[danh818]

I'm a bit late getting this started, but here goes.
I've always liked the body on the Porsche 944 so when I found one about six months ago on ebay only 30 miles away from me I jumped on it. I intend for this car to be driven daily with a 80 or so mile range, but with the ability to give so great stoplight to stoplight performance.
To date I am about 40% complete converting my 1987 Porsche 944. Here is a quick rundown of most of the hardware going into the car:

NetGain Transwarp 11HV
Gear Vendors Overdrive (no transmission)
WarP-Drive Industrial 360v 1400A Controller
384 A123 20ah cells
Full Roll Cage
Currie custom 9" IRS Housing with High Pinion 3rd Member 4.86 gears and and LSD

I have posted more info and tons of pictures on the blog at http://infa944.blogspot.com

I'm looking forward to all your feedback.

I would like to thank everyone who has helped out up to this point for your advice, encouragement, and expertise:

Stephen Johnsen (HPEV in Washington), John Wayland (Plasma boy Racing), John Metric (DC Plasma), Aaron Sacks (Electrical Engineer a.k.a. Homer Simpson), George Hamstra (NetGain Motors), Jack Rickard (EVTV), RWaudio (electricporsche.ca), Sonny Lopez (you never cease to amaze me), Donny @ Advan Carbon (prototype carbon fiber hood and front end) David Katz (for encouraging me to pull the trigger on buying the donor), Stuart Horwitz (my dad and hero), Jonathan Stilz (Suspension Guru), Larry "Bear" Watson (Master Welder), Roger Derryberry (Miata Autocross Conversion), Richard Rodriguez (Porsche 914 Conversion) Onegreenev (blog advice), a BIG Shout Out to Bowser330! Oh and don't let me forget all the OEM's (without all your crap cars I would not have been motivated to do this for myself.

[Yabert]

Originally Posted by danh818

but with the ability to give so great stoplight to stoplight performance.

!!! With this kind of conversion, you will reach the city speed limit under a second...

Please continue to share development. The final result will be impressive!

[danh818]

The fitting of our carbon fiber hood has been delayed until tomorrow. I really hope that it fits well. I wait can't to see how it turned out.

[rwaudio]

Nice to see a thread and blog for this build, great start! Your car is going to be a silent rocket!

I just got my test pack of A123's in for some real world driving. Took my wife for her first drive in it tonight (she drives an '83 944 with the engine out of my '86) she was impressed to say the least, quiet and so much more power off the line it puts her car to shame. Full throttle with a 2nd gear start ~7:1 overall ratio and it's quick on 1000A with 1400A you would do well with taller ratio's. I haven't tried 1st but I'm sure I could light up the tires ~11.8:1 ratio.

Is that a 2 speed? What will your overall ratio(s) be? The LSD should help a lot!

Since you don't have your cells yet, I assume you haven't settled on a connection method, I would strongly urge you to have a look at some testing that Andre Ferron did with his A123's. I gave him some ideas based on my experience with the cells from the results of my testing and he did all the dirty work testing different methods.



He was going for the lowest mv drop in a series connection for a 3P module, the left meter is measuring the left connection which is made from flattened copper tubing and some inexpensive hardware. The right meter is measuring an earlier attempt which is made from an aluminium tube and round bar of suitable diameters to form a half moon clamp but without the tabs overlapping.

This test was at 618A as you can see on the clamp meter.
The secret to it's success is alternating the tab layers, so in the 3P grouping the sandwich is formed from the following layers:

copper bar
group1 cell 1 +
group2 cell 1 -
group1 cell 2 +
group2 cell 2 -
group1 cell 3 +
group2 cell 3 -
copper bar

By alternating the layers with the most practical contact area and not using any separator blocks between the series connections you get the lowest possible connection resistance for a pack of this style.

I assume your pack will be 96S4P so you could expect LESS than a 1.5v drop at 618A due to connection resistance from your entire pack (excluding cell sag of course). Or less than 3.4v at 1400A.... this compares to almost 20v using the same cells with the slightly different but good technique shown on the right.

Good luck with your build!

[danh818]

Thanks for jumping in RW, I have been admiring your build from afar for awhile now. It's really great to hear that your car is on the road.

I did just receive conformation that our cells have cleared customs and will be delivered in a few days. I've got two PL6's that I plan to use for capacity testing, and following your lead I will be grouping cells accordingly. You are right to assume that I will be going with a 4p96s design, although from the get-go I have been planning on slightly undercharging, so its a possibility that I may add one or two more to each parallel string.

I have not seen this "half moon" connection method before, it certainly gives me some new ideas to ponder. Off the top of my head though I think I would machine flats on the top for better terminal contact. This method of alternating polarity from cells of different groups warrants much thought as well, as it is clearly superior in terms of voltage drop. A large concern of mine, like Jack Rickard of EVTV has stated, is movement of the tabs independent of the cell pouch. This will eventually lead to fatigue, connection failure, possible cell damage and/or fire. I have been thinking long and hard bout this and will finally have the ability to experiment when my cells arrive.

I am curious to know how your charger is working out. I have also chosen to go with the DIY 10k, but I have ordered mine built from EMW. Valery emailed me Tuesday to let me know that the build was complete and is now being tested.

[danh818]

Since I'm not running a traditional transmission my first gear is 1:1 with the motor. The Gear Vendors overdrive unit is a .78 so with a 4.86 rear end that gives me a 1st gear of 4.86 and a 2nd will be 3.79. I talked to George Hamstra of NetGain about this, and we both agreed this would be a good starting point, the rear end gearing is by no means set in stone.

[winzeracer]

Killer conversion, I willbe following your thread for ideas for my next car!

[dladd]

I really like my car, but I love the build threads here about the high performance side of life! Watching with interest.

[Joey]

I just subscribed to your blog. Great project. Looks like this isn't your first project with a car. Can't wait to see how your gear ratio selection turns out.

[danh818]

Originally Posted by Joey

I just subscribed to your blog. Great project. Looks like this isn't your first project with a car. Can't wait to see how your gear ratio selection turns out.

Actually Joey it is my first extensive car build. I have a good amount of general technical knowledge and and experience (I own a small contract manufacturing and prototype company), but as far as cars go, my experience stops with bolt on parts for my ICE cars. I have done quite a few high wattage stereo and subwoofer installs in my cars over the years but that is child's play compared to this. The only other experience that might help me out is that I have flown R/C airplanes since I was a kid and have used LiPo's for the last 3 or so years. That also led me to dabble in building some submersible HID flashlights used for scuba diving, but it both cases nothing over 12 volt nominal and a couple amp hours.