# 1991 MR2 + 2004 Prius Transaxle



## Daox (Jan 18, 2008)

Sounds like a very interesting and very in depth project Jeff. Can't wait to hear more.


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## DDDvvv (Apr 2, 2012)

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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## jddcircuit (Mar 18, 2010)

DDDvvv said:


> 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,
> 
> ...


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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## jddcircuit (Mar 18, 2010)

I got the ICE out this weekend.







Degreased the engine bay.







And starting to line up the new motor mounting.








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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## jddcircuit (Mar 18, 2010)

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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## fireblade (Aug 20, 2012)

Check my posts. There are references to CANBUS control of the inverter/converter.


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## jddcircuit (Mar 18, 2010)

fireblade said:


> Check my posts. There are references to CANBUS control of the inverter/converter.


Will do
Thank you


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## jddcircuit (Mar 18, 2010)

I bought myself a transmission jack and lifted the Prius electric tranny in place. Fits like a glove.







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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## tylerwatts (Feb 9, 2012)

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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## jddcircuit (Mar 18, 2010)

tylerwatts said:


> 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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## jddcircuit (Mar 18, 2010)

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.








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.









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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## jddcircuit (Mar 18, 2010)

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.








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.








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.








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.








Here is a picture of the DC bus voltage of about 150V peak and 25V ripple with the flood lights loaded on it.








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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## Arlo (Dec 27, 2009)

Very cool I can't wait to see how this all turns out.


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## tylerwatts (Feb 9, 2012)

JDD how is this coming along? Have you got a thread for your controller hack? And how will you configure the motor to lock the two units together? Looking forward to an update! Thanks


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## jddcircuit (Mar 18, 2010)

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.









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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## e*clipse (Aug 2, 2009)

Very Cool! 

This will be a very fun car - I'm watching closely.


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## jddcircuit (Mar 18, 2010)

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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## bigmouse (Sep 28, 2008)

That's pretty cool! It should make for a nice conversion. I expect it will be very smooth and quiet when it's complete.


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## Tom (Mar 26, 2008)

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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## jddcircuit (Mar 18, 2010)

Thanks Guys for the encouragement

I only have a 6kwh pack (48X40Ah) to put in it at the moment. I hope it is enough to do some neighborhood driving and work out some kinks before spending more.

I have a lot to do but would like to be on the road early next year with this grocery getter phase of the project.

Jeff


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## jddcircuit (Mar 18, 2010)

I like having this holiday time to get some important things done like working on my car

I just got my FOC (Field Oriented Control) working for the main traction motor. This is a milestone for me. I was not sure it was going to work. So far I am pleased.

Previously, I was just modulating the phase voltages based on throttle command and rotor position. Now the throttle commands the motor current (torque) and the voltages go to whatever they need to in order to meet the command. This type of control is what I will need in real world driving.

My algorithm tries to maintain a current vector of -30deg off of what traditionally one uses for BLDC motors. For this type of motor I don't want the Id=0 like other BLDC motors might.

Id = I*sin(-30)
Iq = I*cos(-30)
I am using this Id Iq relationship based on the stall torque graph of this motor published in one of the ORNL document.

This motor is a IPM (Interior Permanent Magnet) motor which has a significant reluctance torque component that overlays the permanent magnet torque component. Id=0 will not take advantage of the reluctance torque from my understanding.

Here is a video of it in action this morning.


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## tylerwatts (Feb 9, 2012)

Great milestone JDD! Congrats. 
And happy new year


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## bigmouse (Sep 28, 2008)

Well done! I wrote a FOC algorithm from scratch as well. I'm impressed you were able to implement it on an Arduino.


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## steven4601 (Nov 11, 2010)

Offtopic: good camera work, as you where not shaking the camera over the place, also a good camera voice & no rubbish info on the side. 

I am very impressed you have got the Prius transaxle to spin .
Protection against overloads, the motor tuning etc may all still involve a lot of work still.. Not sure though, I never played with IPMs.

Eitherway, keep up the work, you may be able to pull something off that enables the re-usage of the Toyota drive train for the people  

What power levels you expect the motor/inverter can go upto? I assume higher than with the ICE still attached, as the coolant used to be shared with the ICE, or was this separate for the traction inverter?


//steven


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## jddcircuit (Mar 18, 2010)

steven4601 said:


> Offtopic: good camera work, as you where not shaking the camera over the place, also a good camera voice & no rubbish info on the side.
> 
> I am very impressed you have got the Prius transaxle to spin .
> Protection against overloads, the motor tuning etc may all still involve a lot of work still.. Not sure though, I never played with IPMs.
> ...


Are you making fun of my camera work

Lots of tuning ahead and lots of unknowns still. You are right about there being many exceptions and overloading handling yet to be implemented. I have already run into some of them.

I hope I don't try and push things too far too soon without the proper controls. However knowing myself and my tendency to cut corners I will probably learn the hard way.

The motor/inverter coolant is separate from the ICE normally with two radiator sections in the Prius. In my MR2 conversion I will be pumping coolant through the main radiator in the front of the car. This should give me good heat transfer and perhaps raise my continuous power ceiling.

(Example of cutting corners) I didn't take the time to figure out and wire in the motor and inverter temperature sensors.

The expected power is a good question. I have several different configurations to explore.

1st option: (approx 40kw) Double the battery voltage. MG2 only and DC boost. I read that MG2 is rated at 50kw and the DC boost is rated at 20kw. Since the Prius battery is around 200V nominal and boosted to 500V, I take these ratings to mean 100 battery amps and 100 motor amps sounds reasonable. The DC boost circuit is the bottle neck. In this configuration I will need more battery volts to increase power. I am thinking of fitting 128 cells for a nominal voltage of 422V which would be 42.2 kw at 100 battery amps through the boost circuit. Boosting the voltage to 500 is helpful for reaching the higher motor rpms. I am not sure if the built in 12V DC to DC can handle the higher battery voltage but this is not a deal breaker.

2nd option: (approx 40kw) Double the DC boost. Still using MG2 only but using the unused MG1 igbts and an extra boost inductor to parallel the built in 20kw DC boost switching. This would allow for more battery amps and my pack voltage can remain lower perhaps 64 cells and 200 battery amps in this case.

3rd option: (approx 70kw) Double the battery voltage and motors and bypass the DC boost circuit. Rigidly connect MG1 and MG2 by welding the planetary gear internally. 160 battery amps and 128 cells. The addition of MG1 will be interesting I think. It spins twice as fast as MG2 for the same voltage so I expect it to add some significant torque at the high end of the rpm range. At highway speeds I expect MG1 will be doing most of the work and MG2 will be deeper in the field weakening region.

I am not sure which route I am going. Perhaps I will try all of them and others as I learn.

I am very open to suggestions and perhaps I can exceed these expectations.

Note: I have bench tested the dc boost circuit at 60amps continuous without any liquid cooling. It gets warm but seems to handle it fine. At 80 amps I think I was hitting a thermal fault limit after some time.

Regards
Jeff


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## tylerwatts (Feb 9, 2012)

Hi Jeff. 

What operation is the Prius inverter doing in your setup please? Have you totally bypassed the inverter control system and are controlling the IGBTs themselves? I'm a little confused about what your controller does to 'control' output if the Prius inverter is still a major factor.

Is it at all possible to hack and 'remap' the Prius inverter and keep the protection and control algorithms as Toyota decided originally and simply tweak key parameters like voltage and Max current? This would be ideal but I suspect there is reason you have not done this. Please share. 

Thank you.


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## jddcircuit (Mar 18, 2010)

tylerwatts said:


> Hi Jeff.
> 
> What operation is the Prius inverter doing in your setup please? Have you totally bypassed the inverter control system and are controlling the IGBTs themselves? I'm a little confused about what your controller does to 'control' output if the Prius inverter is still a major factor.
> 
> ...


The prius inverter has no intelligence. It is only the high voltage high power switches. It provides access to the IGBT gate drivers and will turn on whichever transistor you tell it to without asking if you are sure or not. It also provides some analog signals that represent bus voltage and phase currents.

The Prius ECU is where the inverter plugs in on the Prius. This is where all the Toyota synergy drive decisions and motor control are made. I am not using the Prius ECU. I have never considered trying to use it.

My controller is decoding the rotor angle, sampling the phase currents, and modulating the IGBTs accordingly using the signals available from the inverter.

Jeff


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## tylerwatts (Feb 9, 2012)

Ah right so the hardware is within the inverter and the software in the ecu. That is useful. So all that is needed is a good interface module and control algorithm to run the hardware. I know I'm over simplifying it but that is the basics right? 

May I ask what options you considered for controlling the inverter before going this route please? Thanks


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## jddcircuit (Mar 18, 2010)

tylerwatts said:


> Ah right so the hardware is within the inverter and the software in the ecu. That is useful. So all that is needed is a good interface module and control algorithm to run the hardware. I know I'm over simplifying it but that is the basics right?
> 
> May I ask what options you considered for controlling the inverter before going this route please? Thanks


You are correct. I am working on the interface and control algorithm. Some inverters already have this built in and respond to a command set via CAN bus for example. The Prius inverter does not.

I am not sure I understand your second question.
I enjoy DIY projects. Doing both hardware and software would be a bit too much for me. I am content with learning the software side of things for now and this is a low cost way of getting that experience.

Regards
Jeff


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## bigmouse (Sep 28, 2008)

4th Option: Re-wind MG2 stator to a lower voltage, or switch from Y to Delta winding configuration (the tap point is relatively easily accessed).

I am hoping to get my hands on a Prius transaxle to do something similar to what you've done here. My plan would be to not use MG1 at all, rewind MG2 to a lower voltage, and run my own controller (which is nearly complete, just need to fine tune the software). Winding the stator to 24-26vac (assuming a 50Hz "base frequency" and a total reduction between MG2 and the diff of 8:1 from memory) would take you all the way to 110kph before field weakening starts. With over 300Nm of torque all the way up there, it would make for a quick car. You'd need to handle a load of current and go up to 400Hz though, hence the custom controller. It could be a sub 7s 0-100kph car.


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## jddcircuit (Mar 18, 2010)

bigmouse said:


> 4th Option: Re-wind MG2 stator to a lower voltage, or switch from Y to Delta winding configuration (the tap point is relatively easily accessed).
> 
> I am hoping to get my hands on a Prius transaxle to do something similar to what you've done here. My plan would be to not use MG1 at all, rewind MG2 to a lower voltage, and run my own controller (which is nearly complete, just need to fine tune the software). Winding the stator to 24-26vac (assuming a 50Hz "base frequency" and a total reduction between MG2 and the diff of 8:1 from memory) would take you all the way to 110kph before field weakening starts. With over 300Nm of torque all the way up there, it would make for a quick car. You'd need to handle a load of current and go up to 400Hz though, hence the custom controller. It could be a sub 7s 0-100kph car.


That would be something to see. I have taken a peek at the MG2 stator and rewinding that amount of copper would be . The gear reduction in my 2004 transaxle is 4.11:1 I think.


Yesterday I went ahead and welded the planetary gear between MG1 and MG2 as stated in option 3. As I listed my options this one seemed to make the most sense especially for testing purposes. I should be able to run the motors against each other (One drive and one regen) and test out some higher currents.

Regards
Jeff


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## tylerwatts (Feb 9, 2012)

Jeff
What I was asking is how did you choose the arduino control for your project? 
Also, in your research have you seen much difference between generation 1 and 2 Prius drives? I wonder if it would be easier to find a can bus controlled system for interface purposes where the manufacturer has already programmed control algorithms etc. 

Not knocking your project, I think your progress is excellent and I'd love to do something similar with a Lexus RX/highlander rear transaxle or Camry transaxle for a larger vehicle, just wanting the simplest option to begin as I'm not as skilled as you in electronics or software and not got much time to learn at the moment. 

Thank you for sharing your progress and success.


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## tylerwatts (Feb 9, 2012)

PS, any pics of the welding work please?


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## Tom (Mar 26, 2008)

Hi Jeff,
That is impressive progress. Makes me wish I stayed in EE. 
They asked me to leave.
Probably a good thing.

Keep it coming! You are doing great work!
Tom in Maine


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## jddcircuit (Mar 18, 2010)

tylerwatts said:


> PS, any pics of the welding work please?


http://99mpg.com/projectcars/evinsight/

Go to this site, he did a much better weld than I did. Mine is back together already. Maybe in the next day or so I will have MG1 in play.


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## jddcircuit (Mar 18, 2010)

tylerwatts said:


> Jeff
> What I was asking is how did you choose the arduino control for your project?
> Also, in your research have you seen much difference between generation 1 and 2 Prius drives? I wonder if it would be easier to find a can bus controlled system for interface purposes where the manufacturer has already programmed control algorithms etc.
> 
> ...


Arduino just because I am using it for other hobbies.

I have a Gen1 also. Gen 1 might be better for lower voltage EV than the Gen 2. The big motor, MG2, on the Gen1 spins faster at lower voltage. It has heavier gage windings so it can probably handle more current. It is rated for lower power because of the lower voltage.

I picked the Gen 2 because there are a lot more of them on Ebay.

Basically they are all the same, including the Camry, Highlander, and Lexus.

Jeff


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## tylerwatts (Feb 9, 2012)

Oh thanks Jeff. 

The Highlander is a full electric transaxle which I like, and Lexus tend to be rwd boxes so trickier to package. If they all follow the same principle of ecu controlling the inverter then that is great as one should be able to follow what you are doing with any of them. 

Have you got any pics of the welded gears please? I'm keen to see how that performs. I like your idea of having mg1 give extra torque and power at high speed.


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## jddcircuit (Mar 18, 2010)

tylerwatts said:


> Oh thanks Jeff.
> 
> The Highlander is a full electric transaxle which I like, and Lexus tend to be rwd boxes so trickier to package. If they all follow the same principle of ecu controlling the inverter then that is great as one should be able to follow what you are doing with any of them.
> 
> Have you got any pics of the welded gears please? I'm keen to see how that performs. I like your idea of having mg1 give extra torque and power at high speed.


Check this guys welds out. Mine are not as pretty.
http://99mpg.com/projectcars/evinsight/

There are several working on similar things. Here is another thread.
http://www.diyelectriccar.com/forums/showthread.php/toyota-ipm-motor-controller-design-details-87535.html


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## jddcircuit (Mar 18, 2010)

I was successful in getting both MG1 and MG2 working together.

I was a little concerned about processing overhead. I will hook up a probe to my debug signal to see what my time margin is between interrupts synced to the PWM signal. So far no erratic behavior but that might be dumb luck.

I am only using integer arithmetic so hopefully reducing computation cycles.

I am only running my PWM switching signal at 5kHz. I am sampling the phase currents twice per PWM cycle so 10kHz for the FOC loop. I am also doing the resolver excitation and decoding at this 10kHz frequency. This Arduino Due seems to be holding up.

Since both motors are mechanically connected I only have to use a single resolver for the rotor angle position of both motors which is good since I only have one resolver decoder. After putting the transaxle back together I measured both rotor positions from their respective resolvers to get the angle offset between them.

Here is a cutaway off the internet because I like pictures.









Next step is to get busy with my battery monitoring and charging solution.


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## bigmouse (Sep 28, 2008)

Nice work! I didn't realize you were using an Arduino Due. That explains why you have the processing power to do this. I was baffled when I thought you'd managed to implement FOC on an atmega328, let alone at 10khz!

It would have been nice if you could have aligned the rotors perfectly, then just put the stators in parallel and use a single set of power electronics for both. I suppose since you're using the Prius inverter, the silicone is already there for your method at least.

The AT91SAM3X8E on the Due can do ADC at 1MHz and has DMA. You could use this to increase your PWM frequency and sample as you are now without increasing the CPU load at all, possibly decreasing it if you're not using DMA already.

Which resolver decoder are you using?


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## jddcircuit (Mar 18, 2010)

bigmouse said:


> Nice work! I didn't realize you were using an Arduino Due. That explains why you have the processing power to do this. I was baffled when I thought you'd managed to implement FOC on an atmega328, let alone at 10khz!
> 
> It would have been nice if you could have aligned the rotors perfectly, then just put the stators in parallel and use a single set of power electronics for both. I suppose since you're using the Prius inverter, the silicone is already there for your method at least.


I not sure about that. The motors are different and I think being able to independently control their respective IdIq will have some value especially at higher speeds.




> The AT91SAM3X8E on the Due can do ADC at 1MHz and has DMA. You could use this to increase your PWM frequency and sample as you are now without increasing the CPU load at all, possibly decreasing it if you're not using DMA already.


I am not up to speed on DMA transfers. In my implementation I am using an external ADC chip that can simultaneously sample 8 channels (MG1 phase V&W, MG2 phase V&W, battery voltage, boost voltage, resolver sin & cos)
After the analog conversion I read the values in using a parallel digital bus.

Perhaps I should have put another one of these ADC ICs on board for throttle and temperature sensors. I guess I will have to tap into the Due ADC for these features.



> Which resolver decoder are you using?


I made my own. I implemented this tracking filter in the Due using its two DAC outputs for the sinusoidal excitation and two of the external ADC channels I mentioned above.


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## jddcircuit (Mar 18, 2010)

I made some progress on my Battery charger design. Here is a picture of my scope showing the relationship of the AC line voltage and line current so my Power Factor Correction scheme appears to be working.









In this example I am using the stator of the two motors as the boost inductor elements. I think this may be a patentable method so I will not be able to give details until I decide whether I will pursue patent or not but either way I think I will have a way to charge my battery pack.

I only have 160volts of cells at the moment but charging higher voltage packs ( 400 to 500V) should work. The prius inverter that I am using maintains a 500V boosted bus voltage in normal Prius operation so the power electronics should be able to handle it.

Concept works but has some issues that I will need to solve.
Lots of EMI screwing up my Android controller and my cell voltage monitoring circuit and probably my neighbors radio station.
The charging current also creates torque in the motor since I have permanent magnet motors. Since I have both motors mechanically connected I will need to disassemble the transaxle with the motors and align the stators so this torque is not fighting each other during charging.

AC induction motors I don't think would have the same torque contention problem based on rotor angle as in my case.

Regards
Jeff


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## bigmouse (Sep 28, 2008)

jddcircuit said:


> In this example I am using the stator of the two motors as the boost inductor elements. I think this may be a patentable method so I will not be able to give details until I decide whether I will pursue patent or not but either way I think I will have a way to charge my battery pack.
> 
> (snip)
> 
> ...


Nice work! Using the motor windings as an inductor for charging has been done before and discussed in various forums. There are several motor controllers with built-in chargers that work this way. I think the Siemens EV drive is one example. It's a clever idea nonetheless.

AC induction motors respond to DC current applied to the windings by acting like a brake. As is the nature of asynchronous motors, torque is only developed when the rotor is moved relative to the induced field. Obviously, stationary rotor angle is not important. The Prius motors are 8-pole, correct? After the gear reduction to the wheels, what's the biggest angle at the wheels that would be seen if it was allowed to turn to alignment during charging? I imagine the angle would be very small and likely within the play of the geartrain with the parking pawl engaged. Or is it the effect of the permanent magnetic field on the inductor that you're concerned with?


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## jddcircuit (Mar 18, 2010)

bigmouse said:


> Nice work! Using the motor windings as an inductor for charging has been done before and discussed in various forums. There are several motor controllers with built-in chargers that work this way. I think the Siemens EV drive is one example. It's a clever idea nonetheless.
> 
> AC induction motors respond to DC current applied to the windings by acting like a brake. As is the nature of asynchronous motors, torque is only developed when the rotor is moved relative to the induced field. Obviously, stationary rotor angle is not important. The Prius motors are 8-pole, correct? After the gear reduction to the wheels, what's the biggest angle at the wheels that would be seen if it was allowed to turn to alignment during charging? I imagine the angle would be very small and likely within the play of the geartrain with the parking pawl engaged. Or is it the effect of the permanent magnetic field on the inductor that you're concerned with?



I have been skimming various integrated charger and drive component patents. Lots of activity in this field. I will check out the Siemens EV drive that you mention. Thanks

I am excited it is working. I would be surprised if this is novel and unobvious.

I am not sure what the rotor position does to the stator inductance value for this motor but I can handle a large range of inductance values I think.


Jeff


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## jddcircuit (Mar 18, 2010)

I made a video of some progress for my Integrated Battery Charger solution for my EV project.







I found this web site to be very helpful
Tumanako Charger



Thank you
Jeff


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## eldis (Sep 3, 2013)

jddcircuit said:


> I made a video of some progress for my Integrated Battery Charger solution for my EV project.


Congratulations, that looks great! Did you write some algorithm to sense the mains phase/frequency and using that to time your IGBTs? Also what efficiency are you getting, does the motor used as an inductor introduce any significant losses?


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## jddcircuit (Mar 18, 2010)

eldis said:


> Congratulations, that looks great! Did you write some algorithm to sense the mains phase/frequency and using that to time your IGBTs? Also what efficiency are you getting, does the motor used as an inductor introduce any significant losses?


Thanks

I do not know efficiency. I don't have a current sensor for battery pack yet.
There is much testing to be done still. Of course I will want to achieve higher power levels but this is what I got for now. The inverter and motor are liquid cooled so even if the efficiency is low I should be able to get the heat out.

I am using the built in motor phase current sensor for modulating the current in phase with the AC line voltage. I don't have a sensor for line voltage. I simply scale the switching duty cycle proportional to the line current. This inherently puts the current in phase with the AC line voltage to approach unity power factor. I read this trick in an app note somewhere.

Jeff


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## eldis (Sep 3, 2013)

Some further questions, since you are already experimenting with batteries.
1) What is the sequence you apply/check when starting the inverter (power on)?
2) Do you need a precharge resistor/circuit?

Thanks,
Michal


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## jddcircuit (Mar 18, 2010)

eldis said:


> Some further questions, since you are already experimenting with batteries.
> 1) What is the sequence you apply/check when starting the inverter (power on)?
> 2) Do you need a precharge resistor/circuit?
> 
> ...


My control board is monitoring the pack and bus voltages the come out of the inverter. Pins labeled VH and VL.

I haven't bothered with precharge yet. The inductor in dc to dc boost will limit in rush current for now.
When I go higher voltage or remove boost circuit I will need to use a precharge circuit and the VL and VH values


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## marcexec (Feb 11, 2009)

Love the progress you are making - quite an inspiration regarding reusing the common but "mysterious" Toyota HSD. Would you by any chance have a weight on the transaxle minus all ICA parts? Info on the web is a bit sketchy...


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## jddcircuit (Mar 18, 2010)

marcexec said:


> Love the progress you are making - quite an inspiration regarding reusing the common but "mysterious" Toyota HSD. Would you by any chance have a weight on the transaxle minus all ICA parts? Info on the web is a bit sketchy...


Sorry I don't have any weights. My transaxle is out of the car wired up on the test bench. Perhaps when I start to put it back in the car I can weigh some of the pieces. This would be a good thing to have.


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## Beez (Sep 12, 2014)

Any progress to report?
Im eagerly watching this cool project!


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## AlexanderB (Nov 14, 2014)

I'm actually very impressed with your work so far, and your youtube video's and writings on this forum have convinced me that it should be possible (through lots of effort) to also use a Prius transaxle to power an EV conversion. 

A Prius transaxle is one of the only affordable ways that I could get a streetlegal EV conversion in my country, as the motor+controller needs to be EMI/EMC tested (at very high cost), or taken from an already road-approved vehicle. (So a crashed EV or hybrid.)

I might just fly under the radar if I obfuscate the microcontroller somewhere in the wiring loom, and claim the big box on top (inverter) is the completely original motor controller. 

Perhaps I can help with (and/or learn something from) the ongoing controller development on this forum..

Going back to the other thread(s) now, see you there, I guess.


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## jddcircuit (Mar 18, 2010)

Beez said:


> Any progress to report?
> Im eagerly watching this cool project!


Thanks for asking

I am getting ready to post a video giving some more details and test results of my patent pending integrated battery charger using these inverters and motors.

Today I tested my integrated charger at 4.5kW. I have been able to reduce the current distortion below 5% and the ground leakage current to less than 10mA so it looks like it going to fly.










I hope Toyota decides they like it and want to buy it.

Once I complete this charger development I will be getting back on the motor controller design and build. There are several things I want to clean up on the motor controller.


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## jddcircuit (Mar 18, 2010)

I have been enjoying my hobby of experimenting with these Prius components so much that it has slowly turned into my day job. The company I work for is always looking for investment opportunity but it seems they mostly look outside rather than inside the company so it has been a hard sell to say the least.

In my pursuit of looking for a low cost EV conversion platform using salvaged Prius components, I recently discovered a method for using the inverter and motor as a boost charger for my battery. I have filed for patent with the hope of being given the opportunity to spend more time on my hobby and get paid for it.

This through motor charging is an old idea with a new twist. My hopes is that one of the large PHEV manufactures wants to use it in their vehicles. In the meantime I am going to use it in my conversion.










If you are interested check out my document outlining the new topology and some experimental results. I appreciate all kinds of feedback, the good and the bad.

View attachment Vehilectric_IBC.pdf


Thanks
Jeff


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## tylerwatts (Feb 9, 2012)

Jeff, can't get at the document. Is it me?


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## Coulomb (Apr 22, 2009)

tylerwatts said:


> Is it me?


The lights work fine in my office. (I can see the image and read the document.)

Edit: from two different computers (home and work).


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## dcb (Dec 5, 2009)

Jeff, very interesting, with the buck/boost section in the prius inverter it all kinda falls into place. Any idea on the power factor at higher charge levels (10+kw)? Any pointers to the logic levels/timing/pinout needed for driving the inverter?

Edit, found you thread, lots of good stuff. http://www.diyelectriccar.com/forum...onversion-using-prius-transaxle-52503p10.html


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## jddcircuit (Mar 18, 2010)

dcb said:


> Jeff, very interesting, with the buck/boost section in the prius inverter it all kinda falls into place. Any idea on the power factor at higher charge levels (10+kw)? Any pointers to the logic levels/timing/pinout needed for driving the inverter?
> 
> Edit, found you thread, lots of good stuff. http://www.diyelectriccar.com/forum...onversion-using-prius-transaxle-52503p10.html


Power factor will stay around unity. Usually PF and THD improve at higher power levels.


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## jddcircuit (Mar 18, 2010)

Coulomb said:


> The lights work fine in my office. (I can see the image and read the document.)
> 
> Edit: from two different computers (home and work).


Coulomb,
What do you think about this idea? You seem to know more about this stuff than I do.

Regards
Jeff


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## jddcircuit (Mar 18, 2010)

I made a short video documenting some progress I have made with my Cell Voltage Monitoring circuit. Inverter switching noise is a bitch on the digital data capture.

Each cell circuit draws about 10uA during conversion with less than 1uA difference between circuits. So 1Million hours to create a 1Ah SOC imbalance.

I am only getting about +/- 30mV accuracy but better than +/- 1mV precision with this latest circuit design. This should be more than good enough to detect the fully charged and fully discharged knees of the cell voltage profiles.

I am also excited to see if one cell is sagging more than the others during heavy loads.






Now I will put some of the parts back into my car for some more motor control testing.
I am holding off buying more batteries until more of my sub circuits and systems are operational.

Thanks
Jeff


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## dcb (Dec 5, 2009)

That's a nice workspace your company got for you 

Very gutsy approach on the bms, I think I followed it though (send 3 pulses, then ping the next one to send 3). Are you using something like a 4-20ma "digital" loop between each cell, or just voltage?

edit: also how does temperature affect pulse timing?


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## jddcircuit (Mar 18, 2010)

dcb said:


> That's a nice workspace your company got for you
> 
> Very gutsy approach on the bms, I think I followed it though (send 3 pulses, then ping the next one to send 3). Are you using something like a 4-20ma "digital" loop between each cell, or just voltage?
> 
> edit: also how does temperature affect pulse timing?


The data is passed through the chain as current of about 1.5mA in 30usec pulses if I remember correctly.

The reason for three pulses is to cancel out several sources of error including the RC time constant and its temperature drift. It takes about 5ms per cell to get the pulses.

The trigger pulses go south one circuit at a time and the compare events travel all the way to the north most circuit.

Here is the schematic


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## dcb (Dec 5, 2009)

Cool, so pulse 1-2 gives you the basis for evaluating pulse 2-3, nice.

re: 4-20ma, what I was getting at was using a 4ma signal for low and a 20ma signal for high with constant current drivers (or just a diode and a transistor and a resistor maybe), and that would help actively dampen any external interference. But since yours is one wire bi-directional, not sure how that would work on second thought.

Very nice though!

edit: oh, and check out the silicon labs digital isolator offerings, they look real tight on timing:
http://www.digikey.com/product-detail/en/SI8711CC-B-IS/336-2385-ND/3587164


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## Johnny5 (Aug 11, 2015)

Hi Jeff, 

I was curious if you had any update, also I still have alot to learn but do you think it could be feasible to use 2 of those units for a awd setup. I am impressed how cheap and available they are at the moment but Ill need the "limitless" pill to pull that off any time soon. 

Cheers
Jeff.. also hehe


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## jddcircuit (Mar 18, 2010)

Johnny5 said:


> Hi Jeff,
> 
> I was curious if you had any update, also I still have alot to learn but do you think it could be feasible to use 2 of those units for a awd setup. I am impressed how cheap and available they are at the moment but Ill need the "limitless" pill to pull that off any time soon.
> 
> ...


Not much to update on the car getting on the road. I am still messing around on the test bench. I put the parts in the car and then take them out again over and over it seems.
This is a video I did a little while ago of some testing.






I think an AWD with two of these transaxles would make a lot of sense.

I am thinking of using them for a three wheeled urban vehicle concept. Toyota has sold over 8million Prius to date so the junk pile of parts is going to be there for quite some time.


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## Johnny5 (Aug 11, 2015)

Really interesting and I can see the appeal to reverse engineer a system that is proven to work already but do you think you could get mg1 & mg2 working with a different controller, for those with the lack of skills.


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