Increase In Contact Resistance Research Articles

Analysis of heating defects in extension rods of extra-high voltage direct current overhead transmission lines

This paper studies the overheating defect of an extension rod in a ± 800 kV extra-high voltage direct current overhead transmission line, and proposes various factors that affect the overheating of the extension rod. Establish an equivalent model of an extra high voltage DC transmission line based on equipotential point and line parameter analysis, and calculate the model parameters. The proposed model can also be applied to ultra-high voltage DC overhead transmission lines such as ± 500 kV, and has strong universality. Simulation experiments show that if the equivalent resistance value of the split wire side is reduced by 0.01Ω, the power loss on the extension tie rod can be increased to 380.951 W; if the equivalent resistance value of the jumper side is increased by 0.01Ω, the power loss on the extension tie rod can be increased to 273.41 W. Combined with theoretical analysis and simulation verification, it is concluded that the main factor affecting the overheating of the extension rod is the change in the resistance value on the jumper side caused by the increase in contact resistance. A systematic troubleshooting plan for related defect problems is proposed, which has important reference and guidance significance for such line fault problems.

Modern trends in the application of thermoelectric method in non-destructive testing (review)

The article provides an overview of the main directions of using the thermoelectric testing method in various spheres of the national economy. The thermoelectric method is most widely used in industry. There are publications on the application of the thermoelectric method for quality monitoring of turning and friction stir welding. It is shown that the thermoelectric method makes it possible to increase the reliability of testing and, based on testing data, ensure optimal modes of the technological process of metalworking and welding. A number of articles are devoted to the application of the thermoelectric method to plastic deformation testing, the dependence of thermal EMF on the degree of plastic deformation is revealed. Recently, publications have appeared on the application of the thermoelectric method to testing the thermal resistance of the design “housing of a power semiconductor device-thermal interface-cooling radiator”. This design is very widespread in electronic equipment. In addition, there are articles on the use of the thermoelectric method to testing the transient resistance of contacts in the power supply network. It is shown that with an increase in contact resistance, the value of thermal EMF increases proportionally, which can be used to prevent emergencies in the power supply network. The thermoelectric method has also been successfully applied to diagnose the degree of titanium flooding. The dependence of the thermal EMF value on the degree of hydrogenation has been revealed. The use of the thermoelectric method is not limited to the field of industrial production. The thermoelectric method is successfully used in medicine for the undetectable detection of nucleic acid sequences, for the temperature diagnosis of human teeth, as well as for the diagnosis of inflammatory processes in the human body.

Field Induced Off‐State Instability in InGaZnO Thin‐Film Transistor and its Impact on Synaptic Circuits

AbstractCharge storage synaptic circuits employing InGaZnO thin‐film transistors (IGZO TFTs) and capacitors are a promising candidate for on‐chip trainable neural network hardware accelerators. However, IGZO TFTs often exhibit bias instability. For synaptic memory applications, the programming transistors are predominantly exposed to asymmetric off‐state biases, and a unique field‐dependent on‐current reduction under off‐scenario is observed which may result in programming current variation. Further examination of the phenomenon is conducted with transmission line‐like method and degradation recovery tests, and current reduction can be attributed to contact resistance increase by charge trapping in the source and drain electrode and the channel region. The current decrease is subsequently formulated with a stretched exponential model with bias‐dependent parameters for quantitative circuit analysis under off‐state degradation. A neural network hardware acceleration simulator is utilized to assess the complicated impact the off‐state current degradation could instigate on on‐chip trainable IGZO TFT‐based synapse arrays. The simulation results generally demonstrate deteriorated training accuracy with aggravated off‐state instability, and the accuracy trend is elucidated from the perspective of weight symmetry point.

ИССЛЕДОВАНИЕ ПОЖАРНОЙ ОПАСНОСТИ ЭЛЕКТРИЧЕСКОЙ СИСТЕМЫ АВТОТРАНСПОРТНОГО СРЕДСТВА

The article examines the change of the probability of an emergency mode (failure) of the vehicle's electrical wiring depending on the time of its operation. We revealed necessity of establishing the wear and operation time of electrical wiring in a vehicle. Emergency modes in the vehicle electrical network have been identified and analyzed. The behavior of some contact connections of a vehicle was studied for an increase in contact resistance. It is concluded that it is necessary to develop deterministic and stochastic mathematical models that describe the state of the vehicle’s electrical network in order to assess its fire hazard.

Structural and electrophysical properties of nanoporous carbon materials obtained from apricot pits

The dependencies of the electrophysical characteristics of nanoporous carbon material (NCM) on the compaction degree of its particles have been investigated in the presented study. It has been found that the maximum value of the electrical conductivity is achieved at a pressure of 2.5 MPa. Furthermore, it has been revealed that the formation of O-compounds on the surface of the studied materials leads to a decrease in electrical conductivity. The correlation between structural-adsorption and electrical-conductive properties of NCMs has been established. Moreover, it has been demonstrated that an increase in the amount of potassium hydroxide results in a decrease in electrical conductivity due to the breakdown of small carbon particles and an increase in contact resistance, while the specific surface area enlarges due to the development of porosity and an increase in the total pore volume.

Surface sulfurization of liner and ruthenium metallization to reduce interface scattering for Low-Resistance interconnect

Ruthenium with a low resistivity, high melting temperature and short electron mean free path has been considered to replace copper as the next-generation interconnect metallization. However, its ascending resistivity with linewidth scaling because of the diffuse scattering of electrons at the interface with dielectrics or liners is a concern. Thus, in this study, sulfurization was applied on the surface of titanium-tantalum nitride and ruthenium films to form an ultrathin sulfide layer to reduce interface scattering. The microstructure, chemical composition, bonding configuration, and stability of the layer were characterized, and the resistivity scaling of the ruthenium films was examined. Microscopic observations suggested a crystalline TiTaSx layer formed on the titanium-tantalum nitride films while RuS2 formed on the ruthenium films, both of which changed the binding state/energy of the metals. With the surface sulfurization, the interface scattering of electrons for the ruthenium films was effectively reduced to elevate the specularity parameter from 0.2 to 0.9 and lessen the resistivity scaling for at least 40 % at a thickness of below 10 nm, without a marked loss of interfacial adhesion. However, an increase in contact resistance of molybdenum to the surface-sulfurized ruthenium films needs to be considered.

Needle Penetration Studies on the Dynamics during Internal Short Circuits in Automotive Lithium-Ion Cells: Measurement of Internal Temperature and Short Circuit Current

Lithium-ion batteries (LIBs) have been widely applied in consumer electronic devices and electric vehicles for energy storage. Especially for the battery electric vehicles (BEVs), it is desirable to increase the volumetric energy density of LIB cells due to the limitation of a further volumetric expansion of the battery pack, which amounts to currently 220-400 L depending on the size of the BEV [1]. As an example, the capacity of the Li-ion battery pack in BMW i3s has been improved from 60 Ah over 94 Ah to 120 Ah over the course of a few years. Along with this trend of increasing energy density, however, the reactivity of the cells is increasing. Therefore, the potential safety issues are becoming more important. Between 2015 and 2018, a total of 15 fire incidents of BEVs were reported in Europe. In 2019, 113 fire incidents took place only within China [2]. Considering the decision by the European Union to ban the sale of new petrol and diesel vehicles from 2035, this concern with regards to the safety of LIBs would be growing progressively with the accelerated switch to BEVs.One of the main causes for a thermal runaway is an internal short circuit (ISC) [1,3]. Under many different abuse scenarios, ISC appears to trigger the thermal runaway (TR); (i) mechanical abuse (deformation of separator leading to ISC),(ii) electrical abuse (separator pierced by dendrite resulting to ISC) or iii) thermal abuse (shrinkage or melting of separator causing ISC) [1]. Nail penetration tests have been widely used to reproduce ISCs. Only the temperature on the cell surface and the cell voltage are measured in a conventional nail penetration test. However, there is also a challenge to understand the internal dynamics in a Li-ion cell in which an ISC takes place [4]. This study introduces an advanced needle penetration test that enables the measurement of both the internal temperature and the ISC current.As seen in Figure 1 (a), the amount of ISC current can be measured indirectly by replenishing the lost cell capacity from ISC with a power supply that is set to constant voltage mode (in this case, 4.2 V) and connected to the cell via a shunt. Additionally, the internal temperature can be measured using a thermocouple which is embedded in a specially crafted probe. The needle penetrates Li-ion cells with a slow penetration speed of 0.01 mm/s to understand the effect of piercing individual layers on the ISC with regard to electrical and thermal behaviour.Figure 1 (b) presents the ISC current and the internal temperature measured using this method. In the unstable ISC current signal, sharp periodical peaks are detectable. It is assumed that the ISC current is constantly increasing by several layer-to-layer shorts adding up and that its periodically decreasing profile originates from the increasing contact resistance by cell layers melting or being ruptured. Since thermal energy emerges from the ISC current, the internal temperature fluctuates dynamically corresponding to the ISC current profile, while surface temperature signals do not show any changes. This advanced needle penetration test offers the great research possibility to understand the internal dynamics of ISC that has been barely studied and to determine the internal onset cell temperature for TR.[1] X. Feng et al Energy Storage Mater., 10, 246 (2018).[2] Y.S. Duh et al J. Energy Storage, 41, 102888 (2021).[3] D.P. Finegan et al J. Electrochem. Soc., 164 , A3285 (2017).[4] S. Huang et al J. Electrochem. Soc., 167, 90526 (2020). Figure 1

Order of magnitude improvement in the transport performance of carbon nanotube films by completely removing surfactants

Surfactant-based separation techniques have been developed for the high-efficiency production of high-purity semiconducting single-wall carbon nanotubes (s-SWCNTs), which establish an important material foundation for the preparation of high-performance carbon-based electronic devices. However, surfactant molecules wrapping around SWCNTs during structural separation inevitably degrade the resulting device performances due to increasing contact resistance between the SWCNTs and electrodes and between individual SWCNTs. Here, we developed a simple and effective strategy for completely removing the surfactant molecules around separated s-SWCNTs by annealing and rinsing. With this technique, defects were not clearly increased in the crystal structure of SWCNTs, and the transport performances of SWCNT-based thin film transistors (TFTs), including the on-state current and mobility, were improved by approximately an order of magnitude, while the on-off ratio increased by nearly 1.5 orders of magnitude. Upon shortening of the channel lengths of the devices, high-performance TFTs were fabricated based on an increase in the proportion of individualized SWCNTs that directly connected the source and drain electrodes. The present technique provides an important foundation for promoting the development of carbon-based electronic devices.

Failure of Au-coated metallic bipolar plates for fuel cell in a 3-kW stack under the new European driving cycle

The studies on coating materials and their failure modes are significant for promoting the commercialization of metallic bipolar plates (BPPs) in proton exchange membrane fuel cells. Here in this work, the influence of simulative operation condition in automobile on the degradation of gold (Au)-coated 316 L BPPs is systematically investigated using New European Driving Cycle (NEDC) in a 3-kW stack for 5000 h. The original stack showed 36% decay after 5000 h while negligible change on ohmic resistance (3–5 mΩ) is surprisingly found, indicating the stable interface between aged BPPs and membrane electrode assembly (MEA). However, 15% voltage loss is found in a reassembled single cell using aged BPP and fresh MEA, indicating the degradation of BPPs indeed. Further short stack matching testing and microscopic analysis reveal the well matching state and unobstructed conductivity between BPPs and MEA in the original stack, while it would be broken during reassembly (the high-frequency resistance has increased by about 2 times). The postmortem analysis on degraded BPPs indicates the failure mode of coating including the aggregation of the Au, the growth of oxides and gradual coverage of Au. The failure of coating not only results in the increase of interfacial contact resistance (ICR) from 5.4 mΩ cm2 to 137.8 mΩ cm2 and decrease of contact angle from 63.5° to 0° in some severely corroded region, but also has significant impact on the mass transport due to increased surface roughness. Especially, the formed passive layer is found to be dissolved at high potential, leading to the ion precipitation risk. These results provide guidance for optimizing coating materials, operation conditions, and assembly procedures in the future.

Effect of different gaps in the conductor rail joints on the current-carrying wear performance of carbon skateboards/conductive rail contact

The interconnection of the conductive rail for intercity trains involves multiple sections of steel rails. The presence of gaps in the joints between these steel rails greatly impacts the efficacy of current transmission in collector–conductor rail systems. A total of nine joints with different inclined angles and widths were devised to investigate the influencing characteristics of gaps on the current–carrying friction of carbon skateboards/conductive rail contact. The nine joints were tested by using a pin-disc current–carrying friction tester to evaluate the wear performance of different contact pairs. The findings indicated that the presence of gaps in conductor rail joints resulted in a decrease in the coefficient of friction, but an increase in the electrical contact resistance. Furthermore, these gaps substantially impacted the wear rate of carbon skateboards. Specifically, when the gap width was 1.5 mm, the influence of the inclined angle of the gaps on the electrical contact resistance diminished. Additionally, the gap characterized by a width of 0.5 mm and an inclined angle of 90° exhibited a comparatively reduced influence on the wear performance of the contact pairs.

Improving the joint strength of laser-welded CFRTP/TC4 joints via appropriate groove design

Laser surface treatment can enhance the joint strength of reinforced thermoplastic composites (CFRTP) and metal joints. In this study, an ultraviolet picosecond laser system grooved the Ti-6Al-4V (TC4) surface, and the influence of grooves on the CFRTP/TC4 joints was investigated. 0° parallel, 90° parallel, 45° parallel, 0/90° crossed and ±45° crossed grooves were created on TC4 surface. Compared with the joint without grooves, the joint strength was improved by all groove patterns. The grooves improve the thermal contact resistance at the interface, and buffer the energy input of the CFRTP side, inhibiting the pyrolysis of the CFRTP and eliminating the bubble defects. Meanwhile, the groove enhances mechanical interlocking. The joint with ± 45° crossed grooves was the strongest, being 120.1 % stronger than the joint without grooves (ultimate shear force of 1552 N). Apart from the mechanical interlocking, the compound layer consisting of the CTi0.42V1.58 phase was confirmed and a novel chemical bonding, TiOS, was also discovered at the interface. However, no significant effect of the grooves on chemical bonding was found. The increase in thermal contact resistance and the mechanical interlocking reinforcement after cooling were the main strengthening mechanisms of the grooves.

Effect of thermal management system parameters on the temperature characteristics of the battery module

In the present inquiry, a novel electric-thermal coupled model is devised to delve into the battery module's temperature distribution characteristics at different ambient temperatures and discharge rates. The accuracy of temperature prediction accuracy is contingent upon the experimental determination of the entropy heat coefficient and convective heat transfer coefficient. In the absence of a thermal management system for the battery module, an escalation in the discharge rate correlates with an increase in the average temperature, average temperature rise, and maximum temperature difference, while a decline in the initial ambient temperature relates to a decrease in these values. Under typical vehicle driving cycle conditions, the average temperature curves show peaks before the end of the cycle. The wider speed range, longer testing time, and reduced regularity of the driving cycles cause both the average temperature and maximum temperature difference to increase. Further research is done into the effects of coolant flow rate and temperature, and contact thermal resistance on the efficiency of thermal management systems. Gradual decrease in the average temperature transpires as the coolant flow rate increases, but excessively high flow rates engender a larger maximum temperature difference. As the coolant temperature decreases, both the average and maximum temperature difference decrease, but temperature uniformity is worsened. The average and maximum temperature difference generally rise when the thermal contact resistance increases, and a low thermal contact resistance leads to a more uniform low-temperature distribution.

Tunable Conformal Electrodeposition of Ultra-Thin Polymeric Films for Electrolyte Interphases

Functional coatings and interphases influence the stability and performance parameters of electrodes in various applications. Polymer thin films offer a wide range of molecular structures and compositions for tunable functionalities that can be custom designed to the needs of an application. In solid-state energy storage devices in particular, electrolyte-type polymeric interfaces between battery components and materials with disparate functions, such as the active electrode material and solid electrolyte could overcome some of these incompatibility detriments and the increase in contact resistance over long-term operation. In high-performance micro scale power sources, 3D thin-film all-solid-state batteries show great potential as they take advantage of both short ion diffusion distances for high-rate capability with low heat generation, as well as the third dimension for high material loading and energy density. Therefore, conformal deposition methods for ultra-thin polymeric electrolyte interphases on the interior surface of electrodes with mesoscale 3D architectures and complex porosity are in demand. Here, we report a molecular design concept of dual-functional molecules that contain electrochemically active end groups for self-limiting electropolymerization, and a core molecular motif that determines the thin film functionality. The electrodeposition of this monomer represents a non-line-of-sight coating method for polymer thin films with independently tailorable functionalities and tunable properties on conductive substrates with arbitrary shape. We exemplify this method using monomers with poly(ethylene glycol) (PEG) as the core motif for lithium-ion transport and phenol as electrochemically active end groups. We studied the electrodeposition of the monomers, poly(ethylene glycol) diphenol (PEGDP), and demonstrate their self-limiting film formation mechanism (Figure 1a) which originates from the insulating nature of resulting poly(PEGDP) film that confines the charge transfer reaction. We present an exhaustive exploration of their material-processing-structure-property relationships that reveals the multi-scale control over the ultrathin-film properties. For example, the uniform film thickness is tunable from 10 to 100s of nanometer through electrodeposition conditions and molecular design, while their molecular permeability and electronic resistance can be tailored from pervious to fully blocking. We show that the electrodeposited functional interphases fully coat complex 3D electrode architectures (Figure 1b top: uncoated carbon electrode, bottom: film coated carbon electrode) with retention of their functionality in a battery. This work demonstrates that rational molecular design enables the conformal electrodeposition of ultrathin functional coatings with solid polymer electrolyte properties on 3D structured electrodes that will enable designer interphases in various solid-state battery architectures and chemistries. Figure 1

Significant effect of thin oxide layer on characteristics of p-InGaN/GaN nonalloyed ohmic contacts

In an interconnected high-vacuum illustration system, the surfaces of p-InGaN/GaN heterostructures grown with integrated metalorganic chemical vapor deposition were treated in O2 gas for different times at room temperature and then transferred to another chamber for fabricating ohmic contacts via sputtering Pd/Pt/Au multi-layers. X-ray photoelectron spectroscopy measurements unveil that the proportions of Ga–O of the treated samples significantly increase compared with that of the as-grown sample, indicating that a thin layer of GaOx forms on the p-InGaN/GaN surface after exposing to oxygen or air atmospheres. Meanwhile, the samples exposed to O2 or air were found to have much higher specific contact resistance, i.e., higher by two orders of magnitude than that of the as-grown sample. The specific contact resistance of the as-grown sample was derived as 9.3 × 10−5 Ω cm2 using the circular transmission line measurement. Furthermore, the Schottky barrier height of the samples was determined from the measured I–V curves with the thermionic field emission model and was revealed to be closely related to surface treatments. Despite the fact that the insulating layer of GaOx was as thin as 1.2–1.4 Å for the samples exposed to oxygen at room temperature, it can act as an extra barrier layer causing significant increase in the specific contact resistance via blocking the tunneling of carriers. Therefore, the effective removal of p-InGaN surface oxide plays a vital role in preparing good ohmic contacts.

Improving the performance of titanium bipolar plate in proton exchange membrane water electrolysis environment by nitrogen-chromium composite cathode plasma electrolytic deposition

In the proton exchange membrane water electrolysis (PEMWE), the titanium bipolar plate coated with noble metals is usually used, which puts forward higher requirements for costs. This study investigates the cathode plasma electrolytic deposition (CPED) for the titanium and obtains TiN and TiN/CrN coatings. The TiN coating exhibits the diffusion resistance in the anode PEMWE environment, resulting in an increase in the interfacial contact resistance (ICR). The denser TiN/CrN coating eliminates the diffusion resistance and increases the polarization resistance (Rp) value from 3873 Ω cm2 of TiN coating to 12,320 Ω cm2 of TiN/CrN. After long-term potentiostatic polarization, the ICR of TiN/CrN coating is 8.5 mΩ cm2, which is 3.5 times lower than that of TiN coating. Therefore, the low-cost TiN/CrN coating obtained by CPED has brought a good application prospect for bipolar plates in PEMWE.

Suppression of copper surface oxidation by electrophoretically deposited graphene oxide film

This work investigated the oxidation suppression effect of a reduced graphene oxide (rGO) film applied to a Cu substrate, which may have application in electrical connectors. To ensure prolonged low electrical contact resistance, a thin GO film was formed using an electrophoretic deposition method and subsequently heated to generate rGO. The surface morphology and thickness of the rGO film were assessed using atomic force microscopy and transmission electron microscopy. The thickness of the rGO film was estimated to be 5–7 nm, and the electrical contact resistance for the Cu substrate with and without an rGO film was 20 and 8 mΩ, respectively, at a contact load of 2 N. After accelerating the oxidation of the substrate by heating for 30 min at 180 °C under a dry air atmosphere, the formation of a Cu2O layer on the Cu substrate was confirmed by Raman spectroscopy and electron energy loss spectroscopy. The thickness of this oxide layer with and without an rGO film was 1.5 and 6 nm, respectively. In addition, the electrical contact resistance for the Cu substrate with and without the rGO film was 40 and 200 mΩ, respectively, at a contact load of 2 N. These results suggest that the thin rGO coating suppressed oxidation of the metal substrate while also suppressing the increase in contact resistance.

Room-temperature electroluminescence and light detection from III-V unipolar microLEDs without p-type doping

The twentieth-century semiconductor revolution began with “man-made crystals,” or p-n junction-based heterostructures. This was the most significant step in the creation of light-emitting diodes (LEDs), lasers, and photodetectors. Nonetheless, advances where resistive p-type doping is completely avoided could pave the way for a new class of n-type optoelectronic emitters and detectors to mitigate the increase of contact resistance and optical losses in submicrometer devices, e.g., nanoLEDs and nanolasers. Here, we show that nanometric layers of AlAs/GaAs/AlAs forming a double-barrier quantum well (DBQW) arranged in an n-type unipolar micropillar LED can provide electroluminescence (EL) (emission at 806 nm from the active DBQW), photoresponse (responsivity of 0.56 A/W at 830 nm), and negative differential conductance (NDC) in a single device. Under the same forward bias, we show that enough holes are created in the DBQW to allow for radiative recombination without the need of p-type semiconductor-doped layers, as well as pronounced photocurrent generation due to the built-in electric field across the DBQW that separates the photogenerated charge carriers. Time-resolved EL reveals decay lifetimes of 4.9 ns, whereas photoresponse fall times of 250 ns are measured in the light-detecting process. The seamless integration of these multi-functions (EL, photoresponse, and NDC) in a single microdevice paves the way for compact, on-chip light-emitting and receiving circuits needed for imaging, sensing, signal processing, data communication, and neuromorphic computing applications.

Performance enhancement of coated conductor magnet with double-layer metal insulation

A double-layer metal-insulation method using brass sheets as the double-layer insulators is proposed in this paper. It can enhance the contact resistivity while preserving greater thermal conductivity merit. The underlying mechanism of the contact resistivity enhancement is to increase the number of contact surfaces and to degrade the contact quality between the insulators. Then, we wound a single-layer brass-insulation coil and a double-layer brass-insulation coil to compare their contact resistivities, and confirmed the effectiveness of the double-layer metal-insulation method. Furthermore, since the capacity to withstand the overcurrent is weakened with the increasing contact resistance of the metal-insulation coil, we further investigated the influence of the contact surface resistivity distribution on the coil performance under different scenarios to optimize the double-layer metal-insulation coil for receiving superior thermal stability. The simulation results indicate that dominant second contact surface resistivity and minimal first and third contact resistivity is the optimal design for the double-layer metal-insulation coil to receive the best thermal stability, irrespective of the cooling environment, contact resistivity magnitude, operating current and coil dimension. In addition, with regard to the thermal performance differences caused by the contact surface resistivity distribution, we found that the increment of contact surface resistivity and the overcurrent enlarged the distinctions at different levels.

Einfluss der Mikrohärte der Ober- flächenschutzschicht auf den Verschleiß und die Lebensdauer von elektrischen Kontakten bei Reibverschleißbelastung

The lifetime of electrical contacts is influenced by various factors. Micromotions due to fluctuations in temperature and vibration in the field lead to fretting wear and fretting corrosion of electrical contacts. In case of the contacts with noble coatings, the fretting wear results in the wear through of the coating causing the exposure of the underlying non-noble metal to the surrounding atmosphere which in turn leads to fretting corrosion. These degradation mechanisms lead to an increase in electrical contact resistance and eventual failure of the system. In this study, the extent of contact degradation due to fretting war of galvanically silver-plated electrical contacts is investigated. To compare the extent of war occurring at different stages of the contacts’ lifetime, the fretting tests are conducted up to predefined fretting cycles. XRF measurements of the coating thickness before after the tests are performed and the wear depth after the given fretting cycles is determined via confocal microscopy. The results of two different types of silver plating are compared. Based on this, a prognosis regarding the wear behavior and expected lifetime of different coating systems can be made possible.

Connection fault diagnosis for lithium-ion battery packs in electric vehicles based on mechanical vibration signals and broad belief network

The connection faults between the cells of a battery pack can increase contact resistance and thus result in abnormal heating at the connections, which can seriously damage or even fail the battery pack. This work therefore proposes a novel connection fault diagnosis method based on mechanical vibration signals rather than voltage and current measurements. Firstly, this work simulates the vibration environment, which resembles that of the actual operation of a lithium-ion battery pack in electric vehicles. The optimal sensor placement is achieved via a sparse-learning algorithm, and the vibration signals are collected on this basis. Following that, this work proposes a broad belief network (BBN) for detecting and locating connection faults in lithium-ion battery packs based on the vibration signals. Since fault diagnosis needs to adapt to new data as they become progressively available in real-time, two incremental-learning algorithms are paired with the BBN, such that the network can achieve fast reconstruction and expansion without re-training from scratch. Empirical evidence suggests that the diagnostic accuracy of the proposed method is 93.25%, which demonstrates the effectiveness and feasibility of the proposed method.