# First timer planning AC conversion, unsure about car choices



## electric! (Sep 3, 2011)

Hi, i'm considering a first conversion, but the used car market where i live is limited. I've visited pretty much all the lots within easily travel range, and i've narrowed my choice down to a few options. They're all smallish 2-door coupes, because i want something small and lightweight. I'm mostly interested in having a commuter car. It would be nice to squeeze out some performance too, although this isn't a big priority.

However, i'm not positive that such small cars are built to handle the weight of the batteries i'm going to need, so this is something i'd like advice on.

Ford Escort (03)
Honda Prelude (87)
Pontiac Fiero (86)
I could probably also find a Chevy Cavalier if i wanted, as these are not hard to get in my area.

In the case of the Fiero (my top candidate right now), it's a mid-engine design with a cast iron block. This means that it's likely designed to stand the weight i need, but it also means i'll be mounting my motor in the rear of the vehicle instead of the front. Is this a terrible situation to be in?

Range-wise, i want at least 50 miles per charge. I don't currently travel more than 25 miles per day, but it would be nice to not have to worry about running out of juice if i have to run a few extra errands or if the batteries are starting to age.

Most of my driving will be on a highway that runs through town, with a speed limit of 55. I'd like to be able to go at least 60 mph, although top speed isn't a huge deal to me, and i'm sure the parts i'm wanting will be able to cover it.

I'm hoping to spend around $10,000 by the time it's all done, although this is not a project with a timeframe set yet, and i'm planning on having all of my parts bought before i start working (i'll be driving the car with its ICE until then). Because i'm not on a tight timeframe, i'm not opposed to spending more money if it's needed in the long run, but spending less would obviously be better.

Spec-wise, i'm impressed with what i've read about AC-induction motors. I'd like to go that route if possible, but looking around, it's harder to find the parts i need, and obviously they're more expensive. At any rate, i like their longevity, efficiency, regenerative braking, and quiet running. My controller options will shift with my motor options, so the motor decision is the most important.

I have also not been able to find an AC-to-DC inverter that's up to the specs i'll need. They've all been wall adapters meant for running (at most) 12v appliances in the home. Is this something i should be worried about, or is such a function already built into a controller i would use for an AC motor?

Batteries will be the last thing i buy, so i haven't decided which ones i'll get yet. If i have more money left over in my 10k budget, i may spring for Li-ion. Or if my weight/space constraints mandate it, i may get them even if it puts me over my 10k mark. Otherwise, i'll probably be going with lead/acid batteries.

I also don't have any experience with auto mechanics or fabrication, but that's not a concern. I'll learn what i need as i go and will learn most of what i need before i actually lay hands under the hood. I've bought and read "Build Your Own Electric Vehicle" (the updated 2008 version) and will soon be working on the formulas i'll need to gauge what kind of voltage i'll need for the weight i'm planning on working with, and so on.

This project is still in its inception, and i'm looking to nail down some more solid ideas before getting off the ground. I will probably buy all of my major parts (motor, controller, gauges, potentiometer, etc) before i even start to pull the engine out of the car, so i'm just looking for tips and guidance before i start purchasing.

Also, on the topic of purchasing, i'd love to hear recommended vendors for some of the main components. The Bob Brant book recommends some manufacturers, but several are either out of business or no longer cater to hobbyists thanks to increased production demand.

Thanks in advance!


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## lithiumlogic (Aug 24, 2011)

Just a quick summary of stuff i've seen on this forum with prices from the adds on the right side column..

AC

Only one choice that's seems to be widely available and "Plug and Play" (if that's the right word) 

HPEV EV50 with Controller $4500
108v and 550amp

DC

Lots more choice

Warp 9 motor (seems popular) $1700
Controller 160v and 1000amp $2000

$800 more for AC and you only get 1/3 the power.

Still, that'll do 60mph easy. Someone had a suzuki swift conversion with this motor, clocked about 16 sec 0-60. Pretty nice range on it too, from what i remember.

Batteries will have to be lithium. 50 mile range at 55mph would be impossible otherwise.

Donor vehicle ... highway range is all about wind resistance and battery capacity. For each candidate, what's the frontal area, what's the drag coefficient, and how much batteries could it carry?


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## dladd (Jun 1, 2011)

The Fiero is fairly popular. Do a search at evalbum.com and you'll see what kind of range others have with various battery/motor/controllers in their Fiero's. 

Have you read JRP3's build? it's an AC Fiero. 

http://www.diyelectriccar.com/forums/showthread.php?t=41752&highlight=fiero

i'm just a newbie, but 50 miles on the freeway with lead seems tough to do. Lead conversions are usually more like 30-35 miles.


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## electric! (Sep 3, 2011)

They should all have around .34-.36 drag coefficient.

Frontal area for the Fiero is 18 sq ft.

Total storage room for batteries shouldn't be a problem, since the rear compartment houses the engine and the front compartment houses the radiator and spare tire. I found a page where a guy converted one and fit 20 6v Trojan lead acid batteries (rear compartment that used to house the engine and trunk) so if i go lithium i may not even need that much space.

He also had to mod the front suspension though, since he packed batteries in the front as well


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## DavidDymaxion (Dec 1, 2008)

The center tunnel in a Fiero holds the gas tank -- some folks have put batteries there, also.


electric! said:


> They should all have around .34-.36 drag coefficient.
> 
> Frontal area for the Fiero is 18 sq ft.
> 
> ...


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## lithiumlogic (Aug 24, 2011)

Revisiting my own post here as i'm still trying to understand the numbers.



lithiumlogic said:


> *AC *
> 
> HPEV EV50 with Controller $4500
> 108v and 550amp
> ...


I'm thinking that a Warp 9 wouldn't necessarily give 3x the power in a fairly modest build, because you are limited by the batteries.

Eg. 12 kwh pack, using commodity cells with max discharge of 3C

You can only do 36kw without going out of spec on the batterys anyway, which is about where the EV50 is. The Warp9 would give better torque below peak power RPM however, because of the higher current limit.


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## mizlplix (May 1, 2011)

A couple of small corrections:

When using an AC system you don't get your dc from the AC side of the controller. You use an ordinary dc/dc converter before the controller converts it to AC. The AC only runs the motor.

I don't know where this "1/3 of the power" figure came from.......
My AC50-650amp system is on par with a 9 inch DC motor. A little lower on low speed torque, but has way lots more rpm's. Don't get hung up on regen braking. it is ok as a free be, but should not be a major selection criteria.

My neigbor's jet electrica with a 120vdc system and fla batteries gets 62 miles per charge.......66 if you don't mind 10 mph. 

Now my recommendation: Go DC. Use a 9 inch motor. And at least a 1000 amp controller. 

Do NOT choose your car for cost. Choose the car you WANT to be driving. 

For your $10,000 budget, you can get: motor, controller, small components, adapter/coupler and fla batteries. Not lithiums, not the car.

But the learning curve and skills to be learned will be your limit as to time table. 

I would figure on lithium batteries, you always get them last. Use wooden mockups to build with.


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## cruisin (Jun 3, 2009)

lithiumlogic said:


> Just a quick summary of stuff i've seen on this forum with prices from the adds on the right side column..
> 
> AC
> 
> ...


Correction, AC50 using 130v with the 1238R 650amp controller is listed on this forum for $4400.00. Wider RPM range allowing RPM up to over 8000rpm. Does have less torque at 0 rpm Compare the differant systems looking at the graphs on this forum.


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