30 May 2008

Modification - the vacuum pump

A relatively long time ago, manufacturers started putting an assist on the brakes to make it easier to stop the heavier and heavier cars they were making. Now it is a standard "feature". Usually they use the vacuum generated by the engine. EVs don't have anything that naturally creates a vacuum so converters add some kind of pump. The converters of this car found a nice little box that contains a small pump, a vacuum switch, a muffler, and lots of sound killing foam. One thing with EVs is noise. With no engine roaring all the time you can hear everything your car does. So adding a pump that turns on and off randomly (mostly when you use the brakes) adds annoying noise. Thats why this pump is wrapped in foam.


There was no vacuum reservoir on the car, and I think I will need to add one. The pump is fairly small displacement and pressing the brake pedal it takes an extra second for the pump to catch up. Adding one will reduce the number of on-off cycles the pump makes. Not all cars need a vacuum assist either. It's possible to replace the master cylinder with one designed for no assist and still get the same performance. For now I'll keep the pump, mostly because it involves the least amount of work!


It took me quite some time to figure out where to put the pump. I trial fit it all over the motor bay thinking about how it will fit with the rest of the parts to go in there. Eventually I found a corner where it would fit perfectly, and the hose would have a clean path to the brake booster. So I bent some mild steel into a bracket and welded it together to hang the pump off of. This location really keeps it out of the way of everything, leaving me lots of room for other components. I added a plastic cable sheath to the wires and put a connector on the other end that plugs into a connector on the right side of the motor compartment. The plug connects to ground and through an existing fuse slot in the main fuse box which becomes hot when the key is switched to run.

15 May 2008

Investigate - motor controller

This motor controller has temperature limit, motor current limit, and low voltage shutoff settings set at the factory. It will handle 600 motor amps peak and 200 amps continuous. Maximum voltage is 144 nominal. Low voltage cutoff is XX. Temperature limit is XX.

I wanted to adjust the limits to better suit my setup, but there is no documentation on that anywhere! So what do I do? I open it up for a peek of course! Undoing all the screws around the case, it is siliconed closed. After prying it open, I find a large power board and a little control board inside. I'm an EE and interested in motor controllers, so I immediately identify most of whats going on. The large blue parts are computer grade aluminum electrolytic capacitors. I can identify the push-pull gate drivers, temperature sensor, current sensor, and various chips on the control board. I can see 3 multi-turn potentiometers used to fine tune adjustment points along the end of the control board, but there is no labeling as to what each does! There is another single turn pot farther in on the board that I only guess adjusts the switching frequency. I'll have to get out my multimeter and keep dreaming of an oscilloscope while I try to figure out what the pots adjust.

One complaint I have with these controllers (pretty much all of them except the Zillas) is they use the high voltage as a reference for any signal input/output. Sure it only takes 12V to enable the controller, but it's referenced to the high voltage negative! They should include built in isolators or relays so that the low voltage signal lines are isolated and easier to interface with. I've added my own relays to this controller. One for enable, and one for it's fault signal.

Modification - charge interlock

A problem that EVs have from time to time is when the driver forgets to unplug the car in the morning before leaving. This leaves an embarrassing tail trailing behind the car. The common fix to this is to add some kind of interlock so that the car wont 'start' with the cord attached. Originally this car had a relay hooked up so that if there was AC power present at the charger inputs a pair of wires would open circuit which would then disable the 'start' function. The problem with this method is what happens when the cord is in, but not plugged into the wall? You still have a tail!

My solution was to put a switch (this one is really overkill, but it was free) that opens when the door is open. Now if there is anything in the charge hole, the door can't close, and the switch remains open. The control circuit I'm designing will use this signal to turn on a dashboard indicator and prevent the car from going into start mode.

Fabricate - housing for contactor

The car had a contactor and two shunts mounted out in the open. The contactor (big object in the center of the photo) is a really heavy duty switch/relay that connects the motor controller to the battery pack. The shunts measure current flow to/from the battery pack. There are two shunts because the original conversion just had an analog current meter using the shunt along the top of the photo. Later a digital "e-meter" was added and that had it's own shunt (the little one on the right of the photo). The problem is its too easy to get dust and dirt inside the contacts of the contactor (the large opening on the left). Also all of the bolts in the photo are high voltage (~144VDC). Not something you want to accidentally touch or drop tools onto!

To solve these problems I want to put the contactor and one shunt (get rid of one) inside an plastic weatherproof enclosure. Again I brought home a scrap box from work that might just barely fit the parts.

I made some brackets and fit the e-meter shunt and the contactor in with some room for a control circuit. The big cable will come in from the battery negative and attach to the shunt on the left, then leave out the right to the controller negative. I'll also need to attach the charger between the shunt and contactor as well as add a precharge circuit across the contactor. A precharge circuit saves the contactor from switching the high voltage by slowly (a couple seconds) charging the controller before letting the contactor close.

I'm still working on the control circuits and trying to figure out where to put this box. Eventually I'd like to make a single box that takes both cables from the battery pack, contains the current sensor, two contactors, possibly the circuit breaker, and control circuitry and puts out two cables to the motor controller.

Modification - power steering

Originally the converters added a second motor just to drive the power steering pump. They used a nice 120V 3/4 horse power permanent magnet motor weighing about 25 lbs. There was a lighted switch on the dashboard that would enable the pump and switches setup so that it could turn on in first gear or reverse. The only function for this setup was to make it easier to turn the wheels when moving very slow or not at all. To me it was a waste to carry that much extra weight and use up that much space just to be able to turn the wheels with my little finger when the car is not moving. The balance of the car has been changed enough that the front end is lighter than it was stock (I think). Even with the PS turned off it was still pretty easy to turn the wheels when stopped. When the car was moving it was no different with the PS on or off. I decided to remove it!

After pulling out the motor and pump, I had the hoses left to deal with. I consulted the wisdom of the EVDL and just to keep it simple, I looped a small hose from out to in on the valve. The wheels still turn just fine, but I haven't tested it on the road yet.

Modification - the throttle

Originally the pot box (the little thing that translates the go pedal to the speed controller) was mounted on the main cluster. It had a very large spring attached and really occupied a large space. This particular pot box can be susceptible to dirt and water. With the control arm just hanging out in the air, it would be possible to bump it with the hood open. I want it in an enclosure and I want it tightened up.

So I brought home an old water proof enclosure from work that I though would be useful. Using some scrap aluminum I made a mounting plate to fit inside and hold the pot box. But I couldn't figure out where to put my nifty new box. It had to be at the end of the cable, and I wanted it out of the way of everything. After weeks of thinking and test fitting I decided the cable was just too long. So I took a different approach. First ask "where do I want the box?" and then figure out how to get the cable there. I quickly found some holes on the firewall that I could mount a plate to and now I have a nice flat surface to mount the box to.

Now I must fit the cable. Knowing it will have to be shortened I cut off the stopper on the end of the wire in the motor bay and pull it out of the cable. This wire has chunks of metal formed on the end to pull against and now I will have to figure out how to reattach one end (later). I used a cutoff tool to shorten the cable so it would route to the box. Then I also cut off the threaded adjuster end from the cable and reattached it to the new shorter cable.

To put a new metal chunk on the end of the wire I had an ingenious idea! I made up a little form from aluminum stock that would hold the wire and allow me to pour melted metal into the cavity. At first I was thinking of using aluminum, but then I remembered I had some lead shot (I don't know if it is pure lead or an alternitive). So I melted that up and poured it in. When I tried to remove my new plug, I couldn't get it out! Eventually I was trying to drill it out and the drill bit grabbed it and ended up mangling (and breaking) the wire! Now what?!

I have some aircraft cable sitting around, but it was too big to fit inside the throttle cable. Then I came across some extra bicycle brake cable from my last repair job. It was just a few tenths of a millimeter smaller than the original, and had finer strands. Thats a good thing because I'll be bending the cable tighter than it was originally. This time I cut my stopper form in half so I could just open it up to remove the cable. It worked perfectly! I had a nice metal chunk the same size and shape as the original on the end of my new wire. So I used the same method for the pedal end (after putting the wire into the cable of course). I needed to add a good spring in the system to help pull against the pedal, two springs are safer as well. The original had a very large spring about 8" by 1". I needed one to fit inside my enclosure. So I grabbed some 0.047" music wire that I had and wrapped it around some 1/4" stock in my lathe. Out came a perfect spring that makes the pedal feel just like would in a conventional car!

During testing it became apparent that I made the wire-sitcking-out-of-the-cable too short because when the pedal was pushed to the floor by my lovely assistant, it popped the metal stopper off the end! I didn't like this stopper idea anyway and decided to use a clamp instead. I would also need more wire coming out of the cable to prevent this wire-too-short problem.

I just moved the box farther to the right, which clears up more space on the left for me to mount something else when I think of it. This gave me about 6" of cable to trim down and easily fixed the cable-too-short issues. Now you can floor the pedal and the cable clamp just about touches the cable end. If you're wondering, the red and green wires still need spade connectors on them to connect to the micro switch that indicates when the throttle is all the way off.

I painted the bracket to prevent rust and blend it it. I was going to paint it black, but I noticed a can of copper color paint that matched the car pretty well! I think this is the final incarnation of the throttle assembly and I declare it done (pending the spade connectors)!

Modification - the gauges

I've had everything out of my car for a few months. Now that I'm getting more time and energy to work on it I have to start somewhere. A problem I had with the car was the dysfunctional instrument cluster. Its a full detail cluster: speed, tach, temperature, fuel, and a full compliment of lights. But the first converters only hooked up the basic lights and the speedometer. That left 3 out of 4 of the gauges just sitting there. I want to use the gauges in some useful way. First off is to figure out where the wires are and what type of gauges they are. I probed and traced and probed and found very little. I found the temperature wire in the motor bay, but the fuel wire eludes me, and the tach wire is nowhere to be found.

I decided to tackle the tachometer first. I ran a wire from the cluster connector behind the dash out to the motor bay. Then using a signal generator I found I need 2 pulses per revolution to drive the gauge. Now I need to think of something to generate the pulses. After thinking and researching I decide to use the tail shaft on the motor (which is used to drive the A/C compressor via a pulley and belt). What if I put two magnets on the back side of the pulley and a hall-effect sensor or reed switch? Sounds good, so I chuck up the pulley in my 8x14 lathe and prep it for magnets. Then I take some scrap plastic and make mounts to protect the magnets and provide more area for adhesive. Add in two powerful magnets and you have a recipe for success right? I tested it with a reed switch and it worked pretty well! I need to make a bracket to attach the sensor still. I am still figuring out the sensor portion. I had a reed switch, but I broke it.

I'd like to make a drive circuit for the temperature gauge so I can monitor the controller or motor temperature (not sure which one yet). Thats still a future project. Similarly I'd like the fuel gauge to show a relative power remaining, but thats a complicated issue for later.

parts removed - before the motor

Of course I forgot to mention that before the motor could be removed, I had to remove everything else! The original converters built a "bridge" that holds everything else (controller, fuse/relay board, contactor, shunt, vacuum pump, etc). It attaches at 3 points: the left and right shock mounts and a bolt into the firewall. After undoing these 3 bolts, and disconnecting all the wires going to the unit (lots of em!) all I had to do was lift it out. It's kinda handy to remove all the EV parts in one unit. Then again, it's a pain to disconnect everything too!

While this method is convenient, I don't like it. The contactor and shunt with high voltage are in the open collecting dirt. To get to the under layer with the contactor and shunt means removing the fuse/relay board, which is almost impossible without disconnecting all the wires.

My choice: reorganize all this stuff and make the motor bay less cluttered. Break the components into units and connect them with loomed wires and twist-lock connectors. Use waterproof enclosures for each unit to protect from water, dirt, and fingers.

Parts removed - the clutch and motor

I'm mostly done with my last semester of school. As the weather warms up I get an itch to tinker in the garage. Hey, lucky me there is an electric car in there that needs some work! My first order of business is to remove everything in the engine bay.





The clutch throwout bearing is going bad and makes a noise when the clutch is pressed. Plus I want to see how the adapter is put together. So using a pulley and my brothers help I remove the motor and adapter from the transmission.


The clutch plate is OK. It should be replaced since I have it out. But it's obvious that the clutch has seen more torque than it was intended for. My mechanic (father-in-law, he really was a mechanic!) says I should replace the whole thing with a better one. My wallet says nothing doing. I contemplate removing the clutch entirely for a long time.

In the end I just put it all back together and decide to not use the clutch if I can help it.

I spun up the motor a little on my workbench to check it out. Something is off balance a little bit because it vibrates some. My guess is the adapter extension shaft is the problem. But despite my best efforts and damage I could not remove the adapter plate or extension shaft. The original converters used this funny adapter for a good reason. The motor can't mount directly to the transmission because the front differential is in the way!

I don't know what to do about the vibration, so I'll ignore it for now.

I took photos of the commutator and brushes and asked the knowledgeable people on the EVDL about their condition. The response was they look fine so I put them back. To replace all 8 brushes every 100,000 miles might cost about $60.

14 May 2008

Spring - existing parts

Over the winter of 07-08 I tinkered with the car a few weekends when I had time and could brave my cold garage. Because money was tight I didn't plan on getting new batteries until mid-summer of 2008. In the mean time I decided to redo or at least inspect and clean all the parts. Here is what I found:















The contactor and shunts (two of them) were under the relay/fuse/rat-nest board. One shunt is for the e-meter and the other goes to the analog ammeter. On the right is the A/C pump (and vacuum pump and controller).
















The controller, Curtis pot-box, heater contactor, fuse blocks, power steering contactor, and DC-DC converter are visible in the left picture. The right picture shows the Todd 30 amp converter which takes the 144V pack voltage and makes 12-13 volts to charge/run the 12V system.
















The power steering pump was driven by a seperate 120VDC permanent magnet motor that would come on in 1st gear and reverse, if it was enabled by a switch on the dash board. The vacuum pump is inside the aluminum box on the right.
















The fuse is in the back battery box, and under the car between the rear quarter panel and the battery box is the boost transformer for the charger. Also notice the air shocks on the rear. They are adjustable by a valve by the charge hole.
















The charger is tucked into the side of the trunk space, and where the gas filler was is now a plug.

After that

After that, the semester picked up and we spent a bit less time with the car. I had been driving the car home and back about once a week (~3 miles each way). It needed to be charged at both ends.
We had come to the conclusion that the entire battery pack needed to be replaced. We didn't want to suggest that the school cough up the $1500 for a new battery pack just to let it sit uncared for and go bad again in a year. We couldn't use it much, we couldn't put much money in it (nobody else cared about the car). Eventually my schedule changed and I couldn't work on it anymore. So it returned to taking up space and collecting dust.
I bought a house farther away and had just two semesters of classes left. The spring of 2007 I noticed the car parked outside the high-bay and very dusty. The idea occurred to me that the school doesn't want to keep the car and I should offer to buy it. I started asking around and found the new guy in charge of facilities. He said the departments were talking about getting rid of the car! What luck! I said I want to buy it, he said he'd get back to me. Summer came, classes out, I love having my own house and garage!

When I get back to school in the fall I happily see that the car is still parked outside. I start inquiring again and I don't get much response. Then one day I get a letter in the mail inviting me to bid on the car. The school has to auction off all old equipment, they can't sell directly. I wait until a few days before the deadline and bid $30 because nobody else had bid yet. I win! I was the only bidder, and probably the only one who knew about it.

When I tried to get the title moved to me, the DMV tells me that I have to pay tax on the blue-book value because I payed less than $50 for the car, which turns out to be over $100. So I go give the school another $20, then $13 for the title.

My total cost so far: $63.

My brother towed me home and the car gets stored in my garage. I was not planning on having the car this soon. Money was very tight, I was stressed with work and school, and I had no time. So it sat there for months, but it was mine!

First drive

Here is a little driving video returning to the high-bay. We took it around the block, didn't want to go too far as we had no experience with the batteries or the instruments. (We had removed the hood to work on it, so you see some wires sticking up from our rats-nest wire job).

What a thrill! The EV grin was stuck on our faces for the next few days!

Our timing was perfect. The school homecoming parade would occur a week later. The ME chair got us signed up to drive the car in the parade. So we cleaned it up, gave it a little wash, made some posters and ta-da! we were ready for a parade!

We were positioned in the middle of the automotive school, with a muscle car on a trailer behind us and a import street racer in front. They had their muscle car running and revved it up occasionally. Nobody had any chance of hearing our motor spin! They were stealing the attention with their noise, so I started doing little burn outs every 100 feet or so. The car has low rolling resistance tires, and didnt so much burn out but the front tires would bounce and skip a bit. It worked and I got attention! Maybe a bit too much attention because the ME chair pulled up on his Segway to ask me not to ruin the tires. Oh well, the parade was over anyway!

Under the hood

I took a couple days perusing the drawings and documentation that came with the car. Then when I tried to trace out all the wires it didn't match up entirely. So I decided to reverse engineer it and make a drawing based on what was in there. Most of it was the same, but some things were of course changed and some added.















It looked pretty good. It was setup so that if the A/C was on it would run the motor at a low speed when you took your foot off the throttle. But it wouldnt "start". So we poked around and figured out what to do to make the system turn on the controller and contactor. Eventually we decided to simplify it. We didn't care much about A/C, so we re-wired the whole control board to just run the car.
Our efforts ended up looking more ratty than it started out, but now it would power up and spin the motor! The excitement to make the car move was climbing fast. Some of the instructors in the high-bay had come out to watch when they heard us celebrating our first spin-up. Whats next? Take it for a drive of course!

Batteries


It was sitting at a pack voltage of about 20 volts. First thing we tried was to start the charger up of course! It wouldn't do anything. Poking around we found the fuse was blown. Ordered one and when we got it (and a spare), it still wouldn't start! Our guess was the batteries were too low for the charger to startup properly so we took them all out, gave them a bath and then used a 12V charger to charge each one individually.





After a few days of charging, they were holding something of a charge. At this time we knew little about batteries and treated them like the car starting batteries we knew about and said any charge above 12V was good! We decided to repaint the battery boxes because they were corroding and causing pack to frame shorts. Just for good measure we put a vinyl liner (read used shower curtain) in the box also.

Now we were getting a good pack voltage and the main charger would turn on and buzz, which we assumed meant it was working. The voltage rose and the e-meter showed some charge current. After it charged for a while, we added watter to the batteries and turned to the rats nest under the hood.

Some history

To give some history to the car
It was converted by EcoElectric in Nevada in 1994 at the request of a private individual. The original documents indicate it had a Curtis 1221B controller, a different charger, and possibly sealed batteries. The owner lived in both Nevada and Idaho. At some point the controller, batteries, and charger were changed out.

The way it was when I got to it:
In September of 2004 I noticed the car in the school high-bay. After asking around I learned that it was donated to the school a few years prior. It was used by one group who tried to make a generator trailer for it, but were not successful and did some damage to the systems. I went and talked to the mechanical engineering chair about working on it with a ME friend of mine (I was in school for EE). He gave us full access and a small spending account!

This is what we started with:
















Yes, there are parking tickets on the window. The ME chair took care of those. So we got started checking it out and looking through the good documentation that was kept (except for the prior students).

12 May 2008

First post

As I'm working through updating my electric car, I think to myself that I should publish what I'm doing somehow. I take pictures of my modifications, so I should post them somewhere so that they might inspire someone else. I'll not update regularly, but when I get to it.