Nerdy Technical Details

Spotted a couple of errors in the new schematics as soon as I posted them:

Note: do not read this post if you are not a nerd. Your brain will lock up.

The "Pack Neg" prescaler signal gets moved from the battery side of the Link 10 500A shunt to the Load side. Nothing but the most negative battery post should be on the battery side of the shunt.

The BRB ("Big Red Button") switch needs to be placed in series with the coil of the negative EV200 contactor that's activated by Keyswitch ON. You gotta have a BRB that you can slap if something starts to smoke while you're driving.

The SPST switch in series with the Hairball +14v SLI input is the "sleep" switch, to be placed somewhere near the Hairball in the engine compartment. This is so that the SLI battery can be spared the 70-80 milliamp drain when the car sits for extended periods of time.

Which brings me to a general description of the schematics:

Page 1

Page 1 is the high voltage direct current system. The 12 AGM batteries in series make up the "traction pack", i.e. the pack of batteries that provides the motive power to the traction motor attached to the vehicle transaxle. The voltage across the pack is completely isolated from the metal body of the car. Between the 4-battery sub-pack in the spare tire well and the 8-battery sub-pack behind the back seat there is a 400A 160V Hienemann DC circuit breaker. (This thing is about the size of a loaf of bread.) The breaker is used to "turn off" the traction pack for safety purposes, like battery maintenence or (shudder) flame eruption.

Both the positive side and the negative side of the traction pack have a Kilovac contactor to connect the pack to the rest of the system. When the car is off (no key), both contactors are open and the pack is connected to nothing. When the key is ON, the negative contactor closes. When the key is moved to START, the Hairball will close the positive contactor, making the system "live" (assuming it doesn't detect a problem condition somewhere - remember, it has a computer inside). With both contactors closed, if you step on the "go" pedal, the motor will turn and the car will move. Assuming the wheels are on the ground, of course. Notice how we do not call it the "gas" pedal anymore. That would be sacrilege.

The Zilla controller, which is controlled by the Hairball, is the high-power valve that gives traction pack energy to the traction motor. A little to go slow, or a lot to go fast, or anything in between.

The DC-DC converter takes the place of the alternator in a regular gas-powered car. Something has to keep the 12v low voltage system (lights, turn signals, etc.) battery charged up. The DC-DC converter "steals" a small percentage of the traction pack's power to keep the 12v battery charged up.

The PFC-20 is the battery charger for the traction pack. It is a very high power (e.g. dims your house lights) charger that jams large currents into the high-voltage pack after you drive, to restore the car's motive energy.

Page 2

These are the dashboard meters for displaying important system parameters.

The Temperature display allows selection of multiple temperature monitoring points in the system. Really really hot temperatures in any of these places means that some part of the system has failed. Really cold temperatures for the batteries means you're not going to get very far.

The Motor Amps display shows the motor amps as detected by the Hall Effect sensor between the Zilla and the motor. The amperage can get really high if you are a) going up hill, b) going really fast, c) starting in the wrong gear, or d) trying to race a Ferrari. It's okay to pull really high amperage for a little while, but if you keep it high for too long the brushes in the motor will overheat. Not only that, your range will be greatly reduced. Racing a really fast Ferrari uphill in the wrong gear is to be avoided.

The Aux Battery Volts display lets you keep an eye on the low voltage system battery. It should be at a decent level all the time while the car is running, since the DC-DC converter keeps it charged. If this ever starts to drop below 12 volts, that means your DC-DC converter has stopped working for some reason. Hairballs hate low voltage and will shut down the traction motor if this falls too low. Not good if you are driving on a cold rainy night with the wipers going and the headlights on and the defrosters running.

The Motor RPM display shows the RPM of the motor (doih!). Big DC motors have an RPM limit of about 6000 RPM. If you go over that, the commutators tend to explode from centrifugal force. In the EV community, they call it "splode". As in, "yesterday I hit 8000 RPM and sploded my motor". My motor will have an RPM sensor from the motor to the Hairball, so the Zilla will never make the motor go over the configured maximum RPM. However, if you go downhill in first gear on the freeway, you can over-rev the motor and the poor Hairball won't be able to do anything about it, so you need to see the RPMs. Knowing the RPMs will also help you to figure out your most economical driving habits. Or least.

Page 3

The Zilla is water-cooled. There is a radiator with two 12v fans on it, and a pump for the coolant.

The motor brushes are force-cooled by a Dayton 176 CFM blower, so you can burn rubber and kill your range showing off your tremendous torque like a testosterone-drunk teenager without burning up your motor brushes. There is a block of low-ohm power resistors that are in series with the blower, to provide a slow speed, for when you tone down your childish urges to drag race because your wife is in the car with you. There is a relay to bypass the resistors for high speed, but it does get kind of loud.

Page 4

These are the system status LEDs. The contactors have auxillary contacts that are used to show that the contactors are closed. Good basic system status info. The Hairball drives the Battery LED to let you know if you are running out of juice. It also drives the Check Engine LED to let you know there is some trouble like charger door open or controller getting too hot. The high beam, rear defroster, and turn signal LEDs are just like in a normal car.

The Super Beetle speedometer has six light bulb indicators that I can use for these. Wait, there's seven LEDs - I think I'll put the defroster LED by the defroster switch. I found SuperBright LED holders that fit *perfectly* in the speedometer indicator holes.

The Valet Mode switch is there to tell the Hairball to use a secondary set of configuration parameters (called "Valet mode"). You can set up normal mode to allow high performance driving and Valet mode to make the car nice and slow, for example when you take your wife out for sushi and hand the keys over to some sneaky looking valet. Or when you let your 16 year old daughter take the car to a friend's house. You're supposed to hide this switch.

There's also a switch to put the motor blower in high speed mode, and switches to turn on the defrosters.

Page 5

This is a page to remind me what wires I need to run between the front and the back of the car.

Page 6

Car lights. Normal stuff. All of the filament bulbs have been replaced with LED bulbs, except the headlights.

Page 7

More lights. More normal stuff. The charger door (which used to be the gas cap door) is going to have a switch to tell the Hairball whether it's closed or open. If it's open, the Hairball will prevent the positive contactor from closing and will flash the Check Engine LED. This is so you don't drive away with the extension cord still plugged in.

Page 8

This is the Hairball. This is the computer that monitors important system parameters to make sure it is safe to power up the positive contactor, and translates the position of the hall-effect "go" pedal into Zilla-regulated power to the motor. It also has a serial port that spews out serial data that you can route to a laptop or carputer for performance analysis or parameter display. Why is it called "Hairball"? Well, Zillas and Hairballs were first used by the electric drag race community, who gave nicknames to the components, and the nicknames stuck. The Hairball is a little box that has a dozen or two wires coming out of it, so it looks like a hairball. That's my theory and I'm stickin' to it.

Page 9

This is the Xantrex Link 10. This computerized panel meter watches the 500A shunt at the traction pack negative side over there on Page 1. It keeps track of how much electrical energy goes in and out of the traction pack. It's on all the time, so it can watch electrical usage while driving, and electrical restoration while charging. It acts as a "fuel gauge". It was originally intended for the electrical systems on boats, but it found a use in electric cars too.

The meter also needs to know what the traction pack voltage is. Since it was designed for 12 or 24 volt systems, a prescaler is needed to scale down the 144 volts of the traction pack. The meter is powered by the 12v low voltage system battery. Unfortunately the negative side of the low voltage system is internally tied to the negative side of the traction pack monitor, so if you just connected up the Link 10 to the low voltage system battery, the traction pack negative would be tied to the metal car body. That would defeat the isolation. So there is an isolated DC-DC converter that is powered by the low voltage system battery, and powers the Link 10. Problem solved.

Page 10

This page shows the defrosters and the charging system fans. The rear defroster is the stock rear window heating element, and the front defroster is going to be a small 12v motor home heater. The charging system fans are fans that are powered by the AC power charging input and only run while the car is charging. This is to keep air moving around the batteries and the charger to prevent hot spots while charging. I thought about using 110VAC muffin fans, but those things are like three times as heavy as 12v DC fans. Hence the small 12v power supply.

New Schematics

I've created new schematics. The older schematics were preliminary and didn't include the wiring for the lights and other primary car systems. Besides, the 30-day trial of my schematic capture software expired :)

Paint Shop --> Upholstery Shop

Took some time off this morning. Drove to the body & paint shop with the towing gear, grabbed the bug, and drove it to the upholstery shop. The guys at the shop got pretty excited when I mentioned that this was going to be an electric car. The owner of the shop said that he really wanted to be involved with such a project, and he would do an especially good job. He's done a bunch of VW's!

About the car: I had been watching car colors for months, and the one I really liked was this blue metallic on Toyota trucks. One of the A/C contractors here at work had one, so I approached him one day as he was unloading stuff, and asked him if I could get the paint code off of his door jamb sticker. That's what I told the body shop to use.

I chose Ron Waters Body & Paint in Chatsworth , and Sammy the paint man there did a great job. All of the chrome trim was removed and filled in, as were the fresh air box louvres and rear quarter window vents. Most importantly, the exhaust pipe cutouts were filled in! Won't be needing those anymore.

There was a motorcycle art shop in the same alley. Ed the artist put ghost lightning bolts down the sides of the car. They fade in and out as the light changes. Cool, huh.

You may notice that the car looks pretty high on the suspension. It weighs almost nothing at the moment. When I backed my truck up to put the tow bar on the hitch ball, I was about a foot off to the side. I picked up the front end of the bug and moved it over. Light weight == good.

p.s. sad day yesterday, we put our doggy to sleep. She was almost 15 years old. RIP Jenny.