Solar Team Eindhoven: Building Stella Terra

Blog by Solar Team Eindhoven.

1. Super rapid prototyping

Last year, student team Solar Team Eindhoven from the Eindhoven University of technologies built Stella Terra: The world’s first Solar-Offroad car.

This car proved to be a tough challenge as the requirements are intense: designing a car that can deliver the power necessary for driving off-road whilst also being so efficient that it can drive up to 710km in a day on solar power.

Because of these requirements the electronics team decided to build a completely new electrical system for Stella Terra from the ground up. All-in all resulting in 14 different PCBs that were designed in-house and manufactured by Eurocircuits.

One of the most critical PCBs in this system is the MPPT (Maximum Power Point Tracker) which is responsible for boosting the voltage from the solar panels to the 400V battery voltage. Specifically, it does this in a way that constantly changes the effective impedance seen by the solar panels to always work in the maximum efficiency point of the panels.

All-in all this results in a rather complex PCB with 400V isolation and switching power nets at frequencies up to 500 kHz. This would not have been possible to build and innovate on in such a short time notice without Eurocircuit’s super-fast prototyping services and on-line PCB  analysis for production. Extra features such as Eurocircuit’s automatic layout analysis for footprints and component spacing have managed to remove mistakes from the PCB decreasing development time even more.

All in all these MPPTs enabled us to drive a tour of 1000 kilometers all the way into the Sahara in Morocco powered by nothing but the sun.

2. Powerful planes

When  designing Stella Terra, driving off-road gave rise to a large challenge: In environments such as the loose sand dunes of the Sahara, the power needed by the motors is a lot larger than when driving on the road (just like when cycling through sand). After a choice for these motors was made, together with a battery capable of delivering this power, the final challenge was to develop a Battery Management System (BMS) capable of safely switching all of this power on and off.

For this, Eurocircuits enabled a very elegant design of the high power carrying PCBs through their 8 layer 35um stackup that effectively functions as a bus-bar. This way our power distribution can all be done on a PCB which allows for easy development and a reduction in the amount of cables needed, saving weight, which in turn helps make Stella Terra more efficient.

In total our BMS consists of six PCBs that all communicate together to power the entire vehicle High Voltage and Low Voltage networks, offering diagnostics and monitoring the High Voltage safety and battery safety.

This way, even in the toughest environments we are sure that Stella Terra can safely deliver the power to bring us forward due to excellent PCB quality.