As our very first electric prototype gets developed, it is critical to ensure reliability and functionality under the harsh conditions that are tied to formula student. Eurocircuits has been supporting us during that development process and ensuring the highest quality PCB manufacturing process, allowing us to develop our prototype safely and ensure reliability across all sub-sectors of our electronics.
The main goal for this season is to produce our very first PCBs and learn what needs to be changed/improved for the following prototypes.
Pre-charge relay
The pre-charge relay PCB makes sure we can have a reliable car and not something that moves maybe once or twice and then gets a blown inverter and puts the driver's well-being at risk in the process. Eurocircuit's manufacturing standards when it comes to high power electronics are unmatched and their tools have allowed us to create a working pre-charge prototype that is up to safety standards thanks to thick PCB traces capable of handling higher currents and gaps in the PCB that ensures proper insulation between high and low voltage systems.
Ready-to-drive system
In communication with the Pre-charge relay system, the ready-to-drive PCB is what starts the car. Eurocircuits has made it possible to make reliable communication lines between systems that can be trusted throughout an entire week of competition, whether it is the ready-to-drive system or the CAN nodes.
BMS (Battery Management System)
Our very first 4-layer PCBs, ready for the harsh environment inside the battery pack and possible thanks to the freedom Eurocircuits has given us when designing the BMS to make it all fit in the accumulator container due to their amazing tools and tight tolerances.
We managed to fit, not only the standard cell balancing features that come with a BMS, but also a whole master-slave architecture that ensures safety during the competition, using cell temperature monitoring, keeping track of critical signals that would otherwise be a risk to the driver.
A Master-Slave architecture is used. This design provides accurate cell monitoring (voltage and temperature) while meeting all the competition safety requirements. Key components:
- • 1 BMS Master (BQ79600 + MCU) coordinating all the slave units;
- • 14 BMS Slaves (BQ79616) each monitoring 8 or 9 cell modules of 6 cells in parallel each.
BMS – Slave
Each Slave measures cell voltage with ±6mV accuracy and reliably provides cell temperature monitoring. GPIO pins are a limited resource. Thus, to ensure an adequate coverage of temperature monitoring throughout the battery pack, each slave comes with CD4053BCN multiplexers that switch states using a digital signal controlled by the AMS Master. To guarantee there is digital signal integrity for the multiplexers in all the 14 Slaves, SN74HC14DR gates with Schmitt triggers are implemented into the Slave design to reduce potential electrical noise. The temperature monitoring system is supplied by isolated 5V and GND rails coming from the PDU (Power Distribution Unit), this is to avoid improper switching or damaging the logic gates when using the cell module GND of the BMS slave. This GND can shift its value under load. The thermistors themselves are supplied with the TSREF voltage of the AMS, which shifts alongside the GND to ensure accurate temperature readings.
BMS – Master
There are two versions of the AMS Master, both function similarly the only difference is the MCU chosen to communicate with the rest of the car. One of them uses a standard ESP32 devkit due to its simplicity, approachability and ease of debugging. The other uses Texas Instrument's XMSM0G3507SDGS28R which allows us to use their example code and pre-made firmware as a starting point for a future AMS project.
The BQ79600 can communicate with the MCU using SPI or UART. UART is being used here due to its robustness.
To communicate with the “outside world” the Master here uses an MCP2515 similarly to our CAN Nodes to translate its messages to CAN. Both designs are capable of sending digital signals to the SDC and light up an LED on the dashboard to comply with the FSG rules.
Shutdown circuit
The SDC (shutdown circuit) is the final piece of the puzzle, it takes system critical signals from all over the car, whether it is the BSPD (brake check plausibility device), the BMS or simply a shutdown button in the dash of the car. The SDC ensures the driver is safe by opening the high voltage relays in a matter of instants and latching this state until a full power reset is done when needed according to the FSG regulations.
Future of NEXUS
As this is our first electric prototype there is still lots of room to improve for us. We want to have more PCBs with SMD technology. Currently we have very big PCBs like the TSAL that are mostly done in THT. This does make soldering and debugging easier which is important for a first prototype, however, with our designs now tested and proven to be functional, the next step is to bring SMD into the mix, allowing for more room for maneuver inside the high voltage enclosure of the battery pack and easier, simpler cabling.
For more information visit the Nexus UA Motorsport website.
The post NEXUS UA 2026: The first prototype appeared first on Eurocircuits.
Source: https://www.eurocircuits.com/student-projects/nexus-ua-2026-the-first-prototype/