[valerun]

Hi All,

I am relatively new to this whole thing but wanted to own an electric car for a long time! In fact, I am in line for Tesla Model S delivery sometime in ...2013. But my wife and I have decided that we can't wait that long and that's why we just bought our donor car - a 1977 Fiat 124 Spider. Always had a soft spot for Italian cars and the right kind of California rust-free, bright-red beauty just came along... Runs good so I might not be getting a dead-engine super-deal some of you guys are getting but I figured I'd just try to sell the engine, etc. on craigslist.

My target parameters (edited from the original design):
* Range: 60+ miles (with 50% of those miles on the freeway)
* top speed: 65 (to be able to go on the freeway)
* 0-60mph: less than 6s
* clutch and transmission stay in
* donor car weight is ~2000lbs, I intend to stay under 2500 once all the batteries etc are in.

So after reading a bunch of stuff here, doing some more online research and reading a "Build Your Own Electric Vehicle" book, I have tentatively decided on the following "Big3":
1. Kostov 11" motor
2. Soliton1 340V/1000A controller
2. LiFePo4 192V 100Ah pack.

I was thinking of buying motor and controller and some related parts from EV Source (evsource.com), and batteries from ElitePowerSolutions.com (they seem to have good prices for complete systems).

I know 11" is probably an overkill for this small car but I am thinking to maybe upgrade its tranny later and for now run with controller limited at 500A or something like that. My other car is a tuned BMW 335xi (400+ whp) so I do place some premium on performance LOL :-)

I have some good basic EE and CNC machining skills / experience and am planning to make a lot of things like battery racks, motor coupling plates etc. Maybe even chargers etc if I can't get a good deal from the vendors.

So what do you guys think? Would love to hear some feedback on config, what the best sourcing options are, etc. From what I read, I understand that I am looking at a ~$15K conversion...

Thanks!
Valery.

[madderscience]

Sounds like you've got a pretty good plan and the wherewithal to complete it. Just a couple of thoughts:

1) Make sure that the maximum safe discharge rate on the 60AH lithium cells will be sufficient to provide the oomph that the controller and motor are capable of handling. You will probably be a bit over the 1C rate just to maintain 60mph. You might be better off with 100AH cells. More range too

2) A warp 9" can make plenty of power and will rev up better than the warp 11; especially if it is given the Jim Hustead treatment. Also substantially lighter.

3) Not too familiar with the fiat 124, but if it is a rear drive car then you could think about direct drive in which case the warp 11 would be a good choice and the extra weight would be canceled out by removing the transmission.

Good Luck and welcome to the forum.

11" is most likely over kill but if its what you want and it fits go for it. Nice car by the way. I'd go with the larger AH Lithiums from the start. It would be expensive to upgrade those. Im going to be using an 11" in my VW Bus. Over kill! you bet. Get a Soliton1. It has a proven track record that is excellent even for a reasonably new controller. Warp does not have the coverage as the Soliton1. The Warp 11" is a good motor. Get the newest model as it has the most and most recent upgrades. A very good deal. I am not using one but have two 11" Kostov motors.

Pete

[valerun]

Originally Posted by gottdi

11" is most likely over kill but if its what you want and it fits go for it. Nice car by the way. I'd go with the larger AH Lithiums from the start. It would be expensive to upgrade those. Im going to be using an 11" in my VW Bus. Over kill! you bet. Get a Soliton1. It has a proven track record that is excellent even for a reasonably new controller. Warp does not have the coverage as the Soliton1. The Warp 11" is a good motor. Get the newest model as it has the most and most recent upgrades. A very good deal. I am not using one but have two 11" Kostov motors.

Pete

Thanks Pete & all for feedback! What do you mean by 'coverage'? they spec WarpDrive at 160V x 1000A so should be good for 160kW peak power, no?

Re Warp9 vs Warp11 - I was mostly swayed by higher torque constant of Warp11. As you guys rightly mentioned, I will probably have a hard time reaching very high amperage so I thought motor with higher torque constant would be the ticket.

Re battery pack - you guys do have a point there. I just thought I'd start with 60Ah - put the whole thing in the engine bay together with the motor & controller, and then add another 100Ah pack in the trunk wired parallel to the first pack. Going to be more expensive than just buying 160Ah pack I know but not sure by how much - if just 5-10% more, no big deal I think...

Thanks again for feedback. Driving the donor to my house tomorrow!

[madderscience]

I think by "coverage" Gottdi was basically saying more people are using the soliton 1 and it has built up a good track record so far. The warp controller is the new(est) kid on the block at the moment.

The torque constant for a motor states that for so many amps going through it, you get so much torque. With a bigger motor, you are going to see a bigger torque constant. Its pretty obvious why if you think about it; given a certain amount of magnetic force, the longer its lever arm (the diameter of the rotor) the more torque it can put on the shaft. However what isn't immediately obvious is the maximum RPM for the same amount of power (volts * amps) will be less. In other words, for the same amount of input power, a bigger motor gives you more torque and less RPM and basically the same amount of overall power.

It won't do you any good to have a motor and controller that can handle 160KW if the batteries cannot put it out. That is everybody's concern with the 60AH thunder sky cells you are considering. Neglecting voltage sag under load, you would need 1000A at 156V to get near 160KW. Not a good idea with the 60AH lithiums. 100's might take if for a few seconds at a time, and 160's should be OK as long as it isn't constant. If you really want a small, light pack there are other types of lithium out there such as headway cells, A123s and lithium polymer chemistries whose brand names I can't remember right now that can dish out 10C or more continuously; but they are going to be more complex and more expensive to set up.

[EV-propulsion.com]

Nice project, but there is one error in your battery calculations:
"I just thought I'd start with 60Ah - put the whole thing in the engine bay together with the motor & controller, and then add another 100Ah pack in the trunk wired parallel to the first pack. Going to be more expensive than just buying 160Ah pack "

Never mix different size (AH) batteries in the same pack, either in parallel or series- they will not add together, and in actuality you will still only have a 60 ah pack- (your pack is only as big as your weakest cell) , in theis case 60ah. If you ran this without a low voltage cell warning, you would draw down the 60ah cells to the point of damaging them severly. There is no shortcut way to avoid buying the correct size (ah) battery upfront, the best you can do is start with a lower voltage pack to save some money and get the car moving, then add (the same size) batteries later to give you more voltage.
You could of course parallel equal sets of 60ah batteries that would give you 120ah at the same voltage.
Mike
www.EV-propulsion.com

[dimitri]

Valery,

welcome to the forum and congrats on a beautiful donor!

There are couple of major issues with your plan, however, as many have pointed out. Also, you missed a critical data point, desired EV range, without which all battery discussions lose their point.

You can build a great EV with monster motor and small high performance battery ( not the one you plan, sorry ) , burn rubber every time you step on the pedal and have an exellent performance for whopping 5 miles

Somehow I don't think this is what you have in mind for your Spider. Assuming you want to have at least 30-40 miles range to enjoy your convertible around town, not a race strip, here is what I would suggest.

1. Drop from Warp11 to Warp9. You will gain 100lb and $1000 you can use for more battery. Warp9 can burn rubber in this car, so Warp11 is a waste.
2. Get Soliton1, it will look so beautiful under the hood of that Spider, make it a visual centerpiece, plus gives you proven 1000Amp performance, more than you will ever need. I bet you don't even need water cooling with Soliton1, it won't break a sweat on your tiny car.
3. Forget about 60AH pack, its not going to cut it. Go for at least 100AH at 156V. In fact, see how many 100AH cells you can reasonably put in the car, front and back, to get highest voltage you can get. Soliton1 can take up to 300V and chop it down to any motor voltage you want, increasing motor current and decreasing battery current. This will give you best top speed and best acceleration.
4. As for buying a battery as a kit, its not always best option. You lose flexibility of choices. Its just as good to get cells alone and pick whatever BMS/Instumentation fits your needs and budget. I am biased on the subject, so I will leave it at that

Also, assuming you are keeping the transmission, you didn't mention it, so I want to check. Direct drive won't cut it.

Hope this helps.

[EVfun]

I have a pack of 60 amp hour Thundersky Lithium cells and they are good, but not good enough for what I think you have in mind.

I make my cells pull 5C, 300 amps. My 40 cells sag down to 116 volts at that current level (about 2.9 vpc.) I don't know how much harder they can be flogged while holding an acceptable voltage level though I plan to turn it up to 6C (360 amps) in the future because nothing is getting warm. I catch a certain amount of flack for my willingness to go past 3C but based on how stiff my newer TS cells are under load I don't think it will be a problem.

If you can get 360 amps at 140 volts under load then you would have about 60 horsepower to work with. Your post suggests that you expect more.

[tomofreno]

Lot of good comments here, and agree you have the skills and have done some good preparation. Just want to add to the chorus suggesting larger Ah cells from the getgo or higher power density cells like Headway, or, if you are rolling in money, Kokams, for the reasons already given. I think you will have lots of problems with 60Ah cells under the conditions you plan. Better to avoid the headaches if you can.