International student auto-sport competition provides tough challenge for electronic connectors

Motorsport provides a punishing environment in which to test the performance of components that are used. In any race, power-to-weight ratio is a vital calculation, yet reliability during conditions of extreme shock and vibration is equally important. So when the Global Formula Racing team from the Duale Hochschule Baden-Württemberg-Ravensburg (DHBW-R) in Germany was looking for a battery connector for use on an electric car to be used in the Formula Student competition they faced a daunting challenge.

Formula Student was created in 1981 in the USA by the Society of Automotive Engineers (SAE) and continues today with the support of the Institution of Mechanical Engineers. There are international events around the globe, including the USA, Germany and the UK, and more than 3000 students from all over the world are involved in the design, creation, manufacture, testing and racing of both traditional combustion engine and electric powered cars.

Global Formula Racing

Global Formula Racing is a unique international cooperation between the BA Racing Team from Germany, and the Beaver Racing Team from Oregon State University (OSU), USA, which stretches back to 2009. The two universities share physical and intellectual resources by using advanced communication-technology to create a highly competitive vehicle. Design, manufacturing, and testing occur simultaneously at both schools, across nine time zones and separated by 5400 miles. The supply chain management is unique in Formula Student and very important at that point. Since the 2011 season, two cars a year are built using the same chassis – a combustion car at the OSU campus in Corvallis, Oregon, USA and an electrical car at the campus of DHBW-RV in Friedrichshafen, Baden-Württemberg, Germany.

Explains Oli Fröhling and Lars Hamamm, both students at DHBW who have worked as part of Global Formula Racing for three and two seasons respectively, the notion that electric cars are slow is a fallacy. “Our 2015 car can achieve 160km/hour”, they explain, “which is limited to 120km/hour during the race by the rules of the competition”. Speeds of this order require the all aspects of the race car to be very rugged, since acceleration/deceleration and cornering forces can be considerable, and vibration is an absolute killer of systems that have not been specified correctly.

Battery Management System

One of the innovative aspects of the DHBW electric car is the battery design – which is obviously fundamental to the performance and success of the Global Formula Racing team. The specially-designed lithium polymer cell stack has been designed to limit internal resistance and maximise capacity. Details Fröhling: “In order to ensure we get the most out of every battery stack we need to monitor the performance of each cell during the race. Therefore we have developed a battery management system which measures the output of each cell and adjusts the voltage of each cell accordingly.”

The two main criteria for the battery management system are size and current rating of the contacts. Of course, the conditions – shock, vibration and even possibly temperature were also a factor: as discussed earlier, autosport presents a challenging operating environment for sensitive electronic systems. Therefore, the DHBW team chose to use Datamate Mix-Tek connectors from Harwin.

Secure and reliable

Datamate is a 2mm pitch, hi-rel connector family of board-to-board and cable-to-board connectors designed to withstand harsh operating conditions. The heart of the connector is a unique beryllium copper contact that features four fingers to ensure integrity of connection even under during severe shock and vibration. Devices are used on satellites, in defence applications, in undersea equipment – wherever the connector must not fail. Datamate Mix-Tek connectors combine signal (up to 3A), power (to 40A) and coax (6GHz/50Ω) contacts in one space and weight-saving body. Many different configurations are available off-the shelf. Mouldings are polarised and have a UL94V-0 rating. Mix-Tek connectors comply with BS9525-F0033 and CECC 75101-008 standards and are optionally available with jackscrew terminations for added security in applications which are subject to high vibration.

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