# Mazda Miata Conversion



## RKM (Jun 9, 2008)

Terje,

A friend and I are both planning to convert Miatas. His is a '90, mine is a '96. We would each like to get a minimum of 50 miles per charge and would like to get more. I'm hoping a lithium iron phosphate group purchase by the spring of '09 may allow for an affordable purchase!!

We may have to opt for lead for the first pack but would really want to avoid lead (weight).

We will likely go for a Warp 9 with Zilla 1K controller. I've read of a potential component group purchase of an AC system in Finland (?), also of a possible group buy in California. This type of purchase might be the way to go for savings. 

Glad to hear about another Miata conversion.

Rob


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## paker (Jun 20, 2008)

I've also been thinking of doing a Miata conversion, Probably a 1990, but it seems everything I read indicates light weight trumps aerodynamics, so I'm also looking at the Honda CRX as a possible donor car, mainly because 98% of my driving is on the highway at 60-70 mph.


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## dimitri (May 16, 2008)

I'm in the middle of 2001 Miata conversion now, using the 144V kit from EV-America. The biggest challenge for me is to find a place for 12 US Batteries, which are surprisingly large and heavy 

I will be posting in the upcoming garage section, hopefully soon.


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## RKM (Jun 9, 2008)

What kind of performance do you expect (range/acceleration/top end)? How much weight in batteries?

Thanks


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## dimitri (May 16, 2008)

I bought 12 of these puppies http://www.usbattery.com/usb_us12vxc.html

each weighs 85 Lb

I don't know what to expect for top performance, but my needs are simple, 30-40 miles a day, no need for highway, flat Florida terrain, so I expect to meet my needs and hopefully exceed them.

I am currently waiting for adapter plate, once I can install the motor, I will fit the rest of the batteries around it, the rest is easy, I am very well versed in electric wiring and schematics, mechanical stuff is a little more difficult for me.


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## flycactus (Jun 23, 2008)

Thanks for the replies guys!

Dimitri,
I'll be sure to check out your progress. Space is definately an issue in the Miata. Any particular reason you went with the US Batteries? 

Rob,
The Warp 9 and Zilla controller both look inviting. I was thinking along the same lines. Group buys seem to be the best way to get LiFePO4, but waiting 'til 09 might be hard. An AC system would be great, but it's probably not within my budget right now (but I won't rule it out for the Shelby kit later). Not sure if shipping from Finland would be economic but it's someting to look at. 

I'll add a couple more thoughts to my planning. I live in Little Rock and have quite a few hills around (not mountains, but a few good sized hills). Also, as far a weight savings go, has anyone thought of removing the convertible top? Not sure how much it would save you and you wouldn't want to get stuck in the rain. What's the weight difference between that and the removable hardtop? Probably a bad idea, but I thought I'd throw it out there. What kind of driveline are you planning? Manual transmission or direct drive? I had heard of somebody just attaching the motor to his rear differential and working with the ratios to get the top end he wanted. Is this feasible? Any other random thoughts you guys might have, throw them out there. I probably think of a hundred random ideas every day (lucky for you my internal filter manages to sort out most of the ones that make no sense  )

Thanks again,
Terje


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## dimitri (May 16, 2008)

I needed batteries over 100 Ah to get decent range, choosing between most popular Trojan and US Battery, I found local dealer with good price and free home delivery. If you want decent range you need more Ah, which comes with size and weight, its a vicious triangle 

I can't lose convertible top, its rain season here  , plus it won't give you much weight savings anyway.

I will be using clutch less kit from EV-America, it uses old clutch disk as a coupler, bolted to motor shaft. Seems as most reasonable thing to do for me, I want to retain gears and rear drive without complex motor wiring.


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## paker (Jun 20, 2008)

Here is a page that might interest those of us that are thinking of using a Miata as an ev.

http://www.sqrt.com/ev/


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## JRK5150 (May 18, 2008)

Wow, paker, nice post! Some of those pics are very useful! I'm doing a similar conversion, but only using 6 batteries. I have a very limited speed and range requirement, so I think I can get away with only 6 to start with. If I were to try to stuff 12 batts into my miata I would cram as many as I could in where the gas tank is now. Then I would try and mount the rest under the hood. If there just isn't enough room under the hood for the rest or it weighs too much to be practical, I would build a box for the trunk. Anybody know for sure how many batteries will fit in the place where the miata's gas tank is?


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## JeffD (Nov 10, 2007)

Hello Parker,

What sort of Motor Controller are you using ?


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## Bowser330 (Jun 15, 2008)

For all those interested in Miata conversions please see this conversion that i ran across on evalbums....

http://www.evalbum.com/1651

100mph
100 mile range
~2000NM of torque for blistering acceleration...

Total cost 35K AUD...

USA Conversion Costs: 
Warp 11 Motor = 3000 USD
Zilla 1K = 2000 USD
Batteries (lifepo4) = 15000 USD
Misc. parts = 5000 USD
Miata donor = 5000 USD

Total 30K USD....A car that can closely compete with the Tesla Roadster for 1/3 the price....hmmm...


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## paker (Jun 20, 2008)

JeffD said:


> Hello Parker,
> 
> What sort of Motor Controller are you using ?


Hopefully a Zilla 1K. I haven't started a conversion yet. Maybe within the year.


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## Vwbeamer (Jun 16, 2008)

The top speed is 90 mph and the 100 mile range is optimistic.


Bowser330 said:


> For all those interested in Miata conversions please see this conversion that i ran across on evalbums....
> 
> http://www.evalbum.com/1651
> 
> ...


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## flycactus (Jun 23, 2008)

Even if the range is a bit optimistic, it still looks to be something to keep an eye on. I'd be very happy with the kind of performance he's expecting. I noticed he's using ThunderSky lithiums...I thought there were issues with them, or have they been worked out? His blog has some nice documentaion of the conversion process (still in the works).


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## Bowser330 (Jun 15, 2008)

Vwbeamer said:


> The top speed is 90 mph and the 100 mile range is optimistic.


Whats wrong with being Optimistic? Especially in the face of Big Oil?

I personally think this website and forum were create based on the optimism of people working with DIY EV technology.


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## Weka (May 23, 2008)

I have also been thinking of doing a Mazda Miata conversion. My view is that this is only possible with lithium batteries and I would aim for a 13 k/w battery pack which equals 10 k/w usable. That would be enough for a 50km effective range (with 20 in reserve) in the hilly terrain around our city of Wellington. The issue with the leads is that you can take out about 110 kilos weight with the engine etc but with 12 lead batteries @26kilos you put around 200 kilos into the car plus another 50-odd kilos with the motor. That means that you really need to upgrade the springs etc and the car's handling really isn't designed for that kind of weight.

My thoughts at the moment are to wait for the lithium situation to become clearer. Really I want somebody else to report back on the status of Thundersky lithium batteries. There seem to be serveral people using them, but getting hard evidence about their quality is surprisingly difficult. Also, we need a battery management system that is reliable and manages the batteries in a predictable manner.


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## RKM (Jun 9, 2008)

Weka,

I'm on the same page as you regarding batteries. I'm afraid that using lead for any reasonable range (70 km) would take the Miata out of the Miata, if you know what I mean.

I've asked this question before. Would it be feasible to start with a 15 kwh pack of LiFePO4 batteries, then add a second pack after a year or two (run them in parallel)? Get rolling on lithium, then add range if/when the price and performance improve.

I'll be looking to have batteries by next spring and am hoping that a more affordable and reliable battery/BMS will be available by then.

Rob


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## Vwbeamer (Jun 16, 2008)

Oh, i think it is great car. i just believe in truth in advertising.


flycactus said:


> Even if the range is a bit optimistic, it still looks to be something to keep an eye on. I'd be very happy with the kind of performance he's expecting. I noticed he's using ThunderSky lithiums...I thought there were issues with them, or have they been worked out? His blog has some nice documentaion of the conversion process (still in the works).


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## Weka (May 23, 2008)

RKM

While in thery it should be completely possible to reserve a place for a second set of batteries at the moment, the battery management system I think pretty much needs to be matched to the batteries. So I suspect you would need two BMS systems - and they cost about 1k.

Also, I think you should assume given the speed of the technology advance that the batteries would be different

In theory I can't think of any particular reason why having two sets of batteries in different states should be an issue, but I suspect in practice it could be a problem. My incination would be to run the smaller initial battery pack into the ground and then completely replace the batteries and BMS with the newer technology that would then be available


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## RKM (Jun 9, 2008)

Weka,

I'm inclined to agree with your assessment of what is theoretically possible versus the practical application. I'm torn between starting out with a heavy lead pack which might provide at best a 40 mile range and spending much more on a lithium pack that would provide the range I would like.

I expect that in 2-4 years, lithium or another chemistry will have matured and become proven and affordable. I don't want to wait that long!


The approach you suggest of opting for a smaller pack and letting it run till done has a problem. If lithium will last 5-10 years as projected, that is a long wait before having significant range.

Like others, I need to feel confident that one of the LiFePO4 suppliers has a quality product that lives up to specs and expectations all while being somewhat affordable. A 25 kwh pack and BMS at around $10-13,000 would work for me. Is this a possibility/probability in the next 10 months? Bulk buy?

Thanks.

Rob


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## flycactus (Jun 23, 2008)

RKM said:


> Weka,
> 
> 
> Like others, I need to feel confident that one of the LiFePO4 suppliers has a quality product that lives up to specs and expectations all while being somewhat affordable. A 25 kwh pack and BMS at around $10-13,000 would work for me. Is this a possibility/probability in the next 10 months? Bulk buy?


I posted on this issue on another thread, but I'll repeat it here since I haven't seen much activity on it. I know that I would ideally like to go with LiFePO4 but I can't get any good info on who folks are buying from. I know there are several suppliers, but nobody seems to be posting who they've gone with. I've heard of at least one NOT to got with (LionEV) due to issues they have with actually sending stuff you pay for.  Assuming I've got the money to spend (I probably don't but doesn't hurt to think about it) who should I be giving it to for LiFePO4s? 

In other news I found a possible conversion candidate at a local dealer. 2001 Miata with 160K on the engine. The dealer wants $8k for it, but I'm sure I can talk him down since the engine light is on, the tires are bald and it was owned by a smoker and definately smells like it. 

Terje


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## Weka (May 23, 2008)

Hi

I don't think you could get a 25k/w pack with BMS for USD $13k. I think the price for say 45 Thundersky cells of 3.2V







90Ah = 12960Wh pack, would cost around AUS$12,000 (say US$11,000) with some more on top for the battery management system. With 80%DOD this gives a useable amount of 10368Wh. So at 80km/hr(125Wh/km) this is about 65km per trip. 80% may be too optimistic and it might be better to run at 70% to prolong battery lfe so that's about 58km. The weight including the BMS and battery box would be about 80-90 kilos. A 25k/w pack would I think cost around USD$22k. If you wanted to see waht that looked like I would recommend the ZEVA site as Ian Hooper has a whole lot of photos. Be aware that this means you have to have two sets of battery boxes - and they are not cheap either.


I am thinking of a 9" Warp9 motor and keeping the gearbox to simplify the conversion - also this seems to be standard for every other MX5 conversion I've seen was done with a 9" motor and retaining the gearbox. I would quite like to find somebody who has a patter for the mating part.​ 

If possible I would put all the batteries up front to simplify the conversion, which would slightly change the weight distribution - losing 60kgs from the rear and gaining it on the front (as is likely) would give 430:550 weight split, or around ~44:56. I would need to get an engineering company to custom make the adaptor plate (I can't find any pre-made), and weld some extra framework to the adaptor plate so it attaches to the old engine mounts, since the gearbox doesn't have its own supports. I think I might be able to get the bank of ThunderSkys to fit above motor in the engine bay, which would be nice. I would be interested in any comments on the above. I have found one guy who has done a Thundersky lithium conversion. He tells me he is using 30 x LPF-90 Thunder Sky batteries and the BMS unit was purchased from the same place as the batteries in Australia: http://www.ev-power.com.au/​ 
So far he has done about 183 miles without problems. So that is encouraging


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## joseph3354 (Apr 2, 2008)

RKM said:


> Weka,
> 
> . A 25 kwh pack and BMS at around $10-13,000 would work for me. Is this a possibility/probability in the next 10 months? Bulk buy?
> 
> ...


the possibility exists right now if enough people could get together and do it. in 10 months it may be even more possible with fewer people involved.


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## kittydog42 (Sep 18, 2007)

I have not begun the project yet, but one of my customers is converting a 2000 Miata to a 156V lithium DC system using Valence group 31 U-Charge batteries. The batteries have already arrived and are ahead of everything else. This brand was chosen for the form factor and based on the recommendations of other owners. The batteries did cost around $20,000, however. If anyone is interested in purchasing these batteries, send me a PM and I will connect you with the person that I bought them through. He has a volume discount already set up based on $500,000 sales. I was not directly involved in the battery transaction.

He paid $8600 for the 2000 Miata in pretty nice shape, so I think that for the 2001, you should talk the dealer down to at least $6500.


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## Weka (May 23, 2008)

Kittydog

I am really impressed by anyone putting in a Valence system. Can you advise the total k/w of the solution? I am not familiar with the terminaology, but a 156 voltage system implies a substantial K/w rating.

What motor are you intending to use and where are you going to put the batteries? Above the motor or in the boot? To have Valence as a viable alternative to Thundersky would be fantastic, and 20k (in ignorance of the kw) sounds very reasonable.

On a different note, does this mean that you hold a standard pattern for the manufacture of a coupling plate between the Miata and the motor? Because if you do, I would be interested in knowing if you could manufacture it and supply overseas (that's why I would like to know the motor)


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## kittydog42 (Sep 18, 2007)

I believe that these are the batteries: http://www.valence.com/assets/pdf/ucharge_xp_data_sheet.pdf

They may actually be group 27, not 31. I could be mistaken. I am planning to put most of the batteries in the rear, below the trunk where the fuel tank used to be. I am also going to put several in the front as well. 

The motor is a WarP 9". I will be making the adapter plate and coupler myself, but since I make each one without a pattern, I don't sell pre made adapter plates.


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## Mannyman (Jul 26, 2007)

My buddy Bob converted a Miata.
Here's a cellphone video I took of it.
www.youtube.com/watch?v=c2W-GzK7bGs


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## redcelt007 (Oct 2, 2008)

Flycactus,
I also live in Little Rock, Arkansas. My current project is a 1993 Mazda B2200. How far along are you on your project?


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## flycactus (Jun 23, 2008)

Holy necro-post, hehe. Red, as far as my conversion goes, it isn't. Life has a way of getting in the way of things. I started planning a couple years ago but it never got much farther than what you see in this thread. I'm still keeping it on the back burner and when life is a bit less complex I'll probably start thinking more about it.


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## DIYguy (Sep 18, 2008)

redcelt007 said:


> Flycactus,
> I also live in Little Rock, Arkansas. My current project is a 1993 Mazda B2200. How far along are you on your project?


I did a 97 B4000.... in case I can help with anything...


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## dtbaker (Jan 5, 2008)

RKM said:


> I'm torn between starting out with a heavy lead pack which might provide at best a 40 mile range and spending much more on a lithium pack that would provide the range I would like.
> 
> I expect that in 2-4 years, lithium or another chemistry will have matured and become proven and affordable. I don't want to wait that long!



Go for the Li now... it is already cheaper per mile of service if the life cycles turn out anywhere near claims.

I am in the middle of upgrade from lead, and hate having my car all torn apart and having to re-do a lot of rack work to make the switch.... but I am also upgrading from 96v of floodies to 120v of lithium.


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