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Electric Vehicles Battery Test - Module Level Testing

posted by Rugged Monitoring on 2021-07-26

Electric Vehicles Battery Test - Module Level Testing

What is a Battery Module?

Electric vehicles and hybrid have batteries that operate at high voltages and these batteries are made from battery packs. The battery packs are made from individual cells and battery modules which are multiple cells connected in a series and/or parallel manner. They are usually enclosed in a mechanical structure which maintains the structural integrity of the module. Since there are 3 types of battery cells, (cylindrical, pouch and prismatic) each type of cell has its own type of battery module.

How does a Battery Management System solve the major battery problems of an EV?

The main issue that engineers and battery manufacturers have with battery modules is the intracell temperature. It is difficult to determine the temperature of any two cells due to the space constraint that doesn’t allow traditional sensors to provide readings of the intracell temperature. But monitoring the thermals of a battery using a state-of-the-art battery management system is crucial for engineers as they need to know if there are any hotspots or thermal runaways within the module. Also, the battery management system analyses and identifies the shortcomings of a module along with providing an accurate Age Estimation analytics which will benefit the engineers immensely. Another issue to deal with is the thermal stress that is generated especially due to the demands of having a high capacity and high-performance battery while being smaller. This added with the fact that high currents are needed for rapid fast charging to be possible means that thermal stress will an active issue in almost all the battery cells, modules, and packs being designed for EVs. However, this can be solved by using a BMS which is an intelligent system with algorithms that help identify areas that need to be improved so that the performance of the battery is enhanced and has a longer cycle life. Also, the BMS judges the cooling system’s efficiency mainly under harsh operating and testing conditions where the cooling systems are known to be comprised.

Benefits of Fiber Temperature Sensors over Thermocouples in EV Battery Module Testing

Most traditional sensors such as thermocouples give slow and inaccurate readings that are not repeatable, so the data becomes unreliable. Also, the accuracy of thermocouples is compromised when the sensors are exposed to high electromagnetic frequencies. Since EV battery modules are tested at high voltages, the safety of the prototype and the testing site becomes a huge factor but thermocouples aren’t very safe to be used at high voltages because they are made from metal so there is a risk of a short circuit occurring. On the other hand, FO Sensors have a rugged and compact design with ring terminal connectors which makes them an ideal choice for thermal monitoring in battery modules. Additionally, fiber optics sensors deliver accurate and noise-free readings with 100% repeatability along with being chemically, electrically, and magnetically stable. Unlike thermocouples, FO sensors protect the testing environment and researchers by avoiding the possibility of short-circuiting. Additionally, the sensors are ultra-small so they can be used to the intracell temperature within the battery module which will detect the thermal runaway is occurring or not. Furthermore, Rugged Monitoring’s Fiber optics sensors are specially equipped to have custom and standard ring terminal sizes and they are very easy to use when engineers need to route cables with bundled sensors. Along with being highly stable and durable in EV conditions, RM’s fiber optics sensors have a wide temperature range to cover the extreme environmental conditions.

Rugged Monitoring Thermal Profiling Sensors

Rugged Monitoring’s Fiber Optic battery temperature sensors are being used by battery design/test engineers at each stage for battery performance testing:

  • Battery cell core and anode thermal profiling for fast charging
  • Intercell temperature monitoring in Battery Modules
  • Battery pack abuse testing and HV connectors temperature testing

The CANBUS is implemented to communication with Battery Management System or dataloggers. Also, RM sensors and monitors are easy to use as they don’t require calibration or complex inputs along with being rugged and suitable for all test conditions. Also, RM sensors have a higher immunity to electromagnetic interferences which increases the testing accuracy and reliability while being having a very fast response time of 0.1ms to 1ms that helps identify a sudden shift in the temperature within the cells. The state-of-the-art sensors of RM such as  LSENS-B, LSENS-T, LSENS-R are most reliable option that provides accurate, fast results while being easy to setup and use. The EV test rigs come with built in Fiber Optic temperature monitors, R501, O201 etc.