Update time again - plenty going on in the garage during spring break.
It was revealed to me (earlier in the thread) that the EV-1 was designed with a unique braking system. Electric-hydraulic in the front, and electric only (brake by wire) in the rear. This would have been less of an issue if GM had not removed the Brake and Traction Control Module (BTCM) before donation. But, here we are. Looking around online showed that the rear brake was part of the 12 V (auxiliary battery) system, so we wanted to try and actuate them and see what happened. I worked with Eric from EVA/DC to inspect the rear brakes.
They turned out to be electric drum brakes. There were a couple of wire bundles leading from the rear of the backing plate, up into the trunk, and down to the driver's kick panel.
Here's the plug that used to go into the BTCM, right next to the parking brake button:
By testing for electrical continuity between the plug terminals, we were able to confirm which wires went to which rear wheel (driver's or passenger's).
Putting 12 V across the proper leads engaged the parking brake.
A couple of notes about these brakes - they are an odd size, I think 226 mm. Definitely metric. The bolt circle for the wheel is also 5X100 mm. Finally, the drums themselves are aluminum, meaning that although the brake shoes contacted the drum's inner ~226 mm surface, they were very thick - measuring about 270 mm on the outer surface. This is very thick relative to cast iron drums. GM did all this (electric instead of pneumatic, aluminum instead of cast iron) to save about 4 kg on a 1400 kg car. Very dumb idea if you ask me (not worth it). At any rate, this means that the wheels, which have about 12" of free diameter inside the rims, could have fit a bigger drum and achieved better stopping power.
So, we were able to apply the parking brakes using 12 V on each side, and to lock the brake by putting 12 V momentarily across two other wire pairs also going to each hub connector. But, attempts to do gradual brake movement by applying a range of lower voltages didn't pan out. I therefore decided to order a couple of electric trailer drum brakes
(with a controller
) that are 10" in size. The trick was finding a drum (cast iron this time) that fit the small bolt pattern for the existing wheel. Searching some catalogs online, I found that the 1966 Plymouth Barracuda
used front drum brakes that were 10" and had a bolt circle of 5x4", which is just about the same as 5x100 mm. Raybestos still makes the drums, thank goodness. Two are on the way - should be able to check things out by the end of the month.
In other news, the high voltage system is complete. I made PVC and pine housings for the two modules I assembled myself, and placed them into the tray. Everything was braced, secured, and tied down. This picture was taken before re-installing the rear tray cover, which is where I mounted the contactor and fuse. Note the office chair wheels bolted on the bottom so I can roll the tray around.
Next was connecting them all in series using 4/0 cable and hammer-crimped lugs. I had to bend some of the lugs to fit them in. In the next image you can see the contactor and fuse mounted to the tray frame above the capacitors at the lower right.
Here's the lug connector at the ultimate positive terminal. The one at the ultimate negative is the same kind. There are two set screw connections, as one line (1/0 in size) goes to the motor inverter/controller, and the other line (4/0) comes in from the generator's rectifier.
I wanted to power up the caps in order to see if anything exploded. Here is the setup: (bottom right) digital voltmeter, running on 120 VAC input and measuring total capacitor voltage, (bottom left) capacitor leads (1/0) supported on a PVC plate. The clamps go to the (center left) rectifier, which has its output measured by the (center right) clamp multimeter. The rectifier is fed AC from the (top left) step-up transformer, which acts as a doubler. The transformer is fed by the (top center) 110 V variable transformer, with boost coils. It can put out 150 VAC at 100% from the 125 VAC line voltage from the wall outlet. Current-wise, it's the weak link in the system. I used the clamp-on meter to maintain a charging current of less than 10 A.
When the variac was at 50%, the capacitors stopped charging and settled at 218 V. This is enough to light up the inverter/controller, when the time comes.
At 85%, I got to 350 V. That was enough for me!
For discharging, I used my trusty heater element. I had to pulse it on and off since the input voltage was over 230 V at first. In the future, I'll use a 480 V, 2000 W quartz heater tube (arrived today). I connected the element's leads to two PVC tubes with ring clamps to contact the capacitor leads. This kept me safe from becoming a path to ground. I opened the contactor to knock out the pack's voltage, touched the wires to the leads, then closed the contactor to start the drain. It took about 30 minutes to get down to a voltage safe enough to short the leads by hand.
In preparation for spinning the wheels for the first time, I made up a control panel. It fits nicely into the place where the cupholders were! The regen brake will be hand actuated.
Then I cleaned the dang place up!
Tomorrow I'll wire all the switches, lamps, and buttons on the control panel to a terminal strip, and then that to the controller, etc. Motor spin-up is scheduled for March 26. Keep your fingers crossed.