The blog for conversion of vintage BMW 3.0 CS coupes to Tesla powered electric vehicles
Tying up Loose Ends
Get link
Facebook
Twitter
Pinterest
Email
Other Apps
-
Almost all of the EV conversion work is now done. A few of the things recently taken care of:
On the test drive the brake pedal went to the floor. This was because the pedal itself rotated on the pivot point. I thought it was secured at the factory and all pivoting happened at the pivot tube but I was wrong so had to TIG weld the pedal to the pivot.
Welding the brake pedal to the pivot
This pressed fit from the BMW factory does not prevent rotation
All the cooling lines and hoses and pumps and sensors are all hooked up now. There are two separate cooling loops -- one for the batteries and another for the motor, inverter, onboard charger, and DC/DC converter. Each has its own pump and temp sensor for turning on the fan at different temps.
Brett filling one of the radiators with distilled water (we run a 50:50 mix). It is not easy but it is possible.
Connecting all the lines and hoses for cooling
The water pumps are located below the headlights and the hoses come through the inner fender apron
Fan controllers and water pump
After all the concern about coolant flow, everything came together really nicely. The coolant gets all the way to the rear batteries and flows quite well, even without any swirl pots or expansion tanks. It is a tight fit to open the radiator caps and fill the system but everything is low pressure and temp compared to a gas-engine car so it should be "fill and forget".
I programmed the battery management system and everything looks good. I have nicely balanced cells, good temp readings from the 20 battery thermistors, etc.
I verified all the BMS wiring manually for cell tap voltages and thermistor resistance
All the battery inlet and outlet coolant temperatures
BMS state
Live cell voltages. Note that the cells are well balanced
The front battery box was a fit exposed to speed bumps and stuff so I built a skid plate out of aluminum to protect it. There are thin steel brackets holding it in place that can collapse to absorb energy if necessary.
Skid plate protects the batteries
Really, the car is basically done. Just HVAC, the touch screen, a tunnel cover (mocked in cardboard in photo), and a some small wiring cleanup.
As you probably know, I'm not converting just one BMW 3.0 CS coupe to Tesla power but two. One for me and one for my son-in-law, Alex. In fact, I'm involved in a third project for a customer as well. Brett Perkins at P3 Conversions is handling that build and I just consult a bit but I thought it would be interesting to compare how each project has tackled similar problems in different ways.
There are 350 DC volts of Telsa LiIon batteries in my car but I need a 12 volt source to kick off the electronics that energize all the complex systems such as the precharge controller and traction contactors. Therefore, I use a small LiIon 12v battery designed for a motorcycle. The problem is, I keep some things, like my Raspberry Pi gauge computer constantly running so that everything works instantly at the turn of the key and that drains the little 30 Ah battery pretty quickly, like in a day or two.
As I've mentioned before, my CSE project has taken a backseat to finishing the first CSE for my son-in-law. That car (I'll call it the Silver CSE from here on, versus my Blue CSE) was started by Paul Dexter and was the initial inspiration for my car. It was on the road as a full Tesla-powered EV, albeit in primer, for most of 2021. In late 2021 my son-in-law purchased the car from Paul with the promise of having me finish it. Sizzle Reel - click to view
