(archive clone from deleted jstaubel.com page - modified by brucedp)

Electric Porsche 944

**NEW Stuff**
- 2nd Generation Hybrid Pusher Trailer Completed! Click for details/pictures
- World Record 1/4 mile time (NEDRA SC/B class) 17.28 seconds, 79.4 mph


Top Speed: 104 mph
0-60 mph: 8.7 sec
1/4 mile: 17.2 sec
Battery Capacity: 40Ahrs, 240 volts (~ 9 kW*hrs)
Controller Current Limit: 900 amps (motor or battery), Capable of 1200...but clutch slips
Charger: On-board 6.5 kW, 240/208/120 volts (custom design)

More Pictures

Picture with the hood open Showing the upper motor and the motor controller capacitors (blue) on the left

IGBT close-up

Showing the second version of the custom gate driver board that I made (on the right) and the modified current shunt mounted in series with each IGBT to monitor current sharing and provide a precision linear circuit element in series with each transistor (on the left)

looking under the hood

rear of the car

side with door open

Why an electric car?

Building an electric car is a wonderful challenge and combination of many things that I enjoy working on. Power Electronics, Batteries, Electric Motors, and Micro-controllers all come together. While the range is short (30-40 miles) the performance is great with a high-voltage battery system and a high-current motor controller.

The main challenge of this project has been building a motor controller from scratch. The controller is capable 240 Volts and 1200 Amps (motor or battery) that's 288 kilowatts! The batteries and clutch are really the limiting elements in the car right now, not the controller.

In addition to the general fun of building this project it is also fun to drive with quick acceleration. My commute from Midtown Palo Alto to Stanford is only about 5 miles and the round-trip is easily within range while still driving the car like a Porsche. And let's not forget the standard EV benefits of being relatively quiet, emission-free, and rechargeable in the garage. Our house is now also purchasing 100% green energy from the Palo Alto Municipal Utility (for a 3 cent/kwh premium) so the car is truly a zero emission vehicle being recharged by some mix of wind, small hydro, and geothermal energy. CPAU "Future Green 100" Program Link

Project Details

The Motor Controller:

Features: Programmable current limit 100-1200 motor amps, automatic over-temperature current limit cut-back, water-cooled copper heat sink, low-loss IGBT modules, and motor over-speed limit.

Processor: Microchip PIC 16F877 These are excellent micro-controllers running at 5 MIPS and 20MHz with 8kb of onboard program FLASH memory. They also have two on-board 10-bit PWM generators, eight 10-bit ADC converter channels, and a serial communication generator.

Power Components: IGBT Modules, six 500 Amp 600 Volt modules used (International Rectifier, GA500TD60U), Fast recovery diode modules, four 560 amp modules (International Rectifier HFA280NJ60C), Filter capacitors, six 450 volt 1000uF high ripple current, low ESR, screw-terminal caps (Mallory CGH102T450V3L), Heat sink, custom built water-cooled copper cold plate, isolated DC current transducer from LEM international.

Coolant System: The water cooling system uses a small 12V DC pump for circulation through a small plastic reservoir and an oil-cooler radiator. These radiators can be found at just about any auto parts store and are a good size. The pump is made by ShurFlo (model number 2088-423-344). It circulates around 2.8 gpm with a quiet 3-chamber diaphragm pump and permanent magnet motor. The current draw is between 2-3 amps. West Marine sells a wide variety of these pumps at competitive prices.

West Marine home page

Pictures will be added soon of the various components, the fascinating test setups, exciting test successes, the more exciting test failures, and the complete assembly.

The Motors:

Two, 8" Advanced DC motors belted together and driven in series by the motor controller. One motor has a custom coupler that was machined to mate with the flywheel/clutch pressure plate. This motor is directly in line with the driveshaft running back to the transmission. On the outside of the coupler is a synchronous belt sprocket. This allows power to be transferred from a motor mounted above, through a Gates PolyChain GT belt, into the same coupler and clutch.

The Batteries:

Twenty 12V, deep-cycle Optima "yellow-top's" (D750S) for a total system voltage of 240 and a total pack weight of about 850 pounds. Peak power (at 9 kw per battery) ~180 kw.

Optima Battery Home Page
The Optima Yellow-top

Battery Mounting:

6 batteries in front of the motors roughly where the radiator used to be in front.
4 batteries on the floor behind the passenger and driver seats (well bolted down...)
10 batteries in the back where the gas-tank, muffler, and spare tire used to be.
All of the battery racks are made out of 1"x1" (1/8" thick wall) mild steel angle pieces. Everything was put together in the garage with a small MIG welder. 3/8" all-thread clamps down all of the batteries except those behind the seats, there 7/16" rod was used...just in case.

Other Components:

DC-DC Converter: A custom modified Power-One power supply. This allows for an input of 240VDC with a continuous DC output of 40 amps at between 11-14 volts (adjustable). There were no commercial DC-DC converters available that took an input voltage this high. The converter is used to keep a small sealed lead acid battery topped off for load surges.

Site Last Updated On: Feb/14/2002

(archive clone from deleted jstaubel.com page - modified by brucedp)
- Home -