Golf 2 with Prius Gen 3 Motor and Inverter

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LeonB
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Golf 2 with Prius Gen 3 Motor and Inverter

Post by LeonB »

Hey guys, after reading through the openinverter forum and wiki for months and working on my electric conversion for even longer, I think it is finally time to get active here:
My plan is to convert a Golf 2 using a Prius Gen 3 motor and inverter. The motor (with a welded PSD) is already mounted in the car, the drive shafts are modified to fit into the Golf/ Prius mounts and the inverter is temporarily fixed with some strap clamps:
20210622_145919.jpg
20210622_145910.jpg
With this setup I could already do a small test drive with 10x12V lead acid batteries. MG2 works very well and has a lot of torque in standstill, however it seems to drop off quickly. My driveway is fairly short so I couldn’t test what the maximum speed is. Sadly, MG1 did not perform that well: it produces barely any torque at all. The car reaches turtle speed at best and cannot even move if it is on a slight incline. At the same time, the inverter quickly derates as the heatsink temperature reaches >85°C.

I did the FOC tuning according to the corresponding video tutorial and while the car is lifted in the air, MG1 has no problem spinning the wheels at high RPM. Syncofs seems to be tuned fairly well, it does not spin even at Id=200A and starts spinning as soon as I change syncofs +-500. By the way, MG2 and MG1 have identical syncofs (except from the 65535/2 difference to have them both spin in the same direction), is this typical for a Gen3 motor?
Also, is it normal that tmphs idles around 40-50°C, even shortly after startup? According to the wiki page of the Gen3 board, I selected the Semikron temperature sensor. However, the high idle temperature and the fast temperature derating of the inverter make me believe that it is not the right sensor type. The inverter no. is G9200-47230 with the logic board no F1789-52010. The v1d (small board) works mostly flawlessly, however I had a problem with the 5V power supply (already known problem) and with the -5V power supply. But I will write more about that in the appropriate thread.

The next step will be implementing the real HV battery, 16 of the 18 modules from a MG ZS EV. This makes it a 96s system with ~40kWh. 4 of those modules will go into the front, the rest in the trunk.

Finally, a big thanks to Johannes, Damien and everyone else in the community for making this and many other EV conversions possible.
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by Bratitude »

very cool. Toyota stuff likes the high voltage, torque drop shouldn’t be as pronounced with your full pack.

any photos of the work you’ve done for the cv joints?
https://bratindustries.net/ leaf motor couplers, adapter plates, custom drive train components
LeonB
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by LeonB »

Bratitude wrote: Sat Jun 26, 2021 12:35 am any photos of the work you’ve done for the cv joints?
I have not modified the cv joints, instead I welded together one half of the golf drive shaft to the other half of the prius shaft. Sadly I have made no photos of the process, I just got this CAD design:
driveShafts.PNG
After measuring how long the new drive shafts need to be I cut the Prius/ Golf shafts accordingly. I then turned a sleeve that fits around the thin solid shafts and a solid rod that fits inside the hollow shafts. In order to increase the weld contact area, I cut the ends in an angle and drilled some additional holes.
Just adding one weld spot was enough to increase the runout by 1mm. So after each weld I clamped the shaft in my lathe and searched for the highest spot where I then added the next weld spot. This took quite a long time but in the end I got a nice joint with a runout of a few 1/10mm.
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by geduxaz »

I think cooling is esential to inverters. Have you connected a cooling system to it?
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by RetroZero »

I like the subframe. Making me rethink my Gen2 setup...
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by LeonB »

geduxaz wrote: Mon Aug 02, 2021 10:20 am I think cooling is esential to inverters. Have you connected a cooling system to it?
I haven‘t connected a full cooling system yet, however during the tests I filled up the inverter to simulate the thermal mass of the coolant. I think the temperature rise is way to quick to attribute it to the non-circulating coolant.
RetroZero wrote: Mon Aug 02, 2021 8:37 pm I like the subframe. Making me rethink my Gen2 setup...
Thanks, the subframe is great for integrating the new engine mounts and adding a lot of mounting points without modifying the original car too much.



The battery boxes are coming together nicely and at least the front box is nearing completion:
20210803_182701.jpg
I used 30x30mm aluminum profiles for the outer structure which will later be embedded in a fiberglass shell. I can reuse a lot of the original bus bars from the MG ZS although some custom cables are required and right now, I only have to wait for some cable lugs to arrive to finish the boxes. (Don't mind the prototyping particle boards, they will be replaced ;) )
20210803_182733.jpg
I am using a JKBMS Balancer (JK-DZ08-B1A24S) to measure the cell voltages and (actively) balance the cells. All the cell voltages are available via CAN and the balancing and the other parameters can be controlled as well. An Arduino will later read those and control charging etc..
Main contactor is an EV200 and LEV100 are used for the less demanding applications like precharge and the cabin heater. Speaking about the cabin heater, I have also spent some time with my CNC router and came up with this substitute for the original heat exchanger:
20210803_183448.jpg
20210803_183519.jpg
It is a nice drop-in replacement and includes 2x1000W 230V PTC heaters. I am running those in series on the 400V battery, so I expect a little less than 2000W of heating power.
For safety, the relay that controls the heater is wired through the temperature switches that are on the PTC and I will also add thermistors to measure their temperature (more or less) accurately.
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by JaniK »

Very nice.

BTW, are those ptc heaters like from a standard car inside additional warmer+fan with 230v? Those kind we use in winter in Finland and they are pretty cheap with even 2 stages power button.
Any opinions are my own, unless stated otherwise. I take no responsibility if you follow my way of doing things and it doesn't work. Please double check with someone who knows what they are doing.
LeonB
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by LeonB »

Thanks! I have looked at a few of these inexpensive electric heaters but decided to just buy the PTC elements from aliexpress to get the exact size I needed.
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by LeonB »

Trunk battery box is now in a “not finished, but ready for a test run“-state:
20210809_181517.jpg
20210809_181538.jpg
Besides the 12 battery modules there is an EV200 main contactor and a Tyco service disconnect with a 350A fuse.
BMS is not wired yet and I will do the first test runs without it. The pack is in a nicely balanced state and I will charge and discharge it within rather conservative limits.
HV wiring to the inverter is next and then the car should be ready for another test drive, this time at full voltage.
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by Markos »

Nice project. Do you need to balance the driveshafts after welding those together?

And you use a prius gen3 motor with welded PSD, could you also keep it unwelded and lock the input shaft like with the GS450H transmission?
LeonB
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by LeonB »

Markos wrote: Mon Sep 06, 2021 10:03 am Nice project. Do you need to balance the driveshafts after welding those together?
Thanks. The original driveshafts from the golf and prius had >1mm of runout in the middle of the shafts and I couldn’t find anything that hinted that they were balanced. My new shafts have significantly less runout and thus, I do not think that I have to balance them. However, only the first high speed test will confirm this.
Markos wrote: Mon Sep 06, 2021 10:03 am And you use a prius gen3 motor with welded PSD, could you also keep it unwelded and lock the input shaft like with the GS450H transmission?
The internal oil pump is coupled to the input shaft. Therefore, locking the input shaft would disable the pump.
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by Markos »

Ah I didn't know that, I thought it was connected to the planetary gearset.

I watched this video after your post which explains pretty good how the P410 transaxle works. I don't know if you already know it or if it is useful for you, so I'll just share it:


There is also a more into depth video, which I haven't watched yet, but what might be useful:
LeonB
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by LeonB »

Batteries are now inside the car, HV wiring is done and a coolant system is implemented. The inverter idle temperatures are still a bit high, but a lot better (~10°C above ambient). Temperatures under load are also much better, so the cooling system is helping a lot (who would have thought ;)). I am using a E90 water pump (part no. 7586928) with the original radiator and a custom reservoir that fits in front of the windshield wiper mechanism to free some space in the actual engine compartment.
20210829_165912.jpg
20210829_165926.jpg
20210812_201949.jpg
I have yet to find a place to do some extensive test driving, however, I already had a lot of fun in my short driveway. MG2 has a great performance while MG1 still can’t even move the car properly from a standstill.

Currently I am working on installing a proper charging system into the car as well as getting the batteries and electronics into a presentable state.
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by RetroZero »

Nice progress. 👍
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by Ev8 »

Great job so far, having watched those videos on the gen3 gearbox I would think that by welding up the psd you’ve ended up with a ratio closer to 1:1 from mg1 whereas mg2 has an additional reduction still thanks to the other planetary gearbox, meaning in practice mg1 probably isn’t going to be much use until you’ve got the car up to speed, you could almost use mg2 for acceleration and mg1 for
cruising at speed, but trying to use mg1 from standstill is just going to pull a lot of amps
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by RetroZero »

That's a good point. Will have to take that into account for my Gen2 project. 👍
LeonB
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by LeonB »

After a long time here is an update on the car:
All the structural work in the motor compartment is finished and so everything (except the motor) received a new coat of paint.
20211201_201145.jpg
20211201_201214.jpg
The transaxle housing has a cooling channel for MG2 which seems to be unused in the gen 3 prius. I want to use it for additional cooling of the motor. Thus, I sandblasted/cleaned the surface, recut the threads and made a matching aluminum cover plate. I attached the .dxf file for the plate to this post.
20211129_194203.jpg
20211129_194355.jpg
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CoolingChannelPlate.dxf
(5.47 KiB) Downloaded 116 times
LeonB
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by LeonB »

Front and rear battery boxes are installed, most of the LV and HV wiring done (although it still requires some organizing)
20220313_191139.jpg
20220313_191205.jpg
The dashboard got two new displays: The upper one is a Nexus 7 tablet running Timurs Kernel which enables features like autostart when starting the car. I am using an ESP32 with a CAN Module to disguise as one of those ELM327 OBD2 adapters. It listens to the CAN bus of the motor and the Nexus displays the data via the app Torque.
20220313_191335.jpg
I have done a few longer test drives which showed a problem:
I have regen turned off (brkmax = brknom = 0) and thus, I would expect the motor to freewheel when not pushing the throttle pedal. However, that isn’t always the case. There is a strange behavior when letting go off the throttle pedal at a motor speed close to 2200rpm:

Below 2200rpm (graph below at t=37136): Motor is just freewheeling, no regen current/regenerative braking as expected
Above 2200rpm (graph below at t=38200): Regen braking with ~50A regen current. Quite strong and continuous braking but no stuttering
driving1.png
At ~2200rpm (graph below at t=60700): Inverter input current seems to be oscillating between positive and negative current, motor stutters violently. Plot shows that motor rpm jumps up 500rpm which, in reality, wasn’t the case.
driving2.PNG
The data above was captured with only MG2 connected to the inverter, MG1 was just freewheeling. The motor also shows the same behavior when the wheels are spinning freely in the air.
I would expect some unwanted regen at RPMs where field weakening is active, but 2200rpm should be way below such a speed? Could this be a problem with my syncofs value? I think I got it tuned fairly well and also tried changing syncadv between 10 and 15 which didn’t make a noticeable difference.
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by johu »

Parameters?
Are you running 5.14.R?
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by LeonB »

Yes, I am running 5.14.R. Parameter file is attached.
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by johu »

Nothing sticks out. Now of course FW requirement depends on DC voltage and motor inductance. Are you running on low voltage still? If so you could lower ffwstart, say to 100 Hz
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LeonB
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by LeonB »

Thanks for checking my parameters.
I am using the full 96s pack voltage, ~380V for the tests above. According to the “Evaluation of the 2010 Toyota Prius Hybrid Synergy Drive System” from the US Department of Energy, the back-emf of the motor at 2000rpm is <100V rms. So FW should not be necessary here. But I guess increasing ffwstart would also change nothing, as 200Hz / 4(polepairs) * 60s/min =3000rpm is already above the rpm range where this behavior is happening?
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by johu »

ok, then indeed this is not an FW issue. Maybe syncofs is 180° offset?
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by LeonB »

I did another test run where I tried different syncofs values and played with syncadv a bit. Again, only MG2 was connected to the inverter, the contacts of the MG1 connector were isolated (no short circuits in between the phases)

At 180° offset, so 43500-32768 ≈ 10700, there is basically no torque.
At 18000 the car was drivable in forward direction but no torque in reverse direction. Also, when letting go off the throttle at higher rpms (~1000), there would be an unwanted acceleration.
At 8000 the car could drive in reverse, but not forward direction.
Thus, I resorted back to 43500. Tried a bit more extreme syncadv values (5 to 20) but no change: Whenever I let go off the throttle above ~2200rpm, there is a strong regen till the motor is back below 2000rpm.

I found a post today which basically describes the same problem which I am encountering (viewtopic.php?f=14&t=701&p=26267#p26267). There, lowering curkifrqgain and curki did the trick so that is what I am going to try next.
LeonB
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Re: Golf 2 with Prius Gen 3 Motor and Inverter

Post by LeonB »

Sadly, only lowering curkifrqgain and curki had no effect. I tried values down to curkifrqgain = 0 and curki = 2000. However, increasing curkp at the same time caused the unwanted braking to shift to higher rpms. Thus, I ended up with curkp = 600 which results in the braking only happening above 4500rpm (tested with wheels freewheeling in air). Interestingly, with wheels on the ground this critical value shifted down to ~3000rpm. So better than before, but still not acceptable for real use (3000rpm equates to around 50km/h).Therefore, I will try to further optimize the parameters next.
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