This summer there have been a lot of distractions from working on the car although I have been working on the car when I am not doing anything else. And I have been taking a day off of work here and there to work on the car. What I struggled with was finishing the brake job. In the last blog I talked about the upgrade of the braking system. That upgrade took longer than it should because of various problems. What really stalled me was installing the brake pressure transducer. I had a really hard time coming up with the fittings to adapt the brake pressure transducer to the brake system. The pressure transducer is used the tell the GEVCU to apply regen torque when the brakes are engaged. The problem I ran into is that BMW uses a very special flare on the end of the brake tubing. It is called a bubble flare or convex flare. Although many places make adapter fittings I could not find exactly what I needed. The main problem is the brake transducer came with 1/8" NPT and it has to be mounted on in a tee in the brake line. That meant I had to adapt 1/8"NPT to convex flare. I could not find fittings of the proper sex for the setup I was trying to use. After several tries I finally got all the correct fittings. I had to use a custom made stainless steel braided brake line to accommodate the placement of the transducer and to adapt it to the braking system. Related to the braking system is the clutch slave cylinder. I found I had to replace the slave cylinder and that turned into another big job. The slave cylinder cannot be bled while mounted on the transmission. BMW put the bleed screw on the bottom of the cylinder so the slave cylinder had to be removed and held in a special fixture to be bled. That had to be done first before bleeding the main braking system. I used a pressure bleeder to finish the job.
On the Electrical Vehicle front I now have nearly all the high voltage and low voltage wiring done. The high voltage wiring required the completion of the secondary contactor box that controls high voltage to the PTC heater in the car and the box heaters in the battery boxes. I still have figure out what to do with the thermistor wires coming from the battery box heaters. I don't need precise heating control and the heaters are somewhat self limiting in the amount of heat given off. I also have temperature monitoring in each battery pack via the BMS. The temperature measurement is really only required to determine if the batteries are too cold to charge. That normally will not be an issue for me because my habit with the Leaf is to put it on the charger as soon as I get home. If the batteries were cold from the car sitting in the parking lot all day they will warm up by the time I drive home. But it was a lot easier to add the heaters in the boxes before the batteries were installed, just in case I need to heat the batteries
I also got all the wiring connections completed for the BMS and made up the harness connector for the Cinch enclosure. I really like the Cinch enclosure because of the design and the very strong sealing mechanism. But the harness connectors are harder to assemble than Ampseal. I did not think that was possible. It took me several tries to get all 18 wires inserted into the harness header. Those connectors are supposed to be able to use with 26GA wire. I have 22GA and I really struggled getting those wires in the harness header. That size wire is used for the BMS as a safety feature (no fuses required, if a short occurs the wire will just melt and open the short). I did finally get a completed header assembly and was able to test the BMS. All temperatures and voltages were reading correctly although VBAT2 for the second battery segment had to be negated to read correctly. That means for the ADC the voltage was inverted. I reviewed the layout of the BMS and found there was an issue with the VBAT2 measurement circuit. I came up with a rework on the board that was fairly simple and it worked to fix the measurement problem. I had Collin Kidder send me his board to apply the same rework.
The last major bit of low voltage wiring needed is connecting the GEVCU to the car. I originally thought I would do that connection after I got the engine and DMOC back in the car because I plan to mount the GEVCU to the side of the DMOC. Having the engine out of the engine bay has worked really well to do the wiring because I can climb into the engine bay to work.
Hopefully in the next blog I post I can announce driving the car under electric power. The last time it was on the street as an ICE mobile was November 2013. If I get it rolling soon this conversion will be completed before two years are up.
A video of all this work can be seen here.