[bigmouse]

Hi All. Starting a thread for my new EV project!

This one is going to be this 2001 BMW 330ci. I've been wanting to do an BMW coupe conversion for several years now. I've always loved the way they look and feel, they are beefy enough to carry the weight of the batteries, and the coupe body style allows for the rear seat to be re-purposed for battery placement while maintaining good weight distribution.

The transmission is from a 2007 Lexus GS450h. It contains two electric motors and gear reduction. The output shaft is the same configuration as that used on the BMW it's going in and should be easy to adapt. I've calculated the total combined power from both motors to be around 200kW (270hp).

The inverter will be based on the OEM inverter that the transmission was originally coupled with. There will be a fair bit of modification done to allow this to drive both motors at high power levels. This will be the subject of much reverse engineering and custom circuit boards.

Pictured is 32kWh of Chevy Volt batteries (two cars worth). I'll be putting these batteries in series minus a few modules to keep the voltage within the rating of the inverter. I'll end up using about 29kWh worth of these cells for a range of around 110miles. The total pack will have a nominal voltage of around 640vdc.

I used the data provided in the ORNL teardowns of the Camry hybrid and LS600h drivetrains to calculate the expected performance. The combination of these pieces should allow me to build a car that does 0-60mph between 4-5 seconds, gets around 110-120 miles to a charge, seats two, and has unimpeded trunk space.

Everything in this conversion will be used or salvaged parts from other hybrids or EVs, with the exception of the custom electronics needed to make it all work together.

It should be a very nice car to drive.

 

[hitchhikingmike]

subscribe!

 

[eldis]

Looks like a nice conversion, good luck!

As I've done a lot of experiments with Toyota (and therefore Lexus) components, maybe there will be a few tips to help you get on the road faster.
First the battery voltage - The Lexus GS450h has 288V pack, so parts of the inverter will be designed to operate on this voltage (400V would be no-no). Basically to get this up and running, you will have to remove the Boost IGBT and the inductor, also the DC/DC circuit that was charging 12V battery in Lexus (it would burn on your pack voltage). The final stage (two IGBT motor bridges) you can keep, they will be happy with these voltages. Not sure what voltage outputs the original boost, it will be around 500V, so fine there.

Lexus inverter was designed at the same time/ by the same people as Prius 3rd Gen inverter, so you can expect to find something like this:

 

[bigmouse]

Thanks for the info eldis.

I've actually already started tearing in to my inverter (mine is from an 07, the one you attached photos of is from a later model). My inverter is identical to the Camry Hybrid inverter, with the exception of a larger HV capacitor, some of the LV connectors are different, and mine has an extra set of parallel IGBTs and diodes for MG1.

The original boost converter outputs 650vdc. The capacitor is rated to 750vdc. I may lower my voltage a little bit (at the expense of range) to give myself a bit more overhead for voltage overshoot at IGBT turn-off.

The plan is to connect the batteries directly to the IGBT module bus bars rather than going through the converter. I will retain the converter for reasons to be described in later updates.

 

[favguy]

I'm looking forward to watching this with interest

Are you using a main motor mated to the transmission in place of the engine as well? or just the integral transmission mounted motors?

 

[bigmouse]

I'm looking forward to watching this with interest

Are you using a main motor mated to the transmission in place of the engine as well? or just the integral transmission mounted motors?

Just the motors inside the transmission. The input shaft will be locked (I need to design some sort of fixture to hold it). This will allow MG1 to act as a motor through a fix reduction. The speed rating of MG1 is the same as MG2 in the Camry hybrid (14k rpm), so this configuration will limit me to 110mph due to MG1 speed. MG2 has two speeds, controlled by clutches and a gearset in the transmission. There's an electric oil pump that allows EV mode in the original transmission. I'm hoping that this pump feeds the same oil circuit as the mechanical pump inside. The mechanical one will never turn as it's coupled to the input shaft. I'll need to make sure that the clutches/solenoids get hydraulic pressure as well as the oil cooling for the stators and lubrication of the bearings. I'm trying to get a second transmission that I can tear down to confirm the operation of the oil pump, but if I have to, I'll tear this one down to make sure. If I need to drive the internal oil pump as well as the electric one, I'll rig up a BLDC motor to drive the pump shaft. But I'm really hoping I can avoid that.

 

[tylerwatts]

Hi bigmouse
Fascinating conversion and I follow with great interest and hope for your success. Do you have any schematic for the transmission? Can you explain why you want the motors to run at different speeds and even use 2 speeds. My personal preference would be discard the input and lock MG1 to MG2 so that you effectively have only 1 motor. You could still drive them independently similar to a dual ac35 setup for safety and redundancy but would have a simpler and in my opinion stronger setup.
I'm fascinated as this would make a brilliant transmission tunnel drive arrangement without being direct drive in the sense of attaching straight to the differential, and allows significant battery space in the engine bay.

I look forward to your reply and progress. Forgive me if I'm hijacking your thread somewhat.
Regards
Tyler

 

[bigmouse]

Here's a schematic of the transmission:

The "ICE" shaft will be locked. The two clutches will be retained and used to control the speed of MG2. The LS600h has the transfer case. The GS450 (mine) goes directly to the output flange.

If I'm going to be driving the two motors independently anyway, I might as well take advantage of that ability. It's not really any harder to control them independently at different speeds than it would be if they were locked together. Still need two inverters, still needs two resolvers. I think Toyota's setup will be the strongest setup. As soon as I start welding on gearing, I'm making it weaker.

The biggest complication to my method will be the two-speed system for MG2. Having the motors separate means that MG1 can continue to provide torque while MG2's gearing is changed.

The biggest reason I'm going with my method is performance. Locking the two motors together and with one gear ratio would cripple the performance of this transmission. MG1 doesn't develop a lot of torque, maybe 150Nm. So it relies on the gearing for that to use its full potential. Similarly with MG2. In the low-speed gear, MG2 will be on a higher ratio than in the high-speed gear. If I lock it in the high-speed one, I lose the acceleration advantage of that gearing. If I lock it in the low-speed one, I'd be speed limited to 45mph. It's a beast of a machine, and I want to take full advantage of that.

 

[tylerwatts]

Ok thanks, that makes sense. I don't follow the schematic though, I'll google a bit on it. I wish you every success and am following with interest.

 

[bigmouse]

Ok thanks, that makes sense. I don't follow the schematic though, I'll google a bit on it. I wish you every success and am following with interest.

Here's a link to the paper that describes the transmission (mine is the same minus the transfer case). The GS450h inverter from this same generation is identical to the Camry hybrid inverter. There's also a detailed teardown of that from the same folks.

Transmission: http://www.osti.gov/scitech/biblio/947393/
Inverter: http://www.osti.gov/scitech/biblio/928684

 

[tylerwatts]

Oh cool thanks. Very useful! Is the LS600 the same motors in the transmission as yours? Or what is the transfer case for? I just clicked it must be a 4wd...

 

[bigmouse]

As far as I can tell from the transfer case to the back of the bellhousing the two transmissions are identical. I haven't confirmed it though. The transfer case is because the LS600h is AWD. The difference in power between the two models probably comes from the different engines, power electronics, and battery.

 

[tylerwatts]

Oh great. That means the motors are capable of more than they are tuned for in the gs450h. It should be an excellent system when you have it running. I like the 2 speed option also.

 

[bigmouse]

I put the converter IGBT module on a semiconductor analyzer the other day to determine its properties, mainly the breakdown voltage. The results are below. The VF and VCE values range from 1 to 100 amps.

*T 1; BVCES = 594.1 V
T 2; VF = 470.0MV
T 3; VF = 501.0MV
T 4; VF = 554.0MV
T 5; VF = 606.0MV
T 6; VF = 673.0MV
T 7; VF = 811.0MV
T 8; VF = 980.0MV
T 9; VF = 1.121 V
T10; VF = 1.253 V
T11; VF = 1.493 V
T12; VF = 1.716 V
*T13; VF = 2.141 V
*T14; VF = 2.547 V
*T15; VF = 3.110 V
T16; VCEON = 441.0MV
T17; VCEON = 474.0MV
T18; VCEON = 531.0MV
T19; VCEON = 590.0MV
T20; VCEON = 664.0MV
T21; VCEON = 808.0MV
T22; VCEON = 970.0MV
T23; VCEON = 1.104 V
T24; VCEON = 1.221 V
T25; VCEON = 1.441 V
T26; VCEON = 1.643 V
*T27; VCEON = 2.038 V
*T28; VCEON = 2.416 V
*T29; VCEON = 2.790 V
T30; VGETH = 6.257 V
T31; VGETH = 6.342 V

So it's a 600v rated part, which was the most important thing I wanted to find from the test. I'll have to measure the range of the voltage sense circuit to see where it saturates in order to find the maximum useful voltage I can run on that bus.

 

[bigmouse]

Managed to get the pinouts for the internal connectors figured out. I'm able to drive the inverter with my own signals! I threw together some very simple open-loop code on an Arduino, put 12v on the DC bus, and connected one of the motors on the transmission. The result is seen in the video. It spins!
It spins slowly, but it spins. That's 12v with no real control. 650v with closed loop control will be a very different story.
Very exciting.
I also figured out how to drive the gates on the converter section, but that's not as interesting to show in video.
Moving forward!

Doesn't look like the youtube embed is working. Any advice?

 

[Moltenmetal]

Fascinating- watching with interest!

 

[jddcircuit]

bigmouse

Nice project.
I am also working on using Toyota components in my conversion with custom ECU circuits. You can search for some of my postings if you are interested. I also have some youtube videos at jddcircuit channel.

I am still a bit a way from being on the road but I have made some progress getting things to spin. High rpm levels are going to be challenge for me I expect. I think I will have to switch from my Field Oriented Control producing sinusoidal voltages to a more BLDC type commutation at high rpms. My plan is at high rpms the six step communtation will be frequency modulated instead of pulse width modulated. Hopefully the torque ripple will be minimal at these speeds. IIRC there is simply not enough resolution in my digital control loop and my 16kHz PWM (actually 8kHz center aligned) at high rpms.

You may already know this but I didn't at first, BLDC commutation does not work at lower speeds with these motors. Too much torque ripple. These motors are Interior Permanent Magnet motors which have a reluctance torque vector on top of the permanent magnetic torque vector.

I have also developed a way to use the two motors and two inverters as my battery charger. My charger idea is patent pending but I am using it in my DIY project and hopefully other DIYers will also. You can download my feasibility paper for my charger at www.vehilectric.com if you are interested.

BTW, I live in Florida but I may be in San Jose on business this month. Let me know if you want to get together and talk shop.

Good Luck
Jeff

 

[bigmouse]

Hi Jeff,

I have been following your progress! I was tempted to do a conversion very similar to yours (MR2 with either Prius or Camry transmission), but decided to go this route instead due to the performance available from the Lexus transmission.

I'm using vector control for mine (manually for now at least). I haven't connected the current sensors yet so I'm just adjusting the angle of the voltage vector relative to the rotor manually. It's good enough for low speeds and the 12v that I'm testing with.

Regarding switching to BLDC-type commutation, the changeover from FOC to 6-step might not need to be an actual change. If you let your current-control loops saturate at high speed (attempting to achieve current that is not possible due to field weakening), they will go in to overmodulation. This causes the sine waves to transition to square waves. Resolution also shouldn't be much of a problem since at high speeds, distortion in the voltage waveform is filtered by the stator inductance in to a sine wave (or something close enough) anyway. I don't think I'll need to go that route myself, since my pack voltage will be so high. Time will tell though.

I have my own idea for charging, which is different from yours.

Send me a PM before you get here and we'll arrange something!

-Vincent

 

[jddcircuit]

Hi Jeff,

I have been following your progress! I was tempted to do a conversion very similar to yours (MR2 with either Prius or Camry transmission), but decided to go this route instead due to the performance available from the Lexus transmission.

I'm using vector control for mine (manually for now at least). I haven't connected the current sensors yet so I'm just adjusting the angle of the voltage vector relative to the rotor manually. It's good enough for low speeds and the 12v that I'm testing with.

Regarding switching to BLDC-type commutation, the changeover from FOC to 6-step might not need to be an actual change. If you let your current-control loops saturate at high speed (attempting to achieve current that is not possible due to field weakening), they will go in to overmodulation. This causes the sine waves to transition to square waves. Resolution also shouldn't be much of a problem since at high speeds, distortion in the voltage waveform is filtered by the stator inductance in to a sine wave (or something close enough) anyway. I don't think I'll need to go that route myself, since my pack voltage will be so high. Time will tell though.

I have my own idea for charging, which is different from yours.

Send me a PM before you get here and we'll arrange something!

-Vincent

Very good

When I first spun the motor with no load everything seemed fine. When I put it under a load things were very different. In this first attempt I was reading the resolver and commutating relative to the rotor position. I didn't have the current sensor working at this time.

Now, I am using the AD7609 chip to capture the current sensors coming out of the inverter and doing a simple FOC based on the rotor position and the Id and Iq values. It seems to work pretty well.

I am not sure what the max torque per amp is exactly for this motor. Pretty soon I should be back on the motor control portion and will try to run the two motors against each other to see if I can optimize the efficiency of the control. Having two motors is like having a built in dyno.

Jeff

 

[bigmouse]

Yeah, the voltage vector and the current vector are not in alignment at high speeds or under load. That's why FOC uses current controllers to set the current vector angle.

The torque per amp and torque variation with angle should be in the DOE documents.

I plan on using the motors against each other as a dyno (as you mentioned) to determine the optimal Id/Iq values for speeds. Can't measure torque directly, but I have some ideas on how to make it useful.