This study investigates capacity degradation in 100 Ah lithium iron phosphate (LiFePO4, LFP) battery cells during First-Life and Second-Life use. In a laboratory-based case study, cells achieved up to 9600 cycles, with a maximum loss of 42 Ah over 7 years of Second-Life use and a total loss of 56 Ah over >14 years of total cell age. These results highlight the long-term viability of LFP cells for battery energy storage systems. A power law model based on the first 10 data points effectively described capacity trajectories and identified early signs of accelerated degradation. One cell deviated from the predicted progression at cycle #8000, corresponding to a State-of-Health (SoH) of 48 %. Crossing the +/- 3 standard deviation threshold in the capacity residuals marked the End-of-Second-Life criterion. Incremental Capacity Analysis indicated additional aging mechanisms, such as Loss of Active Material and increased faradaic polarization. Cells with lower initial capacity degraded faster at 70 % SoH, suggesting a History effect overlapping with temperature-dependent aging. Only cells with high initial capacity at 70 % SoH exhibited a linear Arrhenius trend, while cells with low initial capacity degraded slightly faster at 10 degrees C than at 30 degrees C, suggesting different aging mechanisms. Within the stack, temperatures recorded in a 10 degrees C climate chamber reached 22 degrees C, challenging the reliability of setpoints. Spatial temperature variations suggested non-uniform degradation patterns. These findings underscore the importance of considering capacity history, thermal gradients, and early diagnostic indicators when assessing Second-Life battery performance.

Thermal runaway and the subsequent fire of electric vehicle lithium-ion batteries cause a specific type of contamination. In order to assess the resulting risks of damage to critical infrastructure and to human health, we perform practical thermal runaway experiments with lithium-ion battery modules of an approved, commercially available electric vehicle. Extensive chemical analyses identify and quantify the soot depositions in ventilated and non-ventilated rooms. Contamination mainly consists of the metal oxides of the cathode material, lithium and fluoride compounds. Their influence on surfaces, protective textiles as well as their corrosiveness to typical metals and the impairment of electrical and electronic devices is low. The analysis of sprinkling and cooling water shows the necessary extent of its decontamination. Recommendations include preventive and mitigating measures for the appropriate handling of contamination caused by fires from lithium-ion battery powered electric vehicles.

Incidents of electrical vehicle catching fire forced on a root cause analysis. Failure mode and effects analysis (FMEA) and fault tree analysis (FTA) approaches were used for failure analysis and to design experiments on the battery system level. Analysis focused on the behaviour of an internal short circuit of a cell and its effect on the battery system and the vehicle. An internal short circuit of a stand-alone cell leads to venting and the release of dense smoke, however no fire or explosion occurred which complies with manufacturer declaration and hazard assessments according to battery safety standards. When such cell venting was triggered in the battery system it could be demonstrated that electric sparks on the carbonizing cell battery management print ignite the smoke and eventually lead to a fire of the complete vehicle. It has been shown that the use of comparatively safe Lithium-Iron-Phosphate cells does not entail a safe battery. The identification of the fire root cause enabled to develop and successfully test a mitigation method preventing fire caused by this failure mode.

Lithium-ion batteries are well established for use in portable consumer products and are increasingly used in high power electro-mobility and photovoltaic storage applications. In hybrid and plug-in electric vehicles degradation and useful lifetime at standard operation conditions are critical parameters in addition to performance and safety. Here stress-induced ageing of commercially available high power battery cells of the type A123 AHR32113M1 Ultra-B, consisting of a LiFePO4 cathode and a graphite anode have been investigated. A usually accepted capacity loss for electric vehicles of 20% was reached after 8560 stress profiles corresponding to a driving distance of almost 200,000 km. Cycling with a stress profile applying constant power corresponding to the average power and energy of a full stress profile and starting at 60% state of charge showed a much faster capacity loss. Electric impedance measurements show the dependence of the capacity loss and constant phase element at low frequency, indicating Li-ion diffusion blocking in the cathode. Microscopic analysis of anode, separator, and cathode, shows defect formation in bulk material and at interfaces.

Various materials display a constant phase impedance, Z proportional to [i omega](-u), over a wide frequency range. In this paper, we show that this behavior is a natural consequence of charge transport in the macroscopic limit, and that in contrast to the common belief, no assumptions on the "relaxation functions" are required. Our unifying view of the constant-phase-element (CPE) is then employed for analyzing impedance spectra that were recorded during the aging of LixFePO4 cells. We find and explain a significant correlation between their capacity loss and changes in the exponent (u) of the CPE describing cathodic Li-intercalation. Changes in u with the state of charge are also discussed. CPE exponents are shown to be valuable performance indicators for Li-ion batteries. (C) The Author(s) 2015. Published by ECS. All rights reserved.

The failure rate of an example avionics control unit with approximately 7000 electronic components is calculated with the latest state-of-the-art prediction models FIDES Guide 2004 and RIAC-Handbook-217Plus (2006). To allow comparison of the component prediction models a standard civil avionics profile was defined and used for both calculations. Results are compared supported by analysis of the influence of component and application specific parameters such as temperature, temperature cycles, humidity, and vibration. In addition predicted failure rates are compared to field data that has been collected for this unit during 15years.

We shortly review general reliability engineering concepts and methods and attempt to discuss in how far these can be applied to optical components used for optical fiber sensors.

Dual-span failures dominate the system unavailability in a mesh-restorable network with full restorability to single-span failures. Traditional availability analysis based on reliability block diagrams is not suitable for survivable networks with shared spare capacity. Therefore, a new concept is proposed to facilitate the calculations of connection availability. A U.S. network consisting of 19 nodes and 28 spans yielding 171 bidirectional connections is investigated. We find that networks with shared backup path protection can have average connection unavailabilities of the same order of magnitude as those with dedicated automatic protection switching, however, with a much better capacity efficiency. The proposed method can exactly calculate the unavailability of a specific connection with known restoration details or the average connection performance without any restoration details by presuming the dual-span failures to be the only failure mode and an arbitrary allocation rule of spare capacity

Dual-span failures are the key factor of the system unavailability in a mesh-restorable network with full restorability of single-span failures. Availability analysis based on reliability block diagrams is not suitable to describe failures of mesh-restorable networks with widely distributed and interdependent spare capacities. Therefore, a new concept of restoration-aware connection availability is proposed to facilitate the analysis. Specific models of span-oriented schemes are built and analyzed. By using the proposed computation method and presuming dual-span failures to be the only failure mode, we can exactly calculate the average connection unavailability with an arbitrary allocation rule for spare capacity and no knowledge of any restoration details, or the unavailability of a specific connection with known restoration details. Network performance with respect to connection unavailability, traffic loss, spare capacity consumption, and dual failure restorability is investigated in a case study for an optical span-restorable long-haul network.

High availability tops the list of features desired for building a network. Various factors influencing path availability of optical networks with span restoration are investigated from the network design point of view. Network redundancy, number of backup routes, and dual span failure restorability can have important effects on path availability. A formulation to improve average path availability of a network by maximizing dual failure restorability is developed. We also introduce a practical method to optimize spare capacity and path availability of a network at the same time. A case study analyzes how much average dual-failure restorability can be improved in a long haul network with span restoration. Conclusions deduced from the computational and analytical results can help network planners to design a network with high performance and optimized cost and availability.

For wider acceptance of optical fiber sensors standardized products are needed with well understood properties and validated performance characteristics. Reliability, availability, maintainability, validation, and standardization of fiber sensors are discussed.

A new calculation method to estimate path availability under dual failure scenarios for networks designed for 100% restorability against single span failures is presented. This method is applicable to all survivability schemes and considers their respective restoration or protection effect. A case study calculates the availability of all service paths within a long haul network under four protection/restoration strategies: dedicated automatic protection switching, shared backup path protection, span restoration and protection-cycles. The availability optimization potential is estimated based on measures for standard network redundancy and dual failure restorability. Assets and drawbacks of survivability schemes are compared from the availability and capacity efficiency point of view

The foundation pillars of successful technical products are performance, cost, and reliability. The development of reliable components and the operation of highly available systems is a comprehensive engineering task combining probability theory, materials science, and experience. Components have to be as reliable as necessary in order to build systems that are dependable and cost efficient during the whole life cycle. Reliability engineering is an ongoing process starting at the conceptual phase of a product design and continuing throughout all phases of a product life cycle. The primary objective is to identify and eliminate potential reliability problems as early as possible. While it may never be too late to improve the reliability of a product, corrections are orders of magnitude less expensive in the early design phase rather than once the product is manufactured and in service.This paper comprises an introduction to basic reliability engineering terms, reliability analysis methods such as reliability block diagrams, failure mode and effects analysis, Markov processes, the concept of redundancy, failure rate prediction models and the physics of failure approach, qualification and accelerated reliability testing. Examples of electronic and optical components, as well as complex opto-electronic systems and networks are given for illustration.

The paper gives an overview of reliability, availability, and maintainability of fiber optical sensors, three key factors on which standards and validation should be based and which are required for successful industrialization. The examples given are based on two long term applications with fiber optical Bragg gratings - the surveillance of two bridges (civil engineering). However, similar reflections are required for any type of application and any optical fiber sensors. Recommendations are given to improve the confidence and acceptance of possible users in fiber optical sensing systems. It is shown that with proper installation lifetimes of 50 years are possible.

This work is motivated by interest in analyzing and optimizing availability of optical networks under different protection strategies. Methodology dealing with availability calculation, protection strategies, spare capacity, redundancy and sensitivity analysis is described. A case study calculates the availability of all connections within a long haw US-network using three protection strategies: path protection, span protection and protection-cycles. The distributions of connection down time of the three protection strategies are given. The availability optimization potential is estimated based on analysis of its sensitivity on reliability input data. Advantages and disadvantages of each strategy are compared from the availability and spare capacity requirement points of view.

This paper describes analysis tools and characterization techniques for photonic components related materials analysis as well as functionality and reliability testing. Field failures and breakdowns of optical fibers and cables, fiber Bragg gratings, connectors, semiconductor lasers, opto-couplers, micro-optical elements, and others have to be analyzed and failure causes and mechanisms have to be found in order to improve future components. On the other hand, new materials used and new components for future all-optical networks may lead to new failure mechanisms, which have to be analyzed and modeled for lifetime predictions. In this paper some basic principles of instruments and techniques used for reliability and failure analysis rather than a deep treatise are given and may guide the reader to find appropriate methods for a specific problem. Illustrative examples are provided.

Fiber optic sensors are potentially very well suited for condition monitoring of environment, materials, structures, and facilities. However, there is a long way from a laboratory prototype to a reliable industrial sensor system. Based on the examples of two fiber Bragg grating systems, both used for long term monitoring of strain and temperature on bridges, general sensor system reliability will be discussed. In addition, specific reliability considerations and lifetime tests, especially for optical fibers and Bragg gratings, coatings, and adhesives will be presented.