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Discussion Starter #1 (Edited)
Hey guys i am considering going EV instead of FI for my MX-5, I would be doing most if not all of the work myself however I have a pretty good set of skills and range of tools available so this should be fine.
I want to make the car more powerful than its standard 103kw from factory while still maintaining what makes the car great/fun to drive, I was hoping to get the equivalent of ~200kw of performance while still maintaining the ability to get a good range of mileage(say 200-300km or maybe more if i drive light footed).

I don't know a huge amount about EV conversions but am happy to do a lot of research if i can be pointed into the right place.
My budget is pretty fluid and i don't mind spending a bit more if it means I'm doing it right.

Thanks,
Andy
 

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A highway-capable EV tends to run about USD$10k in parts. You can skimp there if you're fine with less than 50mi range, or if you can successfully reverse engineer the CAN bus protocol of various OEM components (meaning you wouldn't have to buy a charger, BMS, controllers, etc). Some have transplanted an entire Leaf (which means the total cost of parts is roughly the cost of the Leaf), but you have to keep the dashboard display and some other stuff that might be tough to fit.
 

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By "pretty fluid", give us a ceiling, see if you're in the right ballpark of what it would cost.

Range is easiest.
200 km = ~30kwh pack. ~650 lbs. (Leaf cells, ballpark weight).
300 km = ~45kwh pack. ~1000 lbs.

Even after you remove engine/exhaust/gastank/etc, does a Miata have room to put 650-1000 lbs of battery? Can the suspension handle that? Does that run afoul of your "great/fun to drive"?


Power is a bit trickier.

What will perform better or feel faster might not actually be a motor that is 200% the horsepower, because of the torque curve. You can probably get away with a smaller motor than you'd think. Else I'd say your car won't be able to fit/carry that much weight.

If you need to sustain 200kw of output, you're probably dead in the water. But if you just need it on tap to do sprints and faster acceleration, that's doable.

What motor option you pick will depend on your budget and preferences.
 

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Discussion Starter #4
Well its going to be a long term project so I'm happy to get the money together and buy the high quality parts that are worth it and then skimp elsewhere to get it going before upgrading down the track.
i was going to spend $6000 NZD to turbo the car then another $3-6k on other upgrades to help the turbo so ~$10k would be my starting budget
I have seen other miatas with an EV conversion but never had a good look at them, the engine with all the accessories and fluids is about ~300lbs(not sure on the fuel tank and what not)
i would want around 300km range, I'm okay with the car being a little heavier than it is now as long as i can keep it as close the the 50/50 weight distribution as possible.
the suspension can be upgraded to handle a bit more abuse so that shouldn't be a problem.
it would be 200kw for acceleration and short bursts.


Is there a few motors/batteries you could recommend i start my research at?
 

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I tend to recommend buying a whole Leaf and using everything you can, but they can be easily found for $6-8k in southern California, which doesn't seem true globally. Teslas are good for salvaging, but even the wrecks are pricey. The Leaf and Tesla motors seem to have off-the-shelf controllers that are reasonably straightforward. Apart from that, you're looking at aftermarket stuff such as an AC51 or Hyper9, or perhaps even a forklift motor.

The Leaf motor bolts apart, which makes it nice for mating with a manual transmission. An adapter would have to be made. If the Miata transmission can handle it, the Leaf motor will smoke the tires on that thing. Another option is to stick the Leaf motor in place of the rear diff, but it looks like that would involve a great deal of fabrication, cutting the trunk, and maybe redesigning the suspension...

Leaf batteries are fairly easy to reconfigure into various Tetris shapes and are pretty cheap if pulled from a wreck. Tesla batteries have better power-to-weight, but cost more and require liquid cooling.

I say Leaf, Leaf, Leaf, but there may be a better candidate with better support in Oceana. There are more models available there that have been in production for longer.

Apart from motor, controller, and batteries, you'll need a charger, BMS, charge controller, DC-DC converter, contactors, fuses, display...There are a few OEM components that have been hacked and can be used in conversions, but most would require some reverse engineering of the CAN bus...That sounded daunting to me, so I spent a few grand buying stuff from Thunderstruck.
 

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Hi WattieX111

Whereabouts in NZ are you?

Your problem is going to be somewhere to fit the batteries - how often do you need the range?
A better solution could be the Miata with a shorter range - and an additional battery pack on a small trailer for the long distances

Which would keep the weight down when you don't need it
 

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Discussion Starter #7
I'm in Christchurch, the longer range is just the rare trip to Dunedin to see family but other than that then most trips will be quite short.
 

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I think if I was doing a Miata I would get hold of a Leaf and rob all of the parts -
HOWEVER that is because I'm quite happy about ripping out the complete rear suspension and subframe and making my own

If that is not you then you could do what I have done

DC motor in the same place as the transmission is now
A guy in Dunedin has them for $200 each
P&S controller - $1000
Battery!
I'm using most of a Chevy volt battery - $3300NZ - all up delivered and tax
Leaf modules might be better - but I don't know if you can be as evil with them

Small trailer for the extra range - connect it so it's one or the other so that you can leave the trailer charging while you drive off with a fully charged car at your destination
 

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Very interested to see where you are taking this.

I have a project also underway with the 2001 NB MX5, however I am not going down the EV route.

Instead I am working on a hybrid setup for it, in the process of setting up the electric motor and controller, so I will be very interested to see what battery pack you use and your location for it.

Are you planning on keeping the gearbox? or making a rear axle mounted motor?
 

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I've got a 2000 MX5 with a whole pack of Leaf batteries, so they can fit, but just barely. I have a impulse 9 motor. My range is about 65 miles, although I have never pushed it that far. I have done 45 and had range left. The Zeva controller from down your way is great. For the range you are wanting I think you would need Tesla batteries.
 

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65 miles from a 24kW pack? Interesting. I was hoping I'd get closer to 100mi out of my lightweight Mini, but maybe that's ambitious, as the MX5 is comparable.

Do you happen to know your range from say, 20-80% and what that maps to in terms of high/low battery voltages?
 

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That 65 is theoretical like I said, I might get 70 if I charged fully, drove conservatively and ran it dead. The Leaf these came from I think had a range of 80 or 85 and it was likely more efficient and had regen, which I do not.
I mainly stay between 80% and 20%. I think about 35-40 miles in that range. It all depends greatly on driving style. I can cruise at 50 mph on 80 amps (at 120 V). However once when I had it up to 75 mph i drew 180 amps, so wind resistance has a big effect. The newer packs are 30kw, so maybe you could get more from those.
I have my pack with sets of 3 modules in parallel. 6p16s really since each module has 2 parallel inside. An 80% charge is 128V and 20% is 118 V. Once you get below 3.6 V per cell, which for me is 115 V it really drops fast.
 
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