Electric Porsche 944

Archive for May, 2020

The most exciting update for my 944 HV

by on May.18, 2020, under Electric Car

After I blew up my Netgain Warp 11HV and Evnetics Soliton 1 controller I opted for a “safe and reliable” system in the Siemens/DMOC645 combination that were leftovers of the bankrupt Azure Dynamics transit connect project. I’ve had this in my car for years, and while it has been flawless, it’s not quite as powerful and exciting as the DC motor system that preceded it. The battery system is also a carryover, the CALB CA60’s have been fantastic however they are heavy and capacity is limited.

The LG/Chevy modules as configured in the Chevy Bolt.

This is all about to change! I’ve been battery hunting for quite a while, seeing what’s available, what’s new etc. I found a deal on LG/Chevy Bolt modules from Battery Hookup: https://www.batteryhookup.com/?rfsn=4165868.2db01c These are 10S3P modules comprised of LG 60Ah pouch cells. This is 180Ah and 36v per module or roughly 6.6kwh each. I have 10 of these modules on order to create a 100S pack or 360v nominal 66kwh total battery pack. Let me remind you that the CALB pack is currently about 15kwh. Now this is fairly large, fairly heavy, and simply won’t fit in my existing battery box. The solution? To remove virtually everything in the car, motor/inverter, adapter/coupler, torque tube and transmission. Split the pack up to 6 modules front and 4 rear, plus a small Tesla drive unit in the rear. This pack is just adequate to power a small Tesla drive unit from a power perspective, but it should work pretty well with some liquid cooling on the battery modules. The overall weight of the car won’t change significantly but going from 100km to over 400km of range will be incredibly exciting.

Bolt module as seen on the WeberAuto youtube channel (Check him out for complete teardown and assembly videos)

Each module is around 70lbs, making the total pack over 700lbs. Currently I have about 450lbs of LiFePO4. This makes it seam like the car will balloon by over 250lbs, however because of the change from the Siemens/DMOC to a small Tesla drive unit, the car will lose roughly 250lbs keeping things roughly the way they are.

Tesla small front Drive unit from HSRmotors
Tesla small rear drive unit from HSRmotors

I have the space to use either the small front, or small rear drive unit in the 944. I technically have the space for the large rear drive unit, however the battery system isn’t capable of putting out that much power. The small drive units are capable of 220kw which is nearly 300hp and should be a welcome change to the Siemens/DMOC coming in around half of that power output.

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An Overdue Update

by on May.18, 2020, under Electric Car

First I’ll say, the car is fantastic, full stop.

The drive system has been flawless, the Siemens AC motor is smooth and powerful. The Azure Dynamics DMOC645 has been great, I had the water pump feeding the DMOC fail and instead of stranding me on the side of the road, it simply throttled down the power to keep itself in a safe temperature range. I was able to gently drive home without incident.

The stock heater core in the 944 (which could very well have been the original making it 33 years old) failed, leaking coolant all over the interior. There is a plan shortly to remove the heater core and switch to PTC heaters in place of the stock heater core.

With various changes over the years more items have ended up in the rear of the car than originally planned. The front battery box was removed when I switched over to the Siemens motor, the 12v car battery ended up in the rear in the form of a 4S LiFePO4 battery pack. The DC-DC converter has always been in the rear but there was always a plan to move it to the front. The Brusa charger also lives in the rear. This wasn’t the original plan for weight distribution where I wanted 50-55% of the weight in the rear.

The total weight of the car is still inline with the initial target, however VERY close. 1360 Kg = 2998 Lbs
Front axle weight is 510 Kg = 1124 Lbs or 37.5%
Rear axle weight is 850 Kg = 1874 Lbs or 62.5%

For this reason I’ve already started the shift forward, the 12v battery, DC-DC converter and the Brusa charger are migrating to the front.

  • 12v battery = 18 Lbs
  • DC-DC converter = 8.5 Lbs
  • Brusa charger = 14 Lbs

Now this only totals 40.5 Lbs, however it has an 80 Lb shift in weight distribution moving back to front. Or almost a 1.5% improvement right there.

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