Development of strategies for the assembly of energy storage devices with regard on possible quality inspections

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TASK DESCRIPTION

Title of the Master-Thesis:

Development of strategies for the assembly of

ener-gy storages with regard on possible quality

inspec-tions

Inv.-Nr.: 22920

Author: Agresti Fiammetta Advisor: Carola Zwicker

Issue date: 01.10.2014 Submission date: 31.03.2015

Initial Situation:

The use of renewable energy sources is getting a dominant subject because of tightened boarders for CO2 emissions and the decreasing amount of fossil ma-terials. An important component for the use of renewable energy is the energy storage.

At the moment, storages are often assembled manually because of a small lot size, processes like cabling, which cannot be automated easily, and custom-designed storages. The assembly of parts for energy storages should be au-tomated regarding the increasing lot size in the future to stay profitable. The need of custom-designed storages brings another challenge about. Different battery cell formats, different module formats, different storage formats, differ-ent technologies for cooling and electronics must be handled with only a few assembly systems.

Purpose:

Object of the thesis is the development of strategies for the assembly of the custom-designed energy storages. Based on an investigation on different stor-age concepts and on the assembly processes, the solutions are gathered in a graphical way, for example in a morphological box. Subsequently, strategies for the assembly are developed with regard on possible necessary quality in-spections within the assembly process. The validation and verification of the strategies by means of real energy storages complete the thesis.

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Approach and method:

1. Research on energy storages and their assembly operations: a. Research on energy systems

b. Research on assembly of battery modules and energy storag-es

2. Identification of energy storage components and processes for the assembly

a. Identification of energy storage components b. Identification of processes for the assembly 3. Illustration of the results in a morphological box

4. Deduction of strategies for the assembly of energy storages a. Deduction of possible assembly priority plans

b. Identification of possible assembly steps c. Deduction of strategies from preview steps d. Reduction of the strategies by comparing 5. Validation and Verification by means of real storages

a. Gathering information on the projects b. Development of a strategy for project 1 c. Development of a strategy for project 2 6. Documentation of the thesis

Agreement:

Intellectual property of the iwb is integrated in this thesis with the support of Mrs. cand.-M.Sc. Fiammetta Agresti by Mrs. Dipl.-Ing. Carola Zwicker. Publi-cation of the thesis or the disclosure to third parties needs approval of the chair’s head. I agree with archiving the thesis in the iwb-owned and only for

iwb employees accessible library as inventory and in the digital thesis data

base of the iwb as pdf document.

Garching, 2014/01/10

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ACKNOWLEDGEMENTS

At first I would like to thank my parents for always having supported and en-couraged me, regardless of the decisions I made. Thanks to them I was able to undertake this experience that helps me mature.

I would like to thank my advisor, Professor Zwicker who has guided and helped me during the development of this work. I would especially like to thank her for providing me the information necessary to compile a section of this the-sis and for the availability and precision she has shown in these months. Her guidance and supervision were fundamental for the achievements of this work. I would also like to thank my advisor Professor Dini who enabled me to live this formative experience. Thanks to him I have experienced a new reality and improved my organizational skills dealing with this challenging work.

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LIST OF FIGURES

Figure 1 Procedure of this work ... 4 Figure 2 Example of a lithium-ion battery pack (Epec 2015b) ... 7 Figure 3 Example of parallel (left) and series (right) connection (after Solar panel 2015) ... 8 Figure 4 Cross section (left) and example (right) of a cylindrical cell (Technick 2015) (left), (Directindustry 2015) (right) ... 9 Figure 5 Cross section (left) and example (right) of button cells (Buchmann 2015a) ... 10 Figure 6 Cross section (left) and industrial example (right) of a prismatic cell (Buchmann 2015a) (left), (Osn 2015) (right) ... 11 Figure 7 Cross section (left) and example (right) of industrial pouch cells

(Buchmann 2015a) (left), (Lawson 2015) (right)... 11 Figure 8 Example of industrial high power cells (Lawson 2015) ... 12 Figure 9 Examples of sheet metal tabs (left) and conductive bus bars (right), (Wikipedia 2015) (left), (Indiamart 2015) (right) ... 13 Figure 10 Example of a molded in circuit (left) and an I-beam structure (right) (Bresin et al. 1993, p. 3) (left), (Dorinski et al. 1992 p. 5) (right) ... 14 Figure 11 Ni-MH battery pack (Epec 2015b) ... 15 Figure 12 Lithium polymer battery pack for medical application (left) and

lithium battery pack in an off-the-shelf case (right) (Epec 2015c) (left), (Lawson 2015) (right) ... 16 Figure 13 Example of heat shrink tubing ES devices (Epec 2015a) ... 17 Figure 14 Example of an integrated BM case with ribs on its outer sidewalls (Inoue et al. 2002, p. 2) ... 18 Figure 15 Prismatic sealed cell type with safety vent (Hamada et al. 1996, p. 2) ... 19 Figure 16 ES device housing with apertures on sidewalls (McArthur 1985) ... 21 Figure 17 Sketch of the four gaps formed by a cylindrical cell inserted into a square shaped accommodation place ... 22 Figure 18 Example of master-slave BMS in prismatic high power cells (left), two cells stacked in column (right) (Endless-sphere 2015) (left), (Epec 2015a) (right) ... 23 Figure 19 Classification of assembly operations (after Lotter & Wiendahl 2012, p. 2) ... 26 Figure 20 Example of separator included in the cover of a low power ES

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Figure 21 Securing cell cluster into battery cases (left), insertion of a cell stack into appropriate holes in the BM housing (Epec 2015a) (left), (Etoh &

Watanabe 2000, p. 2) (right) ... 38

Figure 22 Example of cells insertion into BM case (Konishi et al. 1993, p. 2) . 39 Figure 23 Spot welding (left) and example (right) of metal conjunction tabs coupling cells (Epec 2015a) (left), (Hershberger & Izenbaard 1999, p. 5) (right) ... 41

Figure 24 Example of screwing bus bars to a parallel connection (Holl & Parsippany 1990, p. 3) ... 42

Figure 25 Possible ES configuration after discrete cell stacking (Konishi et al. 1993, p. 4) ... 43

Figure 26 Example of BM housing with cells accommodation and pre-assembled conductive terminals (Hirano 2005, p. 10) ... 44

Figure 27 Securing of a BM (Epec 2015a) ... 45

Figure 28 Example of securing BMs (left) and a BP (right) with mechanical joints (Hirano 2005, p. 6, p. 7) ... 46

Figure 29 Example of discrete devices for securing cells (Holl & Parsippany 1990, p. 2) ... 47

Figure 30 Example (left) and lateral view (right) of securing ES devices together (Marukawa et al. 2004, p. 2, p. 5) ... 48

Figure 31 Gluing of CC into BM housing (Epec 2015a) ... 49

Figure 32 ES configuration including a coolant tubing device arranged with cells longitudinal section (left) and base section (right) (Bindin & Jones 1983, p. 3) ... 49

Figure 33 Example of the cooling device assembly process (Ogata & Hamada 2004, p. 2) ... 50

Figure 34 Example of a BMS secured to a CC formed by cylindrical cells (Epec 2015a) ... 51

Figure 35 Example of connecting CC to the BMS located in BM case (Epec 2015a) ... 52

Figure 36 “Positioning fixture” (left) and example of a supporting frame for prismatic ES formats (right) (Hershberger & Izenbaard 1999, p. 4) (left), (Holl & Parsippany 1990) (right) ... 53

Figure 37 Example of matching test made on pouch cells (Epec 2015a) ... 55

Figure 38 Final test circuit implemented in Epec industries (Epec 2015a) ... 58

Figure 39 Flow chart representing the most important tasks of APST 1 ... 68

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Figure 43 Conductive terminals integrated to the cell case (Hamada et al.

1996, p. 5) ... 77

Figure 45 FAS final phase ... 84

Figure 46 Principle assembly line ... 85

Figure 47 Variant 1 (pre-assembly) ... 88

Figure 48 Variant 2 (supporting frames) ... 89

Figure 49 HVS device in NEXHOS project (Zwicker 2015) ... 91

Figure 50 NEXHOS-device bill of materials ... 93

Figure 51 BM with safety devices attached to each side except the top part (Zwicker 2015) ... 94

Figure 52 Pressure plate, plastic tape assembly and cooling device (Zwicker 2015) ... 94

Figure 53 Slave BMS with attached BM conductive connectors and terminals (Zwicker 2015) ... 96

Figure 54 Integrated BP housing (Zwicker 2015) ... 97

Figure 55 Bridge structure (Zwicker 2015) ... 98

Figure 56 EEBatt ES device, partial view (Zwicker 2015) ... 99

Figure 57 EEBatt bill of materials ... 100

Figure 58 CC of EEBatt project (Zwicker 2015) ... 101

Figure 59 EEBatt device electrical connetion system (Zwicker 2015) ... 102

Figure 60 EEBatt BM without housing parts and with fuse and plug exploded (Zwicker 2015) ... 102

Figure 61 Low power ES device bill of materils (Farley 1996) ... 105

Figure 62 Exploded view of the low power ES device (Farley 1996, p. 4) .... 104

Figure 63 Final assembly strategy chart ... 120

Figure 64 Assembly of NEXHOS BM ... 121

Figure 65 Assembly of NEXHOS BP ... 122

Figure 66 Assembly of NEXHOS C ... 123

Figure 67 Assembly of EEBatt CC ... 124

Figure 68 Assembly of EEBatt BM ... 125

Figure 69 Assembly of EEBatt BP ... 126

Figure 70 Assembly of EEBatt C ... 127

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LIST OF TABLES

Table 1 Morphological box of energy storage components ... 25

Table 2 Distinction between necessary and optional components for cell clusters ... 33

Table 3 Distinction between necessary and optional components for battery modules ... 34

Table 4 Distinction between necessary and optional components for battery packs ... 35

Table 5 Morphological box of energy storage assembly operations ... 63

Table 6 Flow chart symbols ... 65

Table 7 Decision points included in the final assembly strategy (FAS) ... 118

Table 8 Symbols of the assembly operations ... 118

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LIST OF ABBREVIATIONS

Symbol ES s.device m.t.e.c. c.t c.device m.t.secure BMS h.structure v.inspection e.m.d o.m.s. SW PCB PV

SOC state of charge photovoltaics cooling devices

Description

energy storage

safety device

means to electrically connect

conductive terminals

printed circuit board

pc software that checks multiple parameters means to secure

battery management system

helping structure

visual inspection

electric measurement devices

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ABSTRACT

A new approach to energy storage systems is required to establish global en-ergy policies based on a reduction of CO2 emissions and a shift towards inter-mittent renewable power, while maintaining a secure energy supply. This work deals with devices that store energy in an electrochemical form and convert it into electricity. For this reason they can usefully be assimilated to batteries. These devices are multi-beneficial for improving power quality and reliability, reducing transmission/power losses, saving cost and decreasing environmen-tal impacts. ES battery systems are not standardized devices because they have to meet the different mechanical and electrical requirements related to many applications. The customization of these devices brings further ad-vantages such as the optimization of the product performance and additional cost reductions for the intended market. On the contrary, disadvantages affect in particular the assembly processes of these devices. In fact, the assembly process has to deal with small production scales, the necessity for manual op-erations, and the absence of process standardization (that if present, would allow as automatic assembly). This work develops a model to find a prelimi-nary assembly strategy able to combine assembly operations of varying ES devices. Through the investigation of different existing storage concepts and the study of the existing assembly processes, possible solutions were grouped into different clusters. These clusters have allowed the deduction of initial strategies that outline five different types of assembly processes. Assembly operations may be gathered in different sequence configurations from group to group. In the end the final assembly strategy has been developed by compar-ing these initial assembly strategies. This method uses a comparative ap-proach that, despite its generality, outlines the principle similarities among the existing ES devices and some interesting springboard for future developments.

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1 INTRODUCTION

The global energy use will increase around 2% per year in the coming dec-ades. The U.S. Department of Energy forecasts that the worldwide energy demand will increase up to 60% between 2000 and 2025. (Geller 2003, p. 205) In a context where the attention to the environment has become a worldwide hot-spot and the amount of fossil materials is decreasing, the use of renewable energy sources is becoming a dominant subject. This chapter aims to explain the importance of energy storage systems in current and future scenario, the proposed objective of this thesis, and gives an overview of the procedure used to achieve it. This chapter ends with the definition of the used terminology.

1.1 Motivation

European and global energy policies are based on a reduction of CO2 emis-sions, and a shift towards intermittent renewable power while maintaining a secure energy supply. This leads to a new generation of energy storages, as a key component of the future low-carbon electricity system (Europe commission 2013). The concept of “energy storages” is based on devices that buffer ener-gy in any form for later use. There are different types of enerener-gy storages re-garding their storage medium: chemical (batteries), thermal, mechanical (fly-wheel), and electrical (capacitor) (Brown 2015).

Type of energy storage (ES) device discussed in this work

This work deals with energy storage devices that store energy under electro-chemical form so they can be assimilated to batteries. As Dell & Rand (2001, p. 5) state, fossil fuels have some different characteristics compared to renew-able energies. These fuels are stored until their time of use and may be trans-ported by rail, road or pipeline to wherever they are needed. By contrast, most of the renewables (except for biomass and hydro-electric-power) cannot be stored and cannot be transported to the place of use, except by first converting them to electricity. Electricity is the most versatile and preferred form of energy for many applications and therefore it is not surprising that renewable energies and electricity generation are so intimately bound together. For this reason en-ergy storage systems that are able to store enen-ergy under electrochemical form (cells) for use at another time, are important components for using renewable energies.

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Possible applications

Energy storage battery technologies are by far the most discussed technolo-gies. In fact, while expert opinions diverge enormously regarding their cost fu-ture reduction; these devices can be used in several applications. For example they can be coupled with wind farms, PV (photovoltaic) systems, transmission grids or distribution grids. (Europe commission 2013, p.6) The role of storing energy in today's and tomorrow's energy systems is essential to balance sup-ply and demand. Peaks and troughs in demand can often be anticipated and managed by increasing or decreasing generation at fairly short notice. In a low-carbon system, intermittent renewable energy makes it more difficult to vary output. Rises in demand do not necessarily correspond to rises in genera-tion. (Europe commission 2013) Energy storage devices can be multi-beneficial for improving power quality and reliability, reducing transmis-sion/power losses, cost savings and decreasing of environmental impacts (lower emissions, diminished electric/magnetic field effects, integration of re-newables). (Dell & Rand 2001, p. 6) Ibrahim et al. (2012) describe these con-cepts better presenting an overview of additional multiple uses of ES devices. Storing energy can be useful for generate electricity, e.g. store bulk energy at night for use in peak demand periods during the day, or provide electrical dis-tribution grid to reduce any sudden large generation imbalance and maintain-ing a state of frequency equilibrium. Väyrynen & Salminen (2011, p. 80) state that ES devices are applied also in partly or fully powered electric vehicles, industrial vehicles, lifts, cranes, harbor machines, mining vehicles, oats, and submarines.

Advantages and disadvantages of customized energy storage devices

A single type of ES device is not able to fit all purposes of the several fields in which ES systems are used. So the construction of special devices that are able to meet the different mechanical and electrical requirements of all the ap-plications is required. ES devices, as explained better in future work, are built through a combination of cells to larger battery systems. A bigger format re-quires components for electrically connect cells, cool and control (like the BMS) the final device, and making it safety. These components change every time to precisely meet the requirements expected. The use of customized ES devices gives the designer more flexibility to optimize the product performance and cost for the intended market, and allows a better reliability of the device, fewer steps in manufacturing systems, and a less number of components. On the contrary, different existing variants of batteries and a missing standard-ization of battery designs as well as a great number of different assembly

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pro-cess technologies prevent assembly systems from becoming more competi-tive. (Lawson 2015) The assembly processes of energy storages devices should increase their efficiency, flexibility, and effectiveness. Challenges, in-cluding the need for custom-designed storage devices, different technologies for cooling and electronics, and different formats for cells, modules, and stor-ages, must be handled to improve the manufacturing of the energy storages in order to satisfy the increasing market request.

1.2 Objectives and purpose

The aim of this work is to create a model of a general assembly strategy for all different customized ES devices combining their assembly processes. This main objective has been split into two sub-goals. The first is to understand if it is possible to classify different ES devices and assembly processes under same categories. The second is to identify a preliminary possible lay-out of the single assembly strategy, based on these categories. Through the investiga-tion on the existing different storage concepts and the study of the existing as-sembly processes, it is possible to gather the solutions in different clusters. The clusters are then shown in graphical ways like morphological boxes or flow charts. After acquiring a better understanding of energy storage types and their ways of assembly, a new assembly process strategy has been devel-oped. This permits to assemble energy storages with different mechanical and electrical characteristics. In this way a single assembly line is developed that suits for several energy storage types. To verify if the objective of the thesis is achieved the model is applied to actual energy storage systems.

1.3 Method and procedure

In order to accomplish the purpose declared in the present work, a formalized procedure has been set up which intends to guarantee that all necessary steps will achieve the expected results. The method is divided into five main phases. In the first one the study of the state of the art related to the existing cell clus-ter, module and pack formats follows a deep analysis of the information gath-ered in order to identify their main components. As a conclusion of this phase, the identified components are presented in a graphical way. The same proce-dure is applied to the different assembly operations and quality tasks adopted during the process. The second step deals with the identification of the main tasks/phases of the assembly process which are used to deduce the possible

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assembly priority plans. In particular, five different typologies of assembly pro-cess sequences have been found. The third step consists in developing the single final assembly strategy. The five initial strategies are compared one an-other in order to outline the principle operations that constitute the final flexible assembly strategy. The validation and verification of the concept by means of real storages follows. First the information on the projects is gathered; then, their assembly process is applied to the final strategy in order to determine its conceptual effectiveness. The final phase, as a conclusion, will outline the crit-icalities emerged from the validation process, possible future developments and improvements of the model. Figure 1 gives a schematic representation of the procedure just described.

1.4 Definition of the terminology used

There is no consistent use of terms describing the various components of a battery system. The word ‘‘battery’’ is used when referring to both a single cell and a set of cells, for example, a 12 V car battery comprising six cells. This happens because the concept of the energy storage system is still a novelty in current research. Therefore a limited number of English papers exists, and a specific terminology is missing. Despite this poor presence of scientific articles, many patents have been generated over the years with the aim of improving the technical characteristics of the energy storage devices. These have been very helpful to build up general concepts of energy storages.

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In this work, the following terms are used:

 cell: the most basic element of an energy storage device.

 energy storage device/system (ES): device that stores energy in an electrochemical form. The energy storage in this work can be assimilat-ed to a battery (series of electric cells that store chemical energy which can be converted into electrical power);

 cell cluster (CC): the smallest “assembly level” type for an energy stor-age device. It is a collection of cells connected in series, or parallel providing a higher voltage and capacity than a single cell;

 battery module (BM): the second “assembly level” type for an energy storage device. It is more powerful than the cell cluster but less than the following types. Two different typologies of battery modules exist. The first one is a collection of CC connected in series, or parallel (or either in series and parallel) located in a single enclosure. In this type more steps during the assembly process are required. The second is a set of cells secured together with mechanical joints and electrically connected. Here less steps in the assembly process compared to the first typology are needed.

 battery pack (BP): the third “assembly level” type for an energy storage device. It is a set of BMs that are electrically connected (parallel or se-ries connection) and secured with mechanical joints.

 container (C): the last assembly level type for an energy storage device. It is formed by securing battery packs one another and electrically con-necting them together in series, or parallel (or either in series and paral-lel) including the cooling system, and the BMS master unit. It is the most powerful energy storage device among all the four types.

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2 STATE OF THE ART

As already mentioned, batteries are becoming the major device to store re-newable energy. Currently they are applied in several different fields like mili-tary, medical, industrial, and high-volume consumer supply. Although their widespread use, they still have to be improved. The major problems among the ones that have been already mentioned are the small scale of production, the presence of several customized types, and the absence of automatic sembly processes. These problems lead to a loss of efficiency during the as-sembly of the energy storage devices, both in economic and temporal point of view. This section will give an overview of the existing CCs, BMs, BPs, and C, their principle components, as well as, their most common assembly process-es.

The morphological box

The results of the literature analysis have been gathered in morphological boxes to achieve a better understanding of the principle components of ES devices, and what their most common typologies are. The same instrument has been used to show the main assembly operations of ES devices, and their most common technologies. Therefore, the goal of this classification is to ob-tain a consolidated and clear definition of what are the principle component types of ES devices and how they can be assembled. Morphological boxes are a good instrument to provide a clear classification of objects, ideas, and pro-cedures divided into different types and subtypes. This extended classification framework serves as a basis for the deduction of the possible prior assembly strategies developed in chapter 4.

2.1 Energy storage components

This work focuses on energy storage, devices that store energy in chemical form and release it as electrical power. In particular, modular battery systems allow the customer to choose different battery capacities and corresponding driving ranges. The core of a modular ES system are the cells and auxiliary components (such as frames, safety means, and cooling devices) that are stacked in a repetitive pattern, and then secured and packaged. (Li 2012, p. 10)

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Figure 2 shows an example of a CC, which is formed by four lithium-ion cells, safety inserts (marked in light-blue) and spot welded conductive terminals. The cells are electrically connected in series by welded metal tabs (circled in red), and are connected to an electrical control card by wires.

Before describing ES components some important information (such as series and parallel connection or ES format dimensions) is given to better understand the importance of the modular approach used in energy storages.

Voltage and current handling (parallel or series connection)

Depending on their purpose and electrical specifications there are lots of ES typologies. They achieve the desired operating voltage by connecting several cells in series. On the contrary parallel connection attains higher capacity for increase current handling, as each cell heightens to the total current. (Buch-mann 2015b) Whereas cell voltage is fixed by the cell chemistry, cell capacity depends on the surface area of the electrodes and the volume of the electro-lyte, that is, the physical size of the cell. (Lawson 2015) Some packs may have a combination of serial and parallel connections. For example, laptop batteries commonly have four 3.6 V Li-ion cells in series to achieve 14.4 V and two strings of these four cells in parallel (for a pack of eight cells in total) to boost the capacity from 2,400 mAh to 4,800 mAh.

It is important to use the same battery type with equal capacity throughout and the whole storage. A weaker cell causes an imbalance. This is especially criti-cal in series configuration because the battery is only as strong as the weakest cell. (Buchmann 2015b) Parallel connection as it is shown in Figure 3 (left), is made by connecting negative terminals, and positive terminals of two cells re-spectively. Instead, series connection (right) is achieved by linking the positive terminal of one cell, to the negative terminal of the next cell with means for electrical connection.

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Afterwards, to allow the device to communicate with the outside the conductive terminals are necessary (circled in red in Figure 3). (Holl & Parsippany 1990)

As stated in chapter 1.4 ES components can be combined to form four differ-ent major formats: cell clusters (CC), battery modules (BM), battery packs (BP), and the container (C). Every format is an energy storage device, so it is not necessary to have a container at any time because energy can be stored and released by smaller formats like BMs, or BPs, but not by CCs even with lower power and capacity.

In general ES devices are set up of similar components that have different shapes, dimensions and that are placed differently in the battery housing. This chapter will list the basic components that constitute ES systems. They are: cells, means for the electrical connection, means to secure parts together, safety devices, cooling devices, and controlling systems (battery management systems). For each of the main components a brief and general description is given. Then, some examples of the main typologies into which the component can be divided are given.

2.1.1 Cells

The type of cell to be used depends on the ES device applications. The power it requires, the capacity, the cycles, and many other performance characteris-tics are the starting point for the choice of the components designs. The elec-trochemical cell is a container which has a positive, and a negative terminal and is filled with certain chemical active substances. These substances inter-act with one another to generate a potential difference, i.e. a voltage, between the positive terminal and the negative terminal. The magnitude of this voltage depends principally on the specific chemical interaction which takes place within the cell. For example, a mercury cell generates a voltage of about 1.2

Figure 3 Example of parallel (left) and series (right) connection (after Solar panel 2015)

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Volts. To obtain a voltage greater than the voltage generated by a single cell, as mentioned afore, several cells may be assembled into a housing and elec-trically interconnected so their voltages are added, i.e., connected in series. (McArthur et al. 1985) As already mentioned an important characteristic for cells is the shape of their outer case. The case may simply be a robust con-tainer made from glass, plastic or metal, insulated from the electrodes. (Law-son 2015) Cell cases can be classified in four major types: cylindrical cells, button cells, prismatic cells, and pouch cells.

Cylindrical cells are one of the most widely used packaging styles for primary

and secondary batteries. Figure 4 shows on the left the cross section and on the right an example of a cylindrical lithium ion cell. Cylindrical cells have only two electrode strips which simplify their construction and manufacturing.

They have good mechanical stability comparing to the other types of cells and thanks to their shape they can withstand high internal pressures without de-forming and leakage. Dry-out may occur if the membrane breaks. They have higher energy density than prismatic, or pouch cells, but on the contrary they have bad stacking characteristics. Due to their shape, cylindrical cells do not fully utilize the space during the stacking, but create air cavities on side-by-side placement. Usually these empty spaces are used to create cooling chan-nels for improving thermal management. Some typical applications for these cell types are power tools, medical instruments, and laptops. (Buchmann 2015a)

Button cells, also known as coin cells, satisfy the requirement of compact

de-sign in portable devices. Figure 5 illustrates cross section (left) view and ex-amples (right) of button cells. Button cells, are small, inexpensive to build, and

Figure 4 Cross section (left) and example (right) of a cylindrical cell (Technick 2015) (left), (Directindustry 2015) (right)

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easy to stack. They offer high voltage when they are stacked into a tube. Some examples of different applications where rechargeable button cells are used are cordless telephones, medical devices, and security wands at airports. However, most button cells used today are non-rechargeable and they are commonly used in medical implants, watches, car keys, and memory backup. (Buchmann 2015a)

Prismatic cells were introduced in the early nineties. Modern prismatic cells

satisfy the demand for thinner sizes. Figure 6 shows a cross section and an industrial example of prismatic cells. Prismatic cells are formed by a rectangu-lar can. The electrodes are either stacked or in the form of a flattened spiral. They are usually designed to have a very thin profile for use in small electronic devices such as mobile phones. Prismatic cells provide optimal use of space by using layered electrodes.

On the other side they have higher manufacturing costs, lower energy density and a bigger vulnerability to swelling, compared to cylindrical cells. (Lawson 2015) Prismatic cells allow flexible design but can be more expensive to manufacture, less efficient in thermal management, and have a shorter life cy-cle than cylindrical cells. It is possible to find them in mobile phones, tablets, and low-profile laptops with a range capacity of 800 mAh to 4,000 mAh. No universal format exists and each manufacturer designs its own. Prismatic cells are also available in large formats. They deliver capacities of 20 Ah to 30 Ah. Large format prismatic cells are primarily used for electric powertrains in hybrid and electric vehicles. (Buchmann 2015a)

Figure 5 Cross section (left) and example (right) of button cells (Buchmann 2015a)

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Pouch cells were also introduced in the early nineties and presented a radical

new design. Figure 7 illustrates a cross section (left) and an example (right) of a pouch cell. The design of pouch cells is simple, flexible, and lightweight. This new design makes these cells the most efficient in the use of space. Besides, they achieve 90-95 percent of the packaging efficiency, the highest among battery packs. Eliminating the metal enclosure reduces weight, but the cell needs some support in the battery compartment. With furthermore exposure to high humidity and hot temperature service life can be shortening. The pouch pack finds applications in consumer, military and automotive sectors. Stand-ardized pouch cells do not exist, and each manufacturer designs its own. Prismatic and pouch cells have the potential for greater energy than the cylin-drical format but the technology to produce large formats is not yet mature. (Buchmann 2015a)

Figure 7 Cross section (left) and example (right) of industrial pouch cells (Buchmann 2015a) (left), (Lawson 2015) (right)

Figure 6 Cross section (left) and industrial example (right) of a prismatic cell (Buchmann 2015a) (left), (Osn 2015) (right)

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Another difference among cells is between low power and high power cells. With low power cells, there is at least, some standardization. Despite, high power cells are made in a wide range of sizes using many different construc-tion techniques like, foil pouches, plastic or glass box like structures and cylin-drical steel tubes. Figure 8 shows two high power cells, and two AAA low power cells. The high power cells have 3.7 Volt Lithium cells and different ca-pacity. The cylindrical cell has a capacity of 60 Ah while the prismatic one has a capacity 200 Ah due to its bigger volume. An important requirement for high power cells is having low internal resistance, so they should have thick current carriers and low contact resistances between the electrodes and the intercon-nections. Besides, these cells usually heat up because they carry out big en-ergy quantities. The heating up of the cell brings it to swell. Usually cell de-signs include features like voids or special clamps around the outside of the cells to constrain cell expansion to a particular direction and to prevent cell damaging or deterioration. (Lawson 2015)

2.1.2 Means to electrical connect elements (m.t.e.c.)

The name means to electrical connect elements (m.t.e.c.) or conductive con-nector refers to all the devices used to interconnect cells or bigger formats to-gether. These devices are expected to have good mechanical and conductive properties like good resistivity for spot-welding, screwing or other technological processes used to connect the metal links to cell terminals, low electrical re-sistance, resistivity to corrosion, and capacity to do not easy oxidize. (Epec 2015a) In this paragraph the electrical conductive means are divided into two major categories: flat metal sheets and circuits.

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Metal tabs can be named also: straps, metal sheets, or strips. They usually

have a flat shape, and are very thin (few millimeters). (Hershberger & Izen-baard 1999, p. 9) Metal strips, bus bars, or busses are used for electrical pow-er distribution. Cells or othpow-er formats are electrically connected by these means to build bigger and more powerful formats.

There are several different shapes of conductive connectors; here the most common types are briefly described.

Figure 9 shows on the left side examples of possible shapes these devices can adopt. Flat metal tabs are commonly used to connect adjacent cylindrical cells. They can be discrete metal sheets or cross shaped with a surface that can contact more than one cell. In general these means (commonly made of Nickel) are an excellent choice for applications where high electrical conductiv-ity and low electrical resistivconductiv-ity are needed. (Seidle 2015a) While in the right side Figure 9 shows thicker type of conductive connectors than flat metal tabs. These devices are bus bars, usually made in copper, or Nickel plated copper and used to connect adjacent prismatic or cylindrical cells, in series or parallel. They are secured to cell lids (bosses), or terminals (cathode and anode) and form CCs (usually cylindrical cells) or BMs (usually prismatic cells). (Holl & Parsippany 1990, p. 2-3)

Some configurations of ES devices include conductive terminals that are pre-assembled to one end side of each bus. This design facilitates electrical inter-connections between cell formats (BMs, or BPs) and decreases the number of assembly operations. Some configurations of ES devices have integrated con-ductive connectors in the ES housing. These devices are molded in the cases as a part of the BM housing. In chapter 3.2.3 will be given a better explanation of this electrical connection typology.

Figure 9 Examples of sheet metal tabs (left) and conductive bus bars (right), (Wikipedia 2015) (left), (Indiamart 2015) (right)

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Circuits, frames or other conductive structures have the characteristic to

integrate means to electrically connect cells to the components that are used to secure cells into clusters. Bresin et al. (1993, p. 4, column 2) present a cir-cuitry means that is fixed on the surface of a header frame, i.e., BM housing. Figure 10 in the left side presents a section of this circuit configuration. As it is shown in the figure, the circuit on its surface provides means for coupling cells, for providing conductive terminals (numbers 25 to 28) or other devices neces-sary for connecting the ES device to external systems. Another configuration of circuitry means is given from Dorinski et al. (1992, p. 6, column 2) and it is shown in the right side of Figure 10. Dorinski et al. (1992) named this circuit configuration I-beam frame. It consists of an integrally molded circuit to couple cell terminals (number 72 and 74), while the conductive terminals (not shown) are metallized plastic protrusions that extend from the top portion of this frame. Number 80 and 88 constitute the charger contacts. Sometimes to electrically connect elements (like cells, or BMs) printed circuit boards (PCBs) are used. (Lee et al. 2009, p. 15) Printed circuit boards save weight and space, provide more packaging options, and simplify physical interconnections and assembly operations, as well as, eliminate the need for connectors. On contrast, they have high manufacturing costs. (Lawson 2015)

Electrical connection among different cells can be achieved also by fasten cells or ES formats by adhesive conductive tapes as it will be better described in future work.

Figure 10 Example of a molded in circuit (left) and an I-beam structure (right) (Bresin et al. 1993, p. 3) (left), (Dorinski et al. 1992 p. 5) (right)

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The name “conductive terminals” refers to the connection typology that links a format to external devices. For instance, conductive terminals allow the con-nection of the ES format with other formats (such as, CCs to CCs, or BMs to BMs, or BPs to BPs), with external electrical devices, or plugs. The type of these electrical means depend on, the current to be carried, the frequency with which the battery may be connected and disconnected, and the design of the circuit to which the battery will be connected. Figure 11 shows a BM with con-ductive terminals in wire configuration. Wires are usually used for small ES devices, such as portable ES devices. When wires are used as conductive terminals, the red one is used for the positive and the black one for the nega-tive pole as the standard colors. For lower power circuits like laptop batteries that are subjected to frequent insertions, the conductive terminals are gold plated. Conductive terminals for high power applications are usually fixed with metal studs to the top ends of cells or other ES formats, to ensure reliable connections. (Lawson 2015)

In chapter 3.2 conductive terminals and means for electrical connections will be considered as two different categories, while this chapter does not present this distinction. In fact, conductive terminals electrically connect elements to-gether, and also can have same shapes, dimensions and same materials as the means to electrically connect cells. According to these characteristics there is no reason to distinguish between conductive terminals and the other con-nectors in the morphological box (Table 1 located at the end of this chapter). However, in future work especially in chapter 3.2 is necessary to make two categories because sometimes the assembly of conductive terminals and the means to electrical connect cells (assembly of metal tabs, bus bars, etc.) are implemented in different phases of the same assembly sequence.

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2.1.3 Means to secure components together (m.t.secure)

These devices collect, insulate, protect, and interlock the energy storage com-ponents. When battery packs are installed inside the product, they only require a shrink-wrap enclosure. In other cases, battery packs are mounted externally, so they have to protect cells and electronics from possible extremes tempera-ture of the operating environment, or water ingress, or humidity atmosphere, or vibrations (caused by possible drop off of the device or its use on moving vehi-cles). Figure 12 shows examples of a shrink wrap enclosures on the left and a battery pack for external use on the right. (Epec 2015c) It is important to point out that thermal effects need to be taken into account and, tolerances must be allowed for potential swelling of the cells. Some lithium pouch cells may swell over the lifetime of the cell. For this reason usually in low power ES configura-tions, pouch cells can be shrink wrapped, but for higher power applications plastic or metal frames may be used. (Lawson 2015)

The ES device housing has to provide mechanical and electrical interfaces to the product, as well as, to contain all the components that form the ES itself. The means to secure are classified in five types based on their implementa-tion: heat shrink tubing, integrated or single cases, discrete linking, multitask (means like electrical conjunctions, conductive terminals, or safety devices can be pre-assembled to means to secure), and removable (detachable compo-nents) devices.

The most common way to hold a small pack together is to use heat shrink

tubing, or shrink wrap, or vacuum formed plastic. Heat shrink tubing is

typical-ly made of potypical-lyvinyl chloride and varies in thickness based upon battery type and configuration. An example of heat shrink tubing is given in Figure 13.

Figure 12 Lithium polymer battery pack for medical application (left) and lithium battery pack in an off-the-shelf case (right) (Epec 2015c) (left),

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Figure 13 Example of heat shrink tubing ES devices (Epec 2015a)

(Epec 2015a) As already mentioned these solutions are only possible if the battery is intended to be completely enclosed by the finished product. In other cases, battery packs are mounted externally. Therefore, they might need more resistant walls, a base and at least one projection for hand gripping. (Epec 2015d)

Discrete devices are commonly used to secure large packs mostly made by

prismatic cells. Binding members can have prismatic or cylindrical cross sec-tional shape, and are secured to metal end plates. (Marukawa et al. 2004, p. 10, column 3), (Suzuki et al.1998, p. 19)

The integral ES housings are usually formed by a plurality of rectangular prismatic cases in which usually prismatic or pouch cells are inserted. Figure 14 shows an example of this ES housing type. Here the BM housing consists of: a base (number 2) formed by six cell cases (number 3), a cover welded to the base (number 4) that includes the single safety vent (number 10) of the module, two conductive terminals (number 8) at both lateral sides of the hous-ing base, and ribs (number 14) and protrusions (number 17) on both external surfaces.

Another possible configuration of integral battery housing concerns devices used that are usually very large, heavy and subjected to large physical forces as well as vibrations. For this reason substantial fixings are required to hold the cells in place. This is particularly necessary for batteries made from pouch cells which are vulnerable to physical damage. For example, automotive bat-tery packs must withstand abuse and possible accidental damage, so using metal casings during the assembly of the energy storage device will normally be specified. (Lawson 2015)

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Means with pre-assembled components

This configuration consists in assembling ES components to ES housing that accomplish to functions like: electrical connection of cells, hazardous preven-tion, and electrical control (BMS). An example is the printed circuit board (PCB), mentioned in chapter 2.1.2. This device serves to electrically and me-chanically connect battery cells with each other, detect the voltage and tem-perature of the respective battery cells, and secure them to the conductive terminals. (Lee et al. 2009, p. 18, column 9) Some configurations include cir-cuits for the electrically connecting cells included into the housing (by molding them in the inner sidewalls of the housing). With this configuration materials and assembly costs are minimized thanks to a minimum usage of material and fewer operations during the assembly. (Lawson 2015) Moreover, it is common that BM or BP housings present pre-assembled components that allow their securing to the final accommodation place (e.g. to the body of a car, or into the case of a bigger format). For example, Hirano (2005) describes a CC that on the outer surfaces of its case presents screwed means of different shapes useful for securing the formats one another building a BM.

Removable supporting frameworks

Removable frameworks are necessary when the securing of the elements is accomplished late in the assembly sequence. A better description of these de-vices is given in chapter 3.2.8.

Figure 14 Example of an integrated BM case with ribs on its outer sidewalls (Inoue et al. 2002, p. 2)

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Figure 15 Prismatic sealed cell type with

safe-ty vent (Hamada et al. 1996, p. 2)

2.1.4 Safety devices (s.devices)

Batteries have the potential to be dangerous if they are not carefully designed or if they are abused. Likewise, pack manufacturers incorporate safety devices in the pack designs to protect the battery from out of tolerance operating con-ditions. The classification of these devices is based on the dangerous events and failures that may occur during the use of ES devices. In general, cell pro-tection should address the following undesirable events or conditions: leakage of the electrolyte from the inside of the cells, excessive current during charging or discharging, short circuit, state over voltage limits (overcharging), state un-der voltage limits, high ambient temperature, overheating (exceeding the cell temperature limit), pressure build up inside the cell, system isolation in case of an accident (Lawson 2015).

Many of the solutions preventing the occurrence of accidents during the use or assembly of ES devices are already made in the cells. For example, with re-gard to a possible leakage of the electrolyte from the inside of the cells, a possible solution is using a hydrophobic membrane attached on the external bottom of the cell case with a sealing tape. (Konishi et al. 1993, p. 8, column 1) Or another example concerns chemistry of cells that during its electrochemical process can give rise to the generation of gases. This phenomenon is called gassing and builds pressure inside the cell. If gases escape from inside the cell the active mass of chemicals will be

dimin-ished, reducing its capacity and its life cycle. To prevent this situation cell cases usually are sealed. Sealing the cells leads to a different prob-lem. In fact, if gassing occurs, pressure will be built up within the cell case. The rising of pres-sure usually is accompanied by a rise in tempera-ture. The heating of the cell damages the cell it-self and can cause also cell ruptures or wall ex-plosions. (Lawson 2015) Figure 15 shows a safe-ty vent (number 16) that is integrated to the lid of the cell case and releases pressure when the cell exceeds the expected set limit.

Despite the security measures that most affect the assembly of ES devices concern the preven-tion of short circuit, overheating of the cells inside the battery pack, high current handling and the

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entry of unwanted material inside the battery pack.

Short circuit has different causes. It can be caused by a malfunctioning of the

components inside the cell, or by the touching of conductive components dur-ing the use of device or within the assembly process. Once an internal short circuit occurs it can be detected by a sudden drop in the cell voltage. This can be used to trigger a cut off of the device to isolate the battery from the charger or the load. This operation does not solve the problem but prevents the ES de-vice to be seriously damaged. An insulating foil between the cells prevents the conductive metallic skin from causing an electrical short circuit. The foil also shields against heat transfer if one cell gets hot. (Buchmann 2015b) To pre-vent the touching of external conductive components like conductive terminals, or connectors, the components are usually shrouded. The design further pro-tects operators from accidental short circuits, and the connection of incorrect loads or chargers to the battery. (Lawson 2015) Whereas, to prevent the touching of cells against each other insulating tape is usually assembled around the side walls of the cells, or plastic or insulating material separators are inserted in between. In addition, to prevent the contact between connect-ors and the wrong side of cells or the operator binders, or elastic sheets formed by electrical insulating material are sometimes secured on top of CCs. (Hershberger & Izenbaard 1999, p. 1), (Hirano 2005, p. 6)

Possible consequences to the overheat of cells can be the melting of the sep-arators that are typically made of plastic, or in the worst case the shorting cir-cuit between the electrodes. To prevent that the ES devices are severely damaged some devices similar to a resettable fuse are inserted into the de-vice. The melting plastic in the shutdown separator closes up its pores, thus avoiding a short circuit but the action is not reversible. Instead, to prevent the entrance of undesired materials (such as water), devices like inserts can be assembled in the inner part of the case like McArthur et al. (1985, p. 7 column 4) describe in their ES configuration.

2.1.5 Cooling devices (c.devices)

Thermal management is a major issue in high power designs such as BMs, BPs, and C. The operating of energy storage devices in environments with high temperature causes premature ageing, irreversible effects, and safety problems. Similarly, the ES device must be heated if it has to work in cold conditions. ES devices use as coolant device ambient air or liquid circulation through the pack or heat exchanger plates. (Väyrynen & Salminen 2011, p. 84)

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Cooling solutions are mainly divided into: devices integrated in the housing lay-outs and discrete devices that are arranged in the ES formats during the assembly processes. This design of integrated cooling devices refers mainly to low power ES devices, below some major configurations are briefly de-scribed. Figure 16 shows a very common layout for button cells, where the ES housing includes apertures on the walls. These apertures allow air to pass through the housing. (McArthur et al. 1985)

Air is very important for this design because it is necessary both for cooling and for activating the chemical reaction among the cells. (McArthur et al. 1985, p. 7, column 3)

Other ES device housings include interconnected coolant channels in their base. The coolant channels usually are placed in the base of the ES housing to be in thermal contact with all the elements (usually prismatic cells) included in the housing. Coolant fluid usually is inserted from an aperture on one side and flows inside channels, cooling or heating the elements of the ES device, then exit from an aperture located in the opposite side of the entrance. (Corri-gan et al. 2001, p. 11, column 11)

In some configurations outer surfaces of the ES case provide cooling struc-tures, as shown in Figure 14 (chapter 2.1.3). In this design the larger surface of the integral BM hosing provides protruding ribs (number 4) that extend vertically. Furthermore, a large number of relatively small circular recesses (number 16) and protrusions (number 17) are formed at suitable intervals be-tween each two ribs. The ribs and the protrusions have the same height. These plurality of protrusions and recesses, are used for positioning and fitting

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constitute a larger format. The ribs, the protrusions, and the coupling ribs form coolant passages for cooling the cells effectively and uniformly. (Inoue et al. 2002, p. 15, column 5)

Figure 17 shows the gaps (colored in the figure) that cylindrical cells form at four corners when are placed into cell-accommodating portions that have squared cross section. These gaps are used as cooling system during the use of the ES device. In fact, air can flows inside the ES device thanks to radi-ation holes drawn on the covers and basis of the BM housing. The air flowing through the heat-radiation paths cools each cell effectively. (Hirano 2005, p. 7)

In some configuration of ES devices the cooling devices consist in discrete

devices such as spacers. These devices are interposed between cells or

big-ger ES formats. Several shapes and dimension of spacers exist; for example they can be rectangular blocks or flat plates. The more important characteristic of these devices is to be sufficiently endurable to resist to the pressure applied in the stacking direction (due to the expansion of the cell during its use). (Hi-gashino 2006, p. 16, column 4)

2.1.6 Battery Management System (BMS)

Rechargeable battery systems include electronic controls known as battery management systems (BMS) which are crucial for a correct operating of ES devices. (Väyrynen & Salminen 2011, p. 84) The core functions of a BMS are: managing voltage of any cell (to prevent dangerous and rapid fluctuation of its value), measuring the level of the charging (to stop it when the level required has been achieved), preventing the temperature of the ES system from ex-ceeding a limit (by reducing battery current or asking for cooling), and provid-ing relevant status information (e.g. SOC) about the device. The information is sent to the host system and the user via a data link. The BMS are often classi-fied based on how they are installed that can be: directly on each cell, or cen-tralized in a single device, or in some intermediate form (Väyrynen & Salminen 2011, p. 84)

Figure 17 Sketch of the four gaps formed by a cylindrical cell inserted into a square shaped accommodation place

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Two main typologies can be identified:

 master–slave BMS (left in Figure 18): the system comprises multiple identical cards (the slaves), each of them measuring the conditions of a group of cells, and a separate master unit that handles computation and communications. (Väyrynen & Salminen 2011, p. 84)

 centralized BMS (right in Figure 18): is a single card that acts both as a cell conditions detector and electrical controller. All cells are connected to this single unit that usually has got bigger dimensions than slave cards, due to their multiple functions. (Lawson 2015)

Table 1 gathers in a single chart the principle categories (first column) of the components described in this chapter. For each category the major existing configurations (presented in the remaining columns of the table) observed by the literature review are listed. The chart presents abbreviations such as: CC, BM and BP to identify components that are used in specific ES formats like cell clusters (CCs), battery modules (BMs) or battery packs (BPs). When the component type is not specified by any symbol, it means that it can be used for ES formats of any dimension. In fact, its choice depends on other aspects of the device (such as, type of voltage required, final accommodation place, etc.)

Figure 18 Example of master-slave BMS in prismatic high power cells (left), two cells stacked in column (right) (Endless-sphere 2015) (left), (Epec 2015a)

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Cables Bus bars (CC, BM) Flat metal tab (CC, BM) Cross-shaped strap ES case Heat shrink wrappin g Diffrent shaped binders Discrete compone nts

MORPHOLOGICAL BOX OF ENERGY STORAGE COMPONENTS

Cylindrical outer

case Flat (Button) outer case Prismatic outer case Pouch outer case Principle

Components TYPOLOGIES

Cells

Means for electrical connection Mechanical joints (like screws, nuts, screws, bolts) (CC, BM) Circuits (like I-beam frame, structures frames) (BM, BP, C) Pre-assembled/ pre-manufactured conductive projections on/ to the ES housing

Means for securing comp. together Prismatic cell cases (integrated into the case)

ES housing formed by two parts coupled together Slots drawn in inner parts of

housings with shapes complementary to the ES components

(CC, BM) I-beam

structure with molded-in or integral metallized spring fingers (CC, BM) Circuits stamped/ molded on frames (CC+BM) Protrusion and recesses integrated in ES outer housing surfaces (CC, BM) Joints with different sides shaped ( V-grooved ) Restraining binder members

(with different section shapes)+ metal end plates Detachable

component parts (presence of clips, or secured thanks to the shape of the housing)

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Table 1 Morphological box of energy storage components

(Hershberger & Izenbaard 1999), (Konishi et al. 1993), (Inoue et al. 2002), (Holl & Parsippany 1990), (Bresin et al. 1993), (Hamada et al. 1996), (Hope & Kejha 1995), (Ogata & Hamada 2004), (Dorinski et al. 1992), (Etoh & Watanabe 2000), (Hirano 2005), (McArthur et al. 1985), (Amthor & River 1990), (Corrigan et al. 2001), (Suzuki et al. 1998), (Yoon et al. 2011), (Higashino 2006), (Lee et al. 2009), (Bindin & Jones 1983), (Marukawa et al. 2004), (Epec 2015a), (Epec 2015b), (Epec 2015c), (Lawson 2015) Safety vent integrated to the ES case Voltage tap Insulating tape secured around cells Shock pads absorb er of differen t shapes Devices that open circuits when the current handled is to elevate (CC/B M) Temper ature sensor (CC, BM) Projections in the inner surfaces of ES cells made of insulating material (CC, BM, BP) Design of ES components (covers, binders with holes on their surfaces)

Centralized Master- Slave

Battery Management System (BM) Spacers with different shapes Safety devices Insulating inserts and separators of different shapes (discrete components) Vents integreated to outer surfaces of the housing ES housings with

ribs and projections on outer surfaces Radiation holes cut in covers of the ES device Thermal (cooling/heating ) devices (BM) Passages for coolant/ heater fluids (e.g. air, waters) integrated to ES (BM) Metal plates/ heat exchangers of different shapes

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2.2 Energy storage assembly processes

Figure 19 shows a classification of assembly operations made by Lotter & Wiendahl (2012). The chart outlines five major operation types into which the assembly processes can be divided: the joining, the handling, the checking, the adjusting and the non-standard/ special operations. The assembly of ES systems, described in future work, includes almost all of them apart from the “adjusting tasks”. These actions in ES assembly processes play a secondary role because they are usually implemented at every moment. For this reason, they are not described in the future work. This chapter is divided into two main subparagraphs: operative assembly tasks and quality inspections. A brief de-scription of the necessary operations for the ES assembly is given in this chap-ter. Despite in chapter 3.2 a more specific description of these operations re-garding the ES assembly will be presented.

Figure 19 Classification of assembly operations (after Lotter & Wiendahl 2012, p. 2)

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2.2.1 Assembly operations

The assembly system as C.I.R.P. (2011, chapter 2, p. 14) state is “[…] an ar-rangement of facilities that is utilized for the assembly of a product or products, characterized by rigid or loose chaining of individual assembly work stations.” Below the principle tasks that are implemented in the ES assembly processes (listed in Figure 19) are defined with the help of C.I.R.P. to give a more rigor-ous and precise description of them. In this paragraph the assembly tions of joining, handling and manipulating and non-standard/ special opera-tions regarding the ES assembly processes are presented. While the checking processes will be described in the introduction to the quality inspection (chap-ter 2.2.2) for ES assembly processes made in chap(chap-ter 3.3.

Joining

The first assembly operation category that is outlined in the chart (Figure 19) is the joining of components. The joining process is identified as an action for bringing two or more parts together (C.I.R.P. 2011, chapter 3, p. 132). The first main distinction in this process is that the joining of parts can be either secured or fastened, or without the aid of binders or other means to secure. A further distinction between the existing ES joining operations is that either discrete components are assembled together, or pre-assemble components can be joined to discrete components (C.I.R.P. 2011, chapter 3, p. 132). This configu-ration is described better in the chapters 3.2.2 and 3.2.5. The most common joining processes in ES assembly have been observed are putting together, filling/ positioning, pressing on/ force fitting, joining by molding, joining by sol-dering, joining by welding, and gluing.

Filling/positioning: the positioning operations consist of inserting/ placing ES components (like cells, conductive terminals, BMs, BPs and other formats) into bins, supporting frameworks or directly in ES housings. Whereas, the filling task refers to actions of inserting gaseous or liquid material into cavities (like coolant fluids). (C.I.R.P. 2011, chapter 3, p. 136)

Pressing on/ force fitting: the operation refers to processes for interlocking components together. There are several methods for connecting them without the necessity for expensive technological processes. The principle are: intro-ducing components into cut outs parts and then rotated them for securing, or combining complementary shaped components and then pressing them one on the other for securing them together, or pressing one hollow item inside an-other to form an internal sleeve, or snap fitting a component into anan-other (in

Development of strategies for the assembly of energy storage devices with regard on possible quality inspections

TASK DESCRIPTION