Low Voltage Sensing Board -UNICAMP E-racing

We are a Brazilian Formula SAE team, seven-time national champions and two-time world champions at the Lincoln competition in the United States. We are pioneers in Brazil in implementing four-motor drivetrain technology within Formula SAE. Our team is driven by a passion for engineering, performance, and innovation.

Our car relies on several subsystems that require electrical power, and ensuring a reliable and efficient power supply is a significant challenge. To address this, we designed and built our own low-voltage battery pack. While the simplest solution would be to use a commercial automotive battery, at E-Racing we believe that designing and developing our own systems offers a far richer learning experience, while also allowing us to create optimized solutions tailored to the specific needs of our vehicle.

Our low-voltage battery is built using cylindrical lithium-ion cells, providing a total voltage of 36V. To ensure safe operation, we developed a sensing board that acts as the interface between the cells, the Battery Management System (BMS), and the car's safety systems.

Image 1: Low Voltage Sensing Board

Our BMS is powered by a converter that steps down 36V to 12V. Its main function is to continuously monitor the voltage and temperature of each cell. This monitoring is essential to ensure safe charging and to prevent any cell from experiencing overcharge or undercharge, both of which could damage the cells and compromise the battery’s lifespan and safety.

According to the competition rules, the cells cannot exceed a temperature of 60°C. If this limit is reached, the BMS sends a fault signal that, through a relay, immediately shuts down the low-voltage system, ensuring the safety of both the components and the team.

Additionally, we have implemented an LED indicator system, which signals when the low-voltage battery is energized. This provides a simple and effective visual cue to assist with operational safety and monitoring.

Once the energy leaves the low-voltage battery, it passes through the main low-voltage switch, which allows us to safely turn the system on and off. After this point, the power is distributed into different voltage levels: 24V, 12V, and 5V, each used to supply different subsystems of the car.

Image 2: Low Voltage Battery

Even though it is called the low-voltage system, its energy should never be underestimated. It powers critical components such as the cooling pumps, high-voltage pack fans, control electronics, safety circuits, and our entire telemetry and data acquisition system. High reliability is essential since any failure in this system directly affects the car’s safety and performance.

Designing and building our own low-voltage battery is a great opportunity for the personal and technical development of our team members. It serves as the gateway to more complex projects within the car, such as the high-voltage battery pack.

We not only design but also model and simulate the thermal behavior of our low-voltage battery, ensuring it meets the performance and safety requirements. In addition, we carry out extensive laboratory testing to validate our designs and improve the reliability of the system.

As a team, we always prioritize the development and growth of our members above everything else. That’s why we believe that partnering with PCBWay is key to helping us bring this important project to life, providing our members with the opportunity to learn, innovate, and gain hands-on experience with real-world engineering challenges.