Getting Closer
I have been spending the last six weeks working on all kinds of small issues. I needed to make the mounting hardware for all the peripheral components. This includes the radiator/fan cooling unit, the water reservoirs, the water pumps, the vacuum pump and vacuum reservoir and the DC/DC converter. The mounting hardware takes a lot of time because it has to first be designed, then machined and then painted. I also made some mounting hardware to mount the Brusa charger in the spare tire wheel well in the trunk. The Delphi DC/DC converter proved to be a problem mounting because of the cooling lines. The converter has 3/4" connections that required a hose that was more than an inch in diameter to be uses. A hose that big does not bend with a tight radius so I had to adjust the position of the converter to account for that stiff hose. I also had to get some adapters to go from 3/4" hose to AN8. In addition to the mounting hardware I also have been working on wiring all the pumps and cooling fan. These all go through a new fuse box that I setup that will run off the DC/DC converter. Other mechanical issues I have been working on are the brakes. The front brakes got new rotors, calipers and pads and I purchased a upgrade kit for the rear brakes to convert them from drum to disk. The installation of that kit went very well, although removing the left rear wheel hub was quite challenging and required a 5-ton hydraulic puller to break it loose. It probably has never been removed in the car's lifetime. The upgrade kit included some very well written instructions and all the hardware necessary for the conversion, including new hubs, new rotors, new calipers and new brake pads. A link to the brake kit vendor is here (Aardvark Racing). Other work on the brakes included restoring the vacuum booster unit and master cylinder. The vacuum booster was in very bad shape - rusted and paint peeling. So I removed it, wire brushed all the old paint and rust and repainted it. I also rebuilt the master cylinder. I am still amazed that I can get brand new parts (albeit 30 years old) from the BMW dealer. The master cylinder repair kit , the seals and bolts and a new brake fluid reservoir were all available. Some of the parts came from Germany.
On the electric vehicle front I started placing batteries in the battery boxes. I started with the trunk box first. This box is mounted on some sliding rails that allow the box to be slid forward for loading and testing batteries and then slid back and locked in place during vehicle operation. The box design was detailed in a blog and video eariler this year (see below: BMS Respin and Battery Box Mounting). The batteries in that box weigh 254 lbs and I wanted to make sure the rail system worked. I coated the rails with a dry fluro lubricant to help with the sliding. The system worked just as planned and all the batteries were loaded without any issue. Next step is to strap them all together and connect the battery cables. I finished the work on rear seat battery boxes which included sealing and securely attaching the boxes to the seat deck. Batteries were loaded in those boxes, but not strapped up. I also started to work on the wiring for the BMS and battery heaters. Next step will be to strap up all the batteries and finish the peripheral wiring.
Speaking of the BMS I also have been working another version of the BMS board. The new version has a circuit designed to measure the battery current with an external shunt. The board works exactly the same as the earlier version with only difference being the pinout on the connector. To accommodate the shunt connections I had to make one common connection for the thermistor reference line. All the thermistors are referenced to a current-limited +5VDC. The two designs of the BMS boards give people an option to either use the CAB300 flux gate sensor or a current shunt. The flux gate sensor has the advantage of no break in the battery cable. The current shunt has the advantage of higher accuracy.
A video of all this work can be seen here.
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