How iButton Devices Facilitate Electric Car Safety

How iButton Devices Facilitate Electric Car Safety

Like so many events and large gatherings, even the Formula Student Germany competition has been cancelled for 2020. While event organizers look ahead to a time when it's safe to hold the typically annual event once again, let's take a look at what goes into building an electric race car for the design competition.

Formula Student Germany stems from the Formula SAE competition that the Society of Automotive Engineers (SAE) started in the U.S. back in 1981. Since 1988, SAE and the Institution of Mechanical Engineers in England have been hosting annual Formula Student competitions. In this race, it's not just about speed.

Students compete against teams from around the world with their entry: a single-seat, electric formula race car. While the car's speed is a consideration, also important are factors like construction, performance, and financial and sales planning efforts. Each team acts as an automotive manufacturer who is developing a prototypical vehicle that will be evaluated for production. The cars are expected to demonstrate good acceleration, braking, handling, and dependability and be available at a reasonable cost.

Because electric car safety is the top priority for the competition, the students must ensure that the batteries used to power their electric cars are stored properly and at the right temperature in an accumulator container on their vehicles. Each accumulator must be monitored by an accumulator management system (AMS) when the car is active or the accumulator is connected to a charger. The AMS must continuously measure:

  • All cell voltages
  • The tractive system current
  • The temperature of thermally critical cells
  • And, for lithium-based cells, the temperature of at least 30% of the cells equally distributed within the accumulator container

Formula Student Germany participants used the DS1922 iButton temperature logger to monitor their electric race car batteries. Photo courtesy of Formula Student Germany.

In its most recent competition, Formula Student Germany chose the DS1922T iButtonRegistered temperature logger with 8KB data-log memory to meet its temperature monitoring requirements. The DS1922T, which provides temperature accuracy of ±0.5°C from +20°C to +75°C, measures temperature at a user-defined rate and records the results in a protected memory section. The iButton device allowed the students to easily and accurately monitor the safety of their batteries and also comply with the competition's stringent temperature rules.

"We chose the iButton because it is easily implemented, as it does not need any connector or external power supply," said Sarah Battige, who provides electrical inspection from the Formula Student Germany Operative Team. "It is also very robust, so it can handle the harsh environment of a race car with the high amount of vibrations and the raised temperature in the accumulator. It is also not influenced by electromagnetic interference caused by the motor controllers. Additionally, the iButton is quite a small device, so it can easily be installed in the tight space of the race car's accumulator."

This blog post was adapted from the Formula Student Germany testimonial.