertia - property of matter - Cannot be changed! also called Mass

Momentum - Inertia x speed

Kinetic Energy - Inertia x speed x speed (divided by 2) 

Energy - Force x distance, *also* volts x amps, *also* kinetic energy


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## Jan (Oct 5, 2009)

Duncan said:


> Energy - Force x distance, *also* volts x amps, *also* kinetic energy


Small correction: Not energy, but Power = Volts x Amps e.g. Energy = Power x Time.


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## Duncan (Dec 8, 2008)

Hi Jan

Quite right thanks

-Damn - how did I mess that up!


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## Qer (May 7, 2008)

deanbo said:


> To put it another way is it not possible to convert some kinetic energy to electrical power without eliminating all the kinetic energy created by the car once the car is moving?


If that were possible I could just spin up a huge flywheel with an attached alternator, connect my house to it and never ever again have to pay an electrical bill in my entire life.

If you withdraw some of the kinetic energy and convert it to electricity the car/flywheel/whatever will slow down. If it didn't we could stop drilling for oil, use nuclear power plants or whatever this very moment. The only thing we'd need would be solar or wind power to spin up the flywheels and then just tap them for electricity. If we needed more electricity, just build more flywheels and spin them up with electricity from the already spinning ones!

Sorry, this ain't Hogwarts.


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## dragster (Sep 3, 2008)

This has been talked about before,we all have turned an alternator over by the pulley and noted how little force it takes. That is because it is not working to get it to work it must spin at a high rate of speed. Note: this is how the new type alternators start. Once it is working a 90 amp alternator will require 5 HP to keep it producing the 90 amps. They are very good at putting amps back in the battery but as you can see it takes more power to run then you will get back. This is great to charge the battery back up as you drive along thank god we have them as the old genarators sucked.


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## TigerNut (Dec 18, 2009)

deanbo said:


> Understood. But I still tend to think of the alternator being partly "outside the loop" and that you would get some of the energy back from the energy the batteries put in to the motor originally as the car is moving now.


That's a good way to look at it, except that everything that is on your car is inside the loop. Ultimately, all the energy used to move the car comes from the battery. The more places you have that energy is converted from one form to another, the more energy is wasted as heat.
If you happen to drive a route that is lower in elevation at the destination compared to the start, then gravity will help you there... but it will hurt you more on the way back.


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## AmpEater (Mar 10, 2008)

Many cars already have an alternator powered by the inertia of the vehicle. 

It's called a regenerative brake. When you switch it on....it stops the car by converting mechanical energy (inertia) to electrical energy

What you are describing is a regen brake that doesn't slow the car down. (magically)


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## Astronomer (Aug 7, 2008)

> Even though the power coming from the batteries has been switched off the alternator is still producing electricity.


I think I see the disconnect. 

All the energy your electric car has is the electrical potential energy stored in the batteries. That's the sum total of your energy reserve. When you drive your car, you convert that electrical energy to kinetic energy by applying electrical power to the motor. But just because you disconnect the batteries and coast doesn't mean that tapping into the kinetic energy doesn't further deplete the battery, because every bit of the kinetic energy you have came at the cost of the electrical energy in the battery. Replenishing the kinetic energy you diverted to run the alternator will eventually require more energy from the battery.

What you're doing is filling a bathtub with water and turning off the faucet when it's full. Then you're taking water out of the bathtub to water your plants, and you're claiming that the water you're using didn't come from the faucet, because the faucet wasn't running when you took the water from the tub. But no matter when you dip into the tub, whether the faucet's running or not, it all comes from the faucet.

It's the same with the battery. If you tap into the kinetic energy of the vehicle, even when the battery is momentarily disconnected, you're tapping into the battery.


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## deanbo (Jun 7, 2010)

Astronomer said:


> I think I see the disconnect.
> 
> All the energy your electric car has is the electrical potential energy stored in the batteries. That's the sum total of your energy reserve. When you drive your car, you convert that electrical energy to kinetic energy by applying electrical power to the motor. But just because you disconnect the batteries and coast doesn't mean that tapping into the kinetic energy doesn't further deplete the battery, because every bit of the kinetic energy you have came at the cost of the electrical energy in the battery. Replenishing the kinetic energy you diverted to run the alternator will eventually require more energy from the battery.
> 
> ...


Point taken. It does sound more and more to me like I am after some sort of regenerative braking. But take your bath which is full and pull the plug on it. Now turn the faucet. If you turn the faucet far enough you can probably compensate for the draining water and keep the bath full until the water tank empties. 

But what if the water emptying from the bath into the drain ran past a water wheel instead and then into a bucket to bring the some of emptied water back to the water tank? Might have to be a small bucket of water but how much further did you have to open the faucet to do this? You didn't. 

Will you able to stop the water tank and therefore bath from emptying? No, but you should be able to keep the water tank fuller for longer.


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## AmpEater (Mar 10, 2008)

It helps if you don't look at the alternator as a device that creates electricity. It doesn't.

It just converts energy from one from to another

And, like everything in the world, it does this at less than 100% efficiency.

A motor can also be thought of as an energy converter

As can a lightbulb, or a speaker, or a water heater


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## deanbo (Jun 7, 2010)

AmpEater said:


> It helps if you don't look at the alternator as a device that creates electricity. It doesn't.
> 
> It just converts energy from one from to another
> 
> ...


Understood. You might want to read the post above yours though.


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## AmpEater (Mar 10, 2008)

deanbo said:


> Understood. You might want to read the post above yours though.


Funny, I did. My post was actually a direct response, but you changed it so much it before I submitted that it doesn't make any sense now. 

Shoulda quoted I guess. Or maybe you snuck a second post in there...


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## AmpEater (Mar 10, 2008)

deanbo said:


> Point taken. It does sound more and more to me like I am after some sort of regenerative braking. But take your bath which is full and pull the plug on it. Now turn faucet. If you turn the faucet far enough you can probably compensate for the draining water and fill the bath until the water tank empties.
> 
> But what if the water emptying from the bath into the drain ran past a water wheel instead and then into a bucket to bring the some of emptied water back to you? Might have to be a small bucket of water but how much further did you have to open the faucet to do this? You didn't.
> 
> Will you able to stop the bath from emptying? No, but you should be able to turn the faucet down slightly now reducing the drain on the water tank.


Sounds alot like regen to me. You're not changing the motors or the batteries but you're traveling further because at some points you've recaptured energy that otherwise would have been lost in the process.


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## TigerNut (Dec 18, 2009)

deanbo said:


> Point taken. It does sound more and more to me like I am after some sort of regenerative braking. But take your bath which is full and pull the plug on it. Now turn the faucet. If you turn the faucet far enough you can probably compensate for the draining water and keep the bath full until the water tank empties.
> 
> But what if the water emptying from the bath into the drain ran past a water wheel instead and then into a bucket to bring the some of emptied water back to the water tank? Might have to be a small bucket of water but how much further did you have to open the faucet to do this? You didn't.
> 
> Will you able to stop the water tank and therefore bath from emptying? No, but you should be able to keep the water tank fuller for longer.


If you tried to make a pump to automate that process of capturing the drain water and pumping it back up to the tub, where the pump was powered by the water you had on hand, you'd find that it would require more water under pressure direct from the tap. The tub water (equivalent to your inertia energy) wouldn't have enough pressure head to do the job.


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## deanbo (Jun 7, 2010)

Momentum is the word I have been looking for and the process would be regenerative. Think of how much momentum a car can create as the result of potential and kinetic energy. That is what I am referring to. 

Turn your engine off at 100 kph on a flat road with your alernator connected to the to one of the wheels somehow and what happens? The wheels (alternator) keep turning but the engine doesn't. 

The amount of power generated by this momentum can never be enough to continue powering the car on it's own, but it would reduce the surplus requirement of extra energy required from the batteries.


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## Gavin1977 (Sep 2, 2008)

deanbo said:


> Momentum is the word I have been looking for and the process would be regenerative. Think of how much momentum a car can create as the result of potential and kinetic energy. That is what I am referring to.
> 
> Turn your engine off at 100 kph on a flat road with your alernator connected to the to one of the wheels somehow and what happens? The wheels (alternator) keep turning but the engine doesn't.
> 
> The amount of power generated by this momentum can never be enough to continue powering the car on it's own, but it would reduce the surplus requirement of extra energy required from the batteries.


Your going round in circles. We have already answered this. The Wheels _DO NOT _keep turning but slow down due to air drag and friction. If you have an alternator hooked up to one of these wheels, then the car will slow down quicker. If you tried my experiment with the bicycle, then believe me, you would believe! The only way this will help you is if you WANT to slow down your car, ie a stop light, which as eveyone else has said, is regen braking.


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## TigerNut (Dec 18, 2009)

deanbo said:


> Momentum is the word I have been looking for and the process would be regenerative. Think of how much momentum a car can create as the result of potential and kinetic energy. That is what I am referring to.
> 
> Turn your engine off at 100 kph on a flat road with your alernator connected to the to one of the wheels somehow and what happens? The wheels (alternator) keep turning but the engine doesn't.
> 
> The amount of power generated by this momentum can never be enough to continue powering the car on it's own, but it would reduce the surplus requirement of extra energy required from the batteries.


I think you're missing some serious appreciation for the amount of power that it takes to move the car against friction and air drag. The amount of energy stored as momentum of the chassis is fairly small by comparison, which you can tell simply by driving your car, switching off the engine, and letting it coast to a stop. Your notion that "the wheels keep turning" is flawed: The instant that you switch off the engine, the wheels start slowing down. There is not even a fraction of a second where your original speed is being maintained, and to regain that lost speed will cost you more power than it would have taken to maintain a steady speed in the first place, and more power than what you'd have been able to regenerate using an alternator in that time frame.

As the others have said: Do some actual experiments. You may have noticed that you're the only person in this thread that is of the opinion that your idea will work. Frankly, this is not because you're more brilliant than all the other people in this thread. It's because your idea is wrong, and it's based on faulty assumptions.


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## Astronomer (Aug 7, 2008)

> Will you able to stop the water tank and therefore bath from emptying? No, but you should be able to keep the water tank fuller for longer.


But the recovered water (energy) comes at the cost of being able to do less work with the energy you have. So much less, in fact, that you would be better off not trying to recover it at all, and instead simply applying the full power of the water wheel to whatever task you're ultimately trying to accomplish.

I'll add to what TigerNut has said by saying that even if air resistance and mechanical friction were zero, energy recovery through an alternator is a losing (as in ultimately energy-reducing) proposition if your goal is to extend your cruising distance. Spinning the alternator to supply any regenerative load will slow your car down more than the recovered energy is worth.


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## jehan12413 (Feb 4, 2010)

TigerNut said:


> That would work. It can be even easier than that... the idling load (zero field torque input) of an alternator is pretty low, so you can just turn on the field current when you want to brake, and leave it off otherwise. No clutches required.


That's the way I did it but I used a chain and sprocket instead of a belt due to less drag, and used variable field voltage based on how much brake was applied.


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## jehan12413 (Feb 4, 2010)

deanbo said:


> Electricity is now being generated that previously would not have existed as the car is now moving under is own power (kinetic energy) not power from the batteries. Think of a vehicle heading downhill with the batteries but not alternator disconnected. All for a small tax on the glide distance of the vehicle and no tax on the battery system.


Deanbo, A good way to get a feel for how much power it takes to turn an alternator would be to go to a gym and try an exercise bike on the most difficult setting and see how hard it is to peddal. The older models have an alternator inside with a resistor across the output, the highest setting is only about 200 watts!


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## deanbo (Jun 7, 2010)

Gavin1977 said:


> Your going round in circles. We have already answered this. The Wheels _DO NOT _keep turning but slow down due to air drag and friction. If you have an alternator hooked up to one of these wheels, then the car will slow down quicker. If you tried my experiment with the bicycle, then believe me, you would believe! The only way this will help you is if you WANT to slow down your car, ie a stop light, which as eveyone else has said, is regen braking.


I fully realise that the wheels will slow down, keeping on going forever was not what I meant by the wheels keep turning. They just do not stop the moment the batteries are turned off. 

What keeps the car going for a time until stopping or going backwards is the force I am trying to utilize. Clearly braking the car is the only way to utilize that force and turn it into electricity.


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## ElectriCar (Jun 15, 2008)

This thread has really gotten out of hand!

Deanbo, here's how you can find out what everyone is trying to teach you. If you do this you'll find your answer, but first let me explain something to you. If you don't, you'll continue to flounder in your incomprehension of the matter.

Generators make DC. Alternators make AC. A DC motor is basically the same thing as a DC generator but for a few adjustments of the brushes and maybe a slight difference in the setup on the armature, the rotating part of the motor. To connect an alternator to the battery you must convert it to DC which will consume a portion of the generated power.

Obviously it will take some energy to get the generator up to speed, you know that. If you take your vehicle motor and have it up to speed then remove power, it begins to generate power. So a DC motor becomes a generator when you remove power while it is rotating. 

Lots of EV's use the motor to generate power when it's coming to a stop but it takes the proper control & relays to do this. Most who've tried this on DC motors have blown up their controllers. However it's not making free power. You had to power the motor to get the vehicle up to speed and the motor then converts some of the inertia of the vehicle back to electricity which can be put back in the battery. 

Now here's your assignment. Go purchase a generator and light kit for a bicycle, very inexpensive. Take the generator from the kit and turn it by hand without the light connected to it. You'll see it turns very easily just like spinning a top. Anyone who has ever turned an alternator in their hands knows this and is likely the source of your misunderstanding.

Now attach the wiring to the light with the switch is turned on. Next turn the generator by hand. You'll see a dramatic difference in the amount of difficulty it takes to turn it. That's because as you apply a load (battery pack or lights) to a generator/alternator the degree of difficulty to turn it will increase proportionally as the load increases. Add more lights and it gets harder to turn. In order to realize what I'm trying to teach you, you'll have to experience it. 

Now if you're coasting to a stop and need to apply the brakes, that is when you use the alternator because when you connect the alternator to the battery it will slow the vehicle down faster and you may slow enough you don't need the brakes if waiting on a traffic light. 

One more note, in industrial machines using DC motors there are two ways to stop the machine. One is to remove power from the motor which will allow friction and the product in the machine to slow it down gradually. A second and much faster way is to remove power followed by a low resistance load applied to the motor. A low resistance load means current can flow through it with little resistance. Translation: Low resistance load = heavy electrical load. What that does is place a tremendous electrical load on the motor which is now generating power. 

The heavy electrical load will very quickly stop the motor and thus the machine, just as if you connected additional lights to your bicycle generator. If you connected enough lights to your bicycle, it would be very hard to pedal it and you'd quickly tire. If you try to use power from an alternator on your vehicle to recharge the pack you're going to slow the vehicle down unless you remove more power from the pack to maintain your speed. You should understand now that generating power comes at a cost of mechanical drag as it becomes harder to turn the shaft.


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