[Quelhas1123]

Hi all,

I have a miata NC with some engine trouble and I am considering a conversion to EV.

Is there any examples of NC conversions?
Is it complicated?
Any guide?

Thanks

 

[Tremelune]

What are your performance goals? It's complicated, there are no guides, and you should expect the cost of parts to look like $5k if you want highway speeds and 50+ miles of range.

The cheapest way in seems to be buying a used Nissan Leaf and then taking it apart instead of driving it around. You can get by with spending less, but range and power will be significantly reduced.

Sniff around here some. Cost and effort depends heavily on what you want to end up driving.

 

[remy_martian]

The challenge with a Miata is in finding space in the car for the batteries...

You don't tell us your range or performance goals...if you want to go up and down the driveway once between charges, not so difficult.

 

[brian_]

I have a miata NC with some engine trouble and I am considering a conversion to EV.

It can be done, but it will be much more expensive than just fixing or replacing the engine.

Is there any examples of NC conversions?

I'm sure that there have been some. In this forum, the RX-8 (which has essentially the same chassis design but with a different engine and body) is more common... mostly because RX-8 engines die.

Among Miatas, the NA/NB are most commonly converted, because they're older and cheap, and because there are so many years of NA/NB modification experience out there. The NC should be more suitable for conversion because it is a little larger, potentially providing more space for battery.

Is it complicated?
Any guide?

No more complicated than other similar cars, except for the problem of fitting in the battery. As with almost any other car, there is no convenient guide.

The challenge with a Miata is in finding space in the car for the batteries...

You don't tell us your range or performance goals...if you want to go up and down the driveway once between charges, not so difficult.

I agree that space for battery packs is the biggest challenge, and that unless you understand your performance (including range) target, it's impossible to make rational design decisions.

 

[Quelhas1123]

In terms of performance I would like to aim at: 70hp, 50miles range, top speed around 60mph

My budget for the electric part of the ev conversion has a $12k limit.

My basic concerns are:
- Getting the adapter plate, there looks like there is no pre-built ones and I do not trust myself to design one...
- Making the Miata electronics not freak out if the ICE and corresponding ECU are missing...
- motor mount design

I have looked into the leaf based conversion but I am afraid of three things about that: very high voltage, liquid cooling system and inverter to match motor.

I live in Silicon Valley and have not found a garage that could help me on this, I am an electric engineer but really need help in the mechanical part design.

I really appreciate any help, and can pay for some consulting if you guys know anyone that does that kind of thing.

Thanks

 

[brian_]

In terms of performance I would like to aim at: 70hp, 50miles range, top speed around 60mph...

With a reasonable power requirement, small car, and modest range expectation, it should be possible to meet the energy storage requirement with one complete battery pack (one complete set of modules) from a typical plug-in hybrid such as the Chevrolet Volt or Chrysler Pacifica. If you use a low-voltage motor and typical corresponding controller, the modules would need to be configured in two parallel strings to have a suitable operating voltage. Another option is about half of the modules from a battery-only vehicle such as a Nissan Leaf.

 

[Emyr]

I have looked into the leaf based conversion but I am afraid of three things about that: very high voltage, liquid cooling system and inverter to match motor.

I live in Silicon Valley and have not found a garage that could help me on this, I am an electric engineer but really need help in the mechanical part design.

The Leaf voltage isn't that high.
The Leaf battery is air-cooled.
If you're using a Leaf motor, you can also use the Leaf inverter, just changing the logic section. See openinverter.org

 

[brian_]

I have looked into the leaf based conversion but I am afraid of three things about that: very high voltage, liquid cooling system...

The Leaf voltage isn't that high.
The Leaf battery is air-cooled.

"High" is a relative term. The Leaf voltage is no higher than other common current EVs - they're all nominally about 360 V, or a little higher depending on cell chemistry and cell series count (typically 96). This is much higher than an ordinary car electrical system (12 V) or a golf cart (48 V), but once you're up to the 120 to 144 volt range which is typical of traditional DIY conversions, is 360 volts really a problem? Dramatic and scary things can happen even at 120 volts when it is delivered by a battery which is capable of providing hundreds of amps.

The Leaf battery is not actively cooled by anything... it just has ambient air around the case for cooling, so if looking to minimize cooling system complexity the Leaf is an obvious choice. But the Leaf motor and controller are liquid-cooled, and it seems reasonable to assume that any useful controller will likely need liquid cooling and any useful motor will need at least forced air cooling.