Grigor Pahlevanyan
April 9, 2023
High Voltage Electrical Architecture
Figure 1: Current version of the high voltage electrical architecture
If you have already seen our Power Management board and the Precharge board then you may realize that the HV architecture is the extension of both. It shows how power comes from the supplemental battery and the main battery then gets fed into the precharge board and the DCDC converter which drops 96V to 12V for the PMS board. At the moment, our current iteration of the HV architecture is missing the solar arrays and the E-stop. We are in the process of adding these new changes to the drawing.
Figure 2: Previous version of the high voltage architecture
The above diagram depicts the high-level electrical architecture of the solar vehicle. To simplify the layout, the PCBs are represented as boxes, with an emphasis on routing. The connection of components such as CANbus, battery pack, MCU, E-stop, etc. will have a significant impact on the entire car.
One of the challenges we faced was setting up the system to accommodate an emergency stop button, or "E-stop," which can turn off the car with a single press. Unlike the regular stop button, which sends a command to the microcontroller, the E-stop is a direct mechanical switch which is placed before the MCU. Once the MCU loses power, contactors that keep the
Solar Cells and Battery
Figure 3: Solar Cell Arrangement
With the 4 challenges mentioned below, we come up with the solar cell arrangement shown above. The cells narrow down towards the lower back of the car as the body of the vehicle has "shoulders" which can create shadows when the sun in at an angle during the race and not pointing from the top (bird's eye view).
1. You can't use 1 big solar array because the side that has the least amount of sunshine (voltage) will greatly reduct the efficientcy of the whole array.
2. Due to point 1, we need to use many arrays. Each array needs to cover an area of a similar incline, meaning same angle. This way the shadow will be constant.
3. Each array needs a "Maximum Power Point Tracker" (MPPT) which maximizes the power from the solar cells. It will also match the battery voltage.
4. MPPTS are very expensive ($2500 USD). So we need to maximize efficincy AND minimize cost as much as possible. We can't have every solar cell with its own MPPT.
Table 1: Solar Cell Units
For our Multi-Occupant class vehicle, the solar cells would provide 900W of power per hour. This is under average conditions (medium sun, cloudy). Our motors take 2KW of power per hour, which means we consume 4KWh just from the motors at nominal power without the load. With this information we can say that the solar cells would reduce the size of the battery pack by 22.5%.
