It isn't just unknown, it's multiple platforms. VW has talked about their "MEB" EV-specific platform for a long time, but every VW Group EV produced so far has been on an adapted engine-driven platform, and even the coming Porsche Taycan - which apparently has an EV-specific platform - is not on MEB. It's not at all clear to me that that the EV components will be consistent between those vehicles and what they will be building.
Rate my build plan (c3 corvette)
5
Location: San francisco, CA
Budget: Like 15k for the donor car, and hopefully less than 20k for all the conversion parts and any labor costs.
Donor car: 1975 c3 corvette. They're cheap, easy to convert the bumpers back to the wonderful 68-72 chrome bumper design, and have some decent safety equipment upgrades over the early cars. A clean 1975 is like 15k, a clean 1970 is 25k or more, YIKES
also, maybe some race car flair to it, need big rear tires to hold all that torque eh?
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Motor: Tesla model S P85 large rear drive unit OR Tesla model 3 performance rear drive unit. The entire tesla rear subframe and all the suspension components, fabricating mounts so it bolts onto the c3 ladder frame. This could be relatively easy or the hardest, most expensive part of the entire project. The motor 3 motor is more efficient when not under heavy load, and FAR FAR better cooling capacity BUT nobody supports their firmware yet and it isn't clear how many years it'll be until the T-1C supports it.
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Battery: 34kw of chevy volt batteries. I'd like Gen2 but the Gen1s are half the price and only slightly lower capacity. Some in the engine bay with a battery enclosure to make it look like a V8 because yummy under hood candy, like ICON's derelict mercury EV did. the rest of the batteries go where the gas tank used to be, which may or may not hang lower and thus cause the full size spire tire sling to have to go away. Volt batteries have excellent high performance because of almost no voltage sag. They're also cheap, work very reliably, have a nice log-like form factor, and have built in excellent battery cooling. I'm hoping for 80+ miles of range
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Cooling: unsure yet, but the water pump and electrically controller diverter valve out of a tesla. chevy volt batteries and the tesla motors have built in cooling systems so no need to screw around making chill plates.
Controller: EV Controls T-1C, pretty close to turn-key, i'd buy it from EV west specifically so i can lean on them for tech support and general info. This controller's already been used in a few tesla motor/chevy volt battery builds
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Contactor: unsure
Power steering: I really want to keep hydraulic power steering, electric pump driven. It's wasteful but it feels so much better than electric power steering. EV West makes a belt fed pump but i'll probably re-use the one that came with the car.
A/C: MVP might omit this since i live in a SF and A/C is kinda unnecessary
Charger: Not sure how to get there, but i absolutely want to shoot for a 50kw charger which interfaces with CCS. With such a short range this feels like a heavy requirement for this to be driveable. There's some noises about CCS charging for DIY builds but this might be a wait and see, hopefully this becomes a mature thing soon (within a year). For 50kw, maybe just stack 5 of those 10kw tesla chargers...?
Safety: Haven't researched much but i would really like switchable fuses between every 72 volts or so, so at any given moment during assembly or maintenance, if i make an oopsie, i only get shocked with 72v before a fuse cuts it. Also, inertial fuses so in a crash, everything is isolated from everything else. Also, a first responder safety line, mimicking tesla's implementation with a BRIGHT RED WIRE right under the hood with a really obvious label on it.
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Timeline: purchase the c3 within a few months, spend about a year maintaining it, adding quality of life upgrades, more deeply researching the platform, more deeply researching the feasibility of my componentry and fabrication. HOPEFULLY buy most of the drivetrain bits in advance and make sure the entire thing works on a bench, THEN start converting in fall of 2020 and be done some point before fall of 2021
So, what am i missing, what bad assumptions or assessments am i making, etc
Budget: Like 15k for the donor car, and hopefully less than 20k for all the conversion parts and any labor costs.
Donor car: 1975 c3 corvette. They're cheap, easy to convert the bumpers back to the wonderful 68-72 chrome bumper design, and have some decent safety equipment upgrades over the early cars. A clean 1975 is like 15k, a clean 1970 is 25k or more, YIKES
also, maybe some race car flair to it, need big rear tires to hold all that torque eh?
Motor: Tesla model S P85 large rear drive unit OR Tesla model 3 performance rear drive unit. The entire tesla rear subframe and all the suspension components, fabricating mounts so it bolts onto the c3 ladder frame. This could be relatively easy or the hardest, most expensive part of the entire project. The motor 3 motor is more efficient when not under heavy load, and FAR FAR better cooling capacity BUT nobody supports their firmware yet and it isn't clear how many years it'll be until the T-1C supports it.
Battery: 34kw of chevy volt batteries. I'd like Gen2 but the Gen1s are half the price and only slightly lower capacity. Some in the engine bay with a battery enclosure to make it look like a V8 because yummy under hood candy, like ICON's derelict mercury EV did. the rest of the batteries go where the gas tank used to be, which may or may not hang lower and thus cause the full size spire tire sling to have to go away. Volt batteries have excellent high performance because of almost no voltage sag. They're also cheap, work very reliably, have a nice log-like form factor, and have built in excellent battery cooling. I'm hoping for 80+ miles of range
Cooling: unsure yet, but the water pump and electrically controller diverter valve out of a tesla. chevy volt batteries and the tesla motors have built in cooling systems so no need to screw around making chill plates.
Controller: EV Controls T-1C, pretty close to turn-key, i'd buy it from EV west specifically so i can lean on them for tech support and general info. This controller's already been used in a few tesla motor/chevy volt battery builds
Contactor: unsure
Power steering: I really want to keep hydraulic power steering, electric pump driven. It's wasteful but it feels so much better than electric power steering. EV West makes a belt fed pump but i'll probably re-use the one that came with the car.
A/C: MVP might omit this since i live in a SF and A/C is kinda unnecessary
Charger: Not sure how to get there, but i absolutely want to shoot for a 50kw charger which interfaces with CCS. With such a short range this feels like a heavy requirement for this to be driveable. There's some noises about CCS charging for DIY builds but this might be a wait and see, hopefully this becomes a mature thing soon (within a year). For 50kw, maybe just stack 5 of those 10kw tesla chargers...?
Safety: Haven't researched much but i would really like switchable fuses between every 72 volts or so, so at any given moment during assembly or maintenance, if i make an oopsie, i only get shocked with 72v before a fuse cuts it. Also, inertial fuses so in a crash, everything is isolated from everything else. Also, a first responder safety line, mimicking tesla's implementation with a BRIGHT RED WIRE right under the hood with a really obvious label on it.
Timeline: purchase the c3 within a few months, spend about a year maintaining it, adding quality of life upgrades, more deeply researching the platform, more deeply researching the feasibility of my componentry and fabrication. HOPEFULLY buy most of the drivetrain bits in advance and make sure the entire thing works on a bench, THEN start converting in fall of 2020 and be done some point before fall of 2021
So, what am i missing, what bad assumptions or assessments am i making, etc
21 - 40 of 81 Posts
From an outsider's perspective... there are complicated parts of an EV build, and there are simple parts of an EV build. When you absorb it all at once, it all seems equally complicated. So I understand your "go with a known working solution" approach.
However, just so you can make an informed decision... Controllers and motors are agnostic about where the voltage comes from. So while you might be thinking "I want batteries I know will work with X", and intimidated from leaving this known pairing of motor and batteries, that's largely an unfounded fear.
Volt batteries are pretty high power density, but other than that, any battery system you choose would work fine with the Tesla motor. There's really no matching concerns at all. If you wanted to choose a different battery pack, everything will be fine and not additionally complicated. (Also, Tesla batteries for sure were designed for use with Tesla motors
, if you want "proven" solutions then this is proven several orders of magnitude more ).So, that's a huge tradeoff right there.
If lower weight is a priority, then lose range.
If lower weight is a priority, then don't use Volt packs because they are very bulky and heavy for their energy capacity. You could get much lower weight for the same range (like, double) by switching to a different battery.
Not really. Volt packs have awesome power capacity, but terrible energy capacity.
Tesla motors are definitely more awesome than some old DC motor. Regen available, more power, etc. No argument there.
But I'm not sure what aftermarket support you're thinking should/could exist for a DC motor, to ever weigh into your decisions. I.E. What or why would you ever need for support? Change the bearings ever 15 years maybe? They'll be $10 each from any store, standardized for decades. Want it to go faster? Give it more voltage. They're as simple as soup.
I think this is another place your evenly-spread fear of "support" is misplaced.
Cost is probably the reason. Marketing is probably another. People want stuff with Tesla parts in it. There will be enough crashed, pre-engineered Teslas to supply EV West for as much business as they'll ever have. Certainly more than some system they're patching together themselves in low quantities.
Damien just got offered a Model 3 front and rear (they're different) motor on consignment basis that some of his community is trying to crowdfund to pay for. And a few other options. But you're correct. Volunteer open-source controllers are probably the most-abandoned and slowest-progressing facet of DIY EVs. Too highly specialized knowledge required, too huge of commitments to make.
I get where you're coming from, but, when you apples-to-apples it, I don't think that's how it works out. There's no free lunch.
Watts per pound or watts per KWh are going to be fairly comparable. You'll avoid voltage sag by increasing the size of the pack, sure, but keeping the pack size the same? Now it's just down to chemistry. Volt packs are from a hybrid so they're optimized to be a little more power heavy, but they're also old tech and twice the weight.
...
Anyway, it's your project, just trying to help make sure you're making the right choices for you for the right reasons.
While it is a good modern setup the problem is lack of adjustability. They have the advantage of CAD and can model the suspension travel. So you will want to make sure you have the axle center at the same ride height as factory and build your mounting points from that location as the factory or you might find yourself with a camber problem and the factory setup doesn't allow for much adjustment.
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2
ah, that's what you were getting at, yikes, i had not considered that
another thing i hadn't considered, i think this detroit speed kit solves the axle shafts as suspension members problem
https://www.detroitspeed.com/1963-1...3-82-corvette-stock-differential-041740-group
....for $8,800
Although this is making me lean a little more towards the model 3 setup, not sure if that has better adjustment though?
as for track width, there's this c3 image
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and this for the model 3
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the concern is, is the 3's track actually narrower? the problem with these images is..... it's measured rotor to rotor or wheel edge to wheel edge? the c3 image measures both separately which helps
hopefully this means the rotor-to-rotor of the 3 is 62, meaning i get a free 4 inches wider in the rear which is GOOD because i actually WANT to go for a widebody setup to keep this thing on the road!
gains:
-better cooling
-better efficiency
-better adjustment(?)
-more aftermarket support(?)
-better track aligntment
losses:
-not nearly as well understood so far, no turn key systems support it and there's some skepticism if they even will for a while
-possibly narrower track(?)
-slightly lower peak power. Scuttlebutt is that the 3's rear drive can do reliably 500hp with some software tweaking, but that monster p90 rear melon can smash out 600+
another thing i hadn't considered, i think this detroit speed kit solves the axle shafts as suspension members problem
https://www.detroitspeed.com/1963-1...3-82-corvette-stock-differential-041740-group
....for $8,800
Although this is making me lean a little more towards the model 3 setup, not sure if that has better adjustment though?
as for track width, there's this c3 image
and this for the model 3
the concern is, is the 3's track actually narrower? the problem with these images is..... it's measured rotor to rotor or wheel edge to wheel edge? the c3 image measures both separately which helps
hopefully this means the rotor-to-rotor of the 3 is 62, meaning i get a free 4 inches wider in the rear which is GOOD because i actually WANT to go for a widebody setup to keep this thing on the road!
gains:
-better cooling
-better efficiency
-better adjustment(?)
-more aftermarket support(?)
-better track aligntment
losses:
-not nearly as well understood so far, no turn key systems support it and there's some skepticism if they even will for a while
-possibly narrower track(?)
-slightly lower peak power. Scuttlebutt is that the 3's rear drive can do reliably 500hp with some software tweaking, but that monster p90 rear melon can smash out 600+
I don't have access to a model 3 but your track image got me thinking. I not sure your going to be able to fit the unit between the frame rails. Not sure if you seen my build thread but I making a custom frame and using C7 suspension components. The Tesla unit was so wide I had to pocket the upper frame so I could use the C7 sub cradle. Anyway my point is the C7 is much wider than the C3.
So do you know what the distance is between the rails?
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So do you know what the distance is between the rails?
21 - 40 of 81 Posts
