Battery pack temperature measurement, lithium battery fiber optic temperature measurement, how to measure temperature for lithium-ion batteries

Why is temperature monitoring necessary for lithium-ion batteries

Due to its high working voltage, power density, and energy density, long charging and discharging life, no memory effect, and no pollution, it has great application prospects in military systems such as submarines, drones, and individual reconnaissance. Temperature has an impact on the performance of lithium-ion batteries in all aspects, including the working condition, cycle efficiency, capacity, power, safety, reliability, consistency, and lifespan of the electrochemical system, which may in turn affect the performance, reliability, safety, and lifespan of the entire system. Deshalb, measuring the temperature of lithium-ion batteries is very important. At present, the temperature measurement technology of lithium-ion batteries can be mainly applied in the following two fields. Firstly, the measurement of internal and surface temperatures of lithium-ion batteries can be used to verify the relevant thermal models of lithium-ion batteries, in order to assist in the design of battery cells and modules; Secondly, the temperature measurement technology of lithium-ion batteries can be applied in the lithium-ion battery management system. When abnormal changes such as battery temperature exceeding the safety threshold are found, the external circuit is cut off and an alarm signal is sent in a timely manner to avoid danger.

Battery thermocouple temperature monitoring, battery infrared temperature measurement method, fluorescent fiber optic battery temperature measurement

The commonly used temperature measurement methods currently include thermocouples and infrared imaging. Thermocouple temperature measurement technology is mature, has a long history of use, and has a wide variety of products, making it the most commonly used point temperature measurement method in the research field of filed ion batteries; With the development of integrated circuits and the reduction of costs, infrared imaging technology has become increasingly popular, especially occupying a dominant position in surface temperature measurement. Aber, both methods mentioned above have obvious shortcomings in the research and application of lithium-ion batteries. Thermocouples require the use of metal wires, which can easily cause short circuit hazards, and the metal materials used are often very hard, which brings a lot of inconvenience to installation and use; Infrared imaging technology uses infrared signals emitted by objects for measurement, which is easily affected by airflow interference and lacks accuracy. It can only roughly measure the surface temperature of objects, and requires calibration for different emissivities of the measured objects. Subsequent data processing work is complex. In order to overcome the above shortcomings, it is proposed to apply fluorescence fiber optic temperature measurement technology to achieve accurate, fast, and safe measurement of temperature in file ion batteries.

Temperature monitoring of lithium batteries

Lithium ion batteries have advantages such as high voltage, high specific energy, multiple cycles of use, and long storage time. They are not only widely used in portable electronic devices such as mobile phones, digital cameras, and laptops, but also in large and medium-sized electric devices such as electric vehicles, electric bicycles, and electric tools. Deshalb, the performance requirements for lithium-ion batteries are becoming increasingly high. The internal structure of lithium batteries is composed of positive and negative electrode plates and separators. During use, the battery generates a large amount of heat, which affects its cycle life and safety, especially for large capacity batteries. Real time monitoring of internal temperature changes in lithium batteries can directly and effectively determine the health status of the battery. In existing technologies, temperature sensors are installed at the ear of the battery cell or between the battery cells, or between the battery cells and the housing to monitor changes in battery temperature. Aber, this may lag behind the actual temperature changes of the heating source of the battery cell. A new type of lithium battery temperature sensor for temperature measurement is urgently needed.

Temperature measurement principle of fluorescent fiber optic temperature sensor

Fluorescent fiber optic temperature sensors are based on the material properties of rare earth fluorescent substances. Some rare earth fluorescent substances, after being irradiated and excited by ultraviolet light, emit linear spectra in the visible spectrum, namely fluorescence and its afterglow. The decay time constant of fluorescence afterglow is a single valued function of temperature, and usually the higher the temperature, the smaller the time constant. As long as the value of the time constant is measured, the temperature can be calculated. The biggest advantage of this method is that the measured temperature only depends on the time constant of the fluorescent material, and is independent of other variables in the system, such as changes in light source intensity, transmission efficiency, and degree of coupling, which do not affect the measurement results. The fluorescent fiber optic temperature sensor adopts a contact measurement method and can be transmitted over long distances, allowing the sensor’s optoelectronic devices to detach from the temperature measurement site and avoid harsh environments.

Advantages of using fluorescent fiber optic temperature measurement in battery temperature measurement and monitoring

Due to the use of small probes and the absence of metallic materials, the fluorescence fiber optic thermometer has complete electrical insulation and is not affected by high voltage and strong electromagnetic fields. Fluorescent fiber optic temperature sensors are not limited to directional measurement of object surfaces, but their probes can also be inserted into solid substances, immersed in liquids, or introduced into equipment to reach specific areas. Temperature is an important parameter of lithium-ion batteries and has a wide range of applications in battery design and management. Using fluorescent fiber optic technology to measure the internal and surface temperatures of file ion batteries. Compared with traditional methods such as thermocouples, this method avoids the impact of electromagnetic interference on measurement performance. Gleichzeitig, due to the electrical inertia of the fiber optic probe, it reduces the interference of sensor components on battery operation during internal temperature measurement. The fiber optic probe is compact, highly accurate, and corrosion-resistant in electrolyte environments, enabling fast temperature measurement at multiple internal points, meeting the needs of battery temperature monitoring.

How to install a lithium battery fiber optic temperature measurement system

Lithium batteries include a battery cell and an outer shell, with the battery cell located inside the outer shell. The battery cell includes a positive electrode, a negative electrode, and a diaphragm. The installation method of the fluorescent fiber optic temperature sensor is flexible and simple. Fluorescent fiber optic temperature sensor temperature measurement technology is a new type of temperature measurement technology, which is an integrated temperature measurement system based on the principle of fluorescence fiber optic temperature measurement. By combining fluorescence analysis technology with fiber optic sensing technology, it not only has a small size but also high sensitivity.