MN944S

Check his link posted earlier. (post #19) It shows the 12V pack consisting of 12 ~1.2V Lithium cells. This is just for the original 12V systems in the car. The motor pack will be made of a LOT more of those cells.

odurandina

oh yeah, this is going to be hugely successful.

only, ask the automakers why they don't mass produce these and sell millions.

that new, hybrid Porsche 918 concept hybrid only costs about 800 grand. it's not electric. it's a hybrid.

it's so-called green footprint (manufacture) is = to only 11 about hummers.

you would need to drive it about 7 million miles for it's green footprint to show a net savings.

look, nobody wants to see any of you young guys fail with your car projects, or throw your money away.

but seriously, this is a lousy way to prove a point, and just show a more fancy way to destroy another 944.

to make an electric car feel even close to "right" for driving as a sports car in the real world costs millions in development.


you'd have much more fun building a GT40 kit car, that uses a small block Ford engine and Audi gearbox.

Robin W.

This is correct, this is only my 12v system battery. The cells are actually 3.2v and it's arranged in a 4 series / 3 parallel arrangement. The car will be powered by 630 of these cells in a 90 sereies / 7 parallel setup.

Estimated range is 100-150km depending on how I drive. My daily commute is only 37km round trip and I will be able to charge at work as well so about 95% of the time the electric car will work just fine for my lifestyle.

You are 100% entitled to your oppinion and I won't disagree with you, for some people a GT40 kit would be the best thing for them. So you are correct.

That just isn't me though, I'm not a tree hugger, and I'm doing this to "save" the enviroment. I'm doing this to make one slightly greener choice for ME and only me, I also like electricity and electronics much more than grease and oil. Am I enjoying wrenching on my 944's (one of which is getting a working gas engine and will stay that way) I love working on these cars and gas or electric I have become a big Porsche fan.

To those that want to do something different just do it, don't be put off by those set in their ways that say it can't be done, take what they say as a bit of advice, since there there probably is something to it. There is only one comment that I can disagree with that odurandina has said, I won't be distroying this 944. The rest is true, the 800grand price tag, the green footprint, the miles required etc. all true, today. In 10 years, maybe not true.
I can't even disagree with the comment about the driving feeling being "right" the electric motor is a different beast, there is no torque curve, 100% of the torque is available from 0-5000 rpm it's a line, not a curve. No gas engine can do this, so it will feel different that's for sure. Due to the massive amount of torque I will start in 2nd gear (turbo tranny), peak efficiency is at high RPM so I'm not going to shift out of 2nd gear untill about 80-90km/h and thats only if my cruising speed is going to be 100-120km/h and I'll never get past 3rd gear because I don't need to bring the RPM's down to get good efficiency when cruising on the highway. So odurandina is 100% correct, it won't feel the same to drive. But does that instantly make it worse?? Or is there the chance it could be better?? Right now I don't know, but I can say odurandina's comments are some of the most important because it makes me think about if I've missed something in my design, if I've missed something in how the car is going to drive.

Please don't bash the idea without giving it thought and backing it up with honest answers or opinions like odurandina has done. I really do appreciate all comments positive or negative, just back them up.

Robin W.

For those that are interested, here is a small update of some work done on the gas engine transplant ('86 to '83) as well as some photo's of the electric motor that will be going in the '86. (from my blog):

Work has moved towards getting the engine out of the '86 ready for it's transplant into the '83. This involves moving over the entire wiring harness, any sensors or brackets that are different between the two years as well as the entire intake and vacuum system. After stripping down the "blown" engine out of the '83 it turns out the balance shaft belt was broken, however the timing belt was intact. Even with the extensive damage the engine isn't actually seized, the camshaft is seized and the timing belt was strong enough to keep the engine from turning. After sliding the timing belt off (something I'm sure isn't supposed to be possible without loosening the tensioner) the crankshaft still turns nicely. Both balance shafts still turn but one has slightly more "drag" than the other which could have been part of the cause. After removing one of the motor mounts I found the hole is much larger than previous thought.



It looks like all of the parts that I need are in good shape though, and the transfer of parts has gone very smoothly, the engine will be ready to go in the '83 fairly soon.

On the EV side though, the Warp 11 HV has arrived, and I will start the design for the coupler and adapter. The motor is a thing of beauty and I can't wait to start working on getting it into the '86.



Even though the Warp 11 HV is a monster in the EV world, it's still very compact compared to the stock 2.5L Porsche Engine. As shown above with the Porsche engine and starter motor for scale.



I've also been working on the battery charger design, instead of using an off the shelf solution I've decided to create individual cell chargers in the form of industrial quarter brick dc/dc converters. Each of the 90 series groups of cells will be charged by it's own 48v to 3.3v dc/dc converter adjusted up 10% to 3.65v to charge each cell to the perfect voltage every single time. This eliminates the need for a shunting BMS or other intrusive charging monitor. The dc/dc converters will be in groups of 15, with these groups fed by an industrial grade 85-264v AC power supply. By adding more of these power supplies the total charging power is scalable from 1.5kw up to 7.5kw with the existing dc/dc converters. The charger/bms/gauges are all part of the same system and the total cost will be around $1000 instead of $1000-2000 for a charger, a few grand for a BMS and a few hundred for gauges.



All of the systems will be tied together with an Arduino Mega based microcontroller that will monitor each cells voltage, battery current, charging current, battery temperature, cabin temperature, SOC, total pack voltage, and any other systems that need control or monitoring.

techartisan

why do you intend to keep the clutch? It is an unnecessary point of potential failure in an EV application. Coupling directly to the splined end of the drive shaft should be pretty straightforward.

Robin W.

Although the clutch is optional for an EV it's not so simple to say it's not required. I will stil use 2nd and 3rd gear, so it will be easier to shift with the clutch, and depending on my implimentation of air conditioning, I may want to idle the electric motor while stopped in traffic to keep the A/C going so having the clutch would make it the same as driving a normal 944. Also I plan to ensure there is enough room to slide the motor straight forward far enough to do any future clutch work, so it would become a much simpler task. It's also a good place for the drive train to slip under extreme loads instead of just breaking. I have no idea how the drive train will stand up to the huge amount of torque that the electric motor has, so for the moment the clutch is staying. That could change later on though, and a direct coupler could replace the flywheel/clutch assembly.

techartisan

Youll want to kill motor power during shifting to avoid overrevving upon gear change anyway....the inertial contribution of the motors core is not going to provide a significant force to the transaxle.....so Ill stick by my statement of it being unnecessary.

thats alot of battery power to waste for a small measure of comfort. 5-10hp of parasitic loss to keep cool is bad enough...but to continue running the motor during standstill? Not expecting much range are you?

Sitting unpowered in stop and go makes a huge difference.

Roll down your windows...pop off the sunroof.

I think youd be surprised how few of us have functioning AC in our 944's anyway....

Equilibria

would you need to leave it in a certain gear or could you still 'shift' without the clutch? I've heard about doing this in an electric car but not sure why you can or what the compromise is.

Regarding AC - how hot does it actually get in Calgary in the summer? I know in Vancouver I can make it all summer without the AC in my 944, though I'm sure it would be nicer with it (I don't know though... it's never worked :-P). Could you not find a more efficient way to do AC in an electric car than with all the hoses/components that are in there now?

techartisan

A gas engine continues to rotate under power (idling) even with your foot off the gas....so you must clutch....an electric motor will coast adding some inertial mass to the driveline, but not POWER...so no need for clutching.

Ive driven an electric VW Beetle with no clutch. Shifted just fine without...just took my foot off the "gas", which removed all power from the motor, and shifted. Coasting or downshifting to slow down allowed the motor to boost the charge a bit...extending range.

my points exactly

Robin W.

You can still shift without the clutch, and it should be easier than shifting your ~2.5L without the clutch but it's still not as easy as with the clutch.

As far as the summer, the only time I really use A/C is when I'm stuck in traffic, otherwise airflow is plenty to keep the car cool. It really comes down to the A/C works well and it's there so why not just use it? There are systems that are electrically more efficient, not to mention lighter but the 944 A/C already has nice controls and it's integrated into the car. Plus it's FREE! If I had to pay for A/C I'd skip it entirely.

The car also has to be easy to drive for my fiance, as well as when I demonstrate the car for others, so stock controls for everything (not that they are the most intuitive to begin with) but my personal goal of this conversion is that if Porsche put a feature there it should work as expected the only change is the power source and a slighly different driving style (but that's the whole point).

fwb42

Not knowing much about this,I have to ask about reverse. Reverse the motor or use a transmission ?

Robin W.

It's possible to do either, electrically it's as simple as swapping the + and - wires to a DC motor, however when these wires are 4/0awg, very big expensive contactors are required. So for my build I will be using the transmission, but there are many people that do it electrically. A/C motors can usually do it via software in the controller and don't require anything mechanical to impliment reverse.