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Old 02-24-2015, 11:12 PM
bigmouse bigmouse is offline
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Default BMW 330ci conversion

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.
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  #2  
Old 02-25-2015, 12:10 AM
hitchhikingmike hitchhikingmike is offline
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Default Re: BMW 330ci conversion

subscribe!
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Old 02-25-2015, 02:02 AM
eldis eldis is offline
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Default Re: BMW 330ci conversion

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:





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Old 02-25-2015, 02:17 PM
bigmouse bigmouse is offline
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Default Re: BMW 330ci conversion

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.
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Old 02-25-2015, 03:08 PM
favguy favguy is offline
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Default Re: BMW 330ci conversion

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?
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Old 02-25-2015, 03:15 PM
bigmouse bigmouse is offline
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Default Re: BMW 330ci conversion

Quote:
Originally Posted by favguy View Post
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.
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Old 02-25-2015, 04:42 PM
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tylerwatts tylerwatts is offline
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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
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Old 02-26-2015, 09:34 AM
bigmouse bigmouse is offline
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Default Re: BMW 330ci conversion

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.
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Old 02-26-2015, 03:46 PM
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tylerwatts tylerwatts is offline
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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.
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Old 02-26-2015, 03:58 PM
bigmouse bigmouse is offline
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Default Re: BMW 330ci conversion

Quote:
Originally Posted by tylerwatts View Post
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
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