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Locost EV conversion log

10325 Views 86 Replies 11 Participants Last post by  Wayne Alexander
Hi everyone,

I am still in the early planning stages here, but I thought I may as well start a thread to document some of what I'm working on/planning, both for information and feedback.

The car:
-Lotus 7 replica (AKA 'Locost'), built by myself to original book dimensions.
-Currently powered by a 2004 Yamaha R1 motorcycle engine.
-Current weight is about 1200 lbs without driver and half a tank of gas
-Primary use is Autocross, though it is street legal

-Safe and well-built EV conversion
-Torque at low speeds but still possible to cruise on the freeway
-Keep reasonably close to the same weight
-Range isn't a huge concern but 30 miles or so would be nice
-Keep costs under $10k CAD?

Here's a photo from last season:

Tire Wheel Vehicle Car Sky

So the car is obviously a front engine RWD layout (I guess, technically the engine is 'mid' since no part of it is forward of the front axle). The rear axle is a narrowed Ford 7.5" out of a Ranger. From what I can tell, it looks like I can get up to a 4.56 gearset for it. It is currently geared to 3.45, which means the engine is running at 6-7000 rpm on the highway (not good) and still doesn't have as much low end torque as I would like. Also, due to the open intake and limited space for a muffler, I am constantly within a decibel or so of going over the noise limit when I get near redline at WOT. The car will do over 60 MPH in first gear, so I rarely even hit second on the courses we typically run here.

Since I will be left without a transmission after the bike engine is out, and to keep weight down, I am planning to go directly from motor to axle with a two-piece driveshaft. I thought long and hard about a DC motor, but decided against it due to a few reasons, including choice of controllers and availability of suitable motors locally.

So I am looking at either a Leaf motor or a Hyper 9. It would be nice to use a Leaf motor for the lower cost, and bonus if I can get the charger to work with whatever batteries I choose. Right now I can't seem to find much info on using the charger, and even less info on using it with a different battery voltage.

And speaking of batteries, I'm leaning towards second gen Chevy Volt. It looks like I could fit four modules in the car - two under the hood and two in the back where the gas tank is now. The Volt battery comes with three 16s modules and four 12s modules, so I can think of two possibilities:
1. Use two of each module size to get 28s2p (actually 4p since each module is internally 2p) (Good for Hyper 9)
2. Use all three 16s modules plus one 12s in series for 60s (Leaf motor would need at least this much voltage)

Since I designed all the suspension and everything except for the basic layout of the 'book chassis', I already had a CAD model to start with. Here's what it looks like with the Hyper 9 and a Spicer PTO u-joint adapter:
Wheel Tire Vehicle Automotive parking light Motor vehicle

And finally, some of my comparisons. I had to go and wrap my head around how synchronous motors work, so hopefully this is right. I would really appreciate some feedback on this! To get the Leaf numbers, I first took the commonly available graph for the 80kW motor and scaled it up to 110kW at the same RPM. I then scaled the RPM for a given torque value, based on going from 360v to 240v.
Sky Rectangle Astronomical object Slope Parallel

If I did that all correct, it looks like the Leaf motor would give me better torque up to about 40 mph and then the Hyper 9 takes over. The MPH line assumes 4.56 gears. On one hand, I like the added low end power, but on the other hand, power is only useful if you can put it to the ground. Maybe as a next step, I should make another graph that compares wheel torque instead of driveshaft torque, and play around with different combinations of motors and rear end gears.

And that's about where I am at now. Any input is appreciated. My timeline for buying parts is basically most of the summer, then once this season is over I plan to tear the car down and start the conversion as a winter project.

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the full charger and dcdc converter stack is all controllable via can. zombieverter vcu can run the full stack, motor, charger, etc. leaf bms is very easy to talk to. leafspy works great. But volt modules are a good choice. Cheap and power dense.

ether pick up the 160kw inverter or a open-inverter replacement board to push the 80kw inverter to 140kw.
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I'm planning a similar build with a 1972 Datsun 1200 and 4.56 gears. I had really wanted to do a Nissan Leaf motor with a Chevy Volt battery, but realized it would be much heavier it would be than a Hyper 9 setup when all was said and done. Your locost would be better off with a Hyper 9 and Tesla modules. 5 to 7 tesla modules (120v) and a direct drive Hyper 9 in the transmission tunnel. 250lb or so for 26kwh battery vs over 400lbs for a 18kwh Chevy Volt pack - the Tesla modules are much lighter for what you get. The motor is lighter too it seems. And a yoke for a driveshaft can be bought from evwest for the Hyper 9 shaft. You can't easily do that on a Leaf motor. Vibrations are more likely spinning at that high an rpm anyway. So you'd need to add a transmission …
leaf motor is near the 200kw class.
volt batteries leaf motors are cheap.

Or hicost?
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the newer leaf gearboxes use sealed bearings, worth swapping over to with running the gearbox backwards
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Oh, any idea what year that started? I can't seem to find any photos online. I also had trouble finding a sealed bearing that was rated for the same RPM as the motor, it'd be interesting to see what they used.
see this thread here Voltswagen T2 -76 - Page 4 - openinverter forum
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Interesting, thanks. Still not sure what year that started but I believe mine is from a 2015 so it must be after that. Between the two numbers he lists and my existing measurements I'm pretty sure I can get my hands on a set. Then I'll have to take before/after measurements to see if the shims need adjusting or not.
ill shoot arlin a message, he did a bunch of research on what bearings to use for his dual leaf motor crx. (yes that arlin from axiom) he found the correct fit type, as the expansion and contraction of the bearing on the shaft and case, from heat, is a very important metric to get right.

also silicon nitride ball bearings... because arching
I'm also trying to work out a good way to feed a speedometer signal to my dash. Looks like the Openinverter may not have a great way to output pulses with a frequency that changes proportional to speed, so I'm currently looking at ways to mount a hall sensor in here.
just setup rpm to send over can in the web interface, then have a Arduino with a can transceiver and a fet converting it to the pulses for the gauge?
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