April Solar Car Update
The Pink Skies team has made lots of progress since the last update. The first step Kyle and I made was ordering the battery cells. We ordered 600 26650 Lithium Iron Phosphate battery cells from batterybookup.com. Each cell has a capacity of 3800 mAh and a nominal voltage of 3.2v.
The next step was testing, assembling, and spot welding 576 cells into a usable battery pack. The battery layout is 24 cells in parallel and 24 cells in series for a total capacity of 91.2 Ah and a nominal voltage of 76.8v. Putting the battery together was a highly time-consuming and lengthy process.
Shown above is one of two modules beginning to be spot welded together. Overall, the process took somewhere around 40 hours to complete and over 4,000 individual welds.
Once I put together the battery electrically, the battery management system had to be attached. The purpose of the battery management system is to keep the battery in a safe state. The battery management system (BMS) prevents overcharging, discharging, too high or low temperatures, and keeps the cells “balanced”. Working with high voltage should always be approached with caution and was a great learning experience.
Kyle with the Pink Skies
While the battery production process was ongoing, Kyle came home for spring break! It was his first time seeing the vehicle in person and great to have a second pair of eyes and hands on the car. While Kyle worked on installing the steering system, I worked on installing the high voltage electronics.
I borrowed a DC power supply from the University of Michigan Supermileage Team and got the motor spinning for the first time. Kyle and I were able to install the steering system and the front and rear brakes, which meant we could take our first drive -- as long as we had an extension cord long enough to keep the power supply plugged in. Being able to drive the car back and forth under its own power was a super exciting moment for both of us as we could see our dream beginning to materialize.
After a long week of working on the car, I headed back to Ann Arbor, and Kyle headed back to Michigan Tech. Two weeks later, I came back with the fully functional battery and spent the whole week getting the car ready to drive under its own power.
The first thing I had to do was more high-voltage wiring. I had to install our now completed battery and install our throttle, a precharge resistor, the BMS display, and the charge controller (the device that takes in energy from the solar panels and charges the battery).
An inside look of the cockpit of Pink Skies
After installing all of the above high voltage components, there was a laundry list of items to complete:
Installing a new master cylinder for the front brakes.
Modifying the front steering for a lower Ackerman steering angle to assist with low-speed handling.
Strengthening the front forks to better handle the stresses associated with driving on US roads.
Installing shims in the brake calipers to eliminate brake scrub
Having the police department inspect the vehicle for roadworthiness
Going to the secretary of state and applying for a title
I am proud to say that Pink Skies was inspected by a Meridian Township Police Department member and passed with flying colors. After completing the inspection, I went to the Michigan Secretary of State, applied for a title, and was assigned a VIN. We are now awaiting a member of the Michigan Regulatory Monitoring Division to come out and place the VIN on Pink Skies, and then we can get a license plate, and the car will be legal to drive on public roads.
We were successful in beginning to register Pink Skies, and I was also successful in making the changes we needed to make to get the car driving around. Driving the car around under its own power was another enormously satisfying moment and a giant leap we needed to take if we want to drive 3,100 miles in the car this summer.
Currently, the car electrically is ready for the solar array. Before installing the solar array, a few more mechanical and electrical items need to be cleaned up but expect Pink Skies soon to be driving under the sun’s power. For now, I will sign off and catch up on all of the work I have been ignoring.
Will Jones and the Cannonball Sun