# EV from scratch



## im3733 (May 18, 2009)

Hello, I'm new to this site (AKA I found it yesterday). I'm planning to build an EV from the ground up, frame, body, etc. I'm basing the design off of the Lamborghini Embolado, a concept car that looks amazing. I've already figured out the majority of how I'm going to build the body, I'm just needing to know what I'll need for the motor/drivetrain/electronics part of it.

Thanks.

Pics of the Embolado:
http://dminas.files.wordpress.com/2008/08/lamborghini-embolado-2-lg.jpg
http://img.tamtay.vn/files/2008/11/18/ngaothientuan/photos/312163/49316b6d_embolado_2.jpg


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## surgy (May 15, 2009)

beautiful car, you have a HUGE job ahead of you to say the least, but if done right with fiberglass it should show great advantages in your final curbweight, therefor producing greater efficiency and betetr miles per charge. If it were me starting this project I would start with a Pontiac Fiero and chop the boddy off and build my new fiberglass body on top, that way you get to keep the fiero tranny and suspension/subframe. And the Fiero has been converted a million times and is a VERY popular car to convert, not to mention the fact that its rear engine so it matches your car nicely. I would also use a 144V system with LifePo4 batetry packs, this will be an amazing project, and I'm going to be watching very closely, Good luck and I can't wait to see you get started.


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## im3733 (May 18, 2009)

Thanks for the support. I was actually planning on building the frame and all from scratch using either carbon fiber or aluminum. This was mainly because I was going to have custom door hinges on it. Forget Lambo doors, check THIS out! I also run into being able to FIND a Fiero near Lansing, MI. I'm gonna start looking some more, but my internet is being a pain.


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## ithinkidontknow (May 14, 2009)

If you could get that kind of look with the doors designed that way that car would be the BIGGEST HEAD-TURNER EVER! This is wonderful and I am looking forward to your progress!


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## im3733 (May 18, 2009)

Thanks for the support. I'm hoping (once I find and get a donor vehicle, AKA a fiero, kudos to surgy) to post at least weekly on my progress.


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## im3733 (May 18, 2009)

Does anyone have any idea where I might look to find a fiero that is suitable for modding and isn't too overly expensive?


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## dtbaker (Jan 5, 2008)

im3733 said:


> Does anyone have any idea where I might look to find a fiero that is suitable for modding and isn't too overly expensive?


craigslist.com


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## markllar (Apr 28, 2009)

Check the junk yards for the carcass. Good luck. If you are good at electronics give serious thought to an AC system.


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## im3733 (May 18, 2009)

About what level of skill are we talking? What would be the advantages/disadvantages of AC over DC? I'm planning on having a alternator/generator attached to the non-drive axle, and solar panels on the roof.


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## surgy (May 15, 2009)

Lol nice idea with the doors, those would be awesome on a show car, or concept car, but in reality, what happens right after a snow storm when you have been driving around in knee deep muddy slush all day and then your door folds down into it? "OOOPS!!!!!!! there went a $5000 custom door panel!!!" or "Man, these doors are awesome, but the sure do fill the floor up with mudd right after a rain storm" 

Another point on AC you can get WAY more range and power from an AC system than a DC system, but they are WAY more expensive and have more parts and are more complicated. (using WAY as a technicle term here meaning , WAY out of my skill range, lol)


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## im3733 (May 18, 2009)

Actually, the doors fold down into a sealed underbody compartment. They talk about that in other parts of the website. They also tested them and found that the floors and interior actually stay DRIER during a rainstorm than with traditional doors.


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## im3733 (May 18, 2009)

On their website, the one I linked to, it talks about how he doors actually go into a sealed underbody compartment. They also did tests and found that the interior stays drier in a rainstorm than with the traditional door hinges.


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## im3733 (May 18, 2009)

Ok guys. Honestly, I have NO IDEA where to start. This is my 1st EV and I know it's a stretch. My biggest problem is I don't know ANYTHING when it comes to one electric motor vs. another. I am a quick learner, though. But if someone could point me to a site or page that explains the differences and the advantages/disadvantages of each, I'd be forever grateful.


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## ftaffy (Mar 13, 2009)

DC = cheaper and simpler but less effiecient and no real intergrated option for regen braking.
AC = expensive and possibly complicated but more efficient, higher RPM, regen braking.


You have 2 choices:
Direct drive - no gearbox but a diff still in place
Standard drive clutch- gearbox and a clutch. Easier gear changes but losses in the clutch.
Standard drive no clutch - Requires you to "wait" to change gears but more efficient.

The how much power do i need question? Look at the wiki. 
You can also read the calcs i posted in a direct drive thread to help you get started: http://www.diyelectriccar.com/forums/showthread.php?t=29799


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## Anaerin (Feb 4, 2009)

ftaffy said:


> You have 2 choices:
> Direct drive - no gearbox but a diff still in place
> Standard drive clutch- gearbox and a clutch. Easier gear changes but losses in the clutch.
> Standard drive no clutch - Requires you to "wait" to change gears but more efficient.


I count that as 3 choices. 

Also, if you're using a clutch, there is a potential problem with lateral force on the motor's bearings, as the clutch has to "Push away" the motor shaft. If the motor can't deal with a fair bit of lateral force, it may be weakened and degraded by being pushed by the clutch mechanism.

And, as another note, the "Wait" for clutchless gear changes is in the realm of a half-second to a second. Not too bad at all, really, it just means no racing changes up and down the box.


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## im3733 (May 18, 2009)

ftaffy said:


> DC = cheaper and simpler but less effiecient and no real intergrated option for regen braking.
> AC = expensive and possibly complicated but more efficient, higher RPM, regen braking.


Ok. Thanks for that...but i still have a few questions

1. what is regenerative braking? Wikipedia and the internet don't want to tell me it would seem
2. How much more complicated is AC? Like average # of parts, etc.
3. Price range for each? I'm looking at a Pontiac Fiero for a donor vehicle, if that's any help. I'm also rather interested in speed and acceleration (accel being the less of the two).


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## Anaerin (Feb 4, 2009)

im3733 said:


> 1. what is regenerative braking? Wikipedia and the internet don't want to tell me it would seem


The site has given you an answer - Click the dashed link in your (and my) message for a full and complete overview of what ReGen is.


im3733 said:


> 2. How much more complicated is AC? Like average # of parts, etc.


Number of parts is typically the same. Instead of a DC controller, you'll have an AC inverter. The problem is...


im3733 said:


> 3. Price range for each? I'm looking at a Pontiac Fiero for a donor vehicle, if that's any help. I'm also rather interested in speed and acceleration (accel being the less of the two).


DC: Can be done for a "Beer Budget" (Under $1000 - Check out Forkenswift).
AC: Very (Very!) expensive - $4,700+ (bare minimum) for motor, $5,500+ for inverter. Also requires high (300+) voltages, meaning lots and lots of batteries. MetricMind.com has some AC systems (Where I got my prices), and they seem to be the only places that bother to list them, because of the very high price.


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## im3733 (May 18, 2009)

WHOAA!! With price tags like that I'm going with DC. I'm just a poor college kid (I'm actually 17, I just graduated early) working part-time at Arby's. NO WAY could I afford the prices you were talking for AC. DANG! Ok. So. I was able to find some info on reGen, and i get the gist of it. So. What is a realistic range for a DC system on a Fiero. And what would you recommend for voltage? MI has no restrictions that I could find.


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## ithinkidontknow (May 14, 2009)

im3733 said:


> I'm planning on having a alternator/generator attached to the non-drive axle, and solar panels on the roof.


Solar panels on the roof could be nice but aren't really worth the money if you expect to get a whole lot of range out of them. An alternator on the non-drive axle is not really a good idea, you will end up burning more electricity to drive the alternator then the alternator will generate. If you want energy gains from axle rotation, what you need is regenerative braking, where your motor essentially turns into an alternator and will have sort of an "engine braking" effect as you brake your vehicle. Also, there are DC motors that offer regenerative braking, you just have to make sure to get a compatible controller, plus they are usually more expensive. Hope this helps!


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## ithinkidontknow (May 14, 2009)

im3733 said:


> WHOAA!! With price tags like that I'm going with DC. I'm just a poor college kid (I'm actually 17, I just graduated early) working part-time at Arby's.


Exactly how much money do you have to spend? This sounds like a $30,000 project minimum... maybe 20,000 if you have connections.


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## im3733 (May 18, 2009)

$30000? Then where did Anaerin get $1000? I most certainl don't have 20Gs, let alone 30. What are the biggest cost factors you are calculating?


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## im3733 (May 18, 2009)

So is there a way to charge the batteries while driving on a DC system? Or are you stuck with whatever charge you left the house with for the most part?


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## ithinkidontknow (May 14, 2009)

im3733 said:


> So is there a way to charge the batteries while driving on a DC system? Or are you stuck with whatever charge you left the house with for the most part?


The only two ways you can recharge while driving that I know of are through solar panels and regen braking.


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## im3733 (May 18, 2009)

That's what I thought. ReGen braking on a DC motor is dangerous at best, impossible at worst, at least from what I understand. And solar panels don't produce enough juice to really charge the batteries. OK. I guess that's what I got to deal with then. Oh well, maybe I'll figure something out.

Just out of curiosity, what exactly makes it ineffective to use an alternator? Would you need multiple alternators due to the multiple batteries? I'm just trying to figure something out here.


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## ithinkidontknow (May 14, 2009)

im3733 said:


> $30000? Then where did Anaerin get $1000? I most certainl don't have 20Gs, let alone 30. What are the biggest cost factors you are calculating?


I believe the forkenswift EV was something like
1. Free donor car
2. Free forklift motor
3. Semi-free controller
4. Semi-free batteries

These things will normally cost you: 
1. A decent Fiero (rust free) will run around 250-500 bucks if you can find one that isn't running, has a working tranny and other small problems.
2. The cheapest motor you could get would probably be around $1500 not including whatever mounting things and the adapter plate you need to fit it to the tranny
3. A good controller can be between $1000-2000 depending on what you need.
4. A really good battery pack could run as much as $15,000, a decent sized non-lithium one might be around $8,000 and if you sacrifice other things you could probably get that to around $5,000

Take in mind these are the bare essentials for your car to run. If you want to do all these things like make it out of carbon fiber and make cool looking doors, I wouldn't be surprised if all of that cost you about $5,000+ dollars plus hundreds if not thousands of hours of labor. 

Also, solar panels that do anything to the range of your car will cost $5,000+ dollars.

Don't know if I am forgetting anything but all that still adds up to around 20,000 dollars..


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## ithinkidontknow (May 14, 2009)

im3733 said:


> That's what I thought. ReGen braking on a DC motor is dangerous at best, impossible at worst, at least from what I understand. And solar panels don't produce enough juice to really charge the batteries. OK. I guess that's what I got to deal with then. Oh well, maybe I'll figure something out.
> 
> Just out of curiosity, what exactly makes it ineffective to use an alternator? Would you need multiple alternators due to the multiple batteries? I'm just trying to figure something out here.


Regen braking is not impossible with DC motors, it just requires some research and effort. I have heard fairly good reviews from people about certain regen DC motors. (See Sepex motors)
No you wouldn't need multiple alternators if you wire it correctly but the problem is, an alternator only has around a 50% efficiency for turning mechanical energy into electrical energy. Also, keep in mind the mechanical energy from you car is coming from your stored electrical energy. It would go against the laws of physics for you to have any sort of gain in energy for these transitions (unless maybe your only going downhill, and in that case who needs anything more than a frame with wheels).


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## im3733 (May 18, 2009)

Yeah, I just looked at the Forkenswift project and I would not be satisfied with that system. I'm not going to make the body out of CF. My original plan was to use that for the frame, but the Fiero took care of that. I dropped the solar panel idea, and I intend to design and build the door system myself, so it should be at least a bit cheaper.

All in all:
Solar panels: $5000
CF and custom body: $2500 (I'm making my own styrofoam for the body under the fiberglass, compliments of my MSU chemical engineering friend)
So that's about $7500 in (very rough) estimated savings.

Leaving me with:
Fiero: $500
Body: $1000 - 2500
Motor: $1500
Controller: $1500 (sounded like a happy medium)
Battery pack: $5k-8k

Total: $11000 - $13000
Better, still not as good as I'd like it. But if I leave the body alone at first I could do it for 8.5G - 11.5G. And I'm sure I could find at least a few (safe) shortcuts and things I don't REALLY need that will save some $$$.


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## ftaffy (Mar 13, 2009)

You can rewind an alternator (try to find a big one!) to be 144V (pack voltage) and connect it to the drive line (if using a twin shaft motor just connect to the back). Put a pressure switch so it activates when you throttle is less then 50% - simple connection or run on a small controller which measures the throttle position and then activates if its backed off x%. 
That way when its turning there is no circuit for it draw power so in theory (well in my head at least) there should be minimal resistance. You would be luck to get 20% regen on a standard set up, so maybe 10-12% on something like that. Better then nothing.

FYI - i am building a custom EV based around a lotus 7. I came in looking for 100km range, 180km/hr top speed and 0-100km/hr less then 4 sec. 
I will be lucky to get 80km range @ 60km/hr and 0-100 in around 5sec. The batteries are in general shiet. 

For budget batteries:
Lead acids - non sealed - cheap, limited discharge but take punishment
Lead acids - AGM / GEL - Sealed - more expensive, safer, higher dischage, dont like being abused

For a performance build i would be looking at:
Min: 120V, with peak current 500Amps +, 200Amps contin.
Ideal: 192V, 2000Amps peak, 300Amps contin. (THIS WILL KILL BATTERIES!)


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## ithinkidontknow (May 14, 2009)

im3733 said:


> Yeah, I just looked at the Forkenswift project and I would not be satisfied with that system. I'm not going to make the body out of CF. My original plan was to use that for the frame, but the Fiero took care of that. I dropped the solar panel idea, and I intend to design and build the door system myself, so it should be at least a bit cheaper.
> 
> All in all:
> Solar panels: $5000
> ...


You could definitely make a reasonable EV for 10,000 dollars as long as you put the time in. As long as it looks sexy then who cares, right? At 17 you need this to function as a chick-mobile  haha


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## im3733 (May 18, 2009)

I just checked out Sepex. I can get the motor AND the controller for $1050 - 1575 deoending on what amperage, voltage, and HP I want.


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## im3733 (May 18, 2009)

ithinkidontknow said:


> At 17 you need this to function as a chick-mobile  haha


I don't think my fiancee would be too fond of that idea, but it would be sweet to pull away from our wedding in this bad boy. No argument there.


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## ithinkidontknow (May 14, 2009)

ftaffy said:


> You can rewind an alternator (try to find a big one!) to be 144V (pack voltage) and connect it to the drive line (if using a twin shaft motor just connect to the back). Put a pressure switch so it activates when you throttle is less then 50% - simple connection or run on a small controller which measures the throttle position and then activates if its backed off x%.


I suppose this would work, however this is not how a conventional alternator works so make sure you don't just put a bunch of alternators on the drivetrain and expect it to do anything! Never thought of that before ftaffy so thanks, that would essentially act the same as regen brakes and possibly lead to energy gains (plus might save some money over a regen motor).


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## im3733 (May 18, 2009)

Like I said earlier. I think I'm gonna go with a 16 hp 500A 24V-48V sepex motor and controller from Electric Motorsport EV Parts. At $1250 for the pair, my inexperienced mind would call it a good deal. Professional/experienced opinion, anyone?


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## ithinkidontknow (May 14, 2009)

im3733 said:


> I just checked out Sepex. I can get the motor AND the controller for $1050 - 1575 deoending on what amperage, voltage, and HP I want.


Keep in mind, the horsepower listed there is a peak horsepower so you will not be able to run that continuously, you will need an extremely light car if you want to get up to highway speeds with a 25 HP max. 

Take a look at http://www.evparts.com/prod-MT2116.htm. These motors are relatively inexpensive and offer fairly high horsepower and torque. Tons of conversions are done with these motors. Also, if you use ftaffy's idea then there is no need for regen brakes. You will probably save money using this idea, but it will take more man-hours to use.


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## im3733 (May 18, 2009)

Man hours I'm not worried about, I'm taking the summer off from college (mainly cuz all my classes are in a department that isn't offering ANY classes over the summer, go figure). So this will be a good summer project, even though i probably won't finish it in that time. I'm totally sure I understand ftaffy's idea, tho, even though what I did understand sounded great. I understood the pressure switch/controller piece, implementing it would be my problem. I would also have to set it up so that it wouldn't run if the batteries were full, so i don't overcharge. Then I could just put in to like 4th or 5th gear and, depending on my motor, charge my batteries while driving to work/school. The only part I don't understand is what he means by rewinding it. Which part would I need to rewind? (I've replaced a couple alternator in gasaholic vehicles but I've never opened one up, I'm gonna do some google research) Also, what if I started with an alternator designed for semi's? Would that be big enough to do the job?


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## im3733 (May 18, 2009)

Here, what about this one? It has all of the same stats as the one you pointed out, except it's 3lbs lighter, double-shaft, and $45.01 cheaper.


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## im3733 (May 18, 2009)

If I took an alternator like this one, rewound it, and used that, do you think it would be enough? Obviously it'll depend on the rewinding, but i'm still somewhat clueless as to how to find out WHEN you've rewound it for the correct voltage.


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## Jesse67 (May 12, 2009)

Sounds like a cool project. I think you're getting the wrong idea about regen though, it should be spelled out in full, regenerative braking. Ftaffy's idea would add regenerative braking to a DC system which is normally very difficult to do. 

Normal brakes takes your forward motion and using friction at the brake pads turn it into heat. Regenerative brakes works only while you are trying to stop or while going down a big hill, they take your forward motion and using a generator turn some of it into electricity to give a bit of charge back to your batteries.

A generator or alternator is physically hard to turn when its generating electricity, it resists turning and takes work to move, if you had a crank on one you would be sweating just to light up a 100W lightbulb. Because its hard to turn if you hook it to your car wheels while your trying to drive at a steady speed on flat ground it will slow your car down and your car will use more electricity to make up for the drag than the generator is putting back in, period no way around it if it worked that would be perpetual motion. 

Now if you hook up your generator /alternator so it only connects to your battery when you press on the brake pedal the generator will slow your car down because it resists turning. While in the process of slowing down though the generator is making electricity which flows back into the batteries. If the generator/alternator is powerful enough it will have lots of resistance to turning and during a normal stop your regular brakes will not have to come on at all. A good portion of your car's forward motion will be turned back into electricity to charge your batteries. How much depends on the size and efficiency of the generator /alternator. A good regen system might recover 50 to 75% of the energy you used to accelerate your car in the first place but nothing can recover the energy lost from just driving down the road at steady speed, this is lost forever to rolling and wind resistance. 

I hope I don't sound patronizing but its important to understand, good luck with your project and have fun!

Jesse


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## dtbaker (Jan 5, 2008)

Jesse67 said:


> If the generator/alternator is powerful enough it will have lots of resistance to turning and during a normal stop your regular brakes will not have to come on at all. A good portion of your car's forward motion will be turned back into electricity to charge your batteries.



This is IF you batteries can suck up the juice rapidly.... which is a problem in a typical stop. You would typically be dumping energy far faster than batteries can accept without damage when coming to a stop. Unless you have a long gradual braking event, you would still probably be dumping a lot of the energy as heat to avoid toasting the batteries.


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## dtbaker (Jan 5, 2008)

im3733 said:


> WHOAA!! With price tags like that I'm going with DC.


if you go with 8" DC, and 12 or 15 flooded lead 8v batteries, you'll have a zippy little EV for $8k-$9k with all new parts. You might be able to drop a little by scrounging and finding used or ebay stuff, but you end up with a scruffy conversion....

forget the regen, forget solar panels on the car, and keep your clutch.


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## Jesse67 (May 12, 2009)

Good point, you would have to limit the current or pick an alternator/generator that can only put out your max allowable charging current. This would depend on your batteries.


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## im3733 (May 18, 2009)

What if I set up a capacitor system that was carefully balanced with the alternator? One that would charge up upon braking and release the power at a current the batteries can accept, making sure that I wouldn't risk blowing the capacitors in the event of a series of stops.


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## ithinkidontknow (May 14, 2009)

im3733 said:


> What if I set up a capacitor system that was carefully balanced with the alternator? One that would charge up upon braking and release the power at a current the batteries can accept, making sure that I wouldn't risk blowing the capacitors in the event of a series of stops.


Sure, that would work but realize that capacitors are SUPER expensive and you're doing this on a budget, remember? Unless you want to go around pulling capacitors out of old CRT monitors for the next 3 years, it is best to keep it simple!


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## dtbaker (Jan 5, 2008)

im3733 said:


> What if I set up a capacitor system that was carefully balanced with the alternator? One that would charge up upon braking and release the power at a current the batteries can accept, making sure that I wouldn't risk blowing the capacitors in the event of a series of stops.


The capacitor you would need to capture ONE stop would be about .1 Farad. I found one... They are about 8" x 18" x 30", weigh 150#, and cost about $7k.

D


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## im3733 (May 18, 2009)

Well THAT wouldn't work. And I talked to my dad about building a panel with a bunch of capacitors in both series and parallel and he said it would have to be really big, so that's also out of the question. Is there any other component that operates similar to that of a capacitor?


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## Jesse67 (May 12, 2009)

Lets See, 

1000 kg car, 50 km/hr, say bring to a stop in 5 seconds, (this is just a guess for time though)
Ke = 1/2 x mass (kg) x velocity^2 (meters/s)
Ke = 1/2 x 1000 kg x (50km/h / 3.6km/hr/m/s)^2 = 192901
192901 J of kinetic energy, disipated in 5 sec = 38580.2 W
Thats a big alternator! So I guess you need a dedicated generator the size of your motor that turns all the time but only comes on while braking or an AC system to get decent regen braking. Can the batteries take it is a good question though...

say 144V pack
38580W/144 V = 268 amps! Now Thunder sky Lipo4s can charge at max 3C right? so a 100 Amp hour pack could take 300 amps, and that is a reasonable size pack. Now at 3C how much of that energy is lost as heat? Faster speeds would just need a longer stop time to keep it under 3C.

Jesse


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## Jesse67 (May 12, 2009)

So basically you don't need a capacitor bank if you have a good size LiPo4 battery pack. The higher the amphrs your pack the more charge current it can take. 200Amphr pack could take 600 amps, that should slow you down pretty quick. but it also heavier, takes more energy to accelerate etc etc.


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## im3733 (May 18, 2009)

Ok. That males sense, for the most part, the only pats that don't make sense to me is what LiPo4 is, but i'll look it up and know in a few minutes. Another thought, sepex motors are DC motors that are designed to allow ReGen, this is done by wiring the armature and the field are wired seperately and have seperate controller connections. What if I took a larger DC motor (the biggest from sepex is 17 hp) and re wired it to do the same thing? Obviously I'd have to use a special controller, but do you think that would work?


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## ftaffy (Mar 13, 2009)

My thought is that your alternator does not need be that big unless you were trying for all that power, as mentioned it isunlikely your batteries could take it anyway. It was part of the reason i suggested getting a big one!
I cant claim the idea as mine, i saw it on another EV. A citicar i believe but it was connected with a clutch so the alternator was completely disconnected, but unless your producing power no resistance so a switch would be much easier.

Can't help with SEPEX though.

Lip04 are lithium ion batteries, smaller voltage batteries that are much much better then lead acids but require more nursing to keep happy.


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## dtbaker (Jan 5, 2008)

Jesse67 said:


> So basically you don't need a capacitor bank if you have a good size LiPo4 battery pack. The higher the amphrs your pack the more charge current it can take. 200Amphr pack could take 600 amps, that should slow you down pretty quick. but it also heavier, takes more energy to accelerate etc etc.


mmmmmm....... almost.

the 3C rating is for DISCHARGE, not charge! 
no way in hell you can dump hundreds of amps INTO a battery without boiling or blowing it up.

regen to batteries in not real cost effective except for long slow gentle braking. regen to capacitors is not real effective because of size, cost, and weight in a small vehicle. cheaper just to buy more batteries on the charge side to extend range and scrap regen.


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## ithinkidontknow (May 14, 2009)

Thanks for clearing that all up dtbaker, I was about to explode from all the unvalidated theorizing. 

Now, in regards to the Sepex motor, as I said before, 17HP will not be enough to move a 2500 pound car up to highway speeds. If you want this to be more than just a grocery-getter I would advise putting more than one Sepex motor or getting a bigger motor in it.


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## JRP3 (Mar 7, 2008)

Hmmm, where to start. OK, just forget about regen unless you want to go with an AC system, which you probably can't afford, unless you use a lower voltage unit like this one I'm using http://www.thunderstruck-ev.com/AC_drive_performance.htm
Unless you do a lot of stop and go and driving on hills regen just isn't worth it. If you have a 50 mile range pack and you get 10% back from regen that's an extra 5 miles. If you're using lead acid in a Fiero you probably won't be getting 50 miles of range anyway.
Search the www.evalbum.com for "Fiero" and see what others have done.
The cheapest way to go would be to find a used forklift motor in good shape, check out the "Forklift motor" thread, tons of info there. It's all about finding the right motor.
LiFePo4 is Lithium iron phosphate batteries.


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## dtbaker (Jan 5, 2008)

ithinkidontknow said:


> ...17HP will not be enough to move a 2500 pound car up to highway speeds.


...but it WOULD be enough to maintain a reasonable speed if your aero is not horrible. Typical 8" DC with 96v for instance puts out 78HP peak, and will maintain close to 20HP without thermal limit... but for highway you would want 120v or 144v. this PROBABLY means 12v batteries, which means less amp-hr, with shorter range because you are physically limited with how many you can stuff into a small car.

d


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## ithinkidontknow (May 14, 2009)

dtbaker said:


> ...but it WOULD be enough to maintain a reasonable speed if your aero is not horrible. Typical 8" DC with 96v for instance puts out 78HP peak, and will maintain close to 20HP without thermal limit... but for highway you would want 120v or 144v. this PROBABLY means 12v batteries, which means less amp-hr, with shorter range because you are physically limited with how many you can stuff into a small car.
> 
> d


The 15 hp he is talking about is a PEAK horsepower, I do not think this would be enough to accommodate such a large vehicle. This is a motor that handles 48V max. I wouldn't be surprised if this motor couldn't get the car to a top speed of 30mph...


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## dtbaker (Jan 5, 2008)

ithinkidontknow said:


> The 15 hp he is talking about is a PEAK horsepower, ...This is a motor that handles 48V max.


oh no, that would be a disappointment. golf cart at best. for reasonable performance 96v+ and 8" DC motor are minimum.


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## im3733 (May 18, 2009)

No, I'm not talking about using a Sepex motor. That was already covered and moved on. I'm asking about taking a more powerful motor, e.g. a 25, 30, 35, etc HP motor, and rewiring it so that it operates like a sepex motor, with the armature and the field wired separately. This allows for field excitement in such a way that it operates normally going forward, but also allows for regenerative braking with a specialized controller.


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## ithinkidontknow (May 14, 2009)

Sure this is probably possible (I have never seen anyone do this), but the amount of money this could cost plus the risk you would take ruining your motor, probably won't make up for getting the ability to have regenerative brakes.


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## Jesse67 (May 12, 2009)

I got the 3C max charge from the thundersky website data sheet for the 100 amp hr batt found here, check it out. http://www.thunder-sky.com/products_en.asp?fid=&fid2=&page=2

Continuous discharge 3C
Max Charge current 3C
Max impulse discharge 10C

No I havn't validated this, but I imagine someone has.


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## im3733 (May 18, 2009)

How about these batteries? Here is another link that talks about the recharge rate.


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## John (Sep 11, 2007)

Jesse67 said:


> 1000 kg car, 50 km/hr, say bring to a stop in 5 seconds, (this is just a guess for time though)
> Ke = 1/2 x mass (kg) x velocity^2 (meters/s)
> Ke = 1/2 x 1000 kg x (50km/h / 3.6km/hr/m/s)^2 = 192901
> 192901 J of kinetic energy, disipated in 5 sec = 38580.2 W
> ...


I think the problem with using Kinetic Energy for this calculation is that it will give you average power. The power actually tapers off to zero as the speed reaches zero so the initial power that must be absorbed is double. From speed and time you can calculate the deceleration and from the deceleration and the mass of the vehicle you can calculate the decelerative force. Work equals Force times Distance (w = F x d). Power equals Work per Time (P = w/T) so the instantaneous power equals Force times Distance per Time (P = F x d/T) and distance per time you'll recognise as speed. 50/3.6/5 = 2.778 m/s/s. Gravity is 9.81 m/s/s (and 9.81 N/kg) so this is 0.2832g (2.778/9.81). A panic stop could be closer to 1g or maybe even more. So for a 1000 kg vehicle Force equals 1000 x 9.81 x 0.2832 = 2778 N. Power = 2778 x 50/3.6 = 38,586 W. If you notice that my figure is very close to your it's because Ke = 1/2 m.v^2 = 96450 not 192901 as in your first calculation i.e. you didn't multiply by 1/2. The two errors have cancelled each other out.


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## dtbaker (Jan 5, 2008)

im3733 said:


> How about these batteries? Here is another link that talks about the recharge rate.


this article was from 2007.... where are these batteries TODAY?

d


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## ithinkidontknow (May 14, 2009)

dtbaker said:


> this article was from 2007.... where are these batteries TODAY?
> 
> d


"It expects construction of the plant to begin next fall, with batteries coming off the assembly line in 2010."

http://earth2tech.com/2008/12/24/toshiba-to-boost-ev-battery-production-by-2010/

I bet they'll be damn expensive though. 

Some day we will get a fair battery!!!


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## Jesse67 (May 12, 2009)

Very true about the average vs peak power, and yes the half would be important in the kinetic energy equation, oops! 

At constant current the deceleration would be increase untill you came to a stop. AC systems with regen must have a way to limit current to the max that the batteries can handle? I don't know much about these systems but I'd love to learn! With a regen current limit if you hit the (regen only) brakes hard the current would jump to this limit and you will slow down with increasing deceleration untill motor rpms get too slow to function properly as a generator? Where can I got to learn more about this? Like regen current/voltage vs rpm etc?

Fun stuff! I can't wait to start my own!

Cheers


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## ForkenSwift (Feb 3, 2008)

ithinkidontknow said:


> I believe the forkenswift EV was something like
> 1. Free donor car
> 2. Free forklift motor
> 3. Semi-free controller
> 4. Semi-free batteries


FYI, not quite...

1. Donor cars cost $250, but ICE parts sold recovered more than they cost
2. Forklift cost $703, but we got much of that back by selling the chassis to a metal recycler.
3. The golf cart Curtis cost $141
4. Used batteries: first set was free, current set cost $160

I've posted the complete project cost details for anyone who wants to see them: http://forkenswift.com/electric-car-conversion-cost.htm

cheers-
Darin


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## ithinkidontknow (May 14, 2009)

CNCRouterman said:


> Hello im3733,
> 
> Regarding the alternator attached to the non powered wheel. This concept is less than useful for any EV related purpose. If used for generating power to charge the batteries or power the drive motor, you are into the "perpetual motion" argument.



This was already mentioned by me and others earlier in the post. However, there were some clever responses that gave ways to get around this. These ways being having some sort of alternator engage/disengage so that you could control when the axle was driving the alternator. I don't think this would be too hard to do and it seems to be a fairly good DIY regenerative breaking idea! If you are a mechanical engineer or some sort of whiz on fabrication, your input would be helpful.

I was thinking of something like having the axle geared in one location and then have the alternator essentially shift into that gear when needed. You could also rig up a chain and sprocket sort of deal where you engage and disengage the chain with a chain de-railer when necessary.


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