# is this to simple?



## rcprodriver (Oct 19, 2013)

totally new here, but have been interested in EV vehicles for a long time.
I am a RC hobbiest, and run brushless, lipo powered RC trucks....so I know how powerful and efficient electric motors can be.

Here is a idea/question that has been in my head for some time, and I am hoping you guys can enlighten me.

I know that Re-gen braking is now popular on hybrids. And I have seen a vid on youtube of a production car which ran a electric motor for drive...but had a gas motor to run a generator to charge the batteries (gas motor was not connected to the drivetrain, just to generator)

Both of those setups have some merit, but why not run a powerful altenator or a generator off the electric motor??? I realize that doing so would put drag on the motor, but shouldn't we be able to create a setup where that drag is surpassed by the re-charging ability of the system?

In a gas car, if your battery gets drained and you get a jump-start...you only have to drive around for a few miles before the battery now has enough charge to start the car many times. And this is achieved with an altenator which does not provide much parasitic loss to the engine. So, couldn't a much larger/powerful altenator/generator be fitted to the electric motor?

The idea of an altenator on a electric RC car has also been thought up....tho the scale is very small and thus hard to build. Plus, RC cars do not have any on-board system for applying generated power to the battery (power flows one way only)

So, please enlighten me as to why a generator or altenator run off the electric motor will not work. I assume there is some issue because I have not seen it done by the big companies nor by DIY.
Thanx.


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## dougingraham (Jul 26, 2011)

rcprodriver said:


> So, please enlighten me as to why a generator or altenator run off the electric motor will not work. I assume there is some issue because I have not seen it done by the big companies nor by DIY.


Because it won't work. Even at 100% efficiency of all electronic components (which isn't remotely possible today) all you would do is make no change at all to your range. You cant create energy, you can only convert it from one form to another. In our case the motor converts electrical energy into mechanical energy plus some heat. The generator converts mechanical energy back to electrical plus some heat. If you convert all of the mechanical energy back to electrical you have nothing left to move the vehicle and some heat. The best you could possibly do with this arrangement would be to reduce your range by about 20% due to the addition of the generator and the additional losses involved. And that is if you do a really good job. In the worst case the vehicle would simply not move and warm up the space around the vehicle.

We have a special place on the forum for discussions like this one. 

Our special place thread

Read through that thread and hopefully you will understand.


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## rcprodriver (Oct 19, 2013)

thanx
I guess altenators/generators provide more drag than I imagined. In my mind it seemed like it would take less energy to spin the altenator than it would produce.

The other EV issue that bothers me is the batteries. As I mentioned I run Lipo batteries in my RC's. The difference between a NIMH battery and a Lipo battery in a RC is HUGE. Less weight, more power, higher amperage. And these days, you can get a 3s 5000mah lipo for $50. That pack will push many RCs to 60+mph and get you 30 minutes of runtime. Yet, we only see Lipo type batteries in high-end/performace oriented EV cars. I don't buy into the idea that Lipo batteries are to expensive to put in a production EV car. In my mind, that is just the industry not being willing to get things done right.

Side note....in 1983 Honda sold a CRX in japan that had a 1.3L carbed engine that got 70MPGs. My mom's prius gets 45-50mpgs. That is sad considering how complex the prius is in comparison to the crx. Sure, the prius has better performance and more comfort....and thus weighs a lot more. I would love to see a car company build an EV (or even a hybrid) that was stripped down and basic. I don't see why my Mom paid so much for a high MPG car, when the same car has many features that are not needed for driving and thus add weight which reduce the MPGs the car could get if it were lighter.

I like the idea of a small 2wd EV pickup. I am one of those people who owns a small pickup and never go more than 30 miles at any given time with it. A 100hp electric setup would be perfect. And the idea of less parts to maintain sounds so appealing. In a perfect world, all cars would be EV and we would all live within range of the places we wanted to go


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## dougingraham (Jul 26, 2011)

rcprodriver said:


> The other EV issue that bothers me is the batteries. As I mentioned I run Lipo batteries in my RC's. The difference between a NIMH battery and a Lipo battery in a RC is HUGE. Less weight, more power, higher amperage. And these days, you can get a 3s 5000mah lipo for $50. That pack will push many RCs to 60+mph and get you 30 minutes of runtime. Yet, we only see Lipo type batteries in high-end/performace oriented EV cars. I don't buy into the idea that Lipo batteries are to expensive to put in a production EV car. In my mind, that is just the industry not being willing to get things done right.


My battery pack is 51 LiFePO4 prismatic cells of 100AH capacity. It cost me $6885 without shipping. This is a 16.32kwh pack. It weighs about 357 lbs. Using your example that 3s 5000mah pack for $50. That pack is 0.0555kwh. It would take 294 of those to equal my pack in wh. 294*$50 = $14700 or a little over twice as much. And I don't have a big pack.

But here is the rub. Everyone except for Tesla is using LiPo cells in their battery packs. And at the moment only Nissan is making their own cells and thus avoiding paying someone else some profit. The big downside of LiPo cells is they are fragile. You kind of need to keep them within a narrow temp range or they can self destruct (or lifespan is compromised). I think only hybrids are still using Nimh and I read that Toyota is going to switch either this year or next year. For DIY the LiFePO4's as prismatic cells are a lot better deal all around. They are fairly easy to handle, rugged, safe, don't normally need cooling and quite a lot cheaper than LiPo cells. The downside is they are a little bit heavier and a little bit bulkier than LiPo cells but some of that advantage goes away when you add the packaging and cooling to keep them safe.



rcprodriver said:


> I like the idea of a small 2wd EV pickup. I am one of those people who owns a small pickup and never go more than 30 miles at any given time with it. A 100hp electric setup would be perfect. And the idea of less parts to maintain sounds so appealing. In a perfect world, all cars would be EV and we would all live within range of the places we wanted to go


This is ideal for a conversion. Discuss that in the EV builds thread.


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## rcprodriver (Oct 19, 2013)

how does a LifePO4 compare to a lipo cell? In RC, a life cell has less voltage than a lipo cell. 
I don't really buy into lipo's being dangerous....at least not from my experience. I have had a 3s Softcased lipo be thrown from a RC that was goin 40mph and nothing happened. They either have to be punctured or overcharged to catch fire.
And in the best/high powered RC lipos hardly even get warm after hard use.
But I suppose in terms of an EV the amp draw could be much greater.

How does your LifePO4 pack compare to a set of deep cycle marine batteries? How fast can your rx7 go? That car is not what I would expect as the normal EV conversion auto. Tho it is fairly light, so even 100hp motor should move it along pretty good.

Right now I don't have plans to do an EV conversion. I would love to tho. I am mostly wanting to learn as I have trouble understanding why progress seems to be slow (by major auto makers)
Ford is pushing their ecoboost....which is really just a turbo motor with Direct fuel injection which helps make the turbo system more efficient. And they can make a 45mpg engine with over 100hp and 140 of torque....but its still put in a car that is heavier than it needs to be, and in order to achieve that fuel millage you end up with a rather complicated motor which few owners will be able to maintain on their own. Ive worked on turbo cars (1991 Volvo 740) and in turbo terms they were simple. But the ecoboost engines far exceed the complexity and computer control that the Volvo had.

The beauty of the EV is that it is simple. The electric motor is far simpler than a combustion engine and the support systems are far fewer. The only reason combustion engines won out in the 1st place was because gasoline was plentiful and cheap...and ford motor co. had stake in the oil industry at that time.
Can you imagine where battery tech would be now....if the ev cars had won out over combustion engines in the early 1900's?


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## major (Apr 4, 2008)

dougingraham said:


> But here is the rub. Everyone except for Tesla is using LiPo cells in their battery packs.


It is pretty confusing about Lithium cell types. The RC hobby type is commonly called Lipo which I think is Lico. Most EV DIY guys use LiFePO4. Tesla uses LiNCA. Most production BEVs and Plug-in HEVs use LiNMC. Fisker was using A123 LiFePO4.

ref: http://batteryuniversity.com/learn/article/types_of_lithium_ion


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## dougingraham (Jul 26, 2011)

rcprodriver said:


> how does a LifePO4 compare to a lipo cell? In RC, a life cell has less voltage than a lipo cell.


As Major pointed out there are several kinds. The important numbers are LiFe ~100wh/kg LiPo like the RC industry uses is ~130wh/kg. Unfortunately nobody makes available to the DIY crowd large format versions of these cells. So if you want a pack that will drive a car you have a LOT of interconnects to make. The voltage isn't that important since you can just add more cells. With a 51 cell pack like mine you need to tighten 102 bolts. If we used your 3S 5AH example we would need to make 588 interconnects for a similar size pack.



rcprodriver said:


> I don't really buy into lipo's being dangerous....at least not from my experience. I have had a 3s Softcased lipo be thrown from a RC that was goin 40mph and nothing happened. They either have to be punctured or overcharged to catch fire.
> And in the best/high powered RC lipos hardly even get warm after hard use.
> But I suppose in terms of an EV the amp draw could be much greater.


The difference is that if something bad happens in an RC vehicle it runs into a wall or crashes and then catches on fire. Nothing really bad happens. You lost a pack and maybe the vehicle. If this happens in a full size car you get out of the car and watch your car with 15 to 30 thousand dollars of stuff burn to the ground with no good way to put it out. A huge amount of engineering goes into making the battery modules safe in the OEM cars. I've seen a LiPo pack burst into flames a few seconds after an idiot cut off the connector by clipping both wires at the same time. That was enough to cause it to go into thermal runaway.



rcprodriver said:


> How does your LifePO4 pack compare to a set of deep cycle marine batteries? How fast can your rx7 go? That car is not what I would expect as the normal EV conversion auto. Tho it is fairly light, so even 100hp motor should move it along pretty good.


Prismatic LiFe batteries are about 1/4 the weight and take 1/3 the space of Lead Acid batteries and last at least 8 times longer. How fast is my car? 0-60 is about 6 seconds if I make the shift from 2nd to 3rd well. Top speed I have driven it is a few miles per hour over the posted 75mph on the interstate. But I have about 2.5 times the torque and about 50 more horsepower than the car originally had so I see no reason it wouldn't easily do 116mph which would be the 5000 rpm redline in 5th. It could not do this for very long because I have inadequate cooliing on the motor and motor controller. I have not had the opportunity or desire to push it to that point.



rcprodriver said:


> Right now I don't have plans to do an EV conversion. I would love to tho. I am mostly wanting to learn as I have trouble understanding why progress seems to be slow (by major auto makers)


As far as the OEM's are concerned I think we are right on target or perhaps ahead of the game a little. We are not even at the early adopter stage yet. And if everyone woke up Monday morning and decided to go out and buy an electric car the OEM's could not make them. It is going to be a gradual thing no matter how much we want it to happen sooner.

If you want it to happen sooner, budget your funds, pick your car and convert it. Then show everyone just how much better cars powered magnetically are.


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## Karter2 (Nov 17, 2011)

rcprodriver said:


> The beauty of the EV is that it is simple. The electric motor is far simpler than a combustion engine and the support systems are far fewer. ?


Ignoring the mechanical issues,... you are underestimating the complexity of the control and monitoring systems necessary for a practical EV.
Do you know how an electronic speed control system works ( your RC cars ESC) ? .. then imaging how one needed for a 200 -400 volt , 1000Amp 3 phase motor drive !
How about a battery charging or management system for a pack of 100 cells ( 7000 actually in the Tesla !), that must be individually monitored for voltage, charge rate, temperature, etc etc ...also prevent and display any fault conditions etc etc.
There are very few people outside highly experienced professionals, who are competent to work on these systems.
Why dont you try by building an electric powered bicycle or scooter as a start, and see how tricky it can be even on a small scale, then you can begin to respect the advice and abilities of some of the guys on this board. !


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## ga2500ev (Apr 20, 2008)

rcprodriver said:


> totally new here, but have been interested in EV vehicles for a long time.
> 
> Here is a idea/question that has been in my head for some time, and I am hoping you guys can enlighten me.
> 
> ...


Not possible. It would violate the First Law of Thermodynamics:

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

If any process in the Universe had the ability to add energy to a closed system, which is what you are proposing:

battery->motor->alternator->charger->battery (the same one), 

then as soon as this system is turned on, the energy of that system would go infinite, and the Universe would explode.

All energy systems in the Universe have leaks. Efficiency can never be 100% (which would be perpetual motion) or over unity. The leaks convert energy to heat, which can do no further work.

Be glad that the system is set up this way. Any Universe where this law doesn't hold, doesn't exist for very long. Big Bang, Bigger Bang, ceases to exist.



> In a gas car, if your battery gets drained and you get a jump-start...you only have to drive around for a few miles before the battery now has enough charge to start the car many times. And this is achieved with an altenator which does not provide much parasitic loss to the engine. So, couldn't a much larger/powerful altenator/generator be fitted to the electric motor?


This system isn't closed, so it doesn't apply. The external energy is being supplied from gas in the tank. The equivalent of what you are asking for is a gas tank that never empties because the engine pumps more gas into the tank as the car drives.

ga2500ev


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