Anyone ever build an electric car?

[Jay Auskin]

Not fully from scratch, but more of an EV conversion? For some crazy reason this has caught my attention. Maybe it's the whole gas prices thing? I dunno, big cars small cars, I reduced my fuel consumption by living 5 miles from work. So, high fuel prices don't bother me.

I started researching EV conversions. Everyone ends up with 1000 lbs+ of sealed lead acid batteries. First of all, how can that be environmentally friendly? Second, I'm thinking low weight is the key to a good EV. I want to build something that has a solid 40 mile range with lights and heater on. I figure with battery technology, I can always upgrade to longer range and faster speeds. It looks like lithium polymer technology is going to be the next big thing. There are companies like Kokam that make suitable cells, but where do you buy them?? I know the risks of improperly charging LiPo, but it appears that can be handled with battery management.

The EV brainstorming has come about because of warmer Midwest weather. I can bike, but my biking route suks, and I need to go out of my way to not get killed by traffic. Ditto, for scooter/motorcycle Plus, I want to have a winter option. Any thoughts or ideas from the group?

[sewell94]

I haven;t done it but there are 2 guys that built electrics cars and bring them to the drag strip. On is a 944 with like 1300 of tq, he breaks alot drivetrain part and and nissian 240 with like 800 of tq. i don't remeber what the 944 runs but the 240 runs mid 13's. which is respectful.

[svandamme]

www.evproject.com

somebody from the board started that, but i think he moved on and has a friend who took over. no more updates on the site since may 2005 though , so don't know if it's a dead project , or if it's driving by now

[GettinHeadStuds]

Don't know if you've seen this... But this EV beat out the CGT and F Enzo on the strip.

http://wrightspeed.com/x1.html

My imagination: Combustion engines will be equivalent to steam engines in the (not so distant) future.

[Aurel]

0-60: 3s. No gearbox, no clutch. Wow !

Aurel

[Tervuren]

Ok - battery weights.

Lead Acids are perhaps the easiest way as they can support massive amperage loads. They aren't the only chemistry out there though.

A question, is how much are you concerned with safety? If you realy want a light weight eletric, go with Lithium Polymer. The power/weight ratio of these are the best of any battery i have encountered. To get similar wattage out of them as my NMHD's, weight will be about half. The problem is, they can have an extremely violent and hazardess death if overcharged. Shorting one out is also a realy realy bad idea.

This RC truck weighs about 9lb's using GP3300 NMHD's - sub C cells with about 1.6-1.8V unloaded, and 1.2V under a 30 amp load. Capable of spikes into the 100AMP range without too much trouble. The 14 cells weigh about 2lb's.



The Li/poly's, would bring the truck down into the 7-8lb range.

Most eletric motors are design for lower RPM and higher torque, more suited for direct drive then reduction gearboxes a car has. A smaller higher RPM brushed motor will wear faster, but break drivetrain parts a lot less due to similar power output, but less torque.

If you get a good effecient inverter system, go with a three phase sensored brushless motor - then your RPM's are up to the strength of the motor/motors, and the bearings. The one in the truck above, can rev to 60K RPM.

Then you have your motor voltages and amperages, the higher the voltage, the more insulation is needed, as the current can jump through air at higher voltages over short distances. For safety reasons, its best to not set up your batteries for extremely high voltages.

[Jay Auskin]

I have to agree lipo is the best power to weight. But where to get suitable sizes for a real car? No one seems to have anything available. Special order?

[Tervuren]

Originally posted by Jay Auskalnis
I have to agree lipo is the best power to weight. But where to get suitable sizes for a real car? No one seems to have anything available. Special order?

Get someone to make you a system. Basicly, you can wire cells together to increase amperage, and to increase voltage. So if I wired 4 3.5 cells in series, I'd have 14V, then say, these cells are 2AH, and a 10C disharge, if I want to sustain 100amps and 14V for twenty minutes, I'd need 17 stacks of 4 cells in series - 68 cells. Obviously, it can get expensive fairly quickly... 6.4HP potential from that stack of cells.

[91S2]

Check out this electric car!!!

http://www.exn.ca/news/video/exn2005/03/22/exn20050322-eliica.asx

[einreb]

Seems like most of the homebuilt guys use lead-acid batteries.

I like the idea of plug-in hybrids... http://www.calcars.org. Doestn seem to be 'there' yet.

Pretty amazing that what you want is not commercially available. Just makes too much sense? I could fit a lot of batteries in the back of the CRX.

[island911]

The first Dr Porsche built his first car, as an electric. (a motor in each wheel!) He soon found some serios pitfalls of electric.

When I was a kid, I built an electric mini-bike. (had to be different)
In college I got in on a hybrid-electric vehicle project (1993)
My conclusion now is, Electric sucks (compared to IC engines) for passenger vehicles. . . .that the "stack of cells" approach is just more 'thinking inside' the same box many others have thought in before.

[island911]

Originally posted by Jay Auskalnis
.. . Plus, I want to have a winter option. Any thoughts or ideas from the group?

Check on the power output needed of an electric heater, to match that of say, a little 911. Then calculate the number of extra batteries required to run that heater. Then the annual replacemnet ccosts of that option. --this is a good sanity check on the technology for your application.

[Tervuren]

Originally posted by island911
Check on the power output needed of an electric heater, to match that of say, a little 911. Then calculate the number of extra batteries required to run that heater. Then the annual replacemnet ccosts of that option. --this is a good sanity check on the technology for your application.

Letric motors build heat to you know...

The advantage of using liquid fuels, is quick fill up time. I raced my Eltric RC's againt the nitromethanol powered cars, in a 5 minute race, they are toast to my eletric machine. In terms of my driving consistancy, plus the ability to pull out of a low speed corner right in the torque curve, makes up for the lack of horsepower in terms of lap times. (Figure I have about 1/3rd the power of a modern racing MT, my torque is located lower, which reduces the peak power output). Despite the lack of power, I can still keep them behind me, but say, a 15 minute race, every five minutes, spend a couple seconds with a fuel bottle, and the nitromethanol cars are back on the track. Eletric, pull the body off, unclip the battery hold downs, unplug the batteries, pull the batteries out, put the new ones in, clip them down, plug them in, put the body back on - AND I have TWO battery packs. Needless to say, that can put me two laps down. I can ul abou 7 minutes of hard pace on my GP3300's, so thats enough to only have to change once, but being a minute or more lost in battery change, is NOT easy to make up for.

That is why eletric car's are not as common in my opinion, the recharge time. After driving an hour, the car has to sit and recharge for 1-3 hours depending on the batteries charge rate.

[island911]

Yeah, some have addressed this (fairly well) by having a modular power pack. (swap out big batteries quickly to keep the car going)

[Wrecked944]

Check out Issue 5 of Make Magazine. It gives simple DIY instructions for converting a street car to electric. Seems very straightforward. Practical? Probably not. Cool? Hell yes!

[HarryD]

You mean something like this?

Electric Powered Porsche

Or perhaps this saga:

http://www.ztac.net/porsche.htm

[Wrecked944]

I just acquired this tub two nights ago. Shaun84targa and I drove all night to pick it up from a fellow Pelican member named mikey73 in CT. It is a 73T targa and is in better shape than it seems. It has some rust but basically has a complete chassis, complete suspension, steering linkage, windshield and wiring harness.

The motor is gone so it will never be a matching numbers concours candidate. And since it is a targa, it will probably never be a race car. So I am fantasizing about using it as the basis of an EV conversion. I already have an early 915 transmission, recaro seat, and rear deck lid that I can use. I figure I'll throw some glass fenders, bumpers, and hood on it. Then I'll fab a lexan rear window. With so little weight, it might be perfect for EV.

So what are your opinions? I literally got the tub for free. So it would be hard to go wrong. I already have TWO lovely Porsches in great shape. So I wasn't exactly jonesin' for another 911. I can feel free to use this tub for "medical experiments".

[Jay Auskin]

The cost of batteries, motor, and battery management + controller is the big cost. You can either go the current "small block chevy" of the EV world (SLA), or try to get something different. I guess with the cost of a 911 motor, and other NLA Porsche parts, maybe an EV conversion isn't a bad idea.

I'd really like to be able to find real-world prices on "EV sized" lithium polymer batteries. Sure they have the potential for a firery death, but then again...it's a 911 . What I'm thinking is try to get decent technology for the "drive" batteries, and then use SLA for the other items (lights, heater, acc, etc.). They all can be worked into the main charging lead. Again, this is all in my head. but, regarless of what island says, I think it's possible .

We can always talk about this for a while...waiting until battery technology catches up.

[Jay Auskin]

Originally posted by island911
The first Dr Porsche built his first car, as an electric. (a motor in each wheel!) He soon found some serios pitfalls of electric.

When I was a kid, I built an electric mini-bike. (had to be different)
In college I got in on a hybrid-electric vehicle project (1993)
My conclusion now is, Electric sucks (compared to IC engines) for passenger vehicles. . . .that the "stack of cells" approach is just more 'thinking inside' the same box many others have thought in before.

In the above mentioned example, wasn't the NiCad battery "cutting edge"?

No question, IC is a better real world solution, by far. But real world, and what I'm looking to accomplish isn't the same thing. I drive 12 miles every day (round trip). I'd be a giddy school girl if I can double that, in winter, with lights on.

[island911]

So you're already giving-up on the heat option, eh?

You really have a tough road ahead. Chicago in the winter . .. on batteries? - yikes!



So, anyways, on a good day . . .here are a couple graphs for ya. ..

("Power Density" gives punch, "Energy density" gives range.)