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Discussion Starter · #1 ·
I got a new donor car yesterday and I wanted to post to mark the beginning of this conversion. It is a 1991 Toyota MR2. I have a 2004 electric transaxle and inverter out of a Toyota Prius that I am going to put in it. I have been experimenting with the control of the electric transaxle for some time now with partial success. I was trying to fit it into a 1966 VW squareback but I got overwhelmed with the amount of rust and restoration that was needed on the donor body. I should have listened to the advice of others that cautioned about what makes a good donor car. I have to learn the hard way apparently. I may still be in the hard lesson mode since there are not many people trying to use the Prius motors but time will tell.

This car needs nothing but a paint job and the interior is perfect so I can focus solely on the electro mechanical aspects of the project. The mid engine design looks like it will work well for my transaxle and conversion plans.
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I will post some pictures of the engine removal once that happens but the wife has declared that there will be no dis-assembly until the VW shell is gone.

The first phase of my plan is to get the car to a grocery getter stage with the small 48 cell 40Ah pack that I already have. In this stage I am not going to bypass the DC boost within the inverter and I am only going to engage the main traction motor (MG2). In this configuration I will be limited by the boost circuit of a 100 battery amps or so.

Once this is functioning I will attempt to increase the power. This is where the fun will start. In addition to adding more cells I have a couple of ideas how to get a considerable amount of power with the Prius setup. I can either start to include the other motor/generator (MG1) and bypass the boost circuit or I can use the MG1 inverter stage IGBTs and some additional inductors to increase the DC boost circuit capacity driving MG2.

Thanks
Jeff
 

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its nice to see someone attempting to reuse a prius synergy inverter.

im waiting for the inverters to go down in price on ebay, before i grab one to tinker with. theere's many of them for sale, but the idiot sellers dont realise that no one changes a faulty inverter, since its bullet proof, and most times, covered by waranty. very soon, ebay will be flooded with this inverters from wrecked priuses,

i dont mean to bust your bubble but that inverter is not "intelligent". cannot operate by its own, it still needs the main ecu to control the boost converter, mg1, and mg2.

this guy tore one down: http://techno-fandom.org/~hobbit/cars/ginv/

from your post, seems that you have already figured that out. looking forward to your conversion, and success.
 

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Discussion Starter · #4 ·
its nice to see someone attempting to reuse a prius synergy inverter.

im waiting for the inverters to go down in price on ebay, before i grab one to tinker with. theere's many of them for sale, but the idiot sellers dont realise that no one changes a faulty inverter, since its bullet proof, and most times, covered by waranty. very soon, ebay will be flooded with this inverters from wrecked priuses,

i dont mean to bust your bubble but that inverter is not "intelligent". cannot operate by its own, it still needs the main ecu to control the boost converter, mg1, and mg2.

this guy tore one down: http://techno-fandom.org/~hobbit/cars/ginv/

from your post, seems that you have already figured that out. looking forward to your conversion, and success.
Thanks for the encouragement.

I am making my own ECU. I have a couple of versions that are a ways from optimal but do sort of work. I got screwed up with my first donor car which was holding me back quite a bit. I hope I am able to mount the transaxle in this car in relatively short order and get on with the inverter/motor control aspects of the project.

I bought the Prius inverter, transaxle, and half shafts off ebay for $550.

I consider this a low budget conversion project.

Jeff
 

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Discussion Starter · #5 ·
I got the ICE out this weekend.
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Degreased the engine bay.
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And starting to line up the new motor mounting.
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I looks like the MR2 axles might work with only light modifications. The inboard CV joint shaft has the same spline as the prius so should plug right into the differential, but the outer diameter of the CV cup hits the transmission housing. I hope with a little grinding I can make it work. "Better to be lucky than smart".

I have decided to use the 2001 transaxle with MG1 and MG2 welded together in instead of my 2004 transaxle for this first trial. My idea is that this motor will spin at a higher rpm with lower battery voltage without using a battery boost converter. I may have less torque but hopefully good enough and a better match for my smaller battery pack for now.

Now I am working on my motor mounting options. I might build a frame to fill the void left from the ICE to connect to the far motor mount and fill it with batteries to help balance out the weight side to side.

My body is not used to this kind of manual labor. Hopefully I can get past this part of the job without too much injury.

Regards
Jeff
 

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Discussion Starter · #6 ·
I forgot to mention that I also removed the gas tank from underneath the car.

I have no experience with AirCon compressor and refrigerant. You can the see the compressor dangling in the engine bay picture. I would like to purge the refrigerant and remove it for reattachment to the transmission ICE shaft later in the project.

If anyone has experience or suggestions with this to help me avoid any pitfalls I would appreciate it.

Jeff
 

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Discussion Starter · #9 ·
I bought myself a transmission jack and lifted the Prius electric tranny in place. Fits like a glove.
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I had a clearance problem at first but noticed that the MR2 inbound CV cups on the two axles were non-symmetrical. Swapping the left and right gave about an inch extra position shift in my favor.:)

I also thought that I had to grind down the MR2 CV cup for clearance but this was not case so the only modification was swapping the left and right cups.

I am now going to start framing up the mounting. My rough plan is to build a battery support structure where the ICE used to be.

Long term goal is a preassemble transmission + inverter+ battery unit that can be swapped out for the MR2 form factor in a single day with minimal donor modifications. This is my plan even though I don't expect my prototype to resemble this goal at first attempt.

Jeff
 

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Fantastic idea this, if successful you'll have a serious winner! Love the donor choice also! Perhaps would have gone for a later MRs (3rd edition) as it's lighter etc, but then also smaller and more cramped so hard to choose. I follow with great anticipation!
Tyler
 

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Discussion Starter · #11 ·
Fantastic idea this, if successful you'll have a serious winner! Love the donor choice also! Perhaps would have gone for a later MRs (3rd edition) as it's lighter etc, but then also smaller and more cramped so hard to choose. I follow with great anticipation!
Tyler
I made an offer on the MR2 Spyder convertible but the person didn't take it. I then decided it might not be so bad to use a less expensive version to get the kinks out. If it works out my plan is to have a kit for various mid engine and front wheel drive models.

Thanks for your interest. I am sorry if progress will seem slow. I don't get a whole lot time to work on it.

This weekend I spent more time verifying clearance and motor mounting options. I am sure as soon as start cutting and welding I will think of a better design.
 

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Discussion Starter · #12 ·
Seeing the conversions at EVCCON raised the bar on me quite a bit. I was very impressed with the workmanship.

I was trying to mount my prius electric transaxle in place of the original MR2 transaxle all the way against the driver side and then put batteries in place of the ICE to counter balance it. This design would work but I was not thrilled with the complexity of the framing and weight management.
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I then realized that by swapping the long and short axles it would shift the transmission towards the passenger side over 10inches and basically center the weight it in the engine bay. It is very heavy since the electric motors are inside. I would guess the transmission and inverter are over 300lbs combined.

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This picture is just a moch up of what it will look like and I like it much better. I now need to build a beefy cross member and brackets that the transaxle will hang from. I also decided not to use any of the original rubber motor mounts. I figure the cross member will act as a rigid subframe for the motor. I may need to build in some compliance or extra strength in the bracketing to the frame for flexing.

I also only have a portion of my batteries at this time and they will easily fit in the trunk with a very short wire run. This will save me from having to build elaborate boxes to get started on the control electronics. Once I get the thing operational with this pack size I can add more battery boxes in the engine bay on either side of the tranny.
 

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Discussion Starter · #13 ·
I am working on my plans to hack part of my inverter for my battery charger solution. Chargers are expensive and it will be cool if it works out. Here is a picture of my inverter.
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I am using the GenII Prius inverter that has the bi directional boost/buck converter between the inverter and the battery pack. The purpose of the boost converter is to supply up to a 500VDC bus for the inverters to overcome the back emf of the motors at higher rpms. This Bi-Directional Boost Converter also bucks down large back emf voltages to put current back into the battery during regenerative braking. Here is a diagram of the Toyota Prius hybrid power distribution.
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My car will not have the ICE of course and the final configuration of my power setup is TBD pending some experiments and testing but this is what I have to work with.
My first charging configuration test is to tap one of the phases of the 30kW Motor/Generator with AC line voltage. Mainly because I don't have another inductor to use for the test. This puts the AC source in series with the motor inductance and the inverter acts a full bridge rectifier without actively switching it via the IGBT body diodes. I am using a couple 500W flood lights as a load in place of the battery in this experiment.
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Here is a picture of the non-power factor corrected line current using the built in inverter phase current sensors. These signals were very ugly before I made a circuit to clean them up. The phase current peaks are when the line voltage peak exceeds the DC bus voltage as expected.
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Here is a picture of the DC bus voltage of about 150V peak and 25V ripple with the flood lights loaded on it.
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Now the hard work. I will attempt to write the control algorithm that can switch the inverter phases in such a way to produce a power factor corrected boosted +400VDC that the converter can buck down to my battery pack voltage whatever that ends up being. In this experiment I hope to be able to demonstrate controlling the battery voltage output by dimming the flood lights.
I have no experience with Power Factor correcting algorithms but here we go.
Thanks Jeff
 

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Discussion Starter · #16 ·
I have simulated my Bridgeless Power Factor corrected boost battery charger that I am planning using the Prius inverter switches and built in buck/boost converter.

The green line is the single phase line current and the pink line is the ac voltage. The dark blue line is the dc current going into the battery pack. I normalized everything so it would graph together. They are in phase thus the Power Factor Correction.

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The bridgeless part of this is that I don't use a full bridge rectifier like traditional ac to dc boost circuits. Instead it uses the bidirectional inverter half bridges as both boost and rectification at the same time.

If this works the way I am thinking I will basically get a free battery charger since i am using the existing motor inverter. I think I can also use the motor inductance but for now I am using the inductor that is for the Prius dc boost (373 uH).

I have not gone live with the AC part yet but my experiments and simulations with dc to dc boost/buck moving charge between battery packs works as expected.
 

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Discussion Starter · #18 ·
I plugged some things together today and did a video of tires spinning on the jack stands. I hope this helps motivate me. I haven't been spending enough time on this project lately.


I have the transaxle rigidly mounted to the frame. This may have been a mistake. I can feel and hear quite a bit of the vibrations when I am sitting in the car during this test.

Thanks
Jeff
 

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This is my favorite thread on this site.
There is so much potential (pun!?) in dealing with used Prius parts to make
a simple conversion.
Jeff, please consider this encouragement to get this project on the road.
It is really a ground breaking project.
Thanks!
tom in maine
 
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