Thermal Testing Methods for eMobility Applications

Every day it seems we are inching closer to the vision of a more sustainable mobility with green power and autonomous, electrified vehicles on ground, but also in water and air.

This includes a lot of new technologies such as high-capacity/high-power batteries, fuel cells, hybrids, and electric drives, which requires a new way of testing depending on accurate measurements of new types of sensors and signals and the overall data analytics for the many different propulsion solutions and combinations.

As market leader in solution-selling for test and measurement, sound and vibration and environmental testing, HBK gains perfect insights in the requirements and needs of different industries in terms of innovation, product releases and problem-solving for vehicles. It turned out that thermal management is a game changer in modern vehicle setups, going from combustion engine towards hybrids or full electric vehicles.

There were up to 300 temperature measurement spots as well as highly dynamic torque, speed, and pressure measurement on a 6-cylinder combustion engine and exhaust in past times, whereas now the number of measurement channels is just flipping towards the energy storage/high-power battery and the aggregates around. The electric drive is basically covered by a few channels.

What is Thermal Testing?

Thermal Testing is widely established today. The tests are comprised of multiple phases. Testing on environmental stress, performance verification, turn-on demonstrations, thermal hardware verification and numerous of tests from cell over stack to pack are part of this testing method.

In today’s electrified powertrain solutions thermal testing method focusses on:

  • Battery long-term reliability testing focusing on dis/charging cycles (slow, fast), self-discharge
  • Dyno Testing focusing on power, efficiency, reverse load feedback
  • Environmental testing in climate chambers (temperature, humidity, pressure, … combined shaker) running on specific use-case oriented test profile
  • Misuse and impact testing (overload, short-circuit, overheating, mechanical stress, defect)
  • In-vehicle testing, summer/hot, winter/cold testing with transients

Thermal testing methods increase confidence in the design, ensure successful operation and thus its thermal management in all conditions and demonstrate robustness and thermal durability. They verify performances within specifications, measures critical parameters and are used for confirming thermal modelling assumptions.

Although thermal testing is an established testing method, it must deal with upcoming challenges and new requirements, but also to workflow – electrical safety, flexible daily extensions, new sensor and signal types and higher dynamics.

Battery Thermal Management

As mentioned, with new developments also new challenges come along. The poor performance of lithium-ion batteries in extreme temperatures drives the complexity of thermal management systems with the supporting auxiliary aggregates and air-cooling paths. Thus extensive testing and especially thermal validation are also vital in this overall setup.

Testing batteries for long-term reliability cover all many disciplines: mechanical as well as electrics including wiring and electronics / software in all use cases for the calculated life-time. One test covers charging and discharging cycles – slow or fast – and self-discharging. As batteries are often the core of the electrified powertrain, the need to improve the performance and lifetime is urgent and important.

The main requirements are safety in operation, a sustainable production, and the cost factor. The expectations in terms of the lifetime vary from minimum 10 years, 450,000 kilometers or a recharge target time at home of about 5 hours. Also, the re-use of batteries and the second lifetime – of course also regarding the performance – is an important topic.

The thermal management on battery life is crucial to factors like speed performance, security, pricing and many more. Thermal stress is therefore tested on numerous temperature measurement points, always trying to achieve highly accurate results to calculate the best possible performance of all demanded factors.

From Sensors to Analysis

Our end-to-end solution helps you validate and optimize battery storage.

Battery Thermal Testing

To identify the best conditions is not quite easy: they must be hot enough but at the same time also cool enough to be functional and safe and to endure a vehicles’ lifetime. If they become too hot or the environment is too cold, the functionality lacks or the battery itself gets damaged.

Thermal simulation may be conducted in a computer-only simulated system or environment, but this cannot cover all architectures. Therefore, involving a real physical system or test specimen in a genuine test environment is still required.

While monitoring the batteries’ performance in climate chambers, important data is gathered. In this environmental and performance test routine, the impact of extreme temperatures can be discovered. It becomes visible, what cooling systems are the best to reach customer usage and performance targets. Thermal comfort and the interaction of the battery with the whole e-system is explored and thus, the whole thermal management can be improved.

Long-standing Expert in Thermal Testing

HBK develops and offers the necessary components for thermal validation measurement chains for years. These solutions are covered by electrical, optical, or combined - hybrid - measurement chains.

Already combustion engines must deal with the fact that power generates heat. With the electrification of mobility and the upcoming need to develop thermal testing methods also here, HBK looked at existing processes and refined them from a new perspective. Thus, all the experience and knowledge has been processed and adapted to also become a specialist for eMobility thermal testing and within this, for battery testing.

The HBK energy storage thermal testing system measures parameters including voltage, current, temperature, humidity, cooling flow, pressure, and talk-to-battery management system. Calculations are made for power, efficiency, hot spot monitoring, visualization, and analysis. Automation deals with test control and safety.

An HBK data acquisition and analysis solution provides thermocouple measurements for the exterior of the electric drive train and for investigation deep into the battery, including cell voltages, overall voltage, and current measurement. Universal inputs cover universal flow, pressure, humidity, and other required parameters.

HBK is your cost-effective, one-stop-shop solution provider for thermal, mechanical, and electrical test specimen analysis.

Thermal Testing Solutions: Safety Aspects

The most important requirement and thus, a very important benefit of the HBK solution, is ensuring maximum safety:

  • HBK meets the EN61010 electrical safety standard, with VDE certification for all inputs
  • Additional safety is provided by the fact that it is a non-electrical solution
  • Electro-magnetic noise immunity and full isolation
  • Scalable, flexible multi-physics DAQ for measuring all signals in a time-synched way
  • Powerful software delivers online data visualization in any curve style
  • Automatic procedures (e.g. stimulation) ensure reproducibility of results and short processing times
  • Integration in real-time with communications protocols in parallel for high data rates
  • Bench, lab and mobile data acquisition and testing is covered by one single solution, scalable to your needs

 


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