This may indeed be our longest show ever – right at three hours of HD video. We had a number of interesting developments and breakdowns in the shop, and then we introduce the TEN finalists in the EVTV “Build Your Dream” EV components contest.
Each of the sponsors selected two of the 955 entries received, and I selected two as well. In itself, that you had a one in a thousand chance at $20,000 in EV stuff is kind of a remarkable thing. You won’t find that often or everywhere.
In this episode, we attempted to summarize all of them with a “reading” of their entry and a bit of discussion as to why the sponsor may have found that an attractive notion.
In any event, we will running the balloting from now until August 31, 2011 and each of our viewers will have a chance to make a selection. Help me by making your best considered decision as to where to ship this pile of EV components to have maximum effect. You may vote HERE.
We are designing a drive train for the Aptima Motors eCobra. As a bit of an add-on, Paul at Aptima wanted a J1772 charge station like our Texaco gas pump. I completed that work this week. Paul selected a Chevrolet Corvette pump style and we’ve been wiring it for J1772 charging. We show the result in this episode.
I have often said I’ve never met a connector that I liked. I may have finally met my match. The Yazaki J1772 connector has much to recommend it. We are gradually converting all of our cars to work with this connector, and I have gas pumps at the shop and at home. The one at home does not yet feature the J1772 connector, but it will soon. I have fallen in love with them.
Why? They have a very solid feel. You can insert them VERY easily and they lock securely in place with a faint “schnick” as the switch locks in place. We have long eschewed the proper 240 amp connectors on our cars because of the desire to be compatible with 120vac opportunity charging at grandma’s house. So we’ve used Marinco marine covered NEMA 5-15 connectors. They hold up pretty well, but many of our extension cords do not. Over time they become loose and are a bit flimsy. QUITE a bit flimsy compared to the solid cast plastic J1772 connectors.
We had previously published a diagram of how you could wire your car to accept a J1772 charge using a switch, a diode, and about two resistors.
I’ve recently received a number of e-mail questions seeking this information. We now have an index thanks to Christopher Fischer, but it seems a large percentage of our viewership would expect me to know precisely what episode and minute any particular discussion could be found. Google has indeed spoiled us.
The communications between the J1772 Electric Vehicle Support Equipment (EVSE – we call it a gas pump) and the car is really very simple. The EVSE generates a 12v square wave alternating between +12v and -12vdc and applies it to pin 4 of the connector via a 1 kilohm resistor (1000 ohms). The junction of pin 4 (copilot) and the 1k resistor is then monitored to determine its voltage level.
The duty cycle of this square wave indicates how much current the EVSE is able to supply. The charger in the car is then supposed to limit itself to that amount of current. We don’t know of any available charger that can do this. As the nature of such specifications are, we would expect this to be ignored for several years, and at some point in the future, someone will “discover” this feature and use it to communicate something else. It is possible the OEM cars actually look for this waveform, but we would be astounded.
Why? Onboard chargers are rarely of a capacity above 3000 or 3600 watts. They just become to physically large and too physically heavy to fit in a car at much above that. You might see a few 5000 watt units in some select vehicles.
The EVSE seems to have broken into two levels of Level II charging – 32 amp and 70 amp. The first is 7640 watts more or less and the second is 16800. Almost everyone is opting for 70 amp cables and connectors. Either way, its much more power than the car can use in almost every case. And so the recognition of available power is rather moot. And will likely become more so in the future until Level III DC charging becomes a thing.
So the “spoof” we’ve come up with on the car side is simply a diode, to eliminate the negative portion of the waveform, and two resistors that tie back to the neutral pin of the dual phase supply. This supply, identical to your home 240vac of course, consists of two phase lines of 120vac each, and a neutral return which is tied directly to ground in your electrical panel.
When you plug in the car, the diode and first resistor form a voltage divider with the resistor in the EVSE. It is designed to drop the positive portion of the waveform to +9v. The EVSE would detect this as a “vehicle present” signal. When you throw the switch to engage the other resistor in parallel, this drops the vehicle side resistance to about 877 ohms and the voltage to about +6v signaling the EVSE to provide power. There is another level lower yet for signalling for ventilation. This would be for flooded lead acid batteries that produce hydrogen when charging. We don’t expect that to be used at all.
We rather thought someone would develop a little PCB to implement all this on the EVSE side quite properly. David Kerzel threatened to, but never completed the project. And someone should. One viewer sent us a device from Menneckes that purported to do that. It was quite complicated and limited to 32 amps. And it’s somewhat expensive.
So we genned up a horribly simple little spoof circuit to accomplish basically the same thing, but without the square wave. It just uses a simple 12v to energize two Kilovac ANA200 contactors. Each contactor carries a single phase of the power. And so when they are NOT energized, there is NO power in the cable at all beyond the 12v signaling voltage which is provided by a 3 amp 12v supply inside the pump that feeds off a single phase of the input power.
The circuit is shown below.
This circuit is so blatantly simplified and NOT SAE J1772 2010 that I refer to it as J1771 1/2. The entire circuit is mounted on a 1 inch square of PCBoard material. The heart of it is an LM1458 operational amplifier we use as comparator. 12v is applied across a 5k potentiometer to ground. The wiper is adjusted for 6v and applied to the + (non inverting) input of the opamp. The same 12v is applied across a 1k resistor to the – or inverting input. The junction of the 1k resistor and the opamp input is tied to pin 4 of the J1772 connector – the copilot signal.
The output of the opamp switches a fairly sturdy MOSFET which is connected in series with the coil of a small relay. When energized, the relay switches 12v to the two phase contactors, energizing them to apply power to the car. It is somewhat important to tie the neutral pin of J1772 to the common or ground side of the 12v power supply.
In this way, the switch on the car, when closed, drops the voltage to 6v, the comparator output goes positive, the MOSFET turns on, and the relay switches on the contactors. We simply adjust the pot to trip at that point.
So we wind up with much of the safety and sturdiness of the J1772 spec, without the complexity. Eventually, someone WILL do a proper circuit for this with ground fault sensing. Better, use GFI circuit breakers in the panel.
A team of five or six engineering students from Imperial College in London, devised a plan to build an electric car and drive 26,000 kilometers down the Pan American highway from Anchorage Alaska to Urushaia at the southern tip of South America. They filmed this journey and we had ordered a copy when they completed the thing last November. We received it just last week and had actually forgotten we had ordered it as it was six months late in arriving. http://www.racinggreenendurance.com
The thing winds up as eight episodes on two DVD’s. It’s 19.99 British Pounds so about $30 before shipping but you have to see this. It is too comical to believe.
First, they built an open top SRO race car with a massive 50kw Thundersky battery pack and a 3.5 inch ground clearance to drive across the Pan American highway. Idiotic in concept from the get go. The tiny racing shock absorbers were sporting 1100 additional pounds of batteries. Engineering school apparently isn’t what it once was.
But their “mission” was to drive from one press event to another, touting how electric cars were finally here and practical for every day driving. Instead, they rather proved both graphically and dramatically that it takes a half a dozen recent engineering school grads to even keep an electric car rolling at all.
Never at any point in the journey did they pick up on the irony. They wrecked the car twice. It burst into flames several times. And they failed every piece of equipment in the car with the exception of the very sexy EVO motors they had. All four shock absorbers broke at various times in the journey. They burned up their chargers. They burned up their BMS quite frightfully and the DC-DC converter at one point. Almost everything we’ve ever destroyed here in the shop, they managed to tick off the list on the road. No matter how rain bedraggled and discouraged, there they would be at the next press event with the canned speech about how great the electric car was and how well adapted it was to all of this. I watched every minute enthralled.
They never really went into any useful detail on all these failures during the whole series. They would show some discouragement, vaguely describe what they think happened, and then seek the assistance of some Mexican or South American farmer to make the repairs.
One of things I did pick up very early in the first episode was that they used a pair of Rinehart Motion Systems PMX100 controllers to drive the pair of EVO motors, which were direct drive to each rear wheel. And they complained of severe Electro Magnetic Interference (EMI) problems which they initially solved by wrapping the UVW phase cables from the controller to the motor in aluminum foil. Eventually, they replaced the foil with shielded cable.
We had been suffering for months with some gnawing problems with the Mini Cooper. I drive it every day. But there is always a slight shudder on takeoff at low RPMS. Worse, Rinehart has finally implemented a proper brake potentiometer input to control regenerative braking. We use a hydraulic pressure transducer to produce this 0-5v signal and it appears to work quite well. But whenever we had it CONNECTED to the controller, whether using this braking mode or not, we get an over current or over voltage fault at about 3500 rpm and the controller shuts down. So we are stuck with brake light signal regen and have to leave the transducer disconnected to drive the car.
We had actually sent Rinehart one of these transducers. Their car ran fine and they were unable to reproduce the faults. Very puzzling.
After watching the episode, I somewhat loosely wrapped the phase cables in aluminum foil and tied them to ground. The faults disappeared and the shudder as well. Elated, I had Karl remove the aluminum foil and install some braided steel tubing over the cables. To do so, he had to disconnect the cables from the controller.
Each cable was terminated in a ferrule crimped around the strands of the cable and then this is locked in place with some hex bolts in the controller. Unfortunately, when you lock them in, it deforms the ferrule. When you disconnect them, the cable then comes out but the ferrule does not.
To reassemble, he simply stuck the cable back in and tightened it down. But the old ferrules were in the controller. And a strand of the center cable made ground. When we applied power, we blew up the controller.
While this is discouraging, everyone is a bit elated. Rinehart is happy to repair it, and we’re happy to send it off, because this nagging question seems to be solved.
The actual solution is of course the shielded high voltage cable. Unfortunately, this is horrendously expensive. But we think EMI may be the cause of a lot of things – like blown DC-DC converters, instrumentation ghosts, etc. It is particuarlly an issue with AC systems. But we are going to start using this cable anyway on ALL installations. Both battery and motor connections. It is manufactured by Champlain Cable Corporation EXRAD XLX shielded cable specifically for electric and hybrid vehicles. And basically after THIS months long drama, we are simply going to the use of that for everything regardless of expense.
Per usual, Chris Brune of Rinehart Motion Systems had brought up “noise” several times as a cause. He was sufficiently vague about it that I bullheadedly dismissed it each time. Just shoot me. Again, the main value YOU derive from these videos is from me screwing things up – AGAIN. I have on NUMEROUS occasions mentioned the EMI problem, particularly with regards to delicate BMS and instrumentation circuitry. I probably need to watch my own videos a bit. Too soon old. Too late smart. Spend the money on shielded cable and it won’t be a problem. No more welding cable at EVTV.
We received our Tremec TKO600 transmission from Mike Fortes of Fortes Parts Connection this week, along with a Ram 11 inch ceramic clutch and pressure plate, a lightweight aluminum flywheel with steel face plate insert, and hydraulic clutch slave cylinder. Mike has a lot of Cobra experience and has provided some serious adult supervision here on components for the Aptima Motors drive train. This tranny/clutch should handle up to 600 ft-lbs of torque on the eCobra.
Matt Hauber has returned to San Diego to begin his life as electric vehicle converter extraordinaire. I understand he’s starting out with an S10 pickup conversion there. He was a very talented and useful young man here at EVTV. His youthful enthusiasm made us all edgy. Or maybe envious. I’m uncertain which.
We welcome Carl Skircheck to the team. Carl actually had an early career in race cars in Detroit where he grew up and has managed a Chrysler parts department in recent years. Much of the mechanicals we find mysterious here at EVTV seem to come easily to Carl. With a couple of phone calls he has located some Silicon Oxide ceramic bearings for Speedster Part Duh which we are going to try. He is going to mount the Tremec in the Cobra this next week. He immediately brings to mind how embarassingly little Brain and I really know about automobiles and particuarly parts and mechanical assemblies. This may make the 3 lbs hammer entirely unnecessary here at the Motor Verks.