# Planning on converting a 2000+ MR2 Spyder



## kixGas (May 2, 2008)

Welcome to the board.
The MR2 spyder is on my short list of possible cars to convert. Right now I am debating between an MR2, and RX8, or a kitcar. I think that it is a cool option not only for the things you already listed but it also has electric power steering 
To answer your questions:
1. I don't think there would be a huge advantage of either transmission- meaning that I wouldn't let that be the deciding factor on which MR2 to buy (assuming you had 2 to choose from and one was a 5 speed and the other was a 6 speed). However I would stay away from an auto tranny or in the case of the MR2 stay away from the SMT transmission. The MR2 is the only car I know of under $50,000 that has a true SMT and while that is very cool it would be very tricky to get it downshift because it depends on the rpms of the ICE etc.
2. the amps will be limited by your controller and the settings you program into it
3. Another, possibly better, option would be to make your own or go to a local machine shop. Any local machine shop will have the capabilities to make and adaptor for you.
Good luck!


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## slimdigits (Sep 5, 2008)

Thanks! I forgot the mention that it has electric power steering! Which to me makes it the perfect donor 

The MR2 didn't come with a 6 speed stock (except the 03+ SMT) so if a 6 speed wouldn't make much of a difference then I won't worry about it. I won't get an SMT, it would be far to complicated!

You say the amps are limited by the controller, most I see are in the 550-1000A range. Can the WarP and Impulse model motors handle, say 156V at 1000A (15,600 Watts)? Granted this is the maximum of my first project and will only be on days when I want to have some fun with the top down.


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## dimitri (May 16, 2008)

Based on your goals you will need Lithium batteries, so you need a nice budget to go with this nice car 

Power Steering will be nice and easy for you, I have a pump from Spyder in my Miata, works like a charm 

You need to decide on clutch vs. clutchless coupling, read up on it.

And of course, Wiki has most of the answers you need...

Good luck with your project!


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## ClintK (Apr 27, 2008)

slimdigits said:


> Goals
> I'm looking for something get around 100-150 mile range max and have performance settings that will keep up with where it is now. Dual motor is an option for the future, but I want to start with single. I would sacrifice performance on the first project rather than introduce too much complexity that would overwhelm me into giving up.


Just a heads up, have you looked into battery prices yet? Did you have a budget in mind?

Good looking car though, and you'll have a pretty sweet EV when you are done.


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## slimdigits (Sep 5, 2008)

ClintK said:


> Just a heads up, have you looked into battery prices yet? Did you have a budget in mind?
> 
> Good looking car though, and you'll have a pretty sweet EV when you are done.


I haven't looked into Lithium prices yet. I don't really have a budget but I don't want to go crazy! Something like $10k for batteries alone, would be bit much? How much are they? Where would I go to look for the different kinds?

Dimitri, it says that the range of your Miata on a 144V pack is 35 miles? The 99+ Miata and the MR2 Spyder weight the same. Did you do anything to areodynamics or weight reduction such as carbon fiber body parts?


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## dimitri (May 16, 2008)

10k just gets a foot in the door for Lithiums, not enough for performance driving.

Miata is all stock, batteries added 1000 Lb, total of 3200 Lb. I don't have skill or budget to change body parts, my goal was budget and simplicity, I knew I would get 35 miles and it was good enough for 1st generation EV 

I know I can do much better when Lithiums get affordable, meanwhile I am passing gas stations at 55 mph instead of 90 mph  

Look thru EVAlbum to see what results people get with similar cars, its all about how crazy you wanna get with the project


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## slimdigits (Sep 5, 2008)

Messing around with calculator and even with giving the 2200 lb car a drag coefficient of 0.21 and lighting it make I can get is ~40 miles with AGM batteries. The Valance ($1500 a piece) didn't bump it up much farther. Only about 15 miles further at 55 MPH

The maximum voltage of the WarP 9 motor is ~170. Can the battery pack be more than this? What is 'voltage sag'? What is 'motor voltage'?

What if I wired 10 in series with 9 (3x3) in parallel would that give 156V? Never mind space in the little car, is this even possible or a good idea?

How do lifespans compare? Would it be feasible to spend $14k on the Valance batteries if they last 4 times longer than the normal flooded or AGM batteries?


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## dimitri (May 16, 2008)

Its not about motor voltage, its about controller. DC controllers don't go much higher than 156 V. At that point you need to think about AC setup.

Try to buy those Valance batts, I got a nice Email response "sorry, you are too small potato for us, we deal with big guns for now..."

Pretty much your only reasonable option for Lithium is TS bricks sold by various companies like this one http://www.elitepowersolutions.com

You need to get decent Amp hours at reasonable weight and size that fits your car, then see how far you can drive it.


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## kixGas (May 2, 2008)

Slim,

Based on what I learned from this site (IE no real world experience) there are 2 main advantages to Lithuims:
1. A much lower weight battery pack given equal kWh when compared to lead batteries. This will allow you to have a lower (i.e. closer to stock) weight car or further range
2. They can do more cycles than a lead acid battery pack

Of course the disadvantages are:
1. cost
2. The need for a BMS
3. relatively newer technology with out a lot of players in it.

Check out: http://www.elitepowersolutions.com for some batteries


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## bblocher (Jul 30, 2008)

Sounds like a fun conversion. I got lucky on my car with power steering also. After I started the conversion process I realized it had fully electric steering, no hydrolics at all.

Anyways, the 100-150 range. Is this a requirement or just a nice to have? All of us want more miles but reality sinks in when you start doing the math on things. You'd probably need something crazy like $20-25k worth of lithium (including bms, charger). It's really hard to say, every vehicle is different and the type of driving and driving style makes a big difference too.


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## slimdigits (Sep 5, 2008)

Thank you for all of that great information guys!

Dimitri, thank you for warmly befriending an MR2 guy. It seems that often there is a rivalry between the models. Right after posting, I went to read the response you received from Valance. I suppose the timing is just a little too soon.

http://elitepowersolutions.com/products/product_info.php?cPath=1_4&products_id=36
I checked out the Elite Power Solutions site. There products are made for motorcycles and scooters. The EM-60-24 looks like a promising product. You can get the charger, BMS, and batteries all included. The voltage of a pack is 60V-87V (nominal being 76.8V) Two of these in series would work for the current application? ~$5,800 for the two

Thanks for the Link KixGas! I am looking at the life of that batteries: Lead Acid vs Lithium. If it provides lesser weight, comparable kWh, and longer life the advantages might be worth the cost. Still trying to understand everything on here.

Where can I find the formula for kilowatt hours needed? I see the equations to do conversion, but how would one calculate the necessary kWh for a setup. We can use Dimitri's setup for comparison because it is the closest platform I have seen on this site.

Brian, I suppose 100-150 would be nice, but not obtainable with my current platform and resources. 100 max at low amps, to say make it to the beach from Portland, OR for a weekend of leisure. I, as most people, rarely but over ~25mi a day on a car. So settling for the ~30mi range and renting a Prius for said trips isn't out of the question, it's just not nearly as stylish 

Thank you all for your help. I'm continuing to learn, but with your help found here the pictures is becoming clearer!


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## dimitri (May 16, 2008)

> Where can I find the formula for kilowatt hours needed?


Its all in the Wiki here

Make some assumptions - DC motor , 144 V pack, 40 miles planned range, 250 Wh/mile. If your car ends up better than 250, it would be a bonus.

250 x 40 = 10 kWh / 144 V = 70 Ah of usable charge. 

Since you want to stay at min 80% DoD this becomes 85 Ah.

Since your discharge rate will be much faster than 20 hr, Peukert will eat half of your capacity, so it now became 170 Ah.

There is your math, 170 Ah for 40 mile range at 144 V, pretty much matches up with my real life story of 155 Ah for 35 miles.

Now, lithium batts will have different margin for Puekert, so you can get same usable power from less Ah battery pack.

BTW, ELitePower has car packs, they just took them off the site for some reason. My guess is that 90 Ah 144 V pack will be somewhat comparable to my 155 Ah based on better Peukert rate of LiFePo, and also weigh half of it. However, I would rather go for 160 Ah batts for double the range, if I can ever afford it


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## bblocher (Jul 30, 2008)

I forgot to post about it when I read it before. Elitepowersolutions is having supply issues and can't keep enough of the 90+ cells in stock to offer the solutions for the demand they are receiving.

Contact them directly. Last I spoke with them they still had some of the larger solutions in stock and will still take some orders (the delay might be awhile though).

I'm debating myself on going on how big to go. The 160 Ah solution I think would meet my needs for round trip (70+ miles). I, however, have the option of charging at work so the 90Ah batteries should be fine then too but I would be working those batteries much harder on the C rate, plus be recharging more often so then I'm afraid they won't last long enough to justify the cost.


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## slimdigits (Sep 5, 2008)

Quick question. I'm wondering if I should order a new flywheel. They are cheap and I can get them used. Is lighter better in electric applications?

I would assume shaving 5 lbs off of a flywheel would be a good thing, but is there and case where it is not?


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## bblocher (Jul 30, 2008)

The only case I can think of where less weight is bad on a flywheel is when you accidently leave the tranny in neutral and punch the throttle. You could over rev it more easily but there are ways to make this safe with rev limiters


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## slimdigits (Sep 5, 2008)

bblocher said:


> The only case I can think of where less weight is bad on a flywheel is when you accidently leave the tranny in neutral and punch the throttle. You could over rev it more easily but there are ways to make this safe with rev limiters


That is what I was thinking. Just confirming. I fealt as if the world shifted once I stepped over the threshold into the electric realm. It's bright and overwhelming 

As for Elite Power Solutions, I spoke with Jennifer Wenren. She was extremely helpful and speedy! I will be doing some calculations and choosing a battery pack. She sent me a great table showing the weight and dimensions of the various batteries.

The price she quoted me was $1.7/Ah/Cell. For example, if you want 45x 90Ah cells (for 144V) the cost is $1.7*80*45 = $6885

This is incredibly cheap when you factor in longevity. 2000 cycles @ 80% DoD and 3000 cycles @ 70% DoD

As for the table of information,

I will see if I can post this table somewhere on the internet as it is too much to post here (and this board shouldn't allow HTML to be posted)

Does anyone have a page where I can post it?


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## bblocher (Jul 30, 2008)

The cell prices really aren't bad but I wanted to mention the "start up" cost of lithium being the charger and BMS system which are unique and a must. It adds a fair amount 3k+ from them if I recall. You can build your own to save a substantial amount. It's more than I'll want to do so I'll end up buying it I'm sure. They also will give you a one year warranty if you purchase the full system from them so that alone might make it worth the extra cash as we jump into something that isn't known and tested by many here.


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## dimitri (May 16, 2008)

I wouldn't get too excited about 90 Ah, it maybe cutting too close for a car. If these are rated at 3C continuous discharge, that means a limit of 180 Amps for cruising and normal acceleration, which is not enough. Plus you'd be cutting it short for DoD too often to get miles out of it.

I'm afraid that 160 Ah batts would be much better suited for a decent car project which turns it into $14K investment  plus BMS and charger.


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## bblocher (Jul 30, 2008)

dimitri said:


> I wouldn't get too excited about 90 Ah, it maybe cutting too close for a car. If these are rated at 3C continuous discharge, that means a limit of 180 Amps for cruising and normal acceleration, which is not enough. Plus you'd be cutting it short for DoD too often to get miles out of it.
> 
> I'm afraid that 160 Ah batts would be much better suited for a decent car project which turns it into $14K investment  plus BMS and charger.


Opps, I think you mean 270 amps (3C 3*90), not 180. You'd still be exceeding this during starts and acceleration though. For our setups the 160's are perfect giving 480 amps of continuous power rating. Since our controllers can only hit 500 for short periods of time the batteries shouldn't be under any stress at all making for a happy long lived battery 

Edit: Also wanted to add I "think" Elite had the 160 solutions for 15k including charger and bms. Still trying to figure out how to tell the wife about that sticker shock on a project I told her will be 6-10k total hehe


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## dimitri (May 16, 2008)

> I think you mean 270 amps


Doh, brain fart  

Yea, sticker price is shocking, although if they last as advertised, they are comparable to Lead Acid in the long run and much better suited for a car. They came down in price in last 3-4 months too, so if the trend continues they should be more affordable in the future. I know it sucks if you must have them now, I feel your pain  . I am so lucky to have short commute and no need for highway.


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## slimdigits (Sep 5, 2008)

Running the numbers and thinking about all of the other startup costs (and I just bought my first house) I don't think adding another $10k to the project right now is the best thing. The product is in it's infancy. It will become dramatically improved and cheaper over the next couple of years as more full sized EVs are made.

I'll just go with a series of lead acid batteries. That will be enough to get me around town. I can always rent a Prius for the trips to the beach. 

This will allow me to save up for that $55k down on a Tesla.

Thanks for all of your help guys. I have a good grasp now and need to read through all of the wiki. The lead time on the adapter plate from Electro Automotive is 8-10 weeks. I'll let you know when I get a tranny ordered along with a lightened flywheel/clutch combo.


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## booksix (Aug 26, 2008)

I was actually looking into possibly building one of these too. I did some rough calcs with a warp 9 and t-105's and it looks like I should be able to make my 23 mile commute to work where I can charge. It's not ideal having to charge twice a day but after a couple years, even with battery pack swaps, it's still cheaper than gas and hopefully by the time I need my second pack, lithium will be cheap enough.

Hey Slimdigits, any chance you've measured the trunk and engine bay to see how 24 t-105's or US125's could cram in there? That'd be my only concern. Other than that, a warp 9 at 144 volts in that car should be pretty quick and efficient.


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## TelnetManta (Jun 5, 2008)

I would like to see how they will fit myself. Seems like an engineering feet in itself!

Ben


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## booksix (Aug 26, 2008)

Any chance anyone has some measurements? I haven't been able to get a pic of the 'trunk' without that lining in it, but I'm guessing most of the batteries could/would have to fit up there...


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## slimdigits (Sep 5, 2008)

I don't have any measurements. Why are you doing 24 batteries? Why not just 12 12v? 

There is a cross brace in the rear between the engine and the exhaust. I'm going to take that out and putt a battery box in the with integrated bracing. I don't know if I need to, I am repairing and exhaust leak next weekend so I will take some pictures and measurements.


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## mjcrow (Jan 5, 2008)

Doesn't the fuel tank the the 3rd gen mr2 run from side to side behind the seats and is below the behind seat storage? Seems the perfect place for batteries, and you could extend the battery packs up into that storage space if necessary. Would be almost the same positioning as the Tesla batteries.

mjcrow


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## booksix (Aug 26, 2008)

I was thinking 24 to get range. That would allow around 40 miles (calculate at 350wh/mi - figuring high) but I suppose I could run 12 12's (or 13) and still get around the 25 miles I would need. 350 • 25 = 8750 8750 / 156 = 56.08 56.08 • 2.25 = 126.2 Ah


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## slimdigits (Sep 5, 2008)

You are right. The gas tanks is behind the seats on the bottom. It is made to drop right out. That would be a good place, but I don't know the dimensions. It seems to be that it would be hard to fit more that 5 batteries in that location.

With 24 batteries you are talking about 1200+ lbs in added weight just for the battery packs. That is quite a bit with you are starting with a 2200lb two seater.


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## drewjet (May 25, 2008)

I am debating between an S-10 and one of these. It has been a favorite of mine for some time.

I am watching with enthusiasm. and hope it works well for you.


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## dimitri (May 16, 2008)

I often see on the forum that people recommend to stay away from 12v batts. I think its wrong to paint black and white picture like that. Each conversion is different and you can't compare pickup truck with a 2 seat roadster.

When choosing battery you must carefully compare size, weight and AH rate for your target pack voltage. People often compare 6v and 12v batteries out of context of their application. If 12v battery was designed and built for traction application, then it is comparable durability to 6v battery designed for the same application, you gotta compare apples to apples.

Statements of "thicker plates" , etc. maybe applied 10 years ago when there weren't any 12v traction batteries, but today there some nice choices.

I used this US Battery in my conversion, its 155 Ah model , 85 Lb a piece. It gets me 35 miles easily with 70% DoD. 

Fitting 12 batts and dealing with total weight of the pack were most challenging parts of the project. There was no way in hell this could be done with 6v batts.


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## slimdigits (Sep 5, 2008)

Does it make sense to use different brands of batteries with the same voltage? Some have dimensions that would work better in one part of the car, and some better in others. My first thinking would be to steer clear but I'm wondering if it has a simple answer.

Also,

Update: 

I took off the bumper and too some measurements and pictures. I'll post those either tonight or tomorrow.


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## bblocher (Jul 30, 2008)

slimdigits said:


> Does it make sense to use different brands of batteries with the same voltage? Some have dimensions that would work better in one part of the car, and some better in others. My first thinking would be to steer clear but I'm wondering if it has a simple answer.


No this is a really bad idea. The problem is that no two batteries really have the same capacity when it comes to brands. Two batteries can both have a true 100Ah capacity at C/20 but VERY VERY different capacities at C/1. 

For example I've done some studies on Costco's batteries just to see what they would do. They are 115 Ah rated for C/20 but with only a 50 amp load they lasted 45 minutes. So in reality I got about 33 amp hours out of them. Now if you take a Trojan battery that is rated for the same or even slightly less (they advertise numbers to calculate the puekert's effect) you'll see that you can get about 60 amp hours. The only reason I tested the Costco batteries myself was there is no advertised data on them like Trojan has. So, same or very close to the same advertised AH rating, but HUGE HUGE difference for the EV world


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## slimdigits (Sep 5, 2008)

So, the lesser battery could get drained earlier thus killing the chain?


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## dimitri (May 16, 2008)

Most important thing in the battery pack is to keep it balanced, i.e. all individual batteries charge and discharge evenly. This is hard to do even when all batteries came from same production batch, thus need for BMS systems. Balancing the pack with batteries from different sources would be a total nightmare, even if they are rated for same capacity. Also, if 2 diff batts are rated for same capacity and use same chemistry, then they should have same size, volume and weight, although theoretically they can be different shapes.

Bottom line, don't mix different batts in the pack...


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## kixGas (May 2, 2008)

Post those pics when you get a chance. I would like to see what the front compartment looks like under all that plastic. (Wow in the wrong forum that sentence could have an entirely different meaning LOL)


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## slimdigits (Sep 5, 2008)

Sorry that it has taken so long for an update. I will run the numbers when I get rid of this headache!

http://www.uprightape.com/car/


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