Embedded fiber-optic sensing for accurate internal monitoring of cell state in advanced battery management systems part 1: Cell embedding method and performance

Abstract

A key challenge hindering the mass adoption of Lithium-ion and other next-gen chemistries in advanced battery applications such as hybrid/electric vehicles (xEVs) has been management of their functional performance for more effective battery utilization and control over their life. Contemporary battery management systems (BMS) reliant on monitoring external parameters such as voltage and current to ensure safe battery operation with the required performance usually result in overdesign and inefficient use of capacity. More informative embedded sensors are desirable for internal cell state monitoring, which could provide accurate state-of-charge (SOC) and state-of-health (SOH) estimates and early failure indicators. Here we present a promising new embedded sensing option developed by our team for cell monitoring, fiber-optic

Fiber Optic Sensing Technologies for Battery Management Systems and Energy Storage Applications

“…Large-format EV-grade Li-ion batteries with a nominal capacity of 15 to 40 Ah have been studied using a fiber optic sensing approach at laboratory scales. [ 20 , 21 , 22 ].…”

“…Among these, strain (ε) and temperature (T) are of most interest in battery systems, and the contributions of both to Equation (2) can be described as follows: where Λ is the grating period, is the effective refractive index, is the effective photo-elastic coefficient of the fiber core, is Poisson’s ratio and and are the Pockel’s coefficients of the strain optic tensor [ 11 ]. A discrimination method to decipher these parameters is proposed by Raghavan et al [ 21 ], where the internal strain and temperature of a Li-ion pouch cell are measured and further applied to SOC and SOH estimators. Similar to Novais et al [ 118 ], Raghavan et al used a protective heat seal material to ensure the hermeticity of the cell and placed the FBG fiber probes at the most informative center area of the cell in between two separators.…”

Lithium-Ion Battery State-of-Charge Estimator Based on FBG-Based Strain Sensor and Employing Machine Learning

“…Looking in more detail at optical fiber-based methods, Fiber Bragg gratings (FBGs) have been shown to be capable of measuring both surface strain [3] and temperature [4] in these sorts of batteries. Several different types of battery 'packages' have been studied for this purpose, including coin cells [5,6], pouch cells [7][8][9] and cylindrical cells [10]. The fiber optic sensing approach has thus previously been shown to offer important advantages when compared to the use of conventional electrical sensors [9].…”

Development of a Polymeric Arrayed Waveguide Grating Interrogator for Fast and Precise Lithium-Ion Battery Status Monitoring

“…FBG sensors have already been used for status monitoring of lithium-ion batteries by different research groups [18], since they are capable of delivering information beyond conventional BMS. They can serve as simple temperature sensors [19,20], outside and even inside of a cell [21,22], or as functionalized sensor elements that are sensitive to chemical substances and their optical properties [23,24]. Additionally, due to the small fiber diameter of 125 µm, FBG sensors can be integrated in many areas that are usually inaccessible for electric sensors e.g., in a battery system consisting of many densely stacked cells.…”