# Planning porsche 944 conversion



## EV944 (Oct 17, 2013)

Hello EV people. 

As the Title says I plan to join the rank of the EV drivers. I did a bit of research almost 10 years ago when even thinking of using lithium cells cost money.


what is your skill level with auto mechanics and fabrication?
-I am very mechanically inclined although i have never worked on cars beyond the basic maintenance items I can also weld and have been trained in manual and CNC machining. 

What range are you hoping to get (how many miles/charge)?
-my round trip drive to work is under 15 miles in a normal Monday to Friday I will use up about 150 miles with work and other outside trips. i am hoping to start out with 50 - 60 miles, this will create a very practical vehicle for me. the hobbyist side of me wants to see 100.

What level of performance you are hoping to get?
-I am not a lead foot driver and I cruse on the freeway at 70 so topping out at 80 would be fantastic

How much money are you are willing to put into your project?
-With donor car 15K - 20K overall 

What parts you've already considered, if any.
- well i am 80% sure on the 944 although Honda Del Sol keeps creeping in due to cheap and plentiful spare parts that are available for it. beyond that I am completely lost. I know it will be a Lithium battery pack I am reading up as much as i can on the forums about the differences in motors and it seems that warp 9 or 11 are the top used but am unsure which one would fit my needs better. overall I am a bit lost. 

I would like to use a controller and BMS that have an output ability, something i can hook into a raspberryPi or arduous and create a nice screen with battery data and other information. 

I have seen quite a few really great EV conversions on the 944 so far and its every encouraging. I cant wait to get started. 

So let me start by asking 2 very newbie questions. 

1. lets say I build a 144v 80AH pack if I decide to upgrade will I need to match the AH of the first or can i keep it at a 144v and only add 40AH to get a total of 120AH? also follow up question on batteries. if i made a purchase of 45 batteries to build my pack how long can i let them sit unused ? 

2. transmissions - manual/automatic/CVT ?????? and whats this i read about not needing a clutch? the 944 is a manual which I read works better for EV but do you remove the clutch ? 

sorry for the stupid questions.


----------



## rwaudio (May 22, 2008)

Welcome,

Looks like you've done some research and your budget and goals are in line with reality.
I think the 944 is a great donor (of course I'm biased).
With fun but not fast driving my 944 uses about 300wh/mile on average. I can get it lower with effort, but just driving I average 300, so that's a good place to base the calculations.
60miles x 300wh/mile = 18kwh (drop dead range)
For a safe 60 miles you would add on another 20% = 21.6kwh
Depending on controller choice I'd recommend more than 144v
For example you could make 21.6kwh using 67-68 100Ah prismatic cells (216v).
Or you could use fewer larger cells, which would have a lower voltage. The next step up in my favorite brand (CALB) is 180Ah which would put you at a very low voltage, or a much larger pack.

Keep the stock manual, auto's and cvt's would be a waste of time in a 944.

You can add to the battery string, however some people have had issues mixing capacities, or even different batches of the same brand/size cell.
If possible build the pack from a single batch of good cells.

As for the clutch it's somewhat a personal choice. I removed the clutch after feedback from people saying I'd have clutch issues unless I moved up to a high performance racing (expensive) clutch. Also there were no adapter plates or couplers that would allow me to keep the clutch.
The car shifts beautifully without the clutch, it just takes a second or two to let the syncro's do their job. I found myself using 2nd and 3rd gear (944 turbo transmission). I'm in the process of switching from a DC motor/controller to AC and I would expect to use 2nd and 3rd still with occasional use of 1st with the higher RPM range of the AC motor.
With that being said, rebirth auto now has a very nice looking adapter/coupler for the 944/968.

Good luck with your build.


----------



## dougingraham (Jul 26, 2011)

944 is a neat car. I've never driven one but I did get to drive the similar 924 turbo once.

You can parallel in additional cells without too much difficulty. I wouldn't recommend doing it that way however because you have a lot more cell interconnects to worry about. If you start out with 144V (45 cells) of 80ah the easiest thing to do is just add more cells in series. With a DC setup you can tell the motor controller to limit the voltage to what the motor can handle. So if you use a Warp9 for example you could set the motor controller to limit the voltage to 172 volts even if you end up with 98 cells (approximately the max the controllers will tolerate.) I agree with rwaudios suggestion of 100AH cells and 144V is a minimum. The 100AH cells are about the smallest I feel comfortable recommending if you are going to possibly go to 1000 amps. With a 98 cell pack you could limit the battery current and leave the motor current up at 1000 and take advantage of the voltage drop.

It kind of depends on how you plan to drive the car. If you just want a daily driver that feels good to drive you probably don't need anything larger than a WarP9. The HPEVS AC50/144V Curtis combo will do a fine job as well. If you want to do some racing then you will probably want more motor.

I like a clutch. It just doesn't shift fast enough for me if I don't use it. I am certain that removing the flywheel would quicken the clutchless shift time some so maybe I am comparing apples to oranges. I guess I will have to drive someone clutchless and flywheelless setup sometime.

As for transmission type, for your car I agree with rwaudio again. Manual all the way. CVT was invented to hide the narrow torque band issues found with ICE engines and really would be a complete waste on an electric. You will find that for just driving around town that you probably just leave it in one gear all the time. For me that is 3rd gear except for when showing off. Then I use 2nd. First gear is pretty much just for making smoke. It could be made useful if I could change the differential ratio but of the stock ring and pinions for my differential I am already at the 3.909:1 which is the lowest numerical ratio that is easy to find. Something like a 3.6:1 would make that first gear usable. But changing this is not something you really need to worry about. The fact that you have a transmission lets you get a reasonable match to the car. If you were racing this would be a different discussion.

I look forward to reading more about your build.


----------



## MN Driver (Sep 29, 2009)

"CVT was invented to hide the narrow torque band issues found with ICE engines and really would be a complete waste on an electric."

I don't agree, with a CVT you could get maximum torque from the transmission at a stop, have no shifting time, and be able to park the motor speed at the maximum motor horsepower point which will also be where its spinning faster for more ventilation. Of course this maximum horsepower point is pushing a pile of kilowatts through the motor and you are likely to burn it up if you decide to have too much fun or have too heavy of a car.

The other trouble is that often CVTs have transmission controls that rely on engine inputs to control them so you might get stuck trying to use one. There is a guy in my local EAA club who struggled with getting a Porsche automatic transmission working outside of limp mode. For the CVT, the torque capabilities on many manufactures CVTs don't leave you much additional wiggle room for performance.


----------



## EV944 (Oct 17, 2013)

Thank you for all the great information. 

looks like there is a long road ahead. i am hoping in the next 3 - 6 months to pick up my 944 hopefully in a condition where i can drive it for another 6 or so months while i gather up the components and tools i will need to convert it. 

it seems my biggest problem is still the battery pack. looks like i will need something in the 200v range at 180 - 200 AH to get in the miles range i want (100 usable miles). 

I am still not 100% as to how you can shift gears without the clutch but its a bit clearer then it was before. 

looks like i will have to just take this one step at a time and read as much as i can.


----------



## wessss77 (Jan 4, 2013)

Welcome to the forum and cool choice of car. RWAudio I read your build string too as I am just now the proud owner of a currently non-op ICE 1987 944 with Auto. I am hoping to build this up in the next year or so as I start the piggy bank savings. Good to know the 300 whr/mile. (I want to use the 35x2 motor on this one)
Good luck EV944...I look forward to following your build.


----------



## davecover (Mar 26, 2008)

Hello, just happened across your post. I converted a 1987 944 a few years ago, street legal and all. It's been on the road about 5 years now. I have NiCads in it so the range is limited, but it's still a fun car. I have it set up for flat towing and I've taken it from Connecticut south to Maryland for autocross and drag racing and as far north as Limestone, Maine for land speed racing. That's what makes it so fun, it's street legal, yet fast enough to be impressive. But the NiCads are the Achilles heel and the car really needs a good lithium pack. Not in my budget right now.

The basic details; 
Porsche 944 with original 5 speed (limited slip) transaxle, kept the clutch
Warp 11 HV motor
Zilla iK HV
Manzanita Micro PFC-30 charger 
Coil over Konis in the rear to help with the load
Almost new tires on all 4 corners
Just under 300 volts of 30 AH BB600 Nicads, flooded

If you have questions, I might have answers. I've been through a lot with this car, it's amazing what kind of problems I've had to solve, but that's the fun of it.

How far along are you in your project? Still planning? Find a roller yet? 

Here's a link to my car, just the basics, mostly up to date I think.
www.evalbum.com/2149

If you haven't heard of him yet, you should look up Lowell Simmons and the Black Pearl. I met him when I first started down this road. He has a 944 that is amazing, and he's a great guy too. Very inspirational for 944 enthusiasts.

PS My car has some NEDRA and LTA speed records, but you should be able to beat them when you get your car on the road.


----------



## EV944 (Oct 17, 2013)

davecover, 

that's a great build. its very encouraging to see thous kinds of numbers coming out of a non lithium build. 

I sadly just missed out on a great 1986 944 which looked like it had been at a very low speed rear end crash (part of the back bumper was pushed in) but the interior was almost mint. but i was a few hours to late on that one. 


i am hoping to have the car before Feb 2014 until then i am just reading and planing and looking for deals


----------



## EV944 (Oct 17, 2013)

going to look at a possible 1987 944 tomorrow hopefully it will be worthwhile and i can take the second step. 

Dose anyone have experience with EAS: electric auto sports and there GBS Lithium battery kits? i am liking the price of the 96v 200AH pack and 2 would give me 192v 200 AH which I think would get me towards my goal of 100 miles(drop dead distance).


----------



## dougingraham (Jul 26, 2011)

EV944 said:


> going to look at a possible 1987 944 tomorrow hopefully it will be worthwhile and i can take the second step.


Hope this works out for you!



EV944 said:


> Dose anyone have experience with EAS: electric auto sports and there GBS Lithium battery kits? i am liking the price of the 96v 200AH pack and 2 would give me 192v 200 AH which I think would get me towards my goal of 100 miles(drop dead distance).


I have no idea about EAS.

40.96kwh pack will weigh ~860 lbs (391kg). With a pack like this I am guessing your 944 will end up weighing around 3500lbs giving it a rule of thumb 350wh/mile making the estimated drop dead range of 117 miles (189km) or the 80% range of 94 miles (151km).

The only problem is finding a place to put all of them!


----------

