Fiber optic sensors have found a number of applications where there is a strong need for temperature monitoring. The use of Li-ion batteries is no exception, and specialists have learned to use fiber optic sensors for them as well.
Temperature monitoring of Li-ion batteries is an essential aspect of their operation in the field, and the problems of temperature monitoring can be solved with the help of fiber optic sensors.
What are lithium-ion batteries?
Li-ion, or lithium-ion battery is the most common rechargeable battery that uses the reversible reduction of lithium ions to store energy. Each module consists of one or more individual cells, which are consistently connected to follow the necessary rates of voltage, energy demand and power.
Typical Li-Ion BMS includes a few thermistors to monitor on selected cells surface temperature. This means that there is a possibility that cells may heat up invisibly.
Due to the wide deployment and large number of cells in each module, there is a need for modern technologies that can monitor cell operation and prevent future catastrophic failures.
The most common problem is the significant increase in temperature and strain in the cells. The effect of high temperatures and heat production from the cell can induce a series of degradation processes, resulting in reduced capacity and performance degradation. This problem is perfectly monitored with modern distributed temperature sensing modules.
The Temperature Effect on Li-ion Batteries
Distributed temperature sensing is used because the operation of Li-ion batteries can be affected by the influence of low and high temperatures. That’s why it is necessary to maintain comfortable temperatures during operation, storage and charging.
Temperature deviations from the ideal values may occur. However, they should still be within the established operating range. In addition, the critical temperature points shouldn’t be reached. Because of the test fields, continuous use in marginal conditions leads to accelerated wear of the battery and deterioration of its technical parameters.
Cold and overheating are both undesirable and harmful for lithium-ion batteries. In cold temperatures, they can experience voltage drops, deterioration of current output and rapid discharge. However, these symptoms disappear as the temperature rises. Overheating is more dangerous to batteries. It shortens their life and reduces their performance characteristics. There is also a risk of fire in the power source.
Maintaining optimal temperature regimes during battery operation extends battery life and ensures safe use. That’s why monitoring with distributed temperature sensing is an essential element for the correct use of Li-ion batteries and the prevention of emergency situations.
Fiber Optic Sensors for Li-ion Batteries
For Li-ion batteries, fiber Bragg grating sensors have been used to obtain data on distributed temperature and strain on the battery surface in various operating conditions. Specialists use the data obtained from distributed sensing systems in real time to detect abnormal conditions and prevent battery failure.
According to the field experiments, FBG sensors have been proven to sense the temperature either in the cells or between the cells when they are placed between battery cells. As a result, fiber Bragg grating sensors are able to provide the thermal information of each cell in a battery.
Lithium-ion Battery Applications
The lithium-ion batteries are commonly used to provide uninterrupted power in data centers, factories, air and water vehicles, and other facilities. Compared with the other types of batteries, they are smaller and have a longer service life. However, there is one drawback that should be considered in its implementation. A battery contains an electrolyte that decomposes into flammable components. Today, specialists have greatly reduced the potential for explosion to the maximum, but there are still risks. That’s why fiber optic sensors are very useful for monitoring.
The commercial battery industry also includes primary batteries as one of the major segments. However, it has its peculiarities, including non-recyclable materials and hazardous components in the batteries, which also cause ecological problems.
All in all, the knowledge of the temperature distribution in a cell or between several cells is fundamental for the safety of the battery. Fiber optic sensors have proven to be suitable for both temperature and strain gradient monitoring.
Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating sensors, for example, FBG strain sensors, FBG interrogators and multiplexers, Distributed Acoustic Sensing (DAS) systems, Distributed Temperature Sensing (DTS) systems. The company creates and supplies a broad variety of fiber optic solutions for monitoring worldwide. If you are interested in structural health monitoring systems and want to learn more, please contact us at info@optromix.com