THinking about an ev conversion of a c3 vett

8246 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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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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