#cylindricalbatterycells

Cell Core Temperature Monitoring in EV Cylindrical Battery Cells

Thermal management of cylindrical cells in an EV is vital as it helps manufacturers and engineers understand chemical analysis of a battery cell.

The eMobility sector is going through its transformation phase. With the increasing focus on electric vehicle from the public and private sector, every player in the eMobility industry is working relentlessly on increasing the performance of the electric vehicle with higher efficiency, larger capacity and reduced size. The only objective of all this research and development is to make electric vehicle at par or even better than IC engines at a lower cost.

High Voltage EV Batteries, being the most critical component of the electric vehicle are the ones that are focused most for capacity enhancement, performance optimization and Cost/size reduction. Researchers in the entire value chain of EV Battery, Cell, Module and Pack level are constantly working on fast charging and capacity enhancement projects.

INTRODUCTION TO  ELECTRIC VEHICLE BATTERY THERMAL MANAGEMENT :

It is one of the most critical aspect in the design and development of EV Batteries for fast charging and capacity enhancement projects. The crucial steps involved in battery thermal management are first identifying the source of the heating, second localizing the weak points in the design and then finally managing thermal issues either with design changes or with better cooling mechanism. This article is mainly focused on Benefits of fiber optic sensor in core temperature monitoring of cylindrical cell.

WHY TEMPERATURE MONITORING:

Under the fast charging (3C, 4C and more) and discharging (6C, 8C or more) cycles cylindrical cells face tremendous electrochemical and mechanical stress. As a result of these continuous stress, Cells heat up internally and heat gets transmitted to the outer surface in radial and axial directions. It becomes very crucial to understand the stress handling capability of cells under different operating conditions. The EV battery cells must be designed for a wide range of ambient and automotive operating conditions. Identifying thermal issues accurately, during the product development stage and mitigating them effectively is the key for avoiding the huge cost of product recall.  

BENEFITS OF FIBER OPTIC TEMPERATURE SENSORS:

Engineers have been using very small thermocouples to measure the thermal profiling of cylindrical cell core. In order to avoid damage to the cell chemical due to the thermocouples, the sensors are coated with a complex and expensive chemical isolation. The isolation process is complex and still not a full proof solution for safe and accurate temperature measurement of cell core. Therefore, Fiber Optic Temperature Sensors are the most suitable alternative to the thermocouples due to the following features of fiber optic sensors:

Ultra-Small footprint (0.4mm) to fit into Cell Core. This will ensure minimal damage to the mechanical structure of the cylindrical cell.

Safety: Fiber optic sensors are made of silica, Polyimide, Gallium Arsenide (GaAs) crystal and very small Epoxy. Any of the constituents of the complete sensor does not pose any risk to the cell chemical.

Accurate and Noise Free readings – The sensors have an accuracy of ±0.2⁰C (relative) with 100% repeatability. And this accuracy is not impacted by Strain / Pressure inside Cell.

Wide Measurement Range: The rage of measurement is -269⁰C to +300⁰C.

Higher Response Time: The sensors are capable of measuring with 5Hz to 30Hz sampling rate.

Sensors Stability: These sensors are very stable under high electrical, Magnetic and Chemical fields.