I’ve gotten the computer installed and working. It does some very simple processing, that (to be honest) should have been handled by the motor controller.
The embedded computer measures the outside temperature of the motor, and then turns the motor fan on or off, and changes the power level of the motor controller.
Simple stuff, really. I’m sure *someone* could have done it entirely in hardware, but being a computer programmer from years back, this was a better way for me to go.
After getting email from Azure and some really nice folks on the 914 conversion list, I have set the power limit for the motor to 30kw. I’ve also installed some custom-made airscoops.
Net result: no overtemp on the drive home. Yay! We’ll see how this works out for the summertime, but this means I can drive home now without a long stop somewhere. (FTW == For The Win, if you aren’t into the geek slang).
Here’s a picture of the custom airscoop:
I’ve replaced all but the headlights with LEDs and seen a dramatic decrease in current during their usage. What was interesting is that I did not have to replace the blinker relay (apparently you need to on newer cars). I got the LEDs from www.superbrightleds.com.
I’ve also made regen a normal part of driving, so I’ll need to put back the circuit that lights up the brake lights when regen is active. The reason for this is to make shifting easier – when regen is active the motor quickly drops from high RPMs to almost zero within a second or two.
So I’ve done another set of calculations, and I’m getting 350wh/mile driving to and from work. Most of this is freeway driving with some stop-n-go.
I returned from my business trip to Bangkok (long story in itself) to find two boxes waiting for me – the replacement DC-DC converter and new cables for the BMS. It took me about 4 hours to replace the DC-DC converter and the 4 cables, but well worth the effort. The DC-DC converter works as advertised, providing 13.5 volts. The new cables eliminated the intermittent communications problems during charging.
Proof is that the batteries are now fully charged. I can see the car quivering with excitement in the driveway, begging to be driven. I think I’ll do that today. 
BTW, EV Components has been great during all of this – providing excellent customer support and fast shipping of new parts.
I finally figured out which of the interconnects are which. This took some careful reading of the Elithion website (my fault, not theirs) and as a public service present to you which connector is which:
I’ve gotten the current sensor put together, but these tiny wires are enough to drive an older guy crazy. I had to go and buy one of those soldering stations with those clips and the magnifying glass. Sheesh.
Well, the braided copper cable is cool and all that, but for the vast majority of connections, just plain copper bar is gonna be fine. So I bought a whole bunch of pieces made to order at Industrial Metal Supply (very nice people, although you will need to go into the place to make special orders if you don’t have an account). I also picked up the new license plates for the car. Busy day (in addition to doing actual work).
Copper interconnects and the new license plates.
Well, due to the usual delays of business travel, pulled muscle, Thanksgiving and shopping for Christmas, not much was done until this weekend.
I was able to trim the battery boxes to a lower height – making a much better fit in the various compartments. Apparently, the trick is to use a carbide blade with 60 to 80 bits in the power saw. Worked great!
I also started working on the battery interconnects. I’m looking into flat braided copper cable, with silver-solder for the ends. However, I’m not happy with the way the ends have worked out – I don’t think they are flat enough yet. This will take some tinkering to figure out.
Battery Interconnect sitting in the Silver Solder
Yay! I am now the proud owner of 109 Sky Energy 60Ah batteries. All 690 pounds of ‘em (however, some of that weight is the boxes and pallet they arrived on). Gosh, all I have to do now is (list redacted). Shouldn’t take too long. 
Battery Porn:
109 Lithium Iron Phosphate Batteries
I’ve had a busy weekend adding in the plug and getting the wiring set up. The plug is an interesting model – it will automatically eject the plug when the key is turned – very nice feature.
The AC is routed to the relay panel, the charger and to the EKM meter. The EKM meter has a ring around the live wire to the charger so it can record how much power the charger is using.
Rear Trunk with AC lines
Here’s a picture of the new plug.
AC Plug installed
Well, along with the 109 Sky Energy 60Ah batteries, I am getting the Elithion Battery Management System (BMS), the Manzanita PFC20B battery charger, and EVComponents touchscreen interface to the BMS. Oh, and a new DC-DC converter.
All told, this is $15K worth of batteries and support equipment. (YIKES!)
However, I knew that the job was going to be hazardous when I started. Nothing more exciting than being bleeding-edge, is there?
Now that I know what the parts are, I’ve been making mock-ups of the new parts and will be figuring out where to put them into the car. Once I have the new locations figured out, I’ll post photos.
Well, I got smart – I talked to the people that actually manufacture the motor and controller and asked their opinion. I gave them the possible battery packs, and let them choose. Turns out that there is a “no-mans land” that all but the high voltage pack would hit. So I’m going to use the 349 volt pack (consisting of 109 batteries with 60 Amp-hours capability). Not cheap, as I was warned, and completely found out, but it should do the job admirably.
So, I await the billing and will get the controller updated at the factory. Meanwhile, the minor stuff continues to get cleaned up.
I went and did some initial testing on the 12 volt system in the car, and it doesn’t have any obvious shorts, so it is ready for testing.
However. A number of disturbing reports on how badly the car will perform with 1200 pounds of lead acid battery has me very worried. I’ve read several real-world scenarios of max 50 miles and very weak acceleration. Since I need need to have freeway speed and the ability to climb some steep hills, this is just not acceptable.
The only solution is to go for a higher voltage battery pack, and lead acid batteries won’t do it.
Time for Lithium. Lithium Iron Phosphate. Trouble is, that these are only made in China right now. And they are expensive.
Comparison time (shipping not included):
That last pack will take up the same space as the lead acid batteries, but provide much more voltage and almost twice the available capacity. The cost is just astounding though.
I’ll keep you posted on any further thoughts on this.
Sean took the car for a week, and added a new front sway bar (21mm) with chassis re-inforcement, poly-graphite front bushings, and a new rear-trunk release. All very spiffy, and all done VERY nicely. I continue with the minor wiring work for now.
The new sway bar has a minor problem, in that it interferes with the middle battery compartment battery rack. New metal was required.
New front sway bar
The new rear trunk release has the knob just under the driver’s seat. I wouldn’t have seen it if Sean hadn’t told me where to look.
Rear trunk release just under the driver's seat
Sean came over and did 3 hours of hard work under the car while I “helped” by handing him tools and making bad jokes (as if I make any other kind). He replaced the springs and torsion bars, but kept the shocks (as the shocks are very good autocross shocks).
It was a good thing he was looking under the transmission, as the speedo and clutch cables are both “toast”. He’ll be getting me some new ones later this week.
Safety tip: ALWAYS have an expert replace your springs, those things can kill you if you are not careful.
So while I am waiting for the new speedo and clutch cable, I will continue working on the wiring in the front compartment. Lots of fiddly wires and not-so-great documentation. *shrug*
In order to keep things moving at the usual snail’s pace, I picked up a flu on my last business trip. This kept me from visiting relatives in Santa Clara, and from doing anything on the car. However, once the flu left, I decided to install the remaining racks (rear and middle). As always, a few small problems were discovered: no supports for the rear battery rack, and the middle rack angle brackets are too short. I guess I gotta do some metal work now.
Rear battery rack and new relay board
The rear rack is not mounted yet, just sitting in the compartment – the fit was too tight to remove it (oops). The space below that hose is where the support mount is supposed to go. Also, I got tired of the relays being attached to the metal, and after reading some posts about possible arcing across that fuse, I put this ABS plastic board inbetween. Makes for easier mounting, too.
Middle battery rack - with metal that is too short
This is just frustrating, but nothing serious. I can cut new angle bars, paint them with POR-15, and then install. I still have to pound out the body so the plastic battery box can fit into that small space, though (later).
[UPDATE] Electro Auto shipped the rear posts today, and will be shipping the wiring diagram later on. Looks like EA is back in business (yay!)
Wow. Both the big crate (with the battery boxes and stuff) as well as the box with suspension stuff have arrived. Naturally, they arrived while I was gone, but my long-suffering wife was kind enough to deal with it (and now I have to return the favor somehow, but that should be fun). At long last (and only 3 months late) the stuff is here. Minus the manual.
The big crate weighed in at 300 pounds. Most of that weight is from the various components.
Lots of cables, connectors, and such.
Battery boxes!
So now, I just need to get the car cleaned up (rust repair and grease/gunk removal) so I can start hacking away. Oh the fun….
Well, as part of the cleanup, I ordered a new fuseblock from JWest Engineering (http://www.jwesteng.com/porsche/914/).
This will really help with understanding what is under the console. Plus it is a big incentive to remove that old radio (with cassette!) and clean up all the wiring under the console.
HOWEVER
Home has been keeping me busy. VERY busy. The ropes on our double-hung windows (circa 1942) are rapidly decaying. I figured out how to replace them – at 3 hours per window. Our dishwasher needed to be replaced (Maytag did a recall on our model, sent a repair kit but no repair person, so I replaced it with a Bosch). Our dog is STILL being fussy at night, and the cats are not taking too kindly to her yet…
So I hope to be able to get back to the car by this weekend…by which time the fusebox should be in my hands.