Porsche 914 EV Conversion
SEPTEMBER 30, 2007
My friend Rick dropped by tonight to run the accelerator cable and monitor the RPM on the laptop while I put my hands on the motor/tranny to get a better feel for what's going on. We ran the motor with the transmission attached for weight without the clutch friction plate. I also put the transmission in first gear to guarantee that the input shaft was not turning and contributing to any vibration.
Plugs and Cars
SEPTEMBER 30, 2007
Check out today's NY Times story Ethanol’s Boom Stalling as Glut Depresses Price.the ethanol market is suddenly plagued by a glut, in part because the means to distribute it have not kept pace. The average national ethanol price on the spot market has plunged 30 percent since May.And if the bust becomes worse, candidates for president could be put on the spot to pledge even more federal support for the industry.
Plug In Partners
SEPTEMBER 19, 2007
A nother major manufacturer is unveiling their PHEV at a car show. This time, it's Volvo. Here's the story from duemotori.com. "Volvo Cars is introducing the Volvo ReCharge Concept , a plug-in hybrid with individual electric wheel motors and batteries that can be recharged via a regular electrical outlet for maximum environmental benefit. Recharging allows the car to be driven about 100 kilometres on battery power alone before the car's four-cylinder Flexifuel engine is needed to power the car a
Porsche 914 EV Conversion
SEPTEMBER 30, 2007
At the suggestion of Paul J, I started doing research on vibration analysis today. There are several online tutorials regarding vibration analysis. I'm currently reading this one: [link] This paragraph taken from the "Natural Frequencies" section is somewhat noteworthy: 'The multitude of spring-mass-damper systems that make up a mechanical system are called "degrees of freedom", and the vibration energy put into a machine will distribute itself among the degrees of freedom in amounts depending o
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Porsche 914 EV Conversion
SEPTEMBER 29, 2007
After successfully spinning the flywheel and pressure plate at 9000 RPM, I felt confident that things were looking good with the motor. I re-installed the clutch friction disk and bolted on the transmission. After spinning up the system, it started rattling and skittering across the floor around 5500 RPM. Geez. This is a royal pain. After pondering this a bit, I tried the following experiment: I unbolted the transmission, removed the friction disk inside the clutch that attaches to the transmiss
Porsche 914 EV Conversion
SEPTEMBER 28, 2007
Today had some ups and downs. I got the adapter hub from Electro Automotive back today. I installed it on the motor shaft and, to my delight, it had less than 1 mil of runout and wobble! That's how the hub is supposed to work. I put the flywheel and clutch back on and spun them up to 6000RPM without much vibration, so things are looking better. Before I mated the motor to the transmission, I wanted to try out the SPEEDO output on the DMOC445 that Beth at Azure Dynamics talked about in the previo
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Plugs and Cars
SEPTEMBER 21, 2007
A few months ago I attended an eco-event in Fairfax, CA with my electric car. Someone seems to have videotaped me and posted it on youtube. Tags: electric car zev mandate toyota prius RAV4 EV.
Porsche 914 EV Conversion
SEPTEMBER 21, 2007
I recently sent off an e-mail to Azure Dynamics, the maker of the DMOC445 AC motor controller in the 914 kit. I asked how I could tap into the motor encoder signals to create an RPM signal for the tachometer on the dashboard. It turns out that the DMOC controller already has a PWM (Pulse Width Modulated) output that can be used for this. There are also some LED signals that display system status without having to use the serial port.
Porsche 914 EV Conversion
SEPTEMBER 19, 2007
Rats. After putting the adapter hub from Electro Auto onto the motor shaft no less than twenty times, I'm pooped. I tried filing down several different faces of the hub to get the runout and wobble down and failed. It's going back to EA tomorrow morning for a new one. I'm thinking that attaching the flywheel shouldn't be this hard. The flywheel and clutch assembly has been balanced by two different shops and the second shop said the first shop did a fine job, so I'm pretty sure it's not the flyw
Porsche 914 EV Conversion
SEPTEMBER 17, 2007
I took the flywheel/clutch to Dan Halls Machine Shop this morning and just picked it up half an hour ago. Dan basically said that it was fine. He spun it as fast as the machine would go and it was only out of balance by 2 grams on the flywheel and 2 grams on the clutch pressure plate. Apparently this really isn't a lot for flywheels. The motor adapter hub from Electro Auto still has 4 mils (thousands of an inch) runout, so I'll try to attack that next.
Porsche 914 EV Conversion
SEPTEMBER 15, 2007
Since I live in the Pacific Northwest, I get rather concerned that rain entering the engine compartment will cause problems with the electrical wiring. Many other 914 EV'ers have protected their wiring inside conduit boxes and other shields. I just following the ElectroAuto directions and bolted the relays and terminals blocks to the engine compartment wall with wires dangling from them.
Porsche 914 EV Conversion
SEPTEMBER 15, 2007
Well, it's time to bite the bullet again and see what I can do about the car vibrations. My friend graciously helped me remove the motor/tranny from the car again this morning and assisted with crude vibration measurements. We removed the motor/transmission from the car and re-attached it to the AC controller wires while on the ground. After spinning up the assembly to approximately 5000 RPM, the whole assembly started vibrating across the floor like those toy footbal players on the vibrating ta
Porsche 914 EV Conversion
SEPTEMBER 13, 2007
Since I don't work Fridays, this is the end of my second week commuting to work fifteen miles each way. Two things have definitely made the car more fun to drive. 1. The batteries are broken in so I have more current to work with and more importantly 2. I've learned some of the tricks to driving the car. The biggest trick involves starting from a dead stop.
Plugs and Cars
SEPTEMBER 14, 2007
Co-op America has cut through the hype and hyperbole about "clean" cars. They did an excellent issue of their magazine analysing the pros and cons of hybrids, plug-ins, electrics, bio-fuels of all types and hydrogen with a Consumer Reports type objectivity. They found "the truth is, not all of the "new" fuels are created equal. In fact, some are nearly as bad as gasoline in their environmental impacts, and others can't be scaled up in a meaningful way without creating other problems.
Plugs and Cars
SEPTEMBER 12, 2007
From the pricey ads in national magazines devoting serious space to the Volt to today's announcement about the plug-in hybrid Saturn Vue, GM is compelling me to take their expressed interest in plug-in cars seriously. As announced in Frankfort and reported in Detroit , GM hopes for a 2009 release of the first Saturn Vue plug-in hybrid SUV. Leaving wiggle room, "2009-ish" brand general manager Jill Lajdziak said Thursday.
Porsche 914 EV Conversion
SEPTEMBER 11, 2007
I just got an e-mail back from Electro Automotive from CC-Power regarding the failed DC-DC converter. I prefer not to comment on it but simply wish to pass it on to others who might have wondered what the manufacturer said. Here goes: "The converters have been manufactured for over 20 years and we have 10,000+ units operating in South Africa at 120 volts, all using the same build, without any problems.
Porsche 914 EV Conversion
SEPTEMBER 9, 2007
I just drove home from a meeting for half an hour with the headlights on. In the process of driving, the brake lights and turn-signals were also on. This is the first time I've arrived home with the DC-DC converter still working! Yay! I'm going to give it a week and see if anything else causes a failure. In the meantime, I'm going to report my findings to CCPower and Mike at ElectroAuto so perhaps they can modify the design.
Plugs and Cars
SEPTEMBER 10, 2007
Along with a host of the filthy, the ugly and the dangerous, Time and Dan Neil declare the EV1 one of the 50 worst cars ever. Had they wanted to include a crappy electric car, they had plenty to choose from. But no, they picked what might have been the best electric car ever, and said even it sucked. Dan Neil, the LA Times writer who naively blames consumers for the lack of electric cars in the market in the film Who Killed the Electric Car?
Porsche 914 EV Conversion
SEPTEMBER 8, 2007
After studying the oscilloscope waveforms, I believed that the current sense circuit was way too spikey. This is the "amp adjust" potentiometer output in the C400 schematic. I found that the inductive spikes were shutting off the DC-DC converter through the nShutdown pin on the SG3525A and causing craziness in the gate-drive pulse. Soooo, I picked a reasonable (.01uF) capacitor to filter out the current sense waveform and remove the inductive spikes.
Porsche 914 EV Conversion
SEPTEMBER 9, 2007
After talking with various people and realizing that the over-current circuitry was making the FET gate pulses way too large, I decided to hack the DC-DC converter circuit. Here's the new circuit (click to enlarge). I swapped out the IRFP350 FETs with IRFP460 FETs which have a higher voltage and current rating. To compensate for the larger gate capacitance and speed up the rise/fall time of the FET gates, I lowered the gate resistance from 27 ohms to 15 ohms.
Porsche 914 EV Conversion
SEPTEMBER 8, 2007
I spent most of Friday trying to figure out just what was blowing the DC-DC converter. Here's my full testbench setup. On the upper left, I have a 156V DC power supply. On the lower-left sits a 12V battery to act as an accessory battery. The 30Mhz $400 oscilloscope sits ready. The opened up DC-DC converter is front and center. I have the oscope covered with cardboard to shield out excess light so I can take pictures of waveforms.
Porsche 914 EV Conversion
SEPTEMBER 5, 2007
In my efforts to debug the failures of the DC-DC converter, I tried to capture a schematic of the board. I didn't have time to create a component for the SG3525A controller, but all the pin numbers are listed. I replaced the IRFP350 FETs with IRFP460 FETs which have a higher isolation voltage and larger drive current; however, they also have about twice the gate capacitance, which I didn't think of.
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