Certification!
Sorry I have been a bit slack in keeping you posted. I have been busy doing real work on the car.
And now, as of about 1 hour ago she is certified!
I own an official, legally certified electric car. Photos and videos etc to follow.
Every electric car requires a charger. It is the device that puts energy into the battery pack.
The best charger available for the least money is the EMW SmartCharge-10000 by Electric Motor Werks, which is a 10kW charger. It is rated to but out up to 60A, and up to 250V (not at the same time). Given that it can output 10kW continuous I should be able to charge my 19.6kWh battery pack completely in under two hours. In practice it will be longer, as the charging cycle is constant current and than constant voltage, meaning that the entire charge is not at 10kW. The current rating of the socket the charger is attached to is also important. If the socket is not rated to 60A a.c. output than the charging time will be greater.
The charger it self is open source, which is coolio. It is quite simple electrically. It is a mains rectifier and buck converter with a few extra bits for control, including an Arduino microcontroller board. Image 1 is the electrical schematic.
Image 1: Electrical Schematic of the EMW SC-10000 from Electric Motor Werks
The schematic is divided into two parts. The upper part contains the power stages. From left to right:
Fuse and inrush current limiting, ac rectification, input smothing capacitors, topside switch, freewheel diode (the lower IGBT is not used), inductor, output cap, reverse current protection diode, current sensor.
The two squares labelled ‘Hall’ are current sensors that are used to monitor the voltage on the high voltage rails.
The lower part contains the control circuits. From left to right (oh how I wish people’s economic views would make this transition :p ):
BJT arrangement to buffer PWM signal from the Arduino microcontroller, OpAmp of unknown function (something to do with the PWM), another BJT buffer for the PWM this time on the input to the IGBT gate driver chip, +-15V supply for gate driver, three RC filters for current and voltages in the power stage, 12V supply.
Underneath this there is a 5V supply, and below that some circuits relating to heat-sink temperature sensing and a heat-sink fan.
To the right the connections to the LCD unit (A pretty cool unit from 4D Systems. Easy to program and with nice vivid colours.) and the two control buttons.
On the left side there are various connections to the Arduino.
A reasonably good description of the design can be found on the EMotor Werks website. There are explanations of how the various subsystems work as well as PCB files and the like. A kit can be purchased from EMW for around 1000USD, or a completely assembled system for around 2000USD. I purchased a kit as I am arrogantly confident in my electrical assembly skills. I must say though that I think the design is a bit rough in its finish. The PCB could do with a bit of a rework to make it prettier and fix a few problems (which if I have the time I may do 
). Also some of the components were not well selected wrt their terminals – the input capacitors had PCB mounts where screw terminals would have been far superior.
All up though it is a very good design, and was simple to assemble. Also, Valery, the founder of EMW, seems more than willing to provide tech support, answer stupid questions, and help solve stupid problems.
Image 2: Assembled EMW charger
Image 3: Assembled EMW charger from above
Images 2 and 3 show the charger pretty much fully assembled. There are still things to go – I need to install the internal DC-DC that provides a 15V output directly from mains. This is not necessary, as you can run the charger by providing an external voltage input that is above about 13V, but it makes it a bit easier to use – it will work with only one power connection.
You can see from the images the the charger fits easily into the box. One potential improvement would be to optimise the casing and the components to fit well together and give the system a professional look.
Warning
Also it should be noted that the charger is not isolated. Theoretically if you touch the output you may provide a decent return path to the nearest power station which could be rather nasty. Adding an isolating transformer would be a good option. I’m not sure where to get one that can handle the power though, nor exactly what changes would be necessary to make the charger a forward converter (a buck converter but with a transformer in the middle).
Anyways, if you want a good charger head over to EMW. And just maybe you could contribute to the design in good ol’ open source fashion.
Significant Miscellaneous Progress
I have been doing quite a lot recently on the car. Most of it has been quite small, but together it is a lot of progress.
Throttle
The Soliton Controller takes an electrical signal as a throttle input. This signal determines the voltage and hence torque applied to the motor. The throttle box shown in image 1 converts the movement of the accelerator pedal to the desired electrical signal. It is quite a simple device. There is a hall effect sensor inside it that can detect as a piece of metal moves about. The cable from the accelerator pedal moves a lever arm which in turn rotates the sensor. The outputs a 0-5v signal that is proportional to the position. I have quite simply bolted it to the side of the engine bay in a place where the movement of the cable is pretty much in line with the movement of the lever.
Image 1: Hall Effect Throttle from EV Works
DC-DC Converter
To keep the 12v auxiliaries running, including the controller, a stable 12v electrical supply is needed. To minimise extra work I decided to keep as much of the original 12v system as possible. Because I removed the alternator a dc-dc converter that supplies around 14v from the 192v battery pack is necessary. Image two shows the converter above the gearbox and directly in front of the original heating unit. The two inlet pipes will either be removed or sealed depending on how I decided to supply cabin heat. The converter is connected to the same wire as the alternator was originally connected to.
Image 2: DC-DC Converter Positioned Below Heating Unit
Emergency Cut-off Switch
In New Zealand, and I think in most other places, an emergency cut-off switch that removes power to the motor is required. The Soliton has internal contactors (big relays) that it uses to connect/disconnect the battery pack. They are automatically off when the 12v supply is disconnected. As the 12v supply for the Soliton is coming directly from the ignition I decided to install the switch in series with that circuit. It is going to be attached to the side of the console to the right of the stereo. In the future I hope to position it right in the centre of the console but for now getting in there is quite difficult.
Image 3: Emergency Cut-Off Switch under Console
Soliton Controller
Image 4 shows the Soliton motor controller installed in the front of the engine bay. It is in the same position that the radiator used to occupy. Hopefully the airflow will keep it cool without requiring liquid cooling, but given that I desire to take the vehicle to Perth with me I guess the extra cooling may be required.
Image 4: Soliton in Front of Engine Bay
Front Motor Mount
The front motor mount is still unfinished (Sigh) but it is nearing completion. Images 5 and 6 show it from a couple of different angles. I have cut the two flanges to the correct size and will spot weld them on soon. Once they are spot welded into position I will remove the entire mount and get it professionally welded. I will then remove the excess material from the large front plate and soak it in oil to remove the rust. Later on I hope to paint it with anti-rust paint.
Image 5: Front Motor Mount from the Front
Image 6: Front Motor Mount from the Side
Boot Space for Main Battery Pack
I was thinking about the standard for battery restraint that states the restrain must be able to resist 20 times the weight of the battery pack in the forward direction if the batteries are positioned behind the passenger compartment. I figured that I can fit approximately 44 batteries in the boot space where the spare wheel used to be. This space has a rather solid cross member between it and the passenger compartment which should meet the strength requirements. Hopefully.
Image 7: Boot Space for Battery Pack
Misc
I have also been doing quite a bit of 12v wiring work. In the image below there are quite a few red wires visible, as well as blue insulation tape. The red wires provide various important signals to the controller:
12v supply
Brake Input
Motor Over temperature Signal
The blue insulation tape I’ve been using to cover old and now unused connections as well as trying to keep things a bit neater.
Image 8: Engine Bay Overview
I’ve also been working on assembling the 10kW charger. So far I have soldered up the two pcbs. My next step with the charger is to figure out how the main power components are meant to be connected together as well as arranged within the case and in relation to the huge heat sink. If anyone has any experience with power electronics and would know how to test the charger when it is done feel free to give me a shout.
Getting Sherlock on Faraday
Today I have spent quite a lot of time figuring out how the MG’s original electrical system works and restoring it to functionality. A wiring diagram is below. You can see that the black connection from the positive rail of the batteries goes solely to the starter motor solenoid. Having taken the entire ICE system out, including the starter motor, the 12V supply was disconnected from the starter motor and the entire system beyond it. On my MG there are two brown wires that connect to the starter motor. These cables go to the ignition switch and to the alternator. To get the auxiliary systems working again I needed to connect the black cable directly to both of the brown cables. I am thinking that I should connect the dc/dc 15V output to the alternator plug as the dc/dc fulfills the same function as the alternator.
Image 1: 1972 MGB GT Original Wiring Diagram. Click to enlarge.
Hopefully that is actually all I will need to do to get the 12V system working properly. We’ll see.
Advanced Auto Wire is a company (in the USA?) that supplies electrical wiring etc for old British cars such as Triumphs and MGs. If you want a wiring diagram for your MGB here is a set of colour coded diagrams Advanced Auto Wire put together for pretty much all models of MGB. It is where I got my wiring diagram from.
Christmas..
I have received two major packages in the last few day. On Sunday I received a box containing an Evnetics Soliton Jr., a TBS expert pro + paraphernalia, and a 15v DC/DC converter. On Monday I received a box containing a EMotorWerks 10kW charger kit which I will assemble in the next few weeks.
Image 1: Box containing Soliton etc.
Image 2: EMotorWerks 10kW Charger Kit.
I’ve also started creating the front motor mount which can be seen in image 3 as well as have been doing positioning of the batteries in the boot (image 4). The motor mount is made out of 5mm mild steel. This will be eminently strong enough but also quite heavy. I will most likely eventually replace it with a nice aluminium piece when I redo the motor adapter et al in the future.
Image 3: Front Motor Mount with Soliton Jr in Foreground.
The standard for converted electric vehicles in New Zealand requires that batteries behind the passenger compartment are secured against a load 20x the weight of the batteries in the forward direction which makes the car safer in the case of an accident. I wouldn’t want to be squished by 150kg of batteries from behind. That would be most unpleasant.
44 batteries should fit snugly in the boot space where the spare wheel was. This space has a major structural beam right in front of it which should provide the strength necessary to secure the batteries in an accident – the standard actually says they will take original structural members into account. Hopefully putting the batteries here will make my life easier.
Image 4: Polystyrene ‘Batteries’ in Boot.
Trial Motor Installation + Bureaucracy
The adapter that goes between the motor and the gearbox is approximately finished. It requires finishing (to the surface etc) so that it looks nice. Also the threaded rod currently in use is only mild steel – I’ll replace them with some kind of high tensile steel later on. The coupling is also in a similar state of pretty much finished – the only thing left to do is skim the surface to make it look nice, and take it, along with a new clutch and the flywheel etc to a place to be balanced so that it all works nicely. I’ll do that later…
So, after a very intense Friday in the workshop, on Saturday I assembled the motor and adapter etc and tried installing it in the mgb gt.
Image 1: Motor Adapter Fitted to Electric Motor.
The motor adapter is actually pretty haxor. The red plate is the original adapter plate from between the gearbox and engine. To hold the motor the correct distance from the plate there is a piece of slightly machined stainless steel pipe. The is an evil piece of material as it jumped out of both the lathe and the mill and tried to kill me! I think I will avoid SS for the foreseeable future – mild steel and aluminium are so much more pleasant to work with.
It’s all held together with four threaded rods that go between the plate and the motor. I need to hold the plate on with lock nuts. That will happen in the future.
Image 2: Electric Motor Installed in Engine Bay.
The motor and adapter all fit in the car! The first upgrade is going to be one of two possibilities.
1) The best option – get a new motor with a flange as an integral part of the armature shaft so that said flange bolts straight on to the flywheel and the adapter plate bolts on to the front of the motor.
2) The more likely option – shorten both the first motion shaft and the motor output shaft and make completely new coupling, flywheel and adapter out of a decent aluminium alloy.
Image 3: Very Close Fit for Electric Motor.
Bureaucracy
Thanks to Gav for providing me with details of the electric vehicle standards and the like for New Zealand. Usually NZ is pretty bureaucracy free, but some of the details of this standard are more stupid than a land war in Asia, or invading Russia during winter. I guess they just hate electric vehicles, and would prefer me to spend my weekends drinking than doing something productive. Knaves all of them.
About two thirds of the way down on this page are links to all the relevant standards when converting a car to electric in NZ. Here Gav actually explains a bit about the inspection process etc: hyperlink to interwebsite .
The Coupling
I was meant to introduce you to the motor a few days ago but I was busy. As such you will get a formal introduction in the nearish future. For now assume that you are on speaking terms. You have met in passing after all, in the first post.
Image 1 is the schematic for the motor. See the shaft on the right? It is the drive-end shaft – the one that is used to ultimately apply torque to the wheels. To get to the wheels the shaft needs to be rigidly connected to the flywheel/clutch assembly (which you will most likely see later). To do this I designed a coupling. One end would attach to the shaft with a cap-screw and a key. The other end will attach to the flywheel in a very similar way to how the crankshaft on the ICE attached to the flywheel.
Image 1: Engineering Drawing of Netgain Warp 9.
In images 2 and 3 you can see my "engineering drawing" of the coupling. It's very oily as it has spent the last few days in the workshop. In the close up you can easily see the first motion shaft of the gearbox and the (unlabeled) output shaft of the motor. Probably the most important distance is the little "4 mm" up in the top left corner. This is the distance from the inside edge of the bellhousing to the end of the coupling. If this distance is not right the clutch will not engage/disengage properly and the driver will be miserable and wretched.
Image 2: Engineering Drawing of Shaft Coupling.
Image 3: Close up of Engineering Drawing of Shaft Coupling.
If you click on image 3 you can get a good close up of the cutting fluid and coolant stains on the drawing. You can also see the approximate dimensions of the coupling. It ended up being 90 long, rather the the 77 that is kinda shown in the picture. Note that the 40 is the length of the shaft and not the length of the hole the shaft fits in.
I have spent about three reasonably solid days making this piece now. It’s not yet complete, but it is drawing there. Things not shown in the drawing include the internal bush that goes over the first motion shaft. This bush is made out of sintered bronze, or oilite. Also not shown are the two location studs or the bolt holes. Sadly I have had to use 7/16 bolts as Blacks Fasteners could not supply me with 11 or 11.5 bolts. Damn imperial units :/ Urk, why does anyone use them!!
The next two images show the coupling in its near complete stage. The only things that need to be done are cutting the keyway and inserting the bush.
Image 4: Shaft Coupling.
Image 5: Top Down on Shaft Coupling.
The bolt holes and location studs can be easily seen in image 5. Also visible is the neck in the centre of the coupling. A washer will press against this neck allowing a small cap-screw to screw into the centre of the motor shaft.
The Worry
As I said above, I have spent a few days working on this coupling. Days of oft significant worry. Two 9.5 drill bits were destroyed while drilling the bolt holes. Both was destroyed when it became jammed in the hole, and both took much effort to remove. That is why there is a bit of cosmetic damage to the different surfaces. The coupling is made of a piece of medium hardness steel (salvaged hydraulic ram)that I got gratis. I was doing some measurements of the engine bay and the motor+coupling etc and came to realise that there was going to be the steering cross member in the way of the end of the motor! What a fail! Anyways, after much measurement, and lifting the motor into the engine bay with the coupling et al, I figured that I may just have about a centimetre of leeway. Relief. Now I can sleep easy, and wait for the next problem to pounce on me and drag me back to the slough of despond.
P.S. At least one split-infinitive above
