Painting the Rear Battery Racks

There is a lot of road debris collecting in my motor compartment. Dirt, leaves, and pebbles have accumulated and I realize that a belly pan is not just for aerodynamics. I will need to figure out how to shield the rear motor compartment from the hazards of the road.


The rust I expected to see – after all there is bound to be some consequence to leaving bare metal to fend for itself in an automotive environment.


The rust cleaned up well with a bit of sanding and wire brushing.


Primer and paint always take a long time. Two coats of primer and two more layers of paint, with the work needing to be flipped to get to both sides, waiting for rain to let up, and masking for two colors means 8 days of waiting for paint to dry before I could get the boxes back into the car.


I struggled to come up with a better way to restrain my cells in the rack and failed to come up with anything better than nylon strapping. Cheap, non-conductive, strong, fast, easy… To prevent chaffing the strap, and to give the boxes a finished look, I found some metal reinforced plastic trim, and pushed it over raw edge of the battery box.


My upper rack holds 8 cells. To hold the cells securely I used draw latches.  I added some standoffs to mount an acrylic cover.  Welding is much easier if you remember to attach everything before the paint goes on.




The boxes blend in below the bumper line much better now that they are finished in flat black paint.

Brushes and Motor Balance

I’ve been working on the car nearly every day for the last 5 weeks. I feel like I should have more to show. There are lots of small items in progress and I will report on them as I complete them.

To paint my battery racks (the front rack is done, the back racks are in progress), I’ve had to take a lot of components out of the car – 60 battery cells, the controller, wiring, and battery charger, not to mention the battery racks themselves. As long as the car was stripped down, I decided to inspect my motor, and it is a good thing I did. I was surprised to find that the brushes were very heavily worn down.

After doing a little bit of research, it turns out my motor shipped with H49 brushes. H49 are great at transmitting heavy electrical loads but they tend to wear very quickly. Perfect for a drag racing application, but not so good for street use. After 3,500 miles (5,600 km), my brushes were half the original length, or about 80% used up, because you can’t run the brushes all the way down to the embedded pigtail wires. I was expecting to go 50,000 miles (80,000 km) between brush replacements.

New H60 brush on the left. Old H49 brushes in the center and right. I'm not sure why there is uneven wear. A new brush is 1.5 inches (38 mm) long. 

Here is one of 4 brush holders, with a pair of brushes. The brushes are pressed against the commutator with coil springs.

The brushes have worn shallow grooves in the commutator. This is something I've seen reported by others with the H49 brushes.

I ordered a set of H60 brushes. The motor takes 8 brushes. These brushes are supposed to be better for street use. They are also supposed to be a little more efficient that the H49 brushes, reportedly around 10%. When new brushes are installed, even though they come preformed with a radius, only a small portion of the brush face is in direct contact with the commutator. The surface of the brush will eventually seat after several hours of run time. The motor will not be capable of full power until the brushes are seated. The motor was run on the bench with a 12 volt battery and charger for 32 hours to accelerate the seating process.

Also, while the motor was out of the car, I decided to address a small vibration from the motor. At 3,000 rpm I could feel a small vibration in the gear shift knob. The car didn’t vibrate and there was no audible indication of a problem. When I first pulled the gas engine, I took the flywheel to a machine shop for balancing. I should have also brought the clutch disk and pressure plate, to be balanced as an assembly. With just the flywheel, spinning the motor during my brush break-in procedure was vibration free. But when I bolted on the pressure plate, vibration was present above 2000 rpm. The motor spins at about 2400 rpm at 12 volts with no load. The vibration was easily solved by adding extra washers to the pressure plate bolts. Start with a single washer. If the vibration gets worse, move the washer to another position. Once you find the correct position to add mass, keep adding washers until the vibration is gone. I didn’t want a stack of washers all on one bolt. I ended up with one washer each on a grouping of three adjacent bolts. Vibration problem solved.

Enhanced Cooling

The Soliton 1 controller can be air or water cooled. When air cooled, the 1000 amp rating of the controller is peak. With a proper cooling loop, the 1000 amp rating is continuous. In warm weather last summer, with air cooling, I experienced thermal cutback. On acceleration, the car feels low on power. A couple times, while climbing a long incline, I had to pull over for 5 minutes and let the fans cool the controller. I’m now installing a radiator, circulation pump, and reservoir for liquid cooling.

The WarP motor is also air cooled. It has an internal fan that spins with the main motor shaft. I try to operate the motor above 3,000 rpm to maintain a high flow of air through the motor, but the motor is the warmest component after a long drive.  I purchased an external blower to increase the flow of air, even when the motor is not spinning.

 I’m starting to run out of space to place all of my components. I also think that the radiator I purchased is oversized for the job. I determined that the cavity inside the rear bumper is just large enough to fit my cooling components.

 I started by bolting a few chunks of steel to attachment points on the car. Then I fit a couple of square tube rails parallel to the length of the bumper.

Finally, mounting tabs were added for all of the components: blower, circulation pump, and radiator.

 I'm going to try making a composite fiberglass plug that will fill the gap  under the bumper, where the tail pipe once lived.

The result of spending a week of evenings under the car:

100 Countries

I started the electric Porsche project in December of 2011 and from the beginning I've followed the traffic statistics for this site. I get a report on what keyword searches people used to reach my site, which post they most frequently visit, and the country in which they live.  The high water mark for web traffic, with 2,000 hits, occurred in June of 2013, when I took my first electric ride in the car. 

Just recently I've logged a visit from the 100th country and the honor goes to Mauritius.  It's pretty amazing to me that people, literally from around the world are reading about my project.  Just for fun, here is the list of all 100 countries, as recognized by the Google servers:

Antigua and Barbuda, Argentina, Armenia, Aruba, Australia, Austria, Bahrain, Bangladesh, Belarus, Belgium, Bolivia, Bosnia and Herzegovina, Brazil, Brunei, Bulgaria, Cambodia, Canada, China, Colombia, Costa Rica, Croatia, Curaçao, Cyprus, Czech Republic, Denmark, Ecuador, Egypt, Estonia, Finland, France, Gabon, Georgia, Germany, Greece, Guadeloupe, Guyana, Hong Kong, Hungary, Iceland, India, Indonesia, Ireland, Italy, Jamaica, Japan, Jersey, Jordan, Kenya, Laos, Latvia, Lebanon, Liechtenstein, Lithuania, Luxembourg, Macau, Macedonia, Malaysia, Malta, Mauritius, Mexico, Moldova, Morocco, Mozambique, Namibia, Nepal, Netherlands, New Zealand, Norway, Pakistan, Philippines, Poland, Portugal, Qatar, Romania, Russia, Saudi Arabia, Serbia, Sierra Leone, Singapore, Slovakia, Slovenia, South Africa, South Korea, Spain, Sri Lanka, Sweden, Switzerland, Taiwan, Thailand, Trinidad and Tobago, Tunisia, Turkey, Uganda, Ukraine, United Arab Emirates, United Kingdom, United States, Venezuela, Vietnam, and Yemen.

Painting the Front Battery Rack

I’ve been driving the car for 9 months, and since then, my rate of progress on completing the remaining tasks has virtually halted. A short break to recover from the push to get the car drivable gave way to a longer break to enjoy driving in warm weather with the targa top off. Then, the weather got cold, and I don’t think you are supposed to paint in cold weather. It is time to finish off the last few items on my list.

 

The front battery cells are well protected in the front trunk of the 911. The unpainted battery racks looked about the same as they did 9 months ago. And the foam blocks I used to secure the vacuum pump for the brakes look just as bad as they did 9 months ago.

 

With the battery rack out of the way, I was able to properly secure the vacuum reservoir tank and the vacuum pump.



 

Sanding is one of the most boring activities, but it is a necessary evil to getting a decent paint job. I also added 6 mounting points for installing an acrylic cover over the cell terminals. It seems many people are drawn to touch the battery cells, like moths to a porch light, and while 192 volts is about 300 times less than a Taser, the current can be 100,000 times more – enough to ruin your day. The covers will help people to not touch.

 

First coat of primer looks good.

I lined the racks with 3 mm thick closed cell foam.

 The cells look good, securely mounted in the newly painted rack.

Registration and Taxes

I purchased the 911, in gas form, nearly two years ago.  The registration expires next month. Most gas vehicles where I live have to pass a vehicle emissions test as a condition for registration renewal.  By registering the car as an electric powered vehicle, I will be exempt from the emissions testing.  I’ve heard countless tales of bureaucratic confusion surrounding the process of registering a vehicle that has been converted to run on electricity.  I was expecting and prepared for an ordeal.  Fifteen minutes after stepping into the department of motor vehicles office, my car was registered with the state of Oregon as an electric powered vehicle.  The whole event took a little extra time because the clerk was so skeptical that the process could actually be so painless that she called her supervisor over to confirm that there was no inspection, documentation, extra fees, sworn and notarized affidavit, or clearance from a mental health professional required to complete the transaction.  There was just a simple change made to the database under fuel type: electric.

The supervisor commented that he was aware that a number of people have installed fork lift motors on small pick-up trucks, like the Chevy S-10 and the Ford Ranger, but never on a vehicle that was nice, like a Porsche.  The public perception of converted electric vehicles is still dominated by anemic lead acid powered examples.  Without knowing that lithium technology is now viable, the concept of an electric sports car conversion would be incongruent.  My goal that day was to walk out of the office with registration stickers, and everything was going smoothly, so I didn’t feel it was the proper time and place to explain that electric cars have changed and that my conversion could outperform the stock gas configuration.  The phrase, “Anything you say can be used against you…” was on my mind.

   

After confirming that I was now exempted from pollution testing, the clerk commented that I would also not be paying gas taxes, a tacit admonition that driving on public roads without paying the gas tax is dishonorable.  

 Oregon was the first state in the United States to enact a fuel tax, back in 1919, with the revenue to be used for building and maintaining the road system.  I believe a road is a public good, and I support funding well administered public goods.  I also support a tax based on fuel consumption, because it creates an incentive to consume less fuel and produce less pollution.  As the average fuel efficiency of road going vehicles has increased over the years, and people are buying less fuel, the fuel tax revenue has been declining. 

And so I wondered, just how much tax was I avoiding by driving an electric car.  In 2009, the state of Oregon collected $1,394,000,000 USD for maintaining and building roads and 13% of that total was derived from the fuel tax.  I’m still participating in the other 87% of the revenue generating categories, so I’m OK with not paying the gas tax and still using the public roads. 

Here is how the rest of the road funds in Oregon are sourced: 37% from the federal government, 25% from bonds, and 13% from vehicle and motor carrier (commercial) fees.  The remaining funds come from local sources, and an official sounding category – miscellaneous.

(Source: U.S. Department of Transportation- Federal Highway Administration: “Revenues Used by States on Highways”: 2009; http://www.fhwa.dot.gov/policyinformation/statistics/2009/sf3.cfm) 

Wheel Alignment and Weight Distribution

I can’t say enough good things about Rothsport Racing, an automotive shop in Tualatin, Oregon specializing in Porsche.  I took the car in to get an alignment after switching to stiffer torsion bars.  The shop was great. There were six car up on lifts, a machine shop, and several 911s, some set up for full racing. I was a little apprehensive bringing an electric Porsche to a Porsche racing shop, because I wasn’t sure how the car would be received. Jeff Gamroth, the proprietor, introduced himself, and after a quick show and tell, we took the car for a quick spin down the street. He liked the torque, but said the lack of engine noise was strange. We then pulled the car around into the shop bay, and five mechanics immediately flocked to the car. The silent entrance certainly got everyone’s attention. “Was that you guys? We heard a strange sound going down the street.” Everyone seemed OK with the electric modifications, or at least kept their horror in check. There were lots of questions about the batteries, range, safety advice to avoid electrocution while working on the car, and for the first time someone noticed my tachometer sensor mounted on the electric motor tail shaft. One of the guys joked, “At least you didn’t bolt on an LS2,” a jab at the practice of installing a Chevy Corvette V8 motor in a 911.

The alignment did wonders for the handling of the car. The steering is lighter and more precise. As a bonus, they also put the car on a scale. My conversion tips the scale at 3158 pounds (1432 kg), and is 408 pounds (185 kg) over stock. The front is heavier by 231 lbs and the back 177 lbs, shifting the front/back weight distribution from 38/62 to 40/60.