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Discussion Starter · #1 ·
I've been reading through these forums for quite a while now, preparing for my own conversion. I'd love any input as I am sure there are so many here that can say stuff like "well yeah but if you just take this 4 pole 3 phase and make this simple mod to it you can up the HP and get it right in your RPM sweet spot." While I am probably smart enough to eventually get there, the sheer myriad of motor possibilities muddies the waters a bit and any nudges in the right direction are appreciated.

About me:
I am a network security engineer by trade. Lots of 1s and 0s in my life. I also program a lot, so code is my friend. I am fairly mechanically apt, comfortable elbow deep in a Chevy v8. My biggest project so far was a 68 Camaro restore (literally down to the unibody and back up; disk brakes, crate engine, tremec trans, the works). I have dabbled in fab, teaching myself to weld (MIG) for the floor / trunk pans. One of my strong points is learning new things fairly quickly, so that comes in handy with projects like this.

About the project:
I have decided on a '99 Vehicross for the following reasons:
  • Futuristic look from the past
  • Already set up for AWD
  • Body on truck frame (can play with mount points without worrying about messing up unibody structure)
  • Original ICE had horrendous gas mileage (poetic justice?)
  • Rear seats are useless anyway, so it won't hurt to pull them for battery room
  • Found one cheap and everything works
Here is the donor car awaiting its Jenny Craig treatment (gonna go through and drop weight where possible while cleaning and refurbing anything that stays on car):
Tire Wheel Car Land vehicle Vehicle

About the car:
  • 3955lb curb weight + 697lb payload = 4652lb gross (heavy, I know)
  • ICE: 3.5L v6 @ 215HP / 230Torque
  • Automatic trans (not desirable so the plan is to ditch it with the engine)
  • OEM tires: 245/70R16 (9" wide x 29.5" diameter)
  • axle/diff ratio: 4.5:1 (x-fer is 1:1H, 2.48:1L)
  • rear axle is standard full solid axle with 4 link suspension and coils and a small swaybar.
  • front axle is a fixed half axle with diff, then CV to hubs. Independent double wishbone with torsion bars.
Thoughts on motors:
In spite of its weight, this thing feels downright peppy with its modest HP and torque. So I know if I can get close to that HP range, with the extra and more constant torque of electric, it will be a blast. The way I see it I have several options in motor config:
  1. 4 motors (AWD, 1 per wheel).
    • Remove all drive train components
    • Mount motors in axle space center and run CV joints to hubs
    • 4x ~50-70HP motors
    • Will require mods to rear suspension (since it's full axle)
    • Not sure if I can control 4 motors from one inverter / controller
    • Low RPM? This would be direct drive unless there's a gearbox that can go between.
  2. 2 motors (AWD, 1 per axle, use existing axles).
    • Remove engine / transmission / x-fer case
    • Mount motors where transfer case was
    • 2x ~100-150HP motors
    • Easiest? No suspension mods necessary.
    • Same as above, controlling 2 motors
    • Less of an RPM concern with 4.50:1 differential ratio
  3. 2 motors (AWD, 1 per axle, replace existing axles with gearboxes)
    • Remove all drive train components
    • Mount motors where gearbox aligns with original axle location
    • 2x ~100 HP motors with trans (leaf / focus, etc?)
    • Front suspension easy, as it already uses CVs
    • Rear suspension would need mods
    • No RPM concern as you would use gearbox intended for motor
  4. 1 motor (Front wheel drive, replace existing axle with gearbox)
    • Remove all drive train components
    • Mount motor in engine compartment
    • 1x ~200HP motor (cost prohibitive?)
    • Front suspension easy, as it already uses CVs
    • Rear suspension, just remove drive shaft and leave it be?
    • No RPM concern as you would use gearbox intended for motor
While the simplest idea seems to be the 2 motors attached to drive shafts, I don't know how that would affect traction control. The Vehicross has a neat Torque-On-Demand system that monitors wheel speed, axle speed, and throttle position 50x/sec and distributes power accordingly. I am pretty sure there's no way to keep that awesomeness with EV.
Ideally I would love to figure out how to have 4 motors, with the speed controller able to be controlled by my own programming so I could ease the initial torque curve (to avoid the jerkiness of some of the EV conversions I've seen). I could then also have some modicum of traction control, maybe using the stock wheel speed sensors as an input to an arduino? Stop sending power to a wheel if it's free spinning, etc.

Motor RPM thoughts:
I plan to put a couple inches of lift and bigger tires on the project. I know that's counter to EV feng shui but I want this vehicle to be utilitarian as well. Therefore, assuming I go with ~33" tires I'd be looking at about 103.6" circumference, which gives me ~612 turns per mile, or ~713 rpm at 70mph. So direct drive would need to be comfortable at that low RPM or I'd need a gear reducer. If I use the drive shafts and go through the 4.50:1 differentials that leaves me with 3210rpm on the motor shaft.
Of course if I go through the stock x-fer case I can optionally run the thing in 4 low for an additional 2.48:1 for close to 8K rpm motor speed. The thought pains me though as the parasitic loss on that kind of drive train is atrocious.

Controller thoughts:
Man those things are expensive. However, I am guessing that if I want to control the motors with my own programming I'd have to build my own inverter / VFD. I'm not too scared of that but would likely look to people more knowledgeable for advice. I've watched several DIY builds and didn't see anything too far out of my comfort zone; but if someone comes up and says "you can get this pre-built, lighter weight, and it can handle your motors and input desires" I'd be all ears.

Battery thoughts:
Battery pack size would depend on motor setup and overall voltage needs. I understand watts / amps / volts / amp hours / kw hours, series / parallel and all that. My plan is to get the motor / controller setup in place and then size an appropriate pack for the required volts. Start small to proof the system, then move up in range as funds allow. It would be nice to be able to utilize a pre-made pack, say out of a wrecked model 3 or something, but I've also seen a lot of the tear-downs and at their core all these packs are just individual cells with fancy wiring and controllers. In the end it would be nice to have a battery pack that would get me 1 or 2 hundred miles with the ability to charge at a level 2 station, but I know that may take some doing.

Accessory thoughts:
I have working AC and would really like to keep it that way (I live in south Texas). I know that's a pretty big draw on power, but ugh it gets hot here.
Power steering will be a must, especially with a tire size increase. I know there are electric assist racks out there but have no idea what I'd get.
Power brakes as well (I think a power brake pump can be had fairly cheap; I've seen some on ebay from teslas).
In my looking around, it seems that if you could get an additional motor that ran off pack voltage and mount it to a plate with some idler pulleys, you could likely run a compressor, power steering pump, and vacuum pump off the same motor. Use the stock clutch for the AC to ease the load when it's not needed. Of course then you have belt friction to think of. Maybe it's better to run 3 smaller motors off the 12 volt inverter? I dunno.
I'd need the 12V anyway to run lights, radio, blower, etc. But it seems to me running a 12v motor off an inverter is a waste of power when you could possibly run a 3 phase motor right off pack power.

Additional thoughts:
  • It would be neat to work a solar panel in to help with the 12 volt system battery I will most likely use. Maybe mount it in the black hood insert or something.
  • The vehicross is pretty loud, road & wind noise wise. I'm looking for a way to solve for this without upping weight too much. Seals / insulation, etc.
  • Budget is fluid. I have probably around 10K to start with (after vehicle purchase), but that can increase with time and planning (or decrease as I buy a mini split to cool the garage while I work on the shaggin' wagon). Of course if I can save money with DIY then that is one of my driving philosophies in life.

Input I'd like from the community:
Everything. I'd love for this to be a community project. I'm happy with input from motor type to paint color. From you guys I'm looking for Tribal Knowledge. Like "oh, you can get a used warp 11 for $800 if you look here" (no, I have not found any used warps for cheap). Or "this just won't work because I've tried it..." I keep running across posts with cool stuff like "if you take your 4 pole 30HP you can rework it to give you 50HP continuous at lower volts" but no idea which motor to look for, and when I search for motors I have to run through 1000 5HP motors for every higher HP one, plus the EV sites seem to start at $4k for even the tiniest motors.

I am a plan man, used to writing out maintenance procedures, QCing them, and then following the plan. Ideally I'd like to sort out the options above, get a solid plan for the motors in place, which will lead to a plan for the controllers, which will lead to the plan for accessories and pack, etc.
This will start with the disassembly, so I'd like to get a motor plan in place so I know how far to pull apart the drive train and I can work on that and the weight shedding while waiting on shipping.

Thanks in advance for any advice you have!
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