THinking about an ev conversion of a c3 vett

8250 Views 9 Replies 5 Participants Last post by usedtolovegasnowev, May 15, 2012

usedtolovegasnowev

Discussion Starter · Apr 21, 2012

I have a 74 corvette that I love more than my dog(if i had a dog). Although i really hate thats its not a ev because that is really the future. I am graduating as a chemical engineer in a year and right afterI get a job that what I wanna spend my money on. I know its a bit early to start planning but thats how I l ike to do things. I do want to make a good ev conversion though. I have done soem research and this is what I think I want. Please do chime in and let me know what you think btw....

Im thinking a budget of about 15k (I should be able to come up with that after I get a job).
I want a okay range but mainly the power that I have come to love form my ICE engine. I knwo hp ratings are a little different from ICE ratings but I dont go that fast after my last speeding ticket($1300 freaking dollars) but I do love to accelerate to the speed limit as fast as possible. With that being said I think i want a series wound DC motor like the warp 9 or 11. which will be 3k of my budget. Then the controller I was thinking the war drive 1000A one. I was also wandering that a lot of the batteries I see only have above a 1000A discharge rate if I go above 180 Ah's (excepty the CALB's have a 130Ah that can handle 1000A burst discharge rate)... is that true? If so why would someone buy a 1400A controller unless the ran to battery packs in parallel, and who has that kinda space? or money?
because I am still on a budget and space is not in abundance i was thinking of 45 of the CALB's 130 Ah bateries which is a 7.5k.... oouch there goes my budget. And I was wondering on a 3300 pound car what kinda range I would have with a 144 volt, 130 Ah pack running to a warp 9 or 11? And do I need a BMS (I think there are really cool but for another $1500.... idk)
And I know the other 4 k will go to other little things like adapters and electric power steering pump....
I do have the advantage of being really good with tools and I absolutly want to do everything my self(becasue if i dont where is the fun in that).
Also I am actually a welder (I maily work with alum. welding with a tig), so I was thinking I wan just build my motor mount and my batery boxes out of alum. to save weight....
\

Welll i just wrote an essay..... please any input would be ahsome!

Jesse

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Duncan

· #2 · Apr 21, 2012

Hi
Welcome to the madhouse

Batteries/motor current

For a DC series motor and a PWM controller (like OpenRevolt) the controller is a power In = Power Out device

When you are just rolling there is no back EMF from the motor so 500 amps requires only 15v (example)
So the controller has 150v and 50 amps from the batteries and gives 15v and 500 amps to the motor

As the revs rise the back EMF rises and the motor voltage rises

- 2000rpm? - 75v and 500 amps motor = 150v and 250 amps batteries

Battery current and motor current are only the same when the controller maxes out

BMS
You can buy a BMS or become one - I am going to use a half pack bridge and keep an eye on my pack

Range
Think about what you do now - I found that 98% of my daily mileage was under 20Km
When it was over 20Km it was nearly 160 Km

My pack is sized for 30Km

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usedtolovegasnowev

Discussion Starter · #3 · Apr 21, 2012

OH, I thought for some reason that the controller regulated the amperage with constant voltage but your saying it just regulates the voltage? and the amperage is just related to the voltage needed divided by the motors resistance?

and im looking like im going to have to drive up to 45 miles to work when I graduate but Im sure i can plug in at work so I really wanted 50 miles per charge but that's with half being freeway speeds.
And do BMS only keep you from over charging or over depleting your batteries or do they do other fancy stuff like regulate temperature, measure individual battery resistances or make the car fly?

One more question Duncan, what battery pack are you running to get a range of 30 km?

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Duncan

· #4 · Apr 21, 2012 (Edited)

usedtolovegasnowev said:
OH, I thought for some reason that the controller regulated the amperage with constant voltage but your saying it just regulates the voltage? and the amperage is just related to the voltage needed divided by the motors resistance?

The controller switches the power on and off ~20,000 times a second - the "control" is by how long it is on and off in each cycle
10% power = on 10% of the time off 90% of the time
By some magic of AC power and inductance this results in the current multiplication

the amperage is just related to the voltage needed divided by the motors resistance?
Sort of - its the voltage "left over" after subtracting the back EMF

and im looking like im going to have to drive up to 45 miles to work when I graduate but Im sure i can plug in at work so I really wanted 50 miles per charge but that's with half being freeway speeds.
And do BMS only keep you from over charging or over depleting your batteries or do they do other fancy stuff like regulate temperature, measure individual battery resistances or make the car fly?

BMS - depends on what you buy, most stop you overcharging - over discharging - some try to "balance" your individual cells
OEM BMS - do fancy things with temperature
There have been a number of failures caused by BMS - I decided to do without

One more question Duncan, what battery pack are you running to get a range of 30 km?

My pack is 44 series 2 parallel - 16Ah Headway cylindrical cells in a 500Kg 2 seater

I hope this helps, there is a ton of useful stuff on this site

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Salty9

· #5 · Apr 22, 2012

Jesse,

Have you considered keeping your 'vette stock for use on special occasions and converting a lighter car for commuting? You should be able to do it for the same or less money including the cost of the donor vehicle. Also, the 'vette should be worth more stock than converted.

Chuck

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DavidDymaxion

· #6 · Apr 22, 2012 (Edited)

The Corvette does have a heavy motor and tranny.

2500 lb economy car - 300 lbs motor = 2200 lbs.

3000 lbs Corvette - 600+ lbs motor = 2400 lbs.

That's only a 10% weight difference, and the Corvette should have better aero. Plus you can add more weight in batteries to the Corvette and still be at stock weight.

I do agree that generally the Corvette will be a more expensive car to convert, however.

Salty9 said:
Jesse,

Have you considered keeping your 'vette stock for use on special occasions and converting a lighter car for commuting? You should be able to do it for the same or less money including the cost of the donor vehicle. Also, the 'vette should be worth more stock than converted.

Chuck

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Salty9

· #7 · Apr 22, 2012

When I suggested the alternate conversion I was thinking of Duncan's 500kg car which is about a third the mass of the Corvette.

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Frank

· #8 · May 11, 2012

I'm pretty sure that C3's weight closer to 3,500# (dry). It wouldn't be my first choice as a conversion candidate. 45 miles is doable with lithium but it would cost more than you think. I second the suggestion to keep the vette stock and convert something smaller.

On the other hand it would be really cool, especially if the chassis is in good shape. Here's some inspiration: http://www.evalbum.com/2259

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usedtolovegasnowev

Discussion Starter · #9 · May 15, 2012

I know its not the best donor car choice but I do really like the car and working on it and this just seems like the next project (especially since i think ev is the future). I was defiantly going to go lithium ion (hoping the price goes down with them in a few years when i can do the conversion). I was thinking this more or a toy/commuter car. I was thinking about 45 of the gwl/power se100aha lithium lifepo4 cells. The current price would be 6.5K which i s a big part of my budget(but everyone keeps saying a electric conversion is a s good as its batteries are). I know this wont be cheap but the cost spread over the assume year and a half project will be do able. I hear soem people saying that lithium polymer is the future but I can not see why. From what I have seen it has a lower charge density (please correct me if I'm wrong) and the cost is higher, also the cells are more exposed so a container would have to be build for them adding to the custom fab work. And yet white zombie has it in him drag ev?

I was also playing with the idea that I should go crazy and so a double warp 9 with a 288 volt pack running the motors in series with a high voltage/current switch to make the pack a 144 volt going to one motor with double the amp hours.... why? because why not.... it sounds cool (that way I could defiantly have the power i wanted when i want it with the switch of a switch... my original plan for the vette was a 650 hp procharged engine). It would double the cost of the batteries if I went for 90 of the 100 ah batteries but I would probably go for the 60 ah ones.

what are your guys thoughts?

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usedtolovegasnowev

Discussion Starter · #10 · May 15, 2012

and the link with the other vette is what i used for inspiration. I would spend some time to do a frame up restore on mime too... might as well.. that will probably be like 6 months of the project

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