Porsche 914 EV Conversion

Update to Azure Dynamics DMOC Information

Porsche 914 EV Conversion

I've been receiving several requests this past year for the FTP site that contains the information on the Azure Dynamic DMOC445 controller. I just received word from Azure Dynamics that they posted all this relevant information online here: [link] drive/TractionMotorswithDigitalMotorControllers.htm Have a great Holiday Season! Cheers, Tim

2009 100

Saying Goodbye to my 2007 Dream Project

Porsche 914 EV Conversion

I contacted someone who expressed interest in purchasing the 914 a few months ago and that contact came through for me. Here's my parting shot with Dan, the new 914 EV owner. Dan has worked with a Bradley GT EV before, so he knows the ropes. I'm sad to see the car go, but I've got the Civic-EV and it does very well. I'm still active on the 914ev Google Group answering questions, so I'm not completely disconnected. Farewell 914EV. I learned more than I ever expected.

2007 100
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Time to sell the 914

Porsche 914 EV Conversion

It's time to sell the electric 914. It's been a fun road, but I have three cars now (as a single guy) and only a 1-car garage in the middle of the city. The car has been good to me and made the electric Civic project go so much faster. I've learned much and shared many experiences with other people converting 914s. The car has been a major hit at EV shows and with friends.

2009 100

Bypassing theCharger

Porsche 914 EV Conversion

Since my battery voltage never gets above the cutoff point for the Zivan charger bulk phase, I made a special charging cord with a timer built into it. If I leave the Zivan in low-current mode, I only pull 12 amps, which is less than the 15 amp rating of the timer. Since I know how many amp-hours I pull from the batteries during my commute, I can generally pick a good timer setting to get the batteries close to full without "boiling" them too much.

2009 100

Battery Equalizer Schematics Rev 1.0

Porsche 914 EV Conversion

I'm currently working on a battery equalizer for the 914 EV based on the whitepaper at the following link: [link] The above two schematics show the circuit that I'm experimenting with using 12V batteries. It seems to work fine on my bench. The circuit above costs less than $10 per battery in parts and I hope to make this available to everyone to help people make their batteries last longer. By clicking on the images, you can get a much larger version of the pictures.

2007 131

Battery Woes

Porsche 914 EV Conversion

I think my battery pack is dead after 8600 miles and 1.5 years. My Zivan charger alarm has gone off for the past week and I finally looked into it. Apparently the alarm is indicating a timeout that the charge cycle is taking too long for the capacity of batteries that I have. If I charge overnight, I wake up in 40 degree weather and the pack is very warm, around 80 degrees with vigorous "boiling."

2008 100

Fixing the Aux Battery Killer

Porsche 914 EV Conversion

I took the time today to research the 914 wiring diagrams and find the annoying connection that leaves my tail light on after I turn off the ignition switch. If you remove the front dashboard cover and look under the steering column, you should see two connectors. Remove the right one as shown above. On the rear of the connector should be three wires colored grey, grey/red and grey/black. Snip the grey one and seal BOTH ends with heat-shrink tubing or end-wire crimp.

2008 100

Just passed 6000 miles and fixed PakTrakr Issues

Porsche 914 EV Conversion

Two quick updates for the 914 EV since I've started working on the Civic-EV: First, I just passed 6000 EV miles and the car is still going strong. Second, the PakTrakr system has been acting up and reporting battery failures. At first, this really worried me that my battery pack wasn't doing well. Many first-time EV builders burn out their pack early.

2008 100

Switching Gears and Moving On

Porsche 914 EV Conversion

With almost 3000 miles of cheap, reliable operation, I think it's time to move on to something that will help more people do their own conversions. I really appreciated the high-quality parts and detailed instructions provided by Electro Automotive with their 914 kit. I would like to see the same thing done for a more modern, practical vehicle for much less cost.

2008 100

Going back to CAMP914

Porsche 914 EV Conversion

Yesterday was fun. I drove the electric 914 back out to Camp914 where I originally purchased the car and drove it away as a gasoline vehicle. Craig was happy to see me and took several pictures. Since the round-trip drive was 44 miles and included several long hills, I charged up for an hour out at camp just to give myself a bit of breathing room. Overall, the car handled the freeway and hills well. Here's the 914EV charging up at Camp914.

2008 100

Going to the Portland Better Living Show

Porsche 914 EV Conversion

Yesterday was a long day. I spent over seven hours on my feet at the Portland Better Living Show displaying the 914. My throat was hoarse at the end of the day from answering the same questions many times. Overall, people were very interested and I'm hoping a few will show up at the next OEVA meeting. Many thanks to Gary Graunke (who set this whole thing up), Ken (forgot his last name) and Joe Williams (on the left) for hanging out with me during the nine hour show.

2008 100

Installing LED Lights and Fixing the LED Flasher

Porsche 914 EV Conversion

I received a shipment of 3-watt LED lamps and a low-load flasher relay from superbrightleds.com yesterday. The bulb bases were the same, so replacing the bulbs was easy. I ordered the CF13GL-02 LED flasher relay, which is a plug-in replacement for the Porsche 914 relay and responds to the much lower current pulled by the LED lamps.

2008 100

2000 miles and counting

Porsche 914 EV Conversion

I broke 2000 miles with the 914 EV this week. The car has been running smoothly with no complaints. One of the "features" of the 914 is that the turn signals come on (but don't flash) if you leave the turn lever in the "left" or "right" position, even when the ignition is turned off. This presents the dilemma of running down the 12V battery while the main pack is charging.

2008 100

Playing with PakTrakr

Porsche 914 EV Conversion

Many months ago, I installed a PakTrakr ( www.paktrakr.com ) to monitor the state of my batteries and it's been acting rather flakey. The PakTrakr consists of several serially connect "remotes" which drive a "display" unit in the driver compartment. The voltage displayed shows the pack voltage and is supposed to monitor the state of each battery and the State-Of-Charge (SOC) for the pack too. In short, the voltage displayed jumps around quite a bit.

2008 100

Fixing PakTrakr Signal Integrity

Porsche 914 EV Conversion

Well, I played around tonight and looked at some of the PakTrakr signals on the oscilloscope and found some noise on the data line going between the PakTrakr "remote" modules. It looks like each PakTrakr remote has three wires coming out of them: Black - zero volts from that module Red - 11-12 volts from that module Green - 3.3

2008 100

Charging Up on Roadtrips

Porsche 914 EV Conversion

I'm considering taking the car on some slightly longer journeys this summer and don't want to be caught out in the middle of nowhere with a dead battery, so I ran out and purchased a Honda generator that can charge the car for four hours to get a few more miles out of it, if necessary. I tried firing up the generator with a little gas and it didn't go into overload with the Zivan charger at the 60% (12 amp) setting. The generator puts out 1600 VA (technically 13.3

2008 100

New Brakes and Local Lithium Supplier

Porsche 914 EV Conversion

I took the 914 back to A&P Specialties yesterday to upgrade the front brake calipers with ones from a BMW320i. The brake pedal definitely feels different. I can push it a lot farther towards the floor and the pads seem to bite quite a bit more. I hope this will help with any emergency braking I might have to do. Given the sluggish acceleration of the vehicle, I started looking into lighter batteries.

2008 100

Magazine Article and 914 EV Wiki

Porsche 914 EV Conversion

I ran out to Barnes and Noble today and picked up the March issue of Sports Car Market magazine. My 914 was featured on page 38 along with John Benson's 914 DC conversion! I hope Electro Auto doesn't get even more swamped by the publicity. I'm glad these EVs are getting coverage so more people can see what's possible.

2008 100

Smoothing out the DMOC acceleration/braking

Porsche 914 EV Conversion

One of the annoying behaviors of the motor system in my AC 914 kit is that the default DMOC445 parameters causes the acceleration and braking to have oscillations. In physics speak, the application of the positive or negative torque happens so quickly that the system is underdamped.

2008 100

Reflections on Converting a 914 to an EV

Porsche 914 EV Conversion

Many things have passed through my mind over the past year and a half while converting this vehicle. I'd like to capture some of the good and bad things to help keep other people from falling into the same holes as I did. Here goes (in no particular order): Things That Went Well During the Conversion The 914 AC kit from Electro Automotive is a good one. The parts are high quality and the instructions take the user through the process step by step.

2008 100

New Tranny Fluid, Battery Filler and EV Toolbox

Porsche 914 EV Conversion

I tied up a bunch of loose ends today on the 914EV. I replaced the transmission fluid with the synthetic Royal Purple fluid from ElectroAuto. The transmission seems to spin more quickly and run quieter, but that is a highly subjective assessment. I'll know more by the end of next week. I tried using an automatic battery filler from NAPA to fill the batteries, but the nozzle kept jamming and the weight of the water in the tank wore out my arm muscles.

2008 100

DC-DC Installed and New Brake Parts

Porsche 914 EV Conversion

In was eager to get the new DC-DC converter installed so I left work a bit early and got to work so I could still drive the car to breakfast with my girlfriend tomorrow morning. Here's the mostly final installation. The wiring is a bit messy because I had to cut all the tie-wraps off from the original setup. I just wanted to try this out for awhile before taking the time to clean it up. The DC-DC converter fits rather nicely in the old space.

2008 100

New DC-DC here and Tranny Fluid Too

Porsche 914 EV Conversion

I let out a major sigh of relief today when the new Iota DC-DC converter showed up today along with the synthetic transmission fluid that ElectroAuto said they would send me. I'll start the installation tomorrow after finishing my third week of commuting to work. I've been biting my nails over the past few weeks, living in fear that my 12V battery would suddenly run out on the freeway in the rain as I drove with my headlights on. Here's the Iota DLS-45 12V power supply.

2008 100

Opinions and Rants

Porsche 914 EV Conversion

I lost much sleep last night obsessing about how I could fix the DC-DC converter and, as a result, I was very tired and had an irritable day. For those of you who have read my blog entries in the past, you know I've blown up the internal FETs of the DC-DC over five times and spent countless hours reverse-engineering the circuit with experts at work to see just what could possibly be wrong with the system.

2008 100

DC-DC Overcurrent Malfunction

Porsche 914 EV Conversion

It's good to get the extra transmissions out of my garage. I guess it's poetic justice that the guy who bought my side shifter from the original car is going to give it to Jeff at Rothsport systems for a rebuild, the same guy who didn't work on it for 2 1/2 months when I gave it to him. The buyer of the tail shifter transmission is also in the process of doing an electric vehicle conversion, so he asked a bunch of questions about my project.

2008 100

Watt-Hour/Mile ratings and Selling the Trannies

Porsche 914 EV Conversion

I dropped off the 914 with Alan at A&P today to upgrade the brake cylinder and do a front end alignment. Brett, a local guy, is going to purchase my two leftover transmissions and Curt from Salem is visiting today to see the car (hopefully back from the shop). In the meantime, I took some approximate readings from my ammeter and voltmeter as I drove on flat roads this past week. Overall driving at 20mph tends to pull 30 amps at 140 volts.

2008 100

First Day Commuting with the New Tranny

Porsche 914 EV Conversion

Today was the first day on the freeway with the new transmission. Other than watching my amperage, I didn't have any issues and the car drove just fine. Many thanks to all the people who have offered their support during this long wait to get a working transmission. I'm happy to see all the other 914 EVs out there. On Friday I'll be re-aligning the front end for better steering and replacing the brake cylinder.

2008 100

Up and Running Again!

Porsche 914 EV Conversion

My friend Rick and his girlfriend Holly were gracious enough to come over and help me finish putting the transmission back into the car. We worked from 7pm-10:30pm and finished the job. Here's Rick and I under the car re-attaching the CV joints and getting covered with grease. Here's Rick and Holly in the working vehicle. We drove the vehicle around the block and the transmission was very smooth. I'm very grateful to Greg Robbins for shipping a transmission in such good shape.

2008 100

Yay! Less Vibration!

Porsche 914 EV Conversion

Rather serendipitously, my friend Jonathan dropped by this evening and we joined the transmission to the electric motor and spun it up. I was quite relieved that spinning up the new transmission to 5400 RPM produced little, if no vibration. We were a bit nervous when we heard a minor squeal inside the transmission case. We then put the transmission into first gear, allowing the fresh transmission fluid to flow from the bottom shaft onto the gears on the top shaft.

2008 100

New Tranny Here - Salvaging Cracked Parts

Porsche 914 EV Conversion

The newly rebuilt transmission from Greg Robbins showed up via UPS today at 95 pounds. Here is the plastic tub that it was shipped in. The tub doesn't look like UPS treated it very well. Another view of the tub. The fiberglass straps are broken, the lid is totally cracked in pieces and most of the corners are dented in. Here's the transmission removed from the plastic tub in my front hallway with plastic peanuts everywhere. At first glance, everything looks to be in order.

2008 100

Rebuilt Transmission Coming Tuesday

Porsche 914 EV Conversion

I just received an e-mail from Greg Robbins that he shipped a rebuilt transmission to me via UPS and it should arrive next Tuesday! The UPS tracking number concurs with this. This will be a good time to get back into the swing of things since my girlfriend Krista is starting classes next week and the holidays are winding down. Working in the garage is a bit slow since it's cold and rainy, but I should be able to get things put together.

2008 100

Snatching the Transmission Back

Porsche 914 EV Conversion

Well, I'm back to square one again on the tranny. Rennsport Systems kept my transmission for over two months and didn't work on it. I asked the good folks over at 914world.com about the situation and most people suggested that I was waiting far too long and paying far too much for what I was doing. Two folks highly recommended I go out to the Rennsport shop without calling ahead of time and just take the transmission back, just to be sure they didn't start working on it as I drove over.

2007 100

Still waiting for the Transmission

Porsche 914 EV Conversion

Well, it's been over a month since I've posted since the holidays are here and I'm still waiting for the transmission to get back. I talked with a guy at Rennsport Systems last week and he said he'd see what was going on and get back to me. Still haven't heard from him. I'll try again tomorrow. On a more positive note, Ross Cunniff got his 914 AC kit running recently and Bob has been making progress on his BMW 325i performance EV (see links at right).

2007 100

Hair Dryers Installed

Porsche 914 EV Conversion

I took a few hours today to get the small hairdryers installed. In order to have a convenient switch to activate the hairdryers, I hijacked the defroster knob switch. I was lucky enough to have this option on my car. The wires from the defroster knob sit in their own plastic tube, so it was easy to find the yellow/red wire going towards the center wiring column of the car under the clutch pedal. This wire provides 12V when activated, just the thing I need to fire up the 12V DC relay.

2007 100

Serial Port and Hood Pin

Porsche 914 EV Conversion

Today was a bit slow. I received some AMP pins in the mail that fit the special connectors on the DMOC445 controller. To make the serial port more robust, I crimped the pins onto the ends of the 16-gauge wires and inserted them into the 8-position connector that came with the DMOC. Here's the finished connector. It's far more reliable than the simple sockets I had soldered to the end of the cable. See this post for the prior implementation.

2007 100

Dedicated Charging Outlet and Hairdryer Coupling

Porsche 914 EV Conversion

After sleeping for 14 hours last night, I think I'm somewhat recovered from that nasty cold. I dropped by Parkrose hardware after work and picked up some stuff to install in the EV. Since I have a gas range, I replaced the 240V breaker for the non-existant electric range with a 20-amp 120V breaker dedicated to charging the 914 EV.

2007 100

Running the AC24 at High RPM - maybe not

Porsche 914 EV Conversion

I'm still big-time sick today, but recovering quickly. In my efforts to understand the torque of the AC24 motor a bit more, I looked at the datasheet online at Azure Dynamics: [link] Hmm, it looks like the optimal operating point is really around 4500 RPM and torque drops off quite a bit at higher revs than that. In my frenzy to go on the freeway in first gear, I didn't really look at the operating characteristics of the motor.

2007 100

Initial Fuel Gauge Driver Schematic

Porsche 914 EV Conversion

Since I'm stuck indoors today to recover from a sore throat, I put together the following schematic to drive the fuel gauge based on the pack voltage. Click to enlarge the image) With the exception of the 4N25 opto-isolator, which I salvaged from a dead UPS, all parts are available at Radio Shack. I hope to implement this soon. Comments and feedback are welcome

2007 100

Finishing the Rain Gutter for the Engine Compartment

Porsche 914 EV Conversion

The major project of the day was finishing the rain gutter under the engine compartment lid. The original gutter was too deep and interfered with the rear battery box. As described in a previous post, I purchased a piece of ABS plastic from TAP plastics and bent the edges to make a rain catch. Here's the plastic that I bent a few weeks ago.

2007 100

Finishing the Serial Cable and Testing the Fuel Gauge

Porsche 914 EV Conversion

I had a bit more time today to work on some other small projects. Here's the 914 patiently waiting for its rebuilt transmission from Rennsport Systems. It'll be awhile since Rennsport won't start on the rebuild until November. Up until this point, the serial cable from the DMOC445 AC controller to the passenger seat was routed along the outside of the car.

2007 100

Giving up the Tranny to a Higher Mechanic

Porsche 914 EV Conversion

After receiving admonishment from two mechanics about driving around with a resonant frequency, I dropped the transmission out of the 914 and gave it to the experts at Rennsport Systems this morning for a precision overhaul. This is the fourth time dropping the motor/tranny, so I was able to do the whole process in less than an hour. Giving up the tranny was an ego battle for me because I had spent so much time rebuilding the transmission in the first place.

2007 100

On the Road Again

Porsche 914 EV Conversion

I started commuting to work again today. I think the transmission is making slightly more noise than before but otherwise the car is fine. The RPMs are limited to 5300 RPM, so I won't have any resonant activity. I'm really happy that the tachometer is hooked up. It really helps me keep tabs on what happens to the motor/transmission at different speeds under different driving loads. It's also much easier to watch than the speedometer hidden behind the right edge of the steering wheel.

2007 100

Getting the Tachometer and Lights Working

Porsche 914 EV Conversion

After receiving an updated.css file (ccShell config file) from Azure Dynamics for the DMOC445, I was able to access the EE1SpeedoDiv variable. After setting this to a non-zero value, I attached a scope to pin 25 of the main DMOC connector and (yay!) got a pulse train corresponding to the RPM of the motor. Here's the pulse train on the oscilloscope. It has a 50% duty cycle and swings the full 12V range. This makes it ideal to drive the 914 tachometer.

2007 100