[DRIVING] Audi A2 /w Prius Gen2 Transaxle & Inverter  [FINISHED]

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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by RetroZero »

Thanks for all your efforts going into this issue. I'm out of the picture for the moment, but watching from the sidelines. 👌💪👍
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by johu »

I will be away again for 10 days, so next test drive then.

I fixed the fuel gauge. It is driven via an NPN transistor with PWM at 72 kHz and tended to drift away over time. So now I receive the displayed value back from the gauge cluster and do a PI loop on it. Still have some ground bounce going on, when the vacuum pump turns on (powered via VCU GND) the needle goes up, PI counteracts, then needle drops as vacuum pump turns off ;) good enough anyway.
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by Ev8 »

Cool, look forward to more testing, is the bin file you posted above your latest build as I will do some testing once I get over this Covid.

Pi controller for the fuel gauge is fancy! I use simpbms which basically is just pwm gnd, it doesn’t drift much but match the resistance curve of my gauge so I can get 0-50-% fairly accurate but not 50-100%
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by johu »

Yes that's the latest build, source also on github. Not sure why the gauge drifted so much now it's well anyway. Source also on github, stm32-car in audi-a2 branch.

Get well soon!
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by Ev8 »

Thanks
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by Ev8 »

Finally got a chance to do a little testing of the builds you posted, agreed that the throttle limiting is undrivable, even with f/w disabled it was trying to limit throttle… rolled back to your build without the throttle limit and added -5a manual ifw, this totally cures the issues I’ve been having when rolling forward down a slope without throttle that jerked about once the motor hit a certain speed and then resulted in a cogging noise in the motor when applying power. Stopping to stationary and then pulling away again cures this, but it seems keeping the gate drives busy stops it happening altogether, only issue is the value for Manual ifw doesn’t save so next time you restart the inverter it gone, I think this feature is a must for Prius gen2 inverters.
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by johu »

Yes those -5A are very useful. At one point it made some noise and I had to turn it off. So maybe it should stop after being stationary and restart once throttle is touched.
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by johu »

Once again the car project has turned into a motor control project :)
viewtopic.php?p=48144#p48144

Bottom line is in a 400V system the Gen2 Prius transaxle can only deliver around 25 kW at higher speed and about 40 kW at low speed (like below 40 kph). That is with MG2 only. Maybe the smaller MG1 with welded planet gears could add another 50% to those figures, i.e. 36 and 60 kW.

I think it makes the system suitable for small and light cars only where performance isn't a key requirement.

Currently the only way to increase power seems to be upping the voltage to somewhat impractical values. Also I wouldn't expect much help from the boost converter which maxes out at around 100A.
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by RetroZero »

Well, you along with Pete 8000 have given it the full Monty. With all those hours put in, I still hope you'll find a way to up those values safely. I am however thinking of removing Mg1 as the weight gain could help with performance and space. Keeping tuned. Huge thanks to all the work done.
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by MattsAwesomeStuff »

johu wrote: Tue Nov 08, 2022 7:52 pmBottom line is in a 400V system the Gen2 Prius transaxle can only deliver around 25 kW at higher speed and about 40 kW at low speed (like below 40 kph). That is with MG2 only. Maybe the smaller MG1 with welded planet gears could add another 50% to those figures, i.e. 36 and 60 kW.
25kw is going to struggle to reach highway speed.

36kw at highway speed should be "enough". 60kW at lower speed is enough to feel decent acceleration.

For normal driving, that's probably fine.

But yeah, as a single motor, looks like the transaxle isn't viable. Pretty much need to twin MG1 to be practical, and even that's scraping by.

That said, the motor is probably fine for more, and the inverter too, just isn't geared to spin fast enough eh?
Currently the only way to increase power seems to be upping the voltage to somewhat impractical values. Also I wouldn't expect much help from the boost converter which maxes out at around 100A.
Boost converter is 100 amps... at 400v?

As per the other thread, field weakening can't change this to make it spin faster, it's a fairly hard limit?

...

So, what's this say for the DIY EV future of the Prius Gen 2 platform? (Or Gen 3 even?)

Inverter is still the cheapest way to get that kind of power, but, choose a different motor? Or, if you're choosing a different motor, might as well mate it to its matching inverter?

Is Gen 3 any more viable?
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by johu »

Boost converter is 100A at any voltage. So it *should* be able to push around 35-40 kW at 350-400V. But no one has tried and I can't rewire now as I'm using it for charging. 25kW is already with field weakening. Base speed is pretty low around 1000 rpm or so, gearing is 1:4.

So Gen2, it is what it is, take away your own conclusion.

Gen3 would need that test repeated, might be more viable.
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by Romale »

johu wrote: Wed Nov 09, 2022 9:54 am Boost converter is 100A at any voltage. So it *should* be able to push around 35-40 kW at 350-400V.
it seems to me that it may be not only in the motor but also in the inverter.
Johu, do you have the opportunity to connect an inverter from Nissan leaf Gen2 for a test? This will give a lot more information.
I used to make many different motors and sometimes it seemed that the motor was unsuccessful. however, another controller solved this problem.
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by Romale »

by the way, once using iron from the mg2 gen2 prius motor, I created an excellent motor that easily gave out 120 kW and had a speed of 8000 rpm at 144 volts. This is in the projects on the forum, I built a buggy on it.
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by johu »

I'd certainly pinpoint it to the motor, so yes your rewinding scheme to lower inductance will definitely give it a more practical speed range.

Bigpie runs 70 kW with a gen3 inverter that as similar specs as the gen2
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by SciroccoEV »

Some interesting Prius information on this website;

http://roperld.com/science/Prius/PriusPhysics.htm
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by FFMan »

As i'm part way through a Gen3 build I'm interested in this thread. It's beginning to sound like gen3 MG2 is quite a low power approach unsuited to the estate car that I want to power. If there is a time to switch to a bigger motor for my build, now is the time.

> Gen3 would need that test repeated, might be more viable.

do the toyota specs give any clues here as to how gen2 is vs gen3 ?

are there any on the road gen3 conversions that could be used for feedback ?
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by Pete9008 »

Based on the information linked in this post. https://openinverter.org/forum/viewt ... 0#p47770 it looked like the gen3 might be better able to work at higher speeds.

If you have access to one, and can measure the motor inductances, put the numbers into the simulator and see what it says. The numbers it now produces seem to be a reasonable estimate of what you will be able to get out of it.
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by Romale »

FFMan wrote: Wed Nov 09, 2022 2:44 pm ...If there is a time to switch to a bigger motor for my build, now is the time....
gen 2 is designed for 500 volts and gen3 for 600 volts. therefore, from a voltage of 360 volts, it will work even worse. I converted it into a simple motor for a motorcycle with a change of winding. in fact, it has a higher-rated power only due to a higher voltage. the motor itself is made less powerful than gen2. If you need a pleasant driving of a heavy pickup truck, the best thing you can do is to use the motor+ controller EM57 with Nissan leaf gen2
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by FFMan »

> If you have access to one, and can measure the motor inductances,

i have a gen3 motor on the bench but no idea how to measure the inductances. Happy to be remote hands if someone can instruct.
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by Bigpie »

https://www.ebay.co.uk/itm/194320980873 get one of those or other LCR jumper 2 phases together, attach one lead to 1 phase the other to the joined 2. Measure, turn motor slightly and repeat until you've got the highest reading and the lowest.
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by Pete9008 »

FFMan wrote: Wed Nov 09, 2022 4:29 pm > If you have access to one, and can measure the motor inductances,

i have a gen3 motor on the bench but no idea how to measure the inductances. Happy to be remote hands if someone can instruct.
Making the measurements would need a LCR meter. This is the one that EV8 and Bigpie have used to take the same measurements viewtopic.php?p=47388#p47388 and this is how I took the measurements on mine viewtopic.php?p=47050#p47050

Got to say my feeling is that the gen3 will be disappointing in a larger vehicle but that does depend on what your performance expectations are and how heavy the estate is.

This is the plot I've seen which which indicates how the gen2 and gen3 compare with each other, and also with other motors.
image.png
Found here https://www.semanticscholar.org/paper/S ... 5db9322241 - no idea how accurate it is.

If you're invested in the gen3 then it's probably worth taking the measurements to see what might be possible otherwise decide what performance you are looking for and then base the motor choice on that.

It's also worth noting that battery voltage will have an impact on motor performance so you need to know what you will be running and as Romale mentioned the Prius motors normally run at higher voltages (500-600V) so you are not going achieve the performance shown on the graph with a lower voltage pack.

Edit - Bigpie beat me to it :)

Edit2 - Just remembered this post viewtopic.php?p=46927#p46927 which suggests inductance values for the Gen3 that are the same as the ones Johannes is using on the gen2. That would suggest that there won't be an improvement moving from the gen2 to the gen3 :(
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by FFMan »

While we're here may as well get the measurements. i'll order that little device and assuming it arrives in time get some readings over the weekend or a day or two later and post them here.

Have a feeling it's not good news for MG2 though.
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by MattsAwesomeStuff »

FFMan wrote: Wed Nov 09, 2022 2:44 pmdo the toyota specs give any clues here as to how gen2 is vs gen3 ?
It's designed for and rated to a higher RPM. Which is a way of getting more power out of the same package, by spinning it faster.

It runs on higher voltage.

The inverter is more powerful. I think roughly each generation is like, 15-20% more powerful than the previous.

But as someone else said, being designed for a higher voltage makes it less usable for a lower voltage.

If everyone was using 18650s for batteries, this wouldn't be a problem. But for those looking to use part of an OEM pack, with a minimum size you can chop a pack down to, having high enough voltage onboard is a concern.
are there any on the road gen3 conversions that could be used for feedback ?
I think New Electric Ireland in the pre-Covid days did several weekend workshops with Damien where Prius was generally the motor of choice. At least, that's what my fuzzy memory says.

Only a few of those people showed up here, and I can't recall any specifically that are active.
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by johu »

MattsAwesomeStuff wrote: Thu Nov 10, 2022 7:53 am It's designed for and rated to a higher RPM. Which is a way of getting more power out of the same package, by spinning it faster.
Yes, but it also has twice the gearing ratio, so the extra rpm is "lost".
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Re: Audi A2 /w Prius Gen2 Transaxle & Inverter

Post by RetroZero »

Only a few of those people showed up here, and I can't recall any specifically that are active.

I'm still here from the pre covid course with Herr Jack Bauer 😁. I'm at the tipping point. I got my Gen2 running on a Prius pack @ 200v. I was planning on installing a pack@ 300v when all these issues came to light. I could install the 'kit' into a smaller vehicule, or watch and learn from the pro's. Anyhow, I'm focusing on a garage in which to work safely. Again, huge thanks to Johu and Pete (to mention a few)
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