Porsche 911 - will a Nissan Leaf drive train do it justice?

[mcgousha]

I have been meaning to start a project thread on this forum for ages, but never seem to get around to it...changing that today!

I think some of the contributors on here have been following my progress on my YouTube channel:
https://www.youtube.com/channel/UCca95a ... 33wJBAMe5g
but for the rest of you, this project is to convert a Porsche 911 to electric power using the Nissan Leaf drive train and inverter.

The car I've chosen for this is a 1998 Porsche 911, also known as a 996, which was the first generation of water cooled Porsche 911s.

Part of my reason for selecting this car was it was the car that I really wanted when they came out when I was in my late teens, and as luck would have it, they are also now the cheapest way to own a 911. The models older than this have vastly inflated prices due to the nostalgia attached to the air cooled motors and the newer ones are...well..newer, so cost more.

I bought this car sight unseen on Ebay back in April after a beer or two and a couple of days later it turned up on my driveway.


As to the motor, I know a lot of you may say that the Nissan Leaf motor is a strange choice and wouldn't I be better off going with a more powerful Tesla rear drive unit...and you may well be right. However I have never really been one to go with convention and if I get the spark of an idea, I like to run with it and see where I end up.


In this case, I was inspired by some of the work that was coming out a year or two ago, like the guy who got 300+bhp out of Nissan Leaf motor in a Honda CRX. The car I bought originally came with the 300bhp 3.4l engine, so if I can push the Nissan Leaf motor up to close to this figure, then I hope to be able to keep the car as close as possible to its original power and weight figures, but using electric instead of internal combustion.
Oh, and any of the Nissan Leaf motors I could find were also considerably cheaper than any of the Tesla motors I could get my hands on, which was also a factor.

I am of course being a realist with this, I know that getting the Nissan Leaf motor to these power levels will require a fair bit of work, and who knows how much of the original inverter and other control systems will still be in place by the time I reach those levels. For now, the focus is just on getting the car running. Then I will worry about making it run in a manner that befits the name.

I'll try to dig out what pictures I have of my progress, but a lot of this was captured on video, so I will include links to those as well.

[johu]

Great project.
The 300bhp was achieved with a rebuilt inverter and a 450V battery, as far as I know.

It is still work in progress but I'm guessing the drop in board should eventually be able to deliver 160kW with the stock inverter. Purely because Nissan start ramping down the torque at 2900rpm to limit to 80kW and protect the battery. Voltage-wise it should be possible to maintain peak torque up to 5-6000rpm without putting more stress on motor or inverter.

[mcgousha]

Thanks,

Yeah, I figured the stock inverter would have a limit a good bit lower than the figure I'm after, but I'm keen to see how close we can get before the stock inverter has nothing more to give.

Then I'll probably give a custom inverter a go, but I think there's a lot of fun to be had before we get to that point:-) And 160kw is still well above 200bhp, so would be a pretty decent uplift from Nissan's stock figure.

[arber333]

Right now i am working on my car with Leaf motor and Volt inverter. Alone this will give 600A at 400Vdc. This should be achievable as some 200kW with losses and various inaccuracies. So whish me luck with that...

I have a plan however. Volt inverter has two identical IGBT modules coupled by excellent DC link cap. It should be capable of paralelling them and running them at 1000A joint amperage. I have a plan to couple current readings which shoulcarry 500A each and average that inside inverter brain.

But first i have to get my car roadworthy .

[doobedoobedo]

I'm aiming for around 150-170KW through the leaf power stage. If this isn't possible I'll go for a different power stage. I don't think I've seen any hard figures on what's possible.

What batteries are you planning on using? I personally think that choice of battery is as important as choice of controller/power stage if you're looking for decent power.

[mcgousha]

But first i have to get my car roarworthy .

Haha, tell me about it, I keep finding issues with the car as I dismantle things to make space for the electric components.

I'll definitely be interested to see how you get things working with that Volt set up. It sounds interesting.

@doobedoobedo not 100% sure on batteries at the moment. I had initially assumed the Leaf pack would be the easiest way to go, but on reading threads here and on the DIYelectriccar forum it sounds like there may be limitations there in terms of the power delivery, so this is one I am going to have to dig deeper into.

[doobedoobedo]

I'm still in the removing oily bits stage too

I'm pretty sure you won't get 300hp out of a leaf pack, not if you want to use it more than once anyway. Decent power with longevity requires either a high capacity pack or active thermal management, preferrably both I think. The Volt pack has a really good reputation, but they are like hens teeth over here.

[arber333]

I think on using 2x Volt battery packs. I have one at home already, but this will give me like 80km highway range, which is not enough. But power density is very much on the level.
My current battery Mazda are Kokam and have 250A max limit before selfdestruct. They will not be usefull for testing high power...

I am a bit dissappointed though as i find only used up Volt packs. My pack taken from 180KKm Ampera has Ri 0.02mohm, but when i checked other packs they had over 0.05mohm! That is quite a show stopper . Measured with my SM8124A meter.

[jon volk]

Right now i am working on my car with Leaf motor and Volt inverter. Alone this will give 600A at 400Vdc. This should be achievable as some 200kW with losses and various inaccuracies. So whish me luck with that...

I have a plan however. Volt inverter has two identical IGBT modules coupled by excellent DC link cap. It should be capable of paralelling them and running them at 1000A joint amperage. I have a plan to couple current readings which shoulcarry 500A each and average that inside inverter brain.

But first i have to get my car roadworthy .

Is there any documentation floating around the web on paralleled Volt inverters? Id like to do a decent power budget build in a tube chassis and this may be the ticket. I couldn't find anything beyond your reference here.

[arber333]

Is there any documentation floating around the web on paralleled Volt inverters? Id like to do a decent power budget build in a tube chassis and this may be the ticket. I couldn't find anything beyond your reference here.

Well it is all a bit theoretical... . But if you use a bit longer phase cables and paralell them at motor side instead of direct connection between IGBTs, then cable induction should dampen dV that results from switching and you should be able to use at least 1000A from both 600A IGBTs.

I am still working on how to connect current sensors for both IGBT sides into single brain. Some averaging of signal would be required..

Work in progress...

[arber333]

I think on using 2x Volt battery packs. I have one at home already, but this will give me like 80km highway range, which is not enough. But power density is very much on the level.
My current battery Mazda are Kokam and have 250A max limit before selfdestruct. They will not be usefull for testing high power...

I am a bit dissappointed though as i find only used up Volt packs. My pack taken from 180KKm Ampera has Ri 0.02mohm, but when i checked other packs they had over 0.05mohm! That is quite a show stopper . Measured with my SM8124A meter.

I must correct myself. My reading was off. It seems that my meter showed 2mOhm and other measurements showed 0.9 or 0.7mohm!!! I find that quite low resistance for old batteries... Which measurement do you think is correct?

[doobedoobedo]

All may be correct, or none.

How are you testing? What is the state of charge for the tests?

[doobedoobedo]

I probably ought to expand on my previous post.

About 4 or 5 years ago I made a shunt based DC internal resistance tester for hobby LiPos. It worked on the principle of expected voltage drop across the shunt for the measured current vs the actual voltage drop. The internal resistance was calculated from this. It worked pretty well and produced repeatable results.

The state of charge made a significant difference to the internal resistance of a cell.

Commercially they tend to measure AC impedance at I think 1kHz, which gives different results to DC resistance.

[arber333]

All may be correct, or none.

How are you testing? What is the state of charge for the tests?

Yes, i measure at 3.9V per cell. That is still in the "out of balancing" range no? I am not sure where other measurements were done.
Also my 85Ah Kokam cells were also at 2mohm when at 3.85V per cell. So that could make comparison because LiPos should be quite good at Ri.

[doobedoobedo]

Higher state of charge = lower internal resistance in my experience. 2mohm sounds reasonable.

I looked at some reviews of the SM8124A and they seem favourable, one comparison with results of other testers showed how different they all are...

If the pack is reasonably well balanced it may be more practical to do a capacity test on a couple of the cells rather than take as absolute any tester unless it's truly professional grade and calibrated.

[mcgousha]

I'm starting to run out of excuses for not looking in depth into my battery options. I finally got the motor mounted in the car after a couple of months of over analysing it, so it's time to start moving things forward.

Highlights of my last few weeks efforts:






Next step, which I have also been putting off for ages, is to go back to looking into the axle situation. Should be interesting

[arber333]

Higher state of charge = lower internal resistance in my experience. 2mohm sounds reasonable.

I looked at some reviews of the SM8124A and they seem favourable, one comparison with results of other testers showed how different they all are...

If the pack is reasonably well balanced it may be more practical to do a capacity test on a couple of the cells rather than take as absolute any tester unless it's truly professional grade and calibrated.

Yes i agree, i use mine only to compare other cells to mine. Since they work uite good i assume with less Ri cells are even better.
I tried with couple of different model meters and results were different, though not very much different.

Nice work mcgousha!

[johu]

Wow, never realized the series was THAT comprehensive, very nice

Just a word on the integrated relay drivers: they are not exactly powerful, so don't exceed like 200mA on the precharge and 400mA on the DC switch and keep a finger on that ULN2003 chip next to the 26-pin header. I've cheerfully found out that one Nissan contactor overloads the poor thing

I also very much recommend the FOC software, parameters here:
https://openinverter.org/wiki/Configura ... Leaf_Motor

[mcgousha]

Thanks Johu,

I'm looking forward to using the FOC software when I next get the motor connected to the inverter. I looked at the code you released while working on it during the summer, but had only just gotten my head around the existing paremeters, so figured I would save FOC for another day:-)

[arber333]

Wow, never realized the series was THAT comprehensive, very nice

Just a word on the integrated relay drivers: they are not exactly powerful, so don't exceed like 200mA on the precharge and 400mA on the DC switch and keep a finger on that ULN2003 chip next to the 26-pin header. I've cheerfully found out that one Nissan contactor overloads the poor thing

I also very much recommend the FOC software, parameters here:
https://openinverter.org/wiki/Configura ... Leaf_Motor

I allways use another small relay inside inverter to start main contactor outside. Usually i get 12V Arduino dual relay modul. Because you can set hi/lo trigger.

[mcgousha]

Back at it with a vengeance after having to take a couple of weeks off. Finally got started on getting the inverter wiring into the car. I had been putting this off as it meant having to take out some of the interior. But I am glad now that I did it.



Unfortunately that now means I'm going to have to tackle the drive shafts soon. And after that I'm going to have run out of excuses and will need to make a decision on batteries. Fun times ahead.

[NIMMOEV]

Really enjoying your youtube video series mcgousha, your episode on splitting down the Leaf package helped me to get mine split down & off the driveway in no time at all, keep up the great content and progress, cheers

[mcgousha]

Thanks Nimmoev, glad you found some of the videos useful. It actually comes apart pretty easily once you know what your looking at.

Looks like you're making good progress with your conversion, I had a similar frustration with the inverter mount overhang...so I took an angle grinder at it:-)

[NIMMOEV]

Thanks Nimmoev, glad you found some of the videos useful. It actually comes apart pretty easily once you know what your looking at.

Looks like you're making good progress with your conversion, I had a similar frustration with the inverter mount overhang...so I took an angle grinder at it:-)

Hi mcgousha, starting to make a bit of progress now, getting free time is the biggest issue but I'm taking a career break at the end of the year (T-8 days, not that I'm counting) so will be working on the project full time after christmas

I had considered taking the angle grinder to the overhang but chickened out

Looking forward to seeing the Porsche's 1st roll powered by the electrons

[mcgousha]

I've made some good progress since my last update on here, even with a bit of break over Christmas, with the signal wiring installed it in the car and I chopped and welded the four halfshafts I had (2 Nissan, 2 Porsche) to make 2 shafts with Porsche CV joints on the outside and Nissan Leaf CV joints on the inside. Longer term I'll be using these as a template to get an engineering firm to help me cut down and machine new splines on some Porsche driveshafts, but they seem strong enough for my initial testing.


 
Since then the effort has been to get the other components in place, mainly the inverter and precharge circuit and most recently to put in a bunch of small lead acid batteries to use as a test battery back.


With that all in place and now fully wired up, I am running out of ways to put off actually trying to run the motor in the car.
I am doing a complete check of the wiring now, but once that is done, I think my only option is to switch it all on, send power to the inverter, press the accelerator pedal and hope for the best.

​​​​​​​I'll let you know how I get on:-)

@Nimmoev, I hope the start of the career break is going well and that you're getting time with the Caddy.