Thursday, December 25, 2014

My visit to Toyotron Electric Motorbikes in Bangkok

After building the electric 914 and planning a move to Thailand, I was very interested in the state of electric vehicles there, again trying to avoid gasoline-powered transportation.  What I found was disheartening...  There are no pure-electric cars for sale, not even the Nissan Leaf despite Nissan dealers everywhere.  I did find one electric golf cart shop that had an electric scooter from Toyotron but they told me it wasn't legal to drive on the road.  I ended up buying a Honda Click 125cc motorbike, which gets about 110 miles per gallon, so I'm minimizing my use of gasoline the best I can.

I've been watching the Toyotron web site since then to see what electric motorbikes are available, and if and when they will become legal for street use.  Sadly the site hasn't changed so I don't know if they are coming out with new designs or are even still in operation.

I was dropping a friend off at the airport in Bangkok so we stopped by the address on the Toyotron web site for a personal look.

We were greeted by two Thai ladies who spoke no English, but we managed to get some photocopied brochures and a couple of test rides.  The factory is somewhere else in Bangkok and as you'll see from the videos below the showroom is pretty bare and the rear area of the property is piled with old parts and broken bikes.

The main model listed on the web site is the Dragon-G, with a small and large battery pack available.  The Dragon-G body style is much like my Honda Click 125cc bike and several others in use here.  The spec on the Dragon-G Turbo (which shows a distinct lack of marketing prowess as you don't need a turbocharger on an electric motor...) is 40-60 kilometers range and a top speed of 55 km/hour. This is a little small for my use around town and up and back to the next towns. The Dragon-G Super has 60-80 kilometers range and top speed of 65 km/hour. I wish there was still more range and I have a dream of buying one without a battery pack, then building my own pack with CALB LiFePO4 cells and an appropriate charger.  I wonder if they would agree to it?

Strangely, they had two bikes on display called Hunter but no paperwork available and not shown on the web site.  I did a Google search and found this article from 2008 showing how close it looks to a Honda Big Ruckus.  The Thais generally have no respect for copyright law, so I assume they just welded it up based on the Big Ruckus shape.  I have no idea if they're still building it or these are just leftovers.  It has a very upright driving position, with a forward-backward adjustable seat.  The backrest tilts down to make a second seat, and as you can see it has additional storage space available in the saddlebags.

They also have two models which are essentially electric bicycles which I'm not interested in.

The ladies made it clear that the motorbikes can be licensed and driven on the roads, so I'm getting conflicting information.

To wrap up, here are three videos we took of test drives around the back area.  None were brand new, and the Hunter had a nasty grinding noise when it first started rolling, but it has nice pickup.  The Dragon and T-Win felt light with good balance and handling, while the Dragon-G was in very bad shape after nearly 5000 kilometers and nearly no charge remaining in the pack.  The last video also has some footage of the inside of the showroom and the other bikes on display.

While these are competitively-priced with similar sized gasoline bikes, I would be asking for more range than they can deliver so I think my best plan may be to buy a used motorbike with a chassis I like and converting it to full electric with my own design.  I just need to figure out how to make it legal first!

Sunday, November 30, 2014

Formula E electric car race in Malaysia

Here's my video report from the second (after Beijing) Formula E electric car race from Putra Jaya, Malaysia on November 22, 2014.

Monday, August 18, 2014

EVCCON 2014 - Day 5

This is the last official day of the show.  A group of people and several cars went just south of Cape Girardeau to Dyno Dom's Sikeston Dragway.  This is a 1/8th mile NHRA official track, so any fast times set here go into the record books.  Last year Jack's speedster set several records, and we were hoping for good things with John Metric's Miata dragster.

First up was the TVR but about a quarter of the way down the track it went bang and came to a stop.

And here they're pushing the TVR onto the trailer.

This is what the driveshaft looked like after all of that torque.

Next up was the triple AC35 motor with titanium shaft 911.  Lots of power, lots of money!

The 911 then ran against a beautiful hand-built AC Cobra replica.

A beautiful blue electric pickup truck was up next.

To everyone's surprise this electric drag motorcycle showed up for the racing.  He wasn't an EVCCON attendee, but came because he saw that today's racing was sanctioned by NEDRA.  He holds the world record for his voltage class, and you can see why.

This highly-customized electric golf cart (but still with the original gearbox) also holds the world record for its class.

Jason Horak's "Daytona That Wouldn't Die" survived the week of EVCCON without blowing up any parts.

Jack Rickard's Speedster Replica is one of the fastest street-focused home-built electric cars around.

Now we have the 911 vs. the Speedster in a Porsche grudge match.

Then the one we were waiting for all week - John Metric's custom electric Mazda Miata drag racer against the 911.  At the end of this run, the front hood peeled off the Miata and flew into the woods on the right side.

There were also a few gasoline motorcycles on the track that day, but we didn't pay much attention to them, they're so noisy and smelly!

So that wraps it up for EVCCON 2014.  See you next year for EVCCON 2015 from September 29 to October 2015, and if we're lucky there will be an EVCCON Amsterdam sometime soon.

Saturday, August 16, 2014

EVCCON 2014 - Day 4

Today is the last day of presentations, then we go outside for the car show in the park.

First Session - Built It To Last and Build It To Maintain It.  The Myth of No Maintenance Electric Vehicles by Brian Noto

EVTV's very own co-host "The Brain" has spent many hours building, rebuilding and rebuilding again electric cars, so he's in a great position to discuss component choice, build technique and maintenance.

Jack jumped in and discussed the battery situation of the electric Smart car he just bought on eBay.  You can lease a Smart electric car and included in your monthly payment is a battery lease fee.  You can also buy the car and then you also own the battery too, but they still want you to pay the battery lease fee.  They will sell you a new battery pack, but it costs more than the price of a whole new car.  Jack got in contact with the president of Smart USA who promised him the CAN bus documentation so Jack can build his own battery pack for the battery-less Smart be bought on eBay.  We'll see what happens after he talks with the engineers and the lawyers.

There is a growing issue that you can buy a car these days, but you can't fix anything yourself because of a lack of documentation, and more and more of a modern car is embedded computers and software.  Most car companies won't release their specs and that hurts us when we try to understand or update the vehicle we've bought and paid for.

Brian talked about other OEMs that we in the world of electric cars came to depend on like A123, Azure Dynamics, Winston, Netgain Controls, Better Place and my own issues with PakTrakr who are now history.  The issue is someday the company you're depending on may go out of business.  This leaves you without a source for components, replacement parts, service and documentation.  This is the heart of the Build vs. Buy argument that every company has when sourcing components.

We should be moving to more robust and sophisticated techniques and components, like one-twist battery box disconnects rather than running cables through holes, and readily accessible components for replacement like controllers, fuses, and contactors, because things break and you will need to fix or replace.  Due to the high voltage and current, it's important to use hydraulic crimpers on your battery cables, and invest in a good crimping tool for the other wiring in the car.

Quality usually costs more, but do not compromise your car for short-term savings.  Also take time to research components and techniques, don't rush into decisions.

Fred Behning made a point of thanking EVTV for the excellent documentation that comes along with the products they sell.  The JLD404 and the GEVCU are especially good.  Jack recommends having a quality multimeter and sunglasses.  If you can measure it, you can tell if it's working properly.  Brian says to build a small team, each person with specific skills.  Jeff Southern says to get to know your local trade schools.  The point was made about watching the EVTV guys make a mistake, recognize it, make a new plan and succeed - this is how we learn best.

The questions was asked how many people are doing their own electric conversions.  EVAlbum has about 3000, but it includes electric bicycles and couches.  While other people think we are on the bleeding edge and doing impossible things, we think it's just a fun project and then we just drive it around to get to where we want to go.  Jack's theory of publishing is make people go away, and then you're left with the people who are intensely interested in the subject.

Next Session: Helwig Carbon Products with Tom Brunka

Tom recapped his fascinating sessions from previous EVCCONs.  Refer to my notes from EVCCON 2011 and 2012.  He did mention that he built custom brushes and thick shunt wires for John Metric's drag car.  The plasma you see on his videos from yesterday is generated at the point where the brushes touch the motor's commutator.  Without high-amperage and high-temperature brushes, they would self-destruct and probably take out the motor too.

One point that Tom stressed again, that most people don't understand, is that you have to seat your brushes before full power is applied to the motor, i.e. driving it for the first time.  The brushes come from the factory with the contact surface perpendicular to the side, but the brush is rubbing against a round commutator, so enough brush material has to wear off to get the brush into full contact with the commutator.  Tom's rule of thumb is, depending on the grade of the brush, is running the motor at 3000 rpm for between 7 and 17 days.  Yes, a week to almost 3 weeks, 24x7.  This ensures the brush is in full contact with the commutator, allowing maximum current flow across the largest area and lowest temperature.

Next Session: The Future As I See It - Jack Rickard

Jack and Paulo discussed the blitz build of the Smart car.  It was stuck in 4th gear on the first attempt but they got that fixed and it's now fixed in 2nd gear, giving fast acceleration and 55 mph top speed which is great for around-town driving.

Jack then brought us of the Smart car project up on stage, we introduced ourselves and talked about what we worked on.  Jack will have to top it next year, many people called out "boat" so we may have a floating project next year.

Next year's EVCCON 2015 is September 15 - 21, 2015.  It's a little cooler and more predictable good weather.

The boat that Anne built for Jack was supposed to arrive during the show, but is taking a week and a half to make it 300 miles from Chicago by Monday so most of us won't get to see it.  Boats and cars are just two kinds of vehicles that can benefit from electric motion, and even cars are highly specialized for the needs of their drivers.

Jack reiterated his view that all innovation comes from one or two people in a basement or a garage.  We are working in an area that still has incredible opportunity for great ideas.

Ray suggested we have access to a computer where we can copy on pictures and video and others can copy them back off.  Somebody else suggested Flicker.  Jack's looking for a volunteer to handle this next year.

Jack says the Lear company is quietly taking over the world of chargers in EVs and its CAN bus properties are a mystery that needs to be documented.

We now break for lunch then outside for the car show, as long as it's not pouring rain.  And we lucked out, not a drop of rain.  There was a gas car show going on on the other side of the park, so we got some visitors who wandered over from there too.

This is a Twike.  It has pedals and an electric motor and batteries too.

These are the two fastest cars at the show.  The front car holds the world record as the fastest golf cart.  Just behind is John Metric's drag racing Miata.

Hanging out in the back seat of Jack's Tesla Model S.  Well, it's actually Jack's wife Jill's car...

The Model S always had a big crowd.

Closeup of the dashboard.

I easily found my building in Thailand on the satnav, it's the L-shaped white roof in the center.  Unfortunately it wouldn't let me click the Navigate button.  It must have figured out you can't drive from Missouri to Thailand.

After the car show, we went on a very quiet, police escort parade through town.

At the end of the parade we got the cars set up for the traditional group photos.

After the group photos we got dressed up in our finest and had the closing banquet and awards ceremony.  I won the trophy for the furthest traveled attendee!

EVCCON 2014 - Day 3

Today was "fun day" at the Cape Girardeau airport, inside and just outside Jack's hanger.  Since the day is mostly pictures and video, just enjoy.

Jack owns two DC 3s, two helicopters, a biplane, a LearJet and a number of MGs that all still run on liquid fuels.  Maybe someday we'll convert a DC 3 to electric?

This is the cockpit in the DC 3.

Here are the passenger seats in the DC 3.  Much more comfortable than today's planes!

Here's his Huey.  His daughter Jennifer is a certified helicopter pilot.

The next series of pictures are some of the cars lined up for weighing before the drag racing started.  This is a 1960s Datsun pickup truck.

This is the custom-built "Seven" car that came second in the Progressive Automotive X-Prize competition.  They would have won but their clutch blew up in the acceleration test at the end.

A hand-built AC Cobra replica, a TVR and Fred Behning's MG.

This is one of the few new second-generation Toyota RAV4 electrics.  This has the Tesla battery pack and drive train, a product of their technology partnership that has now been dissolved.  The blue thing on the back requires some explanation.  It's a VW Beetle with the body and front wheels stripped off, so it's now a self-powered trailer.  When he's cruising down the road, he turns the RAV4's lights on, and this causes the Beetle engine to start, pushing the RAV4 and trailer down the road.  When he sets the cruise control on the RAV4 and the trailer pushes faster than the car is set for, it goes into regen mode and actually charges the battery as he goes down the highway.  When he taps on the brake, the Beetle engine shuts off.  He drove all the way to Missouri from Utah in this manner and actually used it on his dragstrip runs.  Unconventional, yes.  Wile E. Coyote ingenious, yes!

Nabil's Bradley GT, the quintessential kit car of the 70s, now in full electric mode.

The Mazda Miata makes a great conversion platform - light with great handling, and the transmissions can handle strong electric motors.

The Karmann Ghia in the morning sun.

Jeff Southern's VW Thing.  I got a ride home to the hotel one night in it and we stopped at CVS.  One of the checkout ladies had to run outside and check out the Thing.  He gets that a lot!

Miata, pickup truck, Miata, Jack's Porsche Spyder and Jack's Porsche Speedster, all electric.

All lined up, ready for drag racing to start.

I named this Swamp Thing.

John Metric's world record Miata.  He recently did a segment for MotorWeek, the PBS car show and it should be aired later this fall.  Check out his dyno videos below.

Under the hood, twin 2000 amp Zilla controllers.

This is the business end of a converted 911 from Montreal.  That's 3 HPEVS AC35 motors connected together with belt drive.  The motors were updated with titanium shafts and cases.

This is the inside of the motor controller in the newly completed Smart car.

And here is the Smart, completed and driven over to the hanger from the EVTV workshop.

The Smart now has a JLD404 meter in the coin shelf on the left side, and a state of charge meter in the original round housing on top of the dashboard.

Wednesday, August 13, 2014

EVCCON 2014 - Day 2

Today is the second day of presentations at the A.C. Brase Arena.  We look forward to tomorrow at the airport for drag racing and autocross and dyno testing, then Saturday for 3 morning sessions and the car show in the park.

First Session:  EV Technologies And Racing Applications - Adam Clark and John Metric

Adam and John kicked off by showing their drag racing plasma video I posted yesterday.  Adam and John are leaders in the field of electric drag racing.  They met and decided to build a drag racing Miata and they've set a couple of world records and always beat the gas guys!  Their car is called Assault and Battery, best 1/4 mile time is 8.9 seconds at 149 mph, the fastest car with doors in the world.  Don Garlits is a legend in top fuel drag racing and has come over to the electric side, which is bringing a lot of attention, trying to be the first to hit 200 mph in an electric dragster after being the first to go 200 mph in a gasoline dragster.  John Waylan's car is called White Zombie.  His youtube videos are legendary.

Electric motorcycles are getting fast, 0-60 mph in less than 1 second, 0-200 mph in 6.9 seconds!  The fastest motorcycle at Pikes Peak in 2014 was electric.  The Nissan Deltawing car raced at Le Mans this year, along with the Drayson racing car.  Formula E is a new open-wheel racing series sanctioned by the FIA, the world motorsports leader, and I will be attending the second Formula E race of the season in Kuala Lumpur.

As with conventional racing, a lot of the innovations trickle down to smaller racing series like SCCA and into road cars, and we expect that technology from electric racing will make it to electric road cars too.  Advances in shedding weight by using lighter and stronger materials, advances in battery capacity and power delivery, supercapacitors, controllers, motors, and software for control and data collection will make our road cars better in the future.

Since motors are so key to racing, Adam went into great detail.  Series Wound DC can go very fast for a short period of time, so they're good for dragsters.  Heat and brush wear limit their more general use.  Brushless DC are more suitable for smaller vehicles like go-karts.  AC Induction motors are good for larger vehicles by choosing the desired torque curve.  They run higher voltages which improves efficiency to 95% but the controllers are more complicated and expensive and can't yet offer the power needed for drag racing.  Permanent Magnet AC motors are a little more efficient and a little smaller and lighter than induction AC motors but will demagnetize if they get too hot, so beware.

A study was done comparing AC induction and Permanent Magnet styles.  In the city test, the PM motor was 27% more efficient, but in highway use they were equivalent.

Popular DC racing controllers include the Zilla 2K with 2000 amps at 380V, the Shiva is 3000 A at 425 volts.   AC controllers include the Scott Drive and several Curtis units.  To get more power, you have to increase volts or amps, or cool the units better.

Where do the business opportunities lie around electric vehicles?  Material Science is a key job for the future, trades such as welding and machining, software development, carbon fiber, aerodynamics, energy management devices like DC-DC converters.  Lonestar offers their own DC-DC converter and AC motor controller with 1400A continuous and 2800A burst, up to 1200V in, up to 1.5 megwatt output!

Next Session: AC Drive Systems by Brian Seymour of HPEVS

Brian's father started an electric motor business by rewiring broken motors for friends and family, and the business has taken off.  They got into the golf cart business and pioneered the use of AC motors.  Brian's generation moved into motors for electric cars, delivery trucks, boats and other vehicles.

Brian converted a waterski boat from a gasoline engine to a newly developed stainless steel motor called the AC35x2, containing two motors on the same shaft and oil cooled.  They also supply mounting plates and couplers to Mercruiser drives.  It has dual Curtis AC controllers and 144 of CALB's new CAM72 batteries.

HPEVS offers a wide range of AC motors, either single or dual units on a single shaft.  Some of the motors are air cooled, but most are water cooled now, for the future they're moving to oil cooling.   They're using Dielectric transformer oil, which is really good at getting into contact with every part in the motor and carrying away the heat.  Water cooled motors are just jackets around the hot parts which can't carry away all of the heat.  It also acts as a lubricant for bearings and seals, and allows for higher operating temperatures.  The impact of using oil rather than water or glycol has an impact on the pumps, hoses and radiators used in the cooling loop - they need to be selected for oil and expected temperature.  Mercruiser hoses are readily available, and oil pumps can be found at Summit Racing.  They suggest using the existing automatic transmission radiator.  They've also added an oil filter for safety.

Brian then showed a video of a ride in his boat, nice and smooth and quiet!  He then walked us through the performance charts.  The big takeaway is that his boat was consuming just over 10 X the watt-hours/mile as we would expect in an electric car of the same weight.  This is why you should plan on a very large battery pack in your boat, or take short trips.  Note that getting up on the plane is key to minimize hydrodynamic friction, but there is a big power penalty trying to go past.  At 42 mph, the motor was pulling 1,000 amps!  Changing the prop to hit your target speed at the sweet spot of the motor will minimize your power consumption at your desired top speed.  The weight difference is a net gain of about 100 pounds, so it's almost equivalent of stock.

Next Session: High Performance from Stock Parts, Part 3

A followup session to the first this morning from John Metric, President of the National Electric Drag Racing Association.  John crashed his car last week doing an interview with MotorWeek on PBS, but was calmer than now standing in front of our friendly group.

This is an update from last year's talk.  He uses twinned Warp 9 motors like I have in my little 914, but he's pumping an insane 2000 amps of current through each, using Lithium Cobalt pouch cell batteries.  The batteries he uses have doubled in output current in 4 years.  He hasn't used a BMS for 1.5 years but is still interested in monitoring the each cell, since he only has 30 minutes between runs at the drag strip.  He's built a device that plugs into his pack and gives a quick view of the health of each cell, highlighting the high and low cell in the pack.

He showed several graphs overlaying battery pack performance and controller capability, showing where they match up nicely or are over or under capacity.  He then showed some simulated dynamometer graphs with torque, rpm and horsepower curves.  Air is a real performance problem, with enormous increases in horsepower needed to overcome drag.

What John learned about acceleration of a drag car, is the weight of the car and the road surface coefficient of friction is all that matters.  Torque and horsepower don't even come into the equations.  Another big factor is twisting the chassis due to the spinning motor, he was raising only one tire off the ground, so you have to pre-load the chassis so the car is flat as it's going down the track.

If you want to be entertained, find some youtube videos of electric drag racing!

Next Session: and Electric Boats by Anne Kloppenborg

Anne is the face of EVTV in Amsterdam.  He builds cars, converts boats and is a major EV component supplier for Europe.  He sends Jack a video update nearly every week, so you can keep up with his efforts by watching EVTV.  They've grown so much they're moving to a much larger space about a kilometer away in October.

His first build was a Glastron ski boat, and then moved to boats with less weight and more efficient hull designs.  They then did a Nedcraft Silverback, a beautiful boat.  Then they did the Ray Wright Delta with two drive train revisions.  Now they're working on a cabin cruiser.

He showed the design and construction of the New Delta, which is the basis for the boat that Anne built for Jack.  It's somewhere on the road between Chicago and Cape Girardeau right now.

They're working on a Jeep conversion in the shop right now, and have built a set of adapter plates that and reduction drives that will allow them to mate any supported motor to almost every boat.

One big issue they've run into is the need to pass very strict electrical interference certification testing, which happily they did for their DC motor system, and recently submitted the AC solution, working together with competing companies in the area.  Unfortunately they overheated a resistor but it was an easy fix.

Anne has a goal of crossing the English Channel with an electric boat.  The Guinness Book Of World Records has, at the request of his friend Al Gaida, created a new category of Fastest Crossing Of The English Channel By An Electric Boat.  They will make the attempt early next year.

We are now transitioning to a general boat panel session.

They discussed the cost of ownership vs. gasoline, electrical noise in the wiring, the motor required for a large Amsterdam tour boat, reduction drive belt power handling, converting a personal-sized watercraft and details of the channel crossing.

Next Session: JLD 505 with Paulo Almeida and Celso Menaia

Paulo and Celso are instructors at an engineering institute in Portugal.  They are circuit and circuit board designers and came up with one of the latest versions of the GEVCU boards.  They are also the team leaders on the flash-conversion of the Smart car this week.

In their spare time, they've developed what they're calling the JLD 505.  This is their take on a Chinese device called the JLD 404, which is very popular in the EV world as it not-very-accurately measures voltage, current, amp-hours and watt-hours and controls two relays which are triggered from thresholds you can set.  It has a large blue LED display with buttons to scroll through the various values and is attractive to install in your dashboard.  It is key to determining the state of charge of your pack which keeps it healthy and gives you as the driver the information you need to avoid running out of juice on the side of the road.

Paulo and Celso are introducing to the world the first prototype version of the JLD 505.    It offers a better display and data output.  Their design protects the internal components with a fully isolated power supply, USB port, Bluetooth and CAN bus, two digital inputs, two digital outputs, current-measuring shunt and pack voltage interface.  Final specs include 9-18V power supply input, 500V maximum battery pack voltage, 2.5 uV shunt current resolution (17ma at 500A) and is Arduino IDE compatible for easy software development.  The enclosure will be waterproof and have an Amphenol connector similar to the GEVCU.  Since there is no display, for it to be useful you have to read the values with another device such as a GEVCU or any other device that can show the values on a user's device such as a smartphone or tablet.  Cost is expected around the same price as the JLD 404.

Next Session: EVTV Battery Management System "You've Got To Be Kidding" with Ed Clausen, Collin Kidder, Paulo Almeida, Celso Menaia and Jack Rickard

As anyone who has watched 5 minutes of EVTV video knows, Jack hates the "BMS" or Battery Management System.  These systems generally include a small circuit board attached to every battery that attempts to keep an even charge on each battery across the pack by reading voltage and bleeding off excess power in the higher-voltage cells as heat.  Unfortunately the failure mode for this kind of device usually results in burning down your car and whatever building it was parked in.  This is bad, because the device that's supposed to protect your battery pack actually destroys it.  Living without a BMS is tricky because you don't know the health of each cell, or at the least, each group of cells in the pack.  Jack solves this by carefully bottom-balancing each battery to within a thousandth of a volt and then the nature of LiFePO4 chemistry ensures that the batteries exactly track each other during the charging and discharging phase.  No inter-battery drift means no need to bleed off the high cells means no BMS is necessary.

So why is Jack now working on BMS systems with Paulo, Celso and Ed?  They're making Battery Monitoring Systems, not Battery Management Systems.  The PakTrakr system I had in my 914 was monitoring only, no active management.  This session will give us the first details on what Ed has been tinkering with in his shop.

The BMS will have 4 voltage inputs, giving the voltage of 4 segments of the pack, each being any size.  It will constantly sample the 4 segments and compare them, weighted properly, to see if things are getting out of sync.  The tricky thing is not acting like a parasitic load on some of the batteries and over time unbalance the pack, especially avoiding the ladder effect of multiple voltage measurements.

The heart of the system is a Sendyne SFP100 precision measurement chip, which has a very high reading resolution.  It can measure voltage, current, amperage and 4 points of temperature.  It has continuous calibration built-in to maintain the high accuracy.

The processor is the same ARM Cortex M3 as the GEVCU, and has EEPROM data storage, CAN bus, USB bus, I2C bus, digital interface to a high voltage multiplexer, 4 thermistors and an isolated power supply.  It will be housed like the GEVCU and have an Ampseal connector.  The voltage multiplexing lives on a separate circuit board with isolation on all inputs and I2C communication back to the main board.  The parasitic load is avoided by using a Bidirectional-blocking switch using two opto-isolated MOSFETs.  Each pair of MOSFETs is turned on and off in sequence.  A sampling capacitor takes about 600ms to charge up, then the ADC reads the voltage of that section of the pack.

I asked and Ed confirmed that it's theoretically possible to have one main board and multiple voltage boards, each with 4 voltage inputs due to the way he's multiplexing the voltage reading back to the Sendyne chip.  This way, people can get the amount of voltage sensing they want, from 4 points around the pack all the way down to each battery.

Ed's testing with the system involved charging with a Brusa charger and discharging through a grid-tied solar inverter.  He's seeing a lot of noise on the current sensing but that can be smoothed out in software.  Next steps include writing software for the board rather than the Sendyne test app, integration with the GEVCU, a slight redesign of the circuit board to account for a non-standard package size on the MOSFETs and creating an enclosure for the main board.

After the sessions we went back to the EVTV workshop.  The long Karmann Ghia project got a helping hand from some EVTV attendees and got it wired up and running.

The Smart car is charging and very close to being rolled off the rack and driven down the road!

And that wraps up the day!  Tomorrow we head over to the airport to get liquored up, play with high voltage and drive fast cars!