Friday, September 28, 2012

EVCCON 2012 Day 2

After sleeping through my alarm for 30 minutes, I arrived at the Show Me Center just as Wayne Alexander was starting his session on EV conversions as a business.

He regaled us with pictures and descriptions of a half-done Mazda project he took over.  Literally everything was wrong, so he showed us how he fixed everything and rebuilt it back to a working car.  Then he moved to a Jeep project that had been worked on for 17 months and abandoned.  The work was so bad it was actually dangerous, with the possibility of fire and shorting of the battery pack conductors to the drive shaft.  He showed us his method of mounting non-electronic automatic transmissions to the motor.  He likes to mount the controller, contactor and associated electrical parts on a thick sheet of Lexan and mount it above the motor under the front hood.  He makes his battery boxes out of 1/8" steel.  He suggests that you work on every car that comes across your path, don't be afraid to try new things, but try to standardize on a small set of components that you know and trust.  Simplicity is best, as it leads to fast builds and working EVs.  He stressed that we have to do conversions well because one bad car will taint our whole industry.

Next up was David Kerzel on charging port issues for J1772.

He started by talking about electrical safety, as there is a perception that gasoline is safer than electricity, but there were 250,000 gasoline car fires and a handful of electrics.  The J1772 standard brings together a common connector and an electrical safety protocol.  The connector has a well-thought-out design, with no exposed wiring, ground mates first, the proximity switch engages and then the 3-stage safety protocol happens to ensure the car is ready to be charged, then power starts flowing.
  • J1772 Level 1 is normally 12 amps at 120V.  You can normally get 6 hours per mile of charging time.
  • J1772 Level 2 is normally 23 amps at 240V, giving 27 miles per hour of charge.  A few 80 amp charging stations exist which will give about 93 miles per hour of charge.
  • J1772 Level 3 is a completely different beast.  It is high-current DC power rather than AC power.  It bypasses the charger in the car and dumps power directly into the battery pack, matching voltages as necessary.  Nissan Leafs are equipped with CHAdeMo, which handles 500V DC at 125 amps.  SAE is working on a J1772 standard, which adds two large posts for DC onto the bottom of a Level 1/2 connector.    It is expected to handle 600V DC at 200 amps.  The safety protocol has not been determined yet.  This system has been accepted by GM, Chrysler, Ford, Toyota, Honda, Nissan and Tesla.  No production cars use this yet.
Why are EVSEs (Electric Vehicle Service Equipment, what most people call a charging station) so expensive?  First, is safety, as the connectors and wires must pass strict rules.  Then the units have to be robust to handle years of charging, weather, vandalism, etc.

The Tesla Supercharger network was just announced this week.  Tesla says it is a 90 KW/hour system, taking 20 minutes to charge for a 3 hour drive, but David's calculations show a 20 minute charge will actually take a Tesla Model S about 80 miles.  With all 6 charging bays in operation, that will pull over 500,000 watts of power, as much as my company installs on the roof of a Costco store.  David wonders if the charging will always be free and doubts the $250,000 construction cost quoted by Tesla.

David says when you find a public EVSE, check it over for damage and try to notify someone if it needs attention.  What do you do when a non-electric car is parked in the spot?    Be polite and move your car when done charging and coil up the cable nicely.

David worked through different adapter cable scenarios.  It's important to remember that J1772 connectors are not rated to plug and unplug when energized!  There are several EVSE open source projects on the Internet using Arduino controllers.  David sells his 4th generation EVSE controller and display unit as a kit.  Data connections are important for commercial customers as they want to know how much power and how many cars are being charged, as it's essentially an advertising cost to the business.  If you buy a fully-assembled EVSE it must be UL listed, but if you buy it as a kit, your electrical inspector must approve it, following National Electrical Code Section 625.

David discussed his future plans which include GFI integrated into his products, adding soft current limit, timers and communications to cell phone for commands, settings and statistics.

Next up was Steve Woodruff, talking about his Prius plug-in kit and finding parts to build your EV.

Steve competed in the 2009 X-Prize competition with a heavily modified Prius.  His primary business is to recycle parts from damaged Priuses (Prii?).  He built a stretch Prius plug-in limo.  He supplies repaired Prius touchscreens, shift levers, cables, battery cells or packs, and sells his own supplemental plug-in battery pack.

His tip is to buy the whole wrecked vehicle, as all of the parts can eventually be salvaged.  You can get leads on cars through insurance company auctions, Copart auctions and Mannheim auctions.  Always bid assuming there is more damage than you can see.  You need to be registered as a vehicle dealer and your buyer fee will be $495 and 90c / mile shipping.  If the car has a Certificate of Destruction or Junk title the car cannot be rebuilt, only sold for parts.

A Prius has a 1.5 liter Atkinson cycle engine, which means all 4 cycles of the engine are completed in one turn of the crankshaft rather than the standard two.  There are two large generators in the drivetrain and an AC motor.  It has a continually variable transmission that merges the power from the engine and motor.  He prefers to work on the Generation 2 Prius model although Generation 3s are on the road today.

The Prius doesn't have a power steering pump, belt-driven AC compressor or alternator and no starter motor.  This is a big difference between traditional engines.  There are 28 Nickel-Metal-Hydride cells in the pack which are built into a slab.

There are a couple of other Prius plug-in conversion shops around.  Steve has 22 conversions on the road.  A Prius requires about 1 KWH to move 3 miles so a large 10KWH plug-in upgrade will allow for 30 miles under electric power, then reverts to normal Prius mode.  Steve has also rebuilt several Prius built-in battery packs and has only had one come back with a repeat failure, and Steve stood behind it with a warranty.  It costs about 1/3 of a new pack, so customers are willing to take the chance.  He matches the voltage of the replacement cells with the state of the existing pack to avoid bottom balancing issues.

The key to making a plug-in pack work is that the Toyota software has been hacked to allow for the car to go to at higher speeds in electric mode than was originally designed.

Keegan Han from CALB batteries was supposed to be a speaker, but his parents arrived from China and cancelled his appearance.

Next up was Rich Rudman from Manzanita Micro, maker of chargers and motor controllers.

Rich has a long history in the EV world with chargers, controllers and battery management systens.  His first electric car was a Ford Fiesta drag racer.  The first charger was the PFC-20 which could take 120V or 240V AC.  The PFC-50 came next which would take in up to 50A, giving 10KW of power.  Then the PFC-75 came with up to 20KW of power.  These chargers must be run in a cool environment or they will overheat and derate the output.  New models are coming out with a new enclosure and dial-wheel voltage adjustment.  A new meter shows input voltage, current, KW and power factor.  Additionally they will directly support J1772 protocols.

The Zilla controller is legendary and has gone through a lot of turbulence of owners.  Rich now owns the Zilla product and has brought it back into production.  He is building the current version now and has several enhancements planned for early next year.  The Zilla 1K unit is a compact water-cooled unit running 1000A.  The Zilla 2K unit handles 2000A.  They also have a limited edition Zilla 4K unit.  The Hairball unit moves all of the input signaling out of the main controller box to avoid costly failures.

They offered a BMS system staring in 2008.  He feels strongly that BMSs are required and top-balancing is the only solution to pack setup.  This is in violent disagreement with Jack.  He also said that all Lithium battery manufacturers require a BMS or the warranty is void.  He showed a screenshot of his display which gives a good view of the behavior of each battery, whether he is regulating the top charge or not.  The question came up about running a small wire to each cell, and Rich said it's an issue but solvable with circuit-board solutions, properly bundling wires, etc. and they have not had any failures that weren't traced to installer error.

There was a lively discussion about dissipation of energy during charging shunting phase and throttling back the charger.

A quick break for lunch and we're back for Tom Brunka and his session on The Helwig Carbon Brush in your Series DC EV Motor.  Tom's was the blockbuster session last year, with lots of great information about motor brush compounds and construction and the direct effect they have on your performance and range.  Jack did extensive testing of the split Red Top brush design and Tim found his range was extended by more than 10% just by swapping brushes.

Tom gave us a video tour of his factory.  They manufacture not only brushes but brush holders and constant force springs.  There are 3 different grades of materials
  • Electro-Graphite: High end, used in EVs
  • Metal Graphite: up to 48V DC
  • Graphite: up to 90V DC
Within these types, there are many grades, with different levels of resistivity, strength, hardness, friction and filming, leading to different brushes designed for different applications.  Brushes are sized based on current density.
  • H38: Up to 80A per square inch, long life for street EV usage
  • H49: Up to 100A per square inch, untreated for racing
  • H60 Up to 80A per square inch, street EV usage
  • K254: Below 80A per square inch
The film is an important part of motor operation.  It builds up on the commutator and acts as a dry lubricant allowing the brushes to glide over smoothly.  It should be a nice dark brown color without arcing indications.  Resistance comes into play as it affects the temperature that the brush runs at.  Tamping material can be copper or graphite and bonds the shunt wire to the brush.

Brush wear factors include mechanical friction, electrical arcing, spring force, humidity (helps to create and maintain the film) and commutator wear.  The target spring force for most electric motors is 4 psi at the brush face, in an EV the minimum should be 8 psi due to bouncing and vibration.  You can add one-half to one more bend on the brush spring to gain a bit more brush force.  A sign of not enough brush force is marks on the face of the brush.  Better contact means better electricity transfer and efficiency and therefore less heat.

Arcing has many sources, including the advance/retard of the motor timing, contact area, roundness of the commutator leading to the brush bouncing right off, spring force and heat soak.  

Helwig suggests seating the brush to 80% before using it in a normal application.  This can result in running the motor on a 12V battery in neutral at 3000 rpm for several days.  H49 seats quickest in 6-15 hours, H60 seats in 6-7 days, H38 seats in 17 days!  They suggest beveling each commutator bar at 45 degrees, then lathe cut it round, then polish with 80 grit and 150 grit garnet paper only.

They suggest using a Grounding Brush Kit due to inducing of current into the bearings and the driveshaft.  One customer read 20A being drained off after installing one of these kits.

As the brushes wear, they turn to dust and can lodge inside the motor, starting a frame leak.  Blowing the motor out 4 times per year is a good rule of thumb.  It's also a safety precaution to add an active blower to your motor, which helps with cooling and cleaning out brush dust.

Never use silicone spray, grease or sealer in the vicinity of a DC motor, as it will contaminate and attack the brushes due to the conversion to Silicon Carbide.

Acetone is the preferred cleaning solution, but make sure it's completely removed as it's highly flammable.

New developments on the horizon include new manufacturing processes and grades of brushes to meet the needs of the market.  They are looking at larger shunt wires, tamping materials, higher current handling by adding silver (but expensive) and new brush holder designs.

A question came up about overheating EV motors due to the nature of driving.  Tom suggested adding blowers to keep the motor and brushes cool, they must be below 400F.  As a science experiment you can drill a hole in a brush and epoxy in a thermocouple to directly measure brush temperature.

There should be an ink stamped part number on the side of each brush for easy identification if you're repairing or upgrading a motor.

Tom says they use a fish scale as a crude way to measuring spring pressure in the field.

The last speaker for the day is John Hardy from the UK.  He has contributed videos to EVTV and is speaking on battery testing.

John has a varied background as an engineer, car accident analyst and commercial pilot.

Why do we test batteries?  There is little data, so it was a job that needed doing and he wanted to do an electric car conversion and wanted to make sure he picked the right batteries and charged and discharged them properly.

The conventional wisdom held that batteries drift apart in voltage in a pack and you need a BMS, so he wanted to use science to see if that is actually true.  There is a lot of data out there about Lead Acid cells, strings and batteries.  They self-discharge just by sitting there, called the Peukert Effect.  Many people seem to think that these principles carry over to other battery chemistries.  Lithium Iron Phosphate batteries do not self-discharge, but there is little additional data or analysis.

John built a test rig with a charger, a load and a series of Headway LiFePO4 round cells, and used an Arduino controller to manage his test processes.  His voltage measurement tool consumes 0.2 ma which has a non-trivial effect on the pack, so he added an OpAmp to isolate the metering from the pack.  He used a language called "Processing" and a cloud data service called Pachube and CSV files into Dropbox to collect and store the data.  He then pulls the data and graphs it.

After months of 3C charge and discharge cycles, his results indicate he saw almost no variation between cells at the end of the discharge cycle from his bottom balancing variation, but a small amount of variation around 6 mV between cells during the constant voltage phase of the charge cycle.  By removing the constant voltage charging phase, the cells had nearly zero variance throughout the charge and discharge cycles.  He then added a "top-up" charge after 5 minutes of rest after the constant current charging phase with a tiny variance, then a "double-top-up" charge, with a slightly larger variance, of about 3 mV.  At a lower charging rate of 1C, the pattern remained the same.

The bottom line is there was 10 mv, or 0.3% discernable drift between cells, no matter what the charging cycle or charge and discharge rates.  This is as close to zero as is measurable.  So John has shown that there is no risk of Lithium cell drift in a pack.  As long as the cells are bottom balanced at the time of installation, they will behave beautifully through their lifecycle.  He did have one cell fail around cycle 575, so this needs to be taken into account to detect a failed cell in a pack.

He is going to do another test with CALB cells to see if they also hold up to this profile.

We all packed up and headed over to the airport for 1/4 mile drag racing, autocrossing and dynamometer testing!

This is Jack's hanger at the airport, where the food, drinks and portable dynamometer machine were housed.  Normally there are two DC3 aircraft parked here, along with Jack's collection of MGs you can see below.

Here's a closeup of the portable dynamometer.  Jack paid for it, and it was free to anyone to use for 2 or 3 runs.

The cars started to get staged outside, in preparation for SCCA-sanctioned 1/4 mile drag racing, starting with the weigh-in.

Ron Adamowicz, with his last pennies, brought his unbelievable dragster to the event.  Now the hood is off here, so it's hard to picture, but this is the size and shape of a Funny Car.

It has two 11" DC motors, 2 lithium battery backs and two Evnetics Shiva motor controllers.  I mentioned earlier that each Shiva can pour 3000 Amps and 1.2 million watts of power into a motor.  Now just imagine that Ron's car has *two* of them.  That's 2.4 million watts of power.  Boggles the mind.  Check out his two runs in the drag racing video below.

Here is Fred Behning's gorgeous completed-just-in-time-to-put-on-the-trailer MG TD.  He won the trophy for Best Paint at the awards ceremony.

Alex Smith's Wrightspeed lookalike looked insanely fast but was held back by its lead-acid batteries, same as my 914.  With a lithium pack, this car could beat the Teslas.

Doug Ingraham's RX7 looked fast.

Holding the torch for the 914 brigade was Mark Emon with a crazy 56 200AH lithium cells.  After finishing his build at home, he drove it 2 blocks then put it into the truck and drove to the show.  He spent arrival day in Jack's shop finishing up details like replacing his coolant pump and hooking up the charger wiring.

Next up was Kevin Heath's RX8.  Kevin picked up 3 trophies at the award ceremony for this fantastic car, with a battery pack made from A123 lithium pouch cells.

We got to watch John Allan build this Celica via videos he would record then send to Jack for inclusion in an EVTV episode.

This is Norbert Kedzierski's Boxster.  His company, Red Point Engineering, among other cool things makes electric conversion kits for Boxsters.  It is his daughter's 7th birthday today and she didn't seem to mind spending time with the electric cars.

This is Stella Kostolina's and Zachary Vex's Tesla Roadster Performance machine.  It's black on black on black and looks amazing and goes even better.  Stella and Zachary are making a reality TV show called Electric Trippers which follows their journey as they drive around the country, meet interesting people and try to find places to plug in.

Here is Jack's Porsche 550 Spyder replica.  It used to be owned by Duane Ball, but Jack bought it when Duane decided to go ahead with his Porsche 904 replica project.

Here's the race start position.  The helicopter is not for emergency flights to the hospital!

I got most of the cars racing on the drag strip.

Fred let me take his MG TD for a couple of runs, here is the video:

These are my two run slips.  The first run was good, with a 19.489 quarter-mile time, at 62.5 mph.

The second run was worse, as in my enthusiasm I knocked the throttle linkage off the pedal when shifting into 3rd gear.  I had to reach down and push it back into place, hampering my time to 23.555 seconds and 49.3 mph...

The autocross track was open and most cars headed over after doing a couple of drag strip runs.  Here's a video of Charlie and Tamera in the Opel GT.

As the sun set, most people brought their cars over to the dynamometer test rig.  Here's Charlie's run in the Opel GT.

And his graph shows he's making 104 horsepower, which is excellent for such a light car.

Then Mark's 914 with the enormous battery pack was on the ramp.

Then Caleb Lander got his 1974 Super Beetle up on the ramp.

It has a relatively small lithium pack but made a brave 39 horsepower.

Then things got very interesting when the Evnetics team got Sebastien's 911 ready for testing.  The first two runs actually had a controller shutdown because the 12V power bus voltage was too high.  They solved the problem by turning on the headlights!

And turned in an amazing 356 horsepower!

Next was Stella and Zachary's Tesla.

That's 256 horsepower.

Last up for the day was Jack in the Speedster, a sleeper of a car with a large pack and surprising power.

That's 160 horsepower, folks.  About twice what most of the original cars left the factory with.

After things wrapped up here, a group of us went to a local bar and enjoyed ourselves thoroughly.  Got to bed about 2 AM...