Project Dissertation -Standardization of BEV Battery Module for circular economy copy

Standardization of BEV Battery modules for circular economy

ES327 Final Report

by Othman Laraqui, ID number 1325995

26 April 2016 Supervised by: Dr Antony Allen

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1325995 S TAN DARD ISA TION OF BEV BATTERY M ODU LE FOR CIR CU LAR ECON OMY

Summary

This study is an attempt of standardizing external features related to a BEV battery module,

based on current literature, in order to increase the feasibility of circular economy regarding

batteries. An overall positive impact is highlighted on downstream stakeholders concerned with

the after first life of BEV batteries, which shows that standardisation enhance this concept of

circular economy even though some negative impact is also noticed on stakeholders concerned

with the top of the battery life chain (before its first life).

Author’s self-assessment

This study is based on the analysis of many sets of secondary data, including papers, patents,

reports, books, design concepts and battery affiliate company’s electronic documents.

Assembling and analysing all of these contributes to an attempt of creating standards on a part

of the EV battery. This has never been attempted in the past, for several reasons, including a

immature market.

As it has never been attempted before, this contribution is relevant to engineering and the

electric car industry. In every domain of engineering, standards are developed for several

reasons. For instance, standard are developed for regulating transport of battery, for safety

reasons. This study attempt to develop standards in order to enhance circular economy for

batteries.

This study can be used for redesigning features that fits the standards. OEMs and battery

manufacturer can apply these standard in a circular economy approach, in order to benefit

circular economy. Also, this project can be used to motivate standardisation of other battery

features such as the BMS. Other students may use this contribution in order to improve it by

using primary data analysis.

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As the standards proposed are impacting positively circular economy, the aim of the study has

been achieved, therefore the study is considered as successful. However, many weaknesses

have been noticed. With regard to quantification of the cost-impacts on stakeholders, this is

hasn’t been done, and it’s the main drawback of this contribution. There is no quantification

for priority of stakeholder’s requirements. This provides a higher reliability on the selected

standards. Quantification is a necessary recommendation for improving this contribution.

Table of Contents SUMMARY I

AUTHOR’S SELF-‐ASSESSMENT I

LIST OF ACRONYMS IV

GLOSSARY V

LIST OF FIGURES VII

LIST OF TABLES VIII

1 INTRODUCTION 1

2 AIM AND OBJECTIVES 1

3 LITERATURE REVIEW 2

3.1 HISTORIC VIEW OF THE EV MARKET 2

3.2 LITHIUM-‐ION BATTERIES 3

3.2.1 LI-‐ION BATTERIES HISTORIC DEVELOPMENT 3

3.2.2 LI-‐ION BATTERIES PERFORMANCE 3

3.2.3 LI-‐ION BATTERIES CELL 5

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3.2.4 LI-‐ION BATTERY PACK 8

3.2.5 LI-‐ION BATTERY MARKET 10

3.3 CIRCULAR ECONOMY MODEL 13

3.4 CIRCULAR ECONOMY FOR LI-‐ION BATTERIES 13

3.4.1 THE BATTERY LIFE CYCLE AND STAKEHOLDERS 15

3.4.2 REMANUFACTURING 16

3.4.3 RE-‐USE FOR SECOND APPLICATION 18

3.4.4 RECYCLING 19

3.4.5 CURRENT PROPOSED SOLUTIONS FOR EASE OF CIRCULAR ECONOMY 21

4 METHODOLOGY 25

4.1 METHODOLOGY SELECTION 25

4.2 ELECTRIC CAR SELECTION 25

5 ELECTRICAL STANDARDIZATION OF THE MODULE 26

5.1 OBSERVATIONS AND RESULTS 27

5.2 DESIGN RULES FOR ELECTRIC STANDARDIZATION 28

5.3 STANDARDS PROPOSED 29

5.4 IMPACT ON STAKEHOLDERS 30

5.4.1 STANDARDISATION IMPACT ON STAKEHOLDER’S REQUIREMENT 30

5.4.2 IMPACT OF ELECTRICAL STANDARDIZATION ON STAKEHOLDERS 31

6 STANDARDIZATION OF THE COOLING SYSTEM 32

6.1 THE COOLING SYSTEM: AN ESSENTIAL FEATURE FOR BATTERY SAFETY, RELIABILITY AND DURABILITY 32

6.2 AIR COOLING/LIQUID COOLING 33

6.3 PASSIVE OR ACTIVE SYSTEMS 35

6.4 INTEGRATED LIQUID/ LIQUID COOLING 36

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6.5 IMPACT OF STANDARDISED BTMS ON STAKEHOLDER REQUIREMENT 37

7 INTERFACE AND PACKAGING STANDARDIZATION 38

7.1 MODULE TO MODULE INTERFACE 38

7.2 MODULE TO BMS INTERFACE 39

7.3 MODULE TO CAR (OR PACK) INTERFACE 41

7.4 PACKAGING MATERIAL STANDARD 42

8 COST ANALYSIS 43

9 RECOMMENDATION FOR FUTURE WORK 44

10 CONCLUSION 45

11 BIBLIOGRAPHY 46

12 APPENDICES 55

12.1 APPENDIX A: ACCELERATION AND RANGE THEORY [66] 55

12.2 APPENDIX B: STANDARDIZATION OF THE CELL FORMAT 56

12.3 APPENDIX C: LIST OF TABLES FOR ELECTRICAL STANDARDIZATION [67], [68] 60

List of acronyms

EV: Electric Vehicle HEV: Hybrid electric Vehicle

BEV: Battery Electric Vehicle or fully electrified vehicle

PHEV: Plug-in Hybrid Electric Vehicle BMS: Battery Management System

BTMS: Battery Thermal Management System E-o-L: End-of-Life

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LFP: Lithium-Iron-Phosphate àLiFePO4 LMO: Lithium-Manganese-Oxideà LiMnO

NMC: Lithium-Nickel-Manganese-Cobalt-Oxideà LiNiMnCoO2

LCO: Lithium-Cobalt-OxideàLiCoO2 LTO: Lithium-Titanate-OxideàLi4Ti5O12

NCA: Lithium-Nickel-Cobalt-Aluminium-OxideàLiNiCoAlO2

Q: Charge in Coulombs (C) t: time in seconds (s) or hours (h)

V: Nominal Voltage in Volts (V) P: Power in Watts (W)

E: Energy transformed in Joules (J)

Glossary

Battery Ampere –hour (Ah) Capacity is the total charge Q that can be discharged from a

fully charged battery under specific conditions:

Q= I.t, therefore Q unit is Ah (Ampere-hour)

Watt-Hour (Wh) Capacity is the capacity of the battery in Wh (Watt-hour)

𝑊ℎ = 𝐴ℎ×𝑉

Specific Energy (gravimetric energy density): rated power capacity/Battery massàWh/kg.

. Determines the battery weight required to achieve a given electric range.

Specific power: Rated peak power/Battery massàW/kg. Determines the battery weight

required to achieve a given performance (acceleration) target.

Volumetric Energy Density: is the nominal battery energy per unit of volumeàWh/l. It

determines along with the nrj consumption), the battery size required to achieve a given electric

range

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Power density: W/l. It determines the battery size required to achieve a given performance

(acceleration) target

Internal resistance R is the overall equivalent resistance within the battery. Different for

charging and discharging and may vary as the operating condition changes. The battery

efficiency decreases and thermal stability is reduced as more of the charging energy is

converted into heat.

State of Charge (SOC): SOC is defined as the remaining capacity and it is affected by its

operating conditions such as load current and temperature.

SOC= Remaining Capacity/ Rated capacity

SOC critical condition parameter for Battery management.

Depth Of Discharge (DOD) = 1-SOC, higher DOD induces lower life cycle of the battery.

Cycle life: number of discharge/charge cycle the battery can handle at a specific DOD

(normally 80%). It’s affected by C-rates DOD and other condition such as temperature and size

of the battery.

Calendar life: life span of battery under storage or periodic cycling conditions. Strongly

affected by SOC and temperature during storage

Battery Management System (BMS): Combination of sensors, controller, communication,

and computation hardware with software algorithms designed to decide the max

charge/discharge current and duration from the estimation of SOC and SOH of the battery pack.

Critical for enabling second life

Thermal Management System (TMS): TMS is designed to protect the battery pack from

overheating and to extend its calendar life. Sophisticated and powerful liquid-cooling is

required by most of the Li-ion batteries in EV applications.

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Recommended) Charge Current – The ideal current at which the battery is initially charged

(to roughly 70 percent SOC) under constant charging scheme before transitioning into constant

voltage charging.

State of health (SOH) is the ratio of the maximum charge capacity of an aged battery to the

maximum charge capacity when the battery was new [7]. SOH is an important

parameter for indicating the degree of performance degradation of a battery and for

estimating the battery remaining lifetime.

List of Figures

FIGURE 1: EV HISTORY TIMELINE [1] ...................................................................................................................... 2

FIGURE 3: GRAVIMETRIC VS VOLUMETRIC ENERGY DENSITY FOR DIFFERENT TYPES OF CHEMISTRIES ................ 4

FIGURE 3: CELL INTERNAL COMPONENTS AND REACTIONS [11] [12] .................................................................... 5

FIGURE 4: CELL FORMATS BREAKDOWN [12] [13] ................................................................................................. 6

FIGURE 5: LI-‐ION CHEMISTRIES APPLICATION DIAGRAM [14] ............................................................................... 7

FIGURE 6: BATTERY COMPONENTS BREAKDOWN [17] .......................................................................................... 8

FIGURE 7: BATTERY BREAKDOWN MATERIAL (BOTTOM LEFT) AND MANUFACTURING COST(TOP LEFT)

BREAKDOWN WITH OVERHEADS (BOTTOM RIGHT) [18] ............................................................................. 9

FIGURE 8: EVOLUTION AND FORECAST OF LITHIUM DEMAND PER USE [12] ...................................................... 11

FIGURE 9: HISTORICAL LITHIUM CARBONATE PRICES [12] [13] ........................................................................... 11

FIGURE 10: BATTERY PACK COST FORECAST TOWARD 2030 ............................................................................... 12

FIGURE 11: ELECTRIC VEHICLE SALES (UK) BY YEAR 2010-‐2015 [14] .................................................................... 12

FIGURE 12: CIRCULAR ECONOMY MODEL [21] .................................................................................................... 13

FIGURE 13: BATTERY VALUE CHAIN MODEL [25] ................................................................................................. 15

FIGURE 14: ADAPTED V-‐MODEL METHODOLOGY ................................................................................................ 25

FIGURE 15: COMPARISONS RATIOS BETWEEN ORIGINAL AND STANDARDIZED MODULE CHARACTERISTICS .... 29

FIGURE 16: COMPARISON RATIOS BETWEEN ORIGINAL AND POST STANDARDIZATION RANGE AND

ACCELERATION ........................................................................................................................................... 30

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FIGURE 17: INHOMOGENEITY AND AGEING OF MODULES .................................................................................. 32

FIGURE 18: MODULE/MODULE STANDARDIZED INTERFACE [61] ........................................................................ 39

FIGURE 19: CONTROL MODULE PROPOSED STANDARD [61] ............................................................................... 40

List of Tables

TABLE 1: ADVANTAGES AND DRAWBACKS OF DIFFERENT CELL FORMATS [13] .................................................... 6

TABLE 2: ADVANTAGE AND DRAWBACKS OF DIFFERENT LI-‐ION CHEMISTRIES [14] .............................................. 7

TABLE 3: LMO BATTERY MATERIAL WEIGHT BREAKDOWN [18] .......................................................................... 10

TABLE 4: BATTERY MAIN COMPONENTS COST AND WEIGHT [8] ......................................................................... 10

TABLE 5: BEV CONSIDERED FOR THE CASE STUDY [50] ........................................................................................ 26

TABLE 6: CELL CHARACTERISTICS FOR EACH CAR [51] ......................................................................................... 27

TABLE 7: TABLE OF ELECTRICAL STANDARDS FOR THE BEV MODULE .................................................................. 29

TABLE 8: ADVANTAGE AND DRAWBACK OF LIQUID AND AIR COOLING [54] [55] ............................................... 33

TABLE 9: TYPE OF COOLING SYSTEM USED BY EACH CAR MODEL [55] ................................................................ 34

TABLE 9: COMPARISON TABLE OF DIFFERENT BMS/MODULE INTERFACE CONFIGURATION [61] ...................... 40

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1 Introduction

The battery is one of the he main components of electric vehicle. It’s the power source that

drives and perform the main function of a vehicle. In the past and today, it’s subject to many

research in order to optimise its performance, viability durability, safety, cost in every level,

cell, module pack. As a complex assembly, the battery is always subject to new improvements.

A single battery pack assembly design regroups all the engineering areas including, energy,

environmental, industrial, mechanical, electrical, electrochemical, system and materials. A

battery pack is an assembly of cell, regroup in sub-parts called modules that are connected

together in series or parallel to achieve a required voltage and capacity. These cells and module

have their physical and electrical characteristics managed by a BMS often included on the

battery. Other features of the battery pack include safety devices, wiring and cooling system.

2 Aim and Objectives

The aim of this study is to standardize all features related to a BEV battery module, and to

show the impact of this standardisation on stakeholders concerned with the battery life cycle.

Objectives are:

• Determine who are the stakeholders and their requirements

• Propose an optimum standard, based on current literature and stakeholder requirements,

for external features related to the module which are characteristics (voltage,

resistance…), cooling system, interfaces and packaging.

• Illustrate the impact of each standard on the stakeholder.

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3 Literature Review

3.1 Historic view of the EV market

FIGURE 1: EV HISTORY TIMELINE [1]

In the 1990’s, Environmental concerns have led the restart of the EV market. More energy

policies like the voting of the 1990 Clean Air Act Amendment and the 1992 Energy Policy

Act helped create a renewed interest in EVs in the U.S. More investments are awarded to the

research and development of EVs technologies, especially in the battery area. This led to the

first commercialization of the Lithium-ion cell in 1991 by Sony, which is today the mostly

used chemistry in nowadays, Laptops, Smartphones and EVs [2].

The Global EV Stock (in the end of 2012) represents 0.02% of total passenger cars which

means more than 180,000. [3] The global EV stock reached more than 665,000 units, which

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represents 0.02 of total passenger cars. [3] This marks the start of a new era in the automotive

market. The consumers have now more choices than ever when it comes to buy an EV.

Today, the EV market is widely supported by government policies around the world. In 2009,

the Renewables Directive set binding targets for all EU Member States, so that the EV

constitute 10% of the total EU car fleet by 2020 [4]. The US President Barack Obama launched

in 2012, the “EV Everywhere Challenge”, which aims is to make EVs more affordable than

gasoline vehicles by 2022 [2]. The main challenge is the reducing the cost of the battery pack.

In 2011, the Battery pack cost average account between 30 and 50% of the whole EV cost [5].

In January 2016, four UK cities have been awarded £40 million by the ministry of transports,

to promote green vehicles technology [6].

3.2 Lithium-Ion Batteries

3.2.1 Li-Ion Batteries historic development

Lithium-ion cells are the most widely used cells in the electric automotive industry. This is due

to the work of several researchers. Dr John Goodenough and Dr Koichi Mizuchima developed

the first positive electrode usable in a battery using lithium cobalt oxide 𝐿𝑖𝐶𝑜𝑂,. Dr Rachid

Yazami demonstrated the usability of graphite as an anode in 1984. Finally, Dr Akira Yoshino

developed the first prototype of Li-ion battery, by combining carboneous materials as an anode

and 𝐿𝑖𝐶𝑜𝑂, as a cathode. [7] This has increased the safety of the Li-ion, by using materials

without metallic lithium, and thus allow it’s first commercialisation in 1991 by Sony. [2]

3.2.2 Li-ion Batteries performance

Lithium-ion success is due to it’s high performance versus cost, compared to other type of

batteries. The Ragone chart below illustrate this. Li-ion has the best balance between specific

energy density and specific power density. These parameters are really important as they

directly affect the range, the acceleration and the weight of the car.

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FIGURE 2: RAGONE CHART [8]

FIGURE 3: GRAVIMETRIC VS VOLUMETRIC ENERGY DENSITY FOR DIFFERENT

TYPES OF CHEMISTRIES [9]

The same applies for the volume of the cells required to deliver the same performance. Li-ion

requires less volume than other types of batteries as they have higher volumetric densities

shown in the table above.

Other advantages of Lithium ion cells are:

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• High life cycle: Between 1000 and 2000 cycles to reach 80% discharge.

• Low toxicity compared to Ni-Cd and Lead Acid cells

• Li-ion is the only type of cells with no maintenance required.

• It’s relatively cheap compared to Nickel and Cobalt, which prices are volatile.

• Low self discharge (less than 10%/month versus 30% for Nickel based cells) [10] [8].

However, Li-ions batteries are thermally unstable. Hence a thermal management system

(cooling/heating system) and a Battery Management System (BMS) are required, which

significantly rise the cost of the battery pack. A cost average of a BMS is about $1500. [8]

3.2.3 Li-ion Batteries cell

Li-ion cells are combination of 2 electrodes (cathode and anode) and one electrolyte. The

electrolyte is the chemical energy stored. Using Red-Ox reactions, there is a transfer of

electrons which provides energy to the motor, as shown below:

FIGURE 3: CELL INTERNAL COMPONENTS AND REACTIONS [11] [12]

Lithium-ion cells exist within different formats. The 3 formats that exist in the automotive

industry are: Cylindrical, Pouch, and Prismatic.

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FIGURE 4: CELL FORMATS BREAKDOWN [13] [12]

The advantages and drawbacks of each type of cells is summarized in the table below:

TABLE 1: ADVANTAGES AND DRAWBACKS OF DIFFERENT CELL FORMATS [13]

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Li-ion cells exist also under different combination of chemistries: LFP, LMO, NMC, LCO,

NCA, LTO. Their main areas of application and advantage and drawbacks are summarised in

the figures below:

FIGURE 5: LI-ION CHEMISTRIES APPLICATION DIAGRAM [14]

TABLE 2: ADVANTAGE AND DRAWBACKS OF DIFFERENT LI-ION CHEMISTRIES [14]

According the the figures above, the Li-ion chemistries used for automotive industry and

stationary storage are NCAs and NMCs cells. However, others type of chemistries are also

used in the automotive industry such as LMO LFP, used by Chinese automotive manufacturer

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[15] and LTO’s, used in the new I-Miev [16] for other reasons such as safety, reliability and

cost.

3.2.4 Li-ion Battery pack

A Battery pack is a complex assembly of many components. Each component has a specific

function: charging, connecting, packaging, cooling, fitting, managing, safety. The main

components of the battery pack are highlighted in the figure below:

FIGURE 6: BATTERY COMPONENTS BREAKDOWN [17]

Battery packs features also many type of materials that embed polymers, metals, electronic

components and graphite. Breakdown of their costs are highlighted in the figures below:

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FIGURE 7: BATTERY BREAKDOWN MATERIAL (BOTTOM LEFT) AND MANUFACTURING COST(TOP LEFT) BREAKDOWN WITH OVERHEADS (BOTTOM

RIGHT) [18]

Most of the material costs are related directly to the cell, there is only a little percentage that is

directly related to the module and pack level. In BEVs, 61% (these value varies with the

chemistry used), of the weight of the battery accounts for cells materials.

With regards to manufacturing costs, More, than 91% of manufacturing costs are related to the

cells assembly. Therefore, the main costs are directly related to the battery cell.

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TABLE 3: LMO BATTERY MATERIAL WEIGHT BREAKDOWN [19]

In BEVs, 48% of the battery weight is related to the two electrodes (excluding the BMS and

its interface). Hence, improvement for reducing weight needs to be focused on reducing the

weight of electrodes.

The breakdowns above don’t take into account the BMS, which is the most expensive part of

the battery.

TABLE 4: BATTERY MAIN COMPONENTS COST AND WEIGHT [8]

3.2.5 Li-ion Battery Market

The success of Lithium-ion batteries is illustrated in the graph below, designed by Fox Davis.

It highlights the evolution and forecast demand of lithium until 2017 per use. The increase in

lithium demand is mainly due to the increase in demand of rechargeable batteries.

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FIGURE 8: EVOLUTION AND FORECAST OF LITHIUM DEMAND PER USE [20]

In 2011, 5% of the lithium demand for rechargeable batteries comes from the automotive

industry. It’s forecasted that this percentage will increase to 41% in 2025, making the

automotive industry the largest consumers of rechargeable batteries [21].

Lithium is the main active material of current cells used in nowadays automotive traction

batteries. The weight of lithium material inside a battery pack range from 8kg to 40kg [8].

The graph below shows the evolution of lithium price per ton since 2000 to 2012. It’s clear that

lithium price is increasing. This is mainly due to the increasing demand in rechargeable

batteries as stated above.

FIGURE 9: HISTORICAL LITHIUM CARBONATE PRICES [20] [21]

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However, it’s forecasted that the overall battery pack cost will decrease with time, thanks to

R&D improvements toward weight and cost reduction as shown in figure below:

FIGURE 10: BATTERY PACK COST FORECAST TOWARD 2030

The histogram below shows that there was about 100 EVs sold in 2010. In 2015, 30000 EVs

were sold. This represents a significant increase in the number of EVs in the UK roads.

FIGURE 11: ELECTRIC VEHICLE SALES (UK) BY YEAR 2010-2015 [22]

It’s also forecasted that 100000 EV’s (cars and vans) will be sold in the only year 2022 [23].

As the number of EVs increases year after year in the UK as long as the price of lithium, it’s

important to consider an End-Of-Life (EOL) strategy for the batteries, hence the importance of

circular economy [24].

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3.3 Circular economy model

Circular economy has many definitions. McKinsey refers it as “the removal of wastes during

the life-cycle of a product” [25]. A better definition from the WRAP is valuing a product

differently and creating a more robust economy in the process [26].

The process can be really valuable as it benefits to the overall economy. Between 2008 and

2011, WRAP has generated £2.2billion of benefit to the UK economy, by implementing

circular economy in different sectors [27]. Defra calculates that UK businesses could benefit

by up to £23 billion per year through circular economy [28], whilst McKinsey estimates that

the global value of resource efficiency could eventually reach $3.7 trillion per year [27]. This

shows that there is a high opportunity in creating businesses in the circular economy domain.

FIGURE 12: CIRCULAR ECONOMY MODEL [29]

However, all these forecasts don’t take in account challenges to implement circular economy,

especially for long-term consumer goods such as Li-ions Batteries for electric cars.

3.4 Circular economy for Li-ion batteries

Based on the previous section, there is a:

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• Significant increase in the lithium ore price.

• Significant number of lithium-ion batteries will be introduced in the market.

Following a linear life-cycle for the product, a considerable amount of money is wasted:

• It requires more space to store the increasing number of used batteries (Landfills).

The occupied space will provide no value to the overall economy. This also can be

noxious to the environment when they are stored in large numbers, even though their

low toxicity.

• There is about 80% of remaining capacity inside the battery after first use [30], [31].

Throwing the battery after first use will mean that inherent capacity is wasted.

Moreover, the materials inside the batteries are valuable, as lithium and they can be

extracted through recycling and then re-used (as highlighted in figure 6 above).

Therefore, importing lithium from other countries instead of re-using the available on

inside old batteries is considered as a waste.

Many scientific research papers discuss this issues and addresses solutions in order to integrate

batteries in the circular economy. NREL addresses stated that profitable businesses are possible

in two areas of circular economy: Remanufacturing for same use; and Re-use for another

application [32].

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3.4.1 The battery life cycle and stakeholders

FIGURE 13: BATTERY VALUE CHAIN MODEL [33]

From the value chain above, stakeholders are identified. Each stakeholder’s values common

and different parameters that are related to the battery pack, which are highlighted next to each,

below.

The 7 start steps are related to:

Ø Battery manufacturer (mining supplier are not taken into account) values the

manufacturing process efficiency and customer satisfaction.

Ø OEM values the same as the battery manufacturer.

The 3 last and longest steps are respectively related to:

Ø Car user values the performance, durability, cost and safety of the battery.

Ø Second life user values the same as the first user plus the ease of assembling the

modules in their second life application.

Ø Recycler values are in the cost of recycling. This is related to the ease of disassembling

the modules, and the number of various materials present inside it.

Other stakeholders concerned with the Battery regulation are:

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Ø Governments are concerned with the environmental impact and safety issues.

Ø Standardisation organisms assesses all the standard regarding some part of the battery

such as the charging system [34].

This study aims to standardize all the features above by taking in account parameters that are

valued by the different stakeholders.

3.4.2 Remanufacturing

A general definition of Remanufacturing would be “the process of returning a used product to

like-new condition with a warranty to match.” [35] This process is commonly used in the

automotive industry. It’s estimated that there are 22 million units’ vehicles (Cars and light

vans) remanufactured/ rebuild each year across the E-U [36].

A complete definition would be “transforming a post-vehicle-application battery to once again

meet the standards for use in a moving vehicle.” It involves partial disassembly of the battery

pack, removal of damaged cells, replacement of these cells by new ones, and reassembly of the

battery.

A cost benefit analysis has been made by researcher from Grand Valley State University in the

USA. This analysis is based on reasonable assumptions on overhead, labour, material cost, and

reasonable forecasts on availability of EOL batteries and the demand. These forecasts comprise

optimist, pessimist and middle view [36].

The conclusion that has been drawn is that remanufacturing batteries cost 60% less than brand

new batteries [36].

This shows a real potential for OEM’s, and car users as saving estimation per battery is £7500

[36]. This may be a solution to the key barrier of EV market growth, which is cost related to

the battery. A drop in battery cost will boost EV sales, which bring more batteries in the

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market. Thus, more batteries will be remanufactured, and so on. Therefore, there is a potential

in creating a virtuous cycle, thanks to remanufacturing batteries.

A business model has been created, based on a parallel with a new LG Chem battery

manufacturing plant, as there is no current remanufacturing plant. This model illustrates in

depth the potential of remanufacturing as a business [36].

However, this analysis doesn’t show the negative challenges in remanufacturing,

For a better alternative, a set of questions is raised:

• How many cells need to be replaced until remanufacturing starts to be cost-inefficient?

• What is the maximum difference between the cells SOH allowed, so remanufacturing

can be considered as cost-effective solution?

• How long remanufactured battery will last compared to new batteries, and what is the

difference between their performances?

• What is the range of customer allowance in regard to limited battery performance?

• How the cell inhomogeneity affects the remanufacturing area?

Advantages and disadvantages of remanufacturing are hence listed below:

+ Cost per new battery manufactured is $1515, versus $833 for remanufactured battery

(business model scenario).

+ Remanufacturing plant are easier to manage, as there is less operation required than

a manufacturing new plan

+ Environmental issues reduced, as less space is required. A greener solution as it avoid

storage of Lithium, which rises concerns regarding the environment.

+ Part of the circular economy

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-‐ 30 years’ payback (with the actual forecast, based on the business model scenario).

Most of the investors would never accept a payback over 5 years.

-‐ Cell inhomogeneity issues

A better solution would be a broader business model, which will consider, three solutions of

circular economy.

3.4.3 Re-use for second application

Re-use for another application is the last stream of circular economy considered in this review.

Re-use for another application would be re-using batteries for application other than

automotive.

Re-using batteries allows an extended use of capacity, which increases the inherent value of

the battery.

Andrew Burke and Marshall Millers stated that used batteries are suitable for low power

application and high energy application [37]. Therefore, their main applications of re-use are

stationary application, as grid systems, micro-grids, renewable grids [32] [38].

Sharma and Keeli discuss the uses of second life battery in order to achieve peak load reduction

in commercial buildings [39]. It shows significant benefits in the uses of second life batteries.

For a 30% peak load reduction, which saves about $7812 per year, 51 second life batteries are

used with an 80% SOC. This equivalent a 545 kWh storage of second use batteries. However,

this paper doesn’t include repurposing and maintenance cost, depreciation and recycling costs

or End-Of-Second-Life Costs. This project is already carried out by Nissan, using old Leaf

batteries in order to supply power during mid-day peak energy demand, where electricity is the

most expensive.

A similar project is carried by Nissan Europe, in order to store old Nissan-Leaf batteries to

deliver power for Vehicle-to-grid storage.

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Other applications are residential service. Benefits shows a cost reduction for the overall

community plus a power back up, in case of a blackout [40].

3.4.4 Recycling

Recycling Li-ion cells is a complicated process at every scale. At the cell level, there is a wide

variety of chemistries present in each cells. Active material is under the form of powder, which

makes the process complicated. Foil recovering the cathodes, the outside envelope itself have

different materials. These chemistries need to be separated for recycling. [41]

According to Mr Tatsuo Horiba [42] and section 3.2.3, a single Li-ion cells uses a variety of

different chemistries. Moreover, Li-ion cells are packaged in different format, such as the

Cylindrical Panasonic NCR18650 used by Tesla, and Pouch cells used by the Nissan Leaf.

This might increase the complexity of recycling EVs as more equipment is required, which

increases the cost. [43]

At the battery pack level, the arrangement of the cells into modules makes recycling even more

complexes as the modules have they one circuitry (CLC1 chip). The modules can sometimes

include an integrated cooling system. If not there is a Battery thermal management system that

regulate temperature across all the battery. In both case, disassembly is quite complicated and

requires high and costly equipment. [41]

All of these shows the variety of valuable material that is present inside a Li-ion battery pack.

However, the complexity of separating these materials and the processes to recycle each type

of material makes the whole process expensive. [44]

1 CLC : Configurable Logic Cell : A small circuitry installed on the module, that record temperature and voltage of each cell in the module, and sen dit via busbars to the BMS.

20


Recycling Li-Ion batteries is an unprofitable business for the moment. This is due to the

complexity of its layout and variety of its materials. [36] However, it’s a compulsory duty to

recycle them as the OEMs are responsible of their E-o-L.

There are potential solutions, in order to make recycling easier and possible for Li-ion batteries

would be:

• Standardization of packaging: Uses bolts and nuts instead of welding, in order to ease

assembly and disassembly.

• Standardization of the cooling systems: Uses separate cooling system instead of

integrated cooling system in modules, (trade off with performance).

• Labelling the batteries chemistries in order to help identification (avoid cross-

contamination2) [44]

• Standardization of format and materials

• Reduce the number of materials

• Regulations would assure safe transport and handling, and discourage any sort of

cross-contamination. [44]

However, these requirements that are part of the design for recycling requirement shouldn’t

affects battery performance and safety.

Therefore, recycling must come as the final step of circular economy. In other terms, when the

battery capacity is no more useable for any other applications and have no more inherent value.

2 Cross-contamination : Battery cell contamination by external features such as dust.

21


3.4.5 Current Proposed solutions for ease of circular economy

Dr Ahmed Pesaran assesses a methodology in order to asses the feasibility of second life

project. [32] This is achieved by dividing the processes into 3 phases, first is to assess the merit

of second uses applications and strategies, second verify performance (testing) and finally

facilitate implementation of second use programs. In every phase, assets of useful

requirements are derived. These Pesaran requirements address a wide range of potential

issues regarding regulation, safety, durability, technical (testing) and profitability. This

feasibility methodology can be extended to the whole value chain. For the final phase, the

requirements are [32]:

-‐ Disseminate study findings to inform the market of the potential profitability of the

second use of traction batteries

-‐ Provide validated tools and data to industry

-‐ Develop design and manufacture standards for PHEV/EV batteries that

facilitate their reuse

-‐ Propose regulatory changes to encourage the reuse of retired traction batteries in other

applications

A lot of current research tries to address the second requirement, as they provide many

validated tool and data regarding testing of the batteries at their E-o-L.

Ciccone [30] demonstrates the feasibility of second life of Li-Ions cells using ageing test. Then

a technical analysis shows for how long they can be re-use. Finally, a Life Cycle Analysis

shows the environmental gain of it. This approach contains many issues:

• No information is provided on the time and manner of testing. If the cells are tested

one by one, the methodology will be time constraining regarding disassembly and

time for testing. No information is provided on the time of testing.

22


• This approach only considers the technical and environmental aspect, whereas the

economical and safety aspects are neglected, and strongly related to the point above.

• It doesn’t consider the entire SOH of the battery.

Andrew Burkes and Marshall Millans [37] proposes a similar methodology but applied to

modules, which significantly reduces the time constraints.

An NREL study [45] proposes a set of tools and testing in order to identify the State Of Health

of the battery. Another NREL study [46] shows how calendar effects, driving behavior can

affect the SOH of a battery. These are the reasons of the variability of the SOH of battery packs,

and hence why these parameters are important to consider in testing the batteries. This same

study considers also a techno-economical feasibility analysis of a second life application,

highlighting all the steps, from battery collection to storage of the modules inside a grid system.

They highlight all the testing requirement and the cost incurred with it, based on reasonable

assumptions.

Gladwin and Stone established a broad sets of conditions metrics that should be tested in order

to enable second life, which concerns physical conditions of the battery, pack terminal voltage,

pack impedance, pack capacity, and BMS recorder data [47].

Fangdan, Jiushun and others [48] proposes a way to establish capacity estimation of large scale

Li-ion for Second Use based on Support Vector Machine.

Other methodologies are also proposed, in order to optimize the implementation of second life

application:

Stanciu [40] sets that a challenge for second life implementation is minimizing the size of

storage systems considering an economic profit and limiting the ageing of the batteries

(inhomogeneity of cells).

23


Keeli and Ratnesh [39] focus on maximizing the second life time by setting an ideal

charge/discharge pattern.

Other methodologies are used in order to assess the feasibility and the techno-economic

feasibility of second use.

Cready and Lippert [49] shows a technical-feasibility analysis for Ni-MH batteries, which

proves that re-use for second life seems to be a viable concept. This study, doesn’t take into

consideration the Li-ion batteries. This factor challenges the whole paper as it doesn’t show a

long term viability. In facts chemistries are in continuous evolution.

Many of the literature above tries to address the two first Pesaran requirements. However, this

is not the case for the third requirement.

This is the potential gap has been identified in order to ease not only the re-use but the whole

circular economy model. This gap is design for second life and recycling, and this can be made

in first step toward standardization of the EV Battery module. Design for circular economy,

would be designing the product at an early stage in order to meet requirement for first use, but

also second use, and recycling. In fact, standardizing the module has the potential to reduce

costs for businesses in circular economy.

In his book, [31] John Warner assess that standardization of the module wouldn’t occur in the

near future for two reasons. The first one is that each vehicle manufacturer and Energy Storage

Systems (ESS) has their own way to design the battery pack that can fit one or two car models

or stationary grids, which is actually true for the moment. The second reason is that there is

wide variety of Hybrid-Electrified Vehicles (HEV), and therefore the battery packs are

designed to fit between the combustion engines, and therefore have different designs.

Indirectly, he defines standards as a precise value of each characteristic of the module or battery

pack (size, voltage, weight, internal resistance, location), but this is only a small type of

24


standard rules. Standards could be defined as a limit, a range, a manufacturing process, rules

of transports, recommendations… An international standards of electrical connectors and

charging mods of all EV settle is by the IEC62196, that settled 4 modes of charging and three

type of plugs (SAE J1772, or Yazaki connector for North America; Mannekes Connector for

Europe, and CHAdeMO for Japan) [34].

In this paper, standardization of the BEV module is considered. HEV battery packs are smaller

and have lower requirement regarding performance of their batteries, and have higher

constrains regarding weight and volume of their batteries. This includes electrical

characteristics, cooling systems, external mechanical fittings, external packaging and

Module/BMS interface. A possible attempt inner standardization is then carried out. Finally, a

set of recommendations for different stakeholders is made, and benefits for them will be

highlighted.

Standardizing other parts of the battery pack is complicated, but can be considered in future

work. This includes standardization of:

• The chemistry of the cells used in the battery pack.

• Material used for packaging the battery pack.

• Electrical features of the battery pack (Contactors, battery back fuses, HVIL3).

• Standardizing the BMS circuit, and software for first and second uses.

• Standardize the electrical parameters of the battery pack, weight and size for each

vehicle category (Motor bikes, small, medium, large, luxury cars, small and large

vans, trucks…)

• Standardize the location of the pack.

3 High Voltage Interlock Loop : A safety device tha consist in series of switch that close the circuit when measured voltage by the BMS are high.

25


4 Methodology

4.1 Methodology Selection

The V-model methodology used in system Engineering is chosen to carry out the study. A V-

model different from the original is adapted to this study as shown below:

FIGURE 14: ADAPTED V-MODEL METHODOLOGY

Standard rule is settled to match a maximum of stakeholder’s requirements referred in section

3.4.1.

4.2 Electric Car Selection

Six models of different EVs car are considered. Their choice is based on the UK, as the study

considers than the six most presents BEVs in the UK’s road. The six models are ranked below:

26


TABLE 5: BEV CONSIDERED FOR THE CASE STUDY [50]

5 Electrical Standardization of the module

Referring to section 3.4.1, stakeholders values a number of features in the module, including

performance and safety. Therefore, the aim of this section is to set a number of rules regarding

five parameters: Voltage, current capacity Ah, maximum current capability, weight and size of

the module.

Voltage and current are factors that affects respectively Wh capacity of the battery and power

delivered to the motor of the car, which are respectively key factors for driving range and

acceleration (see appendix A section 12.1). These two feature are valued by customers (first

and second users).

4 Based on the European Car Segmentation 5 C: Medium Car 6 B: Supermini Car 7 F: Luxury car 8 M: Minivan 9 A: Mini Car

Nissan

Leaf Renault Zoe Tesla Model S

Nissan e-

NV200

Renault

Kangoo Z.E Peugeot iOn

Type of car

Small size

car Small size car

Large size

luxury car Van Van Small size car

Number in

the UK

(end 2015)

10441 2401 1346 896 731 250

Segment4 C5 B6 F7 M8 M A9

27


5.1 Observations and Results

Data has been gathered on 6 cars regarding the type of cell used, shown in the table below:

Cell Maker AESC Panasonic Li-Energy

Japan

Toshiba LG Chem

Chemistry G/LMO-

NCA

G/NCA G/LMO-NMC LTO/NMC G/LMO-

NMC

Format Pouch Cylindrical Prismatic Prismatic Pouch

Capacity Ah 33 3.1 50 20 36

Voltage (V) 3.75 3.6 3.7 2.3 3.75

Weight (kg) 0.8 0.045 1.7 0.52 0.86

Volume (L) 0.4 0.018 0.85 0.23 0.49

Volumetric Energy Density (Wh/L) 309 630 218 200 275

Gravimetric Energy Density

(Wh/kg)

155 248 109 89 157

Car used Nissan

Leaf/e-NV

200

Tesla S Peugeot Ion Peugeot Ion Renault

Zoe/

Kangoo Z.E

TABLE 6: CELL CHARACTERISTICS FOR EACH CAR [51]

Tables embedding the characteristics of the car are in Appendix C (see section 12.3). Some

observations while carrying the research on those characteristics are made:

• The nominal voltage is settled according to the car manufacturer, this voltage can be

chosen at different State-of-Charge of the battery (mainly between 60 and 85% SOC).

28


• Most of the cars model, have differences between the battery voltages calculated

using the cell nominal voltage and the nominal battery voltages given by the OEM.

The same applies for all cars, with regards to both Ah and Wh capacities.

5.2 Design rules for Electric standardization

From the previous observations, a set of design rules is derived:

• The nominal values, given by the OEM for each car characteristics, are used as targets

for standardization. Therefore, the standards design is based on these nominal values.

• The Battery characteristics calculated using the cell characteristics are used as

comparison tools. These are compared to the new battery characteristics calculated

similarly using a cell-basis. This method gives a realistic view on the differences

between the characteristics.

• Module volume of the Tesla is calculated by using a rectangular conversion of the

cylindrical cells, in order to match better the real module size.

• Standardized Modules are assumed to be in a rectangular box format.

• The New standardized Battery Weight of each car is calculated using the value of

cell-to-battery weight ratio (CBW).

𝐶𝐵𝑊 =𝑇𝑜𝑡𝑎𝑙 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑐𝑒𝑙𝑙𝑠𝑇𝑜𝑡𝑎𝑙 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑏𝑎𝑡𝑡𝑒𝑟𝑦

𝑁𝑒𝑤 𝐵𝑎𝑡𝑡𝑒𝑟𝑦 𝑊𝑒𝑖𝑔ℎ𝑡 𝑓𝑜𝑟 𝑐𝑎𝑟 𝑥 = >?@ ABCDE F?GHIC BJ K?EEL MNF

.

• The impacts of post-standardize modifications are presented under the form of positive

and negative ratios.

• Customer satisfaction is assumed to be affected under 5%, under current performance of

the car.

These rules are applied in the tables available in appendix C (see section12.3).

29


5.3 Standards proposed

Standardized

Characteristics

Standardized

Value

Comments

Voltage (V) 15 ± 0.75 As pretty all the voltage modules are over 300V, taking 5% of this value will

ensure a matching percentage lower than 5%.

Max Current

Capability (A)

510 Based on the highest motor power which is Tesla’s

Max charging rate 1C Charging above 1C=Ah Capacity, causes faster degradation of the modules,

hence reducing its life cycle. If not appropriately supervised, an overcharge of

the circuit can be caused. Avoid Ultra-fast charging. Allows a controlled

degradation of batteries.

Max Weight (kg) 7 Based on the heaviest module of the set of cars (I-Miev), using the less

performant cells (Li-Japan). No specific limit for height, width and length of the

modules. Format/Volume (L) Rectangular /4

TABLE 7: TABLE OF ELECTRICAL STANDARDS FOR THE BEV MODULE

Applying the standards above on the cars (see appendix C, see section 12.3). Percentage of

fitting for each characteristic derived from the table is presented in the chart below:

FIGURE 15: COMPARISONS RATIOS BETWEEN ORIGINAL AND STANDARDIZED

MODULE CHARACTERISTICS

-‐10.00

-‐5.00

0.00

5.00

10.00

15.00

20.00

Percen

tage Fitting

Car models

Ratio Voltage (%)

Ratio Ah Capacity (%)

Ratio Wh Capacity (%)

Ratio Weight (%)

Ratio Volume (%)

Ratio Power (%)

30


The main positive impacts on the Tesla S is a higher Wh capacity. The standardized capacity

has a closer value to the nominal capacity of 85 kWh, as the non-standardized pack have 79

kWh to 80 kWh. In counterpart, there is a negative impact, as there is a 1% increase in weight

and size. In counterpart there is a 4% power losses for the same car. Regarding the Kangoo,

there is a 16% increase in power, whereas a 1% decrease in power for the Ion is noticed.

The range and acceleration affection is calculated based on theory available in appendix C, see

section 12.3.

FIGURE 16: COMPARISON RATIOS BETWEEN ORIGINAL AND POST STANDARDIZATION RANGE AND ACCELERATION

There is no negative affection on range and acceleration of each car selected, as the highest

negative impact is 4% drop of initial acceleration for the Model S. The Standardization rules

are then acceptable for stakeholders with regard to performance of the car.

5.4 Impact on stakeholders

5.4.1 Standardisation impact on stakeholder’s requirement

Common Impact of standardization on stakeholder’s requirements are:

o Manufacturers and recyclers:

-‐10.00

-‐5.00

0.00

5.00

10.00

15.00

20.00

Percen

tage ratio

Car models

Ratio Range (%)

Ratio Acceleration (%)

31


Ø Reduction of the cost of equipment and testing facilities for manufacturers

and recyclers due to standardization. In this case, settling standard rule means

reducing the characteristics range of modules. Therefore, it’s a first step toward

multi-testing facilities, as one facility is required to test battery of each type of

car model.

o Second life users:

Ø Standardisation of features increases the availability of second use features,

which reduces costs for all second life application.

o All stakeholders (except government):

Ø Cost reduction at the top of the battery life cycle positively impacts

stakeholders concerned with the bottom life cycle of the battery. (see section

3.4.1).

o All stakeholders:

Ø First step toward BMS and battery standardization, as reducing the range of

characteristics, reduces the variety of safety and thermal issues. Then the variety

of BMS software’s is needed, and reduce the threat of warranty (risk costs).

These four points are positive impacts related to standardization in each section

5.4.2 Impact of electrical standardization on stakeholders

Impact of electrical standardization on stakeholder’s requirements are:

o OEM:

Ø Reduce costs due to transportation. Limited Ah Capacity allows OEMs to

reduce their transportation costs as it’s proportional to the ELC, which is the Ah

capacity module times 0.3.

32


6 Standardization of the cooling System

6.1 The cooling system: an essential feature for battery safety, reliability

and durability

Temperature is an important factor to consider for first and second use of the battery.

It affects battery performance, safety and durability.

Heat generation increases with higher rates of SOC and lower temperature, which will cause

faster degradation of the battery. Li-Ion cells generates heat in a smaller volume and are

sensitive to extreme cold and hot, so a complete thermal battery management system is required

[52].

Uneven temperature distribution causes inhomogeneity in the modules. Modules under high

temperature area age faster than others in low temperature area as shown below:

FIGURE 17: INHOMOGENEITY AND AGEING OF MODULES

Even distribution of temperature within the battery pack optimizes the power and energy

density, efficiency and the life of the pack.

Many failures are related to high and low temperature operating condition, for instance thermal

runaways, where heat generation is higher than the heat dissipated, or power decrease due to

decreasing temperature condition (as chemical reaction decrease with temperature). An

optimum balance of operating temperature would be between 20°C and 40°C [53].

33


Therefore, cooling systems (or battery thermal management systems) are critical for optimizing

battery life. According to the NREL: a battery thermal management system is used for reducing

variation of temperature within the modules and the pack [54].

Ideally, standardized cooling system need to be:

Ø Compact, lightweight.

Ø Reliable and serviceable.

Ø Low-cost.

Ø Easily packaged (For second life). [54]

6.2 Air cooling/Liquid Cooling

There are two types of cooling systems that are used in nowadays packs: Liquid and Air

cooling. Their advantages and drawbacks are summarized in the table below:

Air cooling Liquid cooling

+ Low cost - High Cost

+ Easier maintenance - High cost and complicated maintenance

+ Simple design - Complex design

- Less effective heat transferàLarge pressure drops + Higher heat transfer rate

- Low volume efficiencyà runs on the battery + Compact design

- Location sensitive10 + Location insensitive

+ Handle a large pulse of power

- Potential of leakage

TABLE 8: ADVANTAGE AND DRAWBACK OF LIQUID AND AIR COOLING [54] [55]

10 If the location present lot of variation of temperature

34


EV model Cell shape Cooling Method

Nissan Leaf Laminated Prismatic Passive air

Renault Zoe Pouch Active air

Tesla Model S Cylindrical Active-‐liquid

Nissan N-‐EV200 Laminated prismatic Passive air

Renault Kangoo Z.E Pouch Active air

Peugeot Ion Prismatic Active air

TABLE 9: TYPE OF COOLING SYSTEM USED BY EACH CAR MODEL [56]

Many of this characteristics should be taken in account while designing the standardized

module. “Good pack thermal design starts with good module thermal design”. A local analysis

is made in order to determine whether a liquid or an air cooling system is more suitable for EV

batteries in the UK:

• American manufacturers such as Tesla uses liquid cooling for their batteries as they

are mainly implemented in the US, which has high variation of temperature inside its

territory (minimum average is -18°C whereas maximum average is 30°C within a

year, for the state of North Dakota) [57].

• However, the UK has low variability of temperature inside its territory (minimum

average is 0°C and maximum average is 22°C [58]), hence liquid cooling can be seen

as a useless additional cost.

• Volume and power: Liquid system takes less space than air system, therefore the

volumetric energy and power density are affected. Less volume will provide a better

range and acceleration of the car.

35


• NREL recommend the use of liquid cooling for pure EV batteries and series HEV as

it will reach the optimal thermal performance. This shown in the table above, as the

only pure EV car that uses air-cooling, this for low cost purpose. [54]

Liquid cooling are recommended to be used as a standard purpose. The channels within the

battery needs to be layout in a parallel flow line, so the temperature is evenly distributed.

Parallel flow means that the coolant have many entries. [54]

6.3 Passive or active systems

Passive systems are used for ambient temperature, whereas active system are used for extreme

temperatures.

From this table, it’s shown that all American EV models uses active cooling. This is mainly

due to their market location where extreme variation of temperature exists. BMW and Nissan

have mainly their market in Europe. There is low-variation of temperature in central and

southern Europe, and passive cooling system are less complicated, have lower cost and lower

number of components and they consume less energy.

Therefore, standardizing the system must depend on the location. For the moment, different

European Governments such as the UK must set standards regarding the systems, by testing

their batteries under average maximal and minimal conditions. This will decide on which

system to use. For other countries where extreme temperatures are obvious, such as the US,

will set the standard to active systems.

However, having different standards in each country is an issue for OEMs. They will need to

assemble both, passive and active systems for a same model, regarding on where the model

will be used. This will increase costs on the manufacturing process, if the EVs are assembled

outside the country of use. Also, there is issue with second life application for two main reason:

36


• Disassembling: Active and passive system have different layout. Therefore, it requires

more equipment, and a trained workforce. It may require a second work chain, one for

passive, and another for active. All theses parameters will increase the total cost of

repurposing.

• Second life application: Modules under active system must be repurposed in a

different application than those under passive system, in order to avoid

inhomogeneity of the modules in second life. This is die to the difference in efficiency

between the two systems.

Moreover, research is carried out in order to decrease the cost of active system, in order to have

a less complicated layout with an increase in efficiency.

Therefore, a global standard should be set to active systems. Ducts must be implemented

between each module.

6.4 Integrated Liquid/ Liquid Cooling

• According to the NREL: Integrated liquid cooling in a module reduces temperature

distribution in addition to lowering the overall temperature for large modules, which

is good for electrical balancing. Also it provides a better control of temperature

variation as it’s located at a module scale [59].

• However, integrated liquid cooling systems in the modules are expensive and makes

assembly and disassembly of the pack more difficult, hence increases the number of

equipment. Moreover, it adds costs in recycling the modules, as the number of

channels has increased, and are more expensive to manufacture.

Therefore, it’s recommended to set the standard to liquid only-system.

37


6.5 Impact of standardised BTMS on stakeholder requirement

From the previous points, the issue of cooling systems is addressed by using active liquid

cooling system using parallel flow standard for BEVs. The main drawbacks are initial costs of

manufacture and purchase and complexity. However, theses drawbacks are overcome as most

of the requirement for stakeholders are met:

o Common Impact: (see section 5.4.1)

o Manufacturers:

Ø Economy of scale: Ordering higher quantity of different components

composing the BTMS decrease its manufacturing cost per unit produced. à

this feature in the 5th point of the common advantages of standardization

and added to section 5.4.1).

o First users:

Ø Increasing performance, due to less volume and weight occupied by the

BTMS, more module can be added.

Ø Increase Reliability and Efficiency due to higher heat transfer., which increase

durability of the car

o Second users:

Ø Same advantage as first users

Ø Ease of testing and fitting of the battery thanks to standardisation: A standard

type of cooling system is used, hence any battery using this standard fits to the

ESS.

o New Businesses:

Ø First step toward the creation of a new type of business: Cooling system

manufacturer for EVs. Due to the increasing demand of EVs (see section

3.2.5) and standardisation of cooling system, there is high demand of a same

38


cooling system, it can be manufactured in high batches with a fully automated

system, an opportunity for new business.

7 Interface and packaging standardization

The module interface is a set of electrical components that allows communication between

modules and the Battery Management System.

7.1 Module to Module Interface

Inter-module connections are subject to electrical transient and EMI/EMC due to high

operating temperature. [60] Therefore, the communication scheme standardization would

feature:

• Copper Strap Format Bus Bars for inter-module communication [61]. Bus Bars

need to handle between 100A and 510 A ampacity (see section 5.3), Only thickness of

bus bars is subject to variation regarding the module current capability, for

standardisation purposes. Bus-bar connection with modules is made by clamps, in order

to reduce manufacturing costs relating to bolting, and ease of assembly and

disassembly.

• Capacitive coupling (coupling of both capacitors and transformers) for DC

isolation. [60]

• Layout of the modules must be symmetrical, two-wire, bi-directional,

asynchronous daisy chain for series connections; distributed for parallel connections.

[62]

• Combine both voltage and current mode scheme [60]: in order to minimize electrical

transient and EMC/EMI interface.

39


• Connectors close to each other [60] in order to contain current in a restricted area and

avoid electrical transient across the PCB.

• Zener Diodes [60] as protection devices placed before the cable termination points on

the PCB. Simple and cost-effective device.

• High quality multi-layer PCB [60], with a continuous ground plane layer.

FIGURE 18: MODULE/MODULE STANDARDIZED INTERFACE [60]

Impact on stakeholders are:

o First users:

Ø The model offers a high reliable and safe module to module interface, with

risk of failure reduced.


7.2 Module to BMS Interface

Different configuration of BMS/Module interface are compared in the table below:

40


TABLE 9: COMPARISON TABLE OF DIFFERENT BMS/MODULE INTERFACE CONFIGURATION [63]

The Table base comparisons on 5 aspects, which are accuracy, reliability, manufacturability,

cost and power consumption. These serves as a measure of impact on different stakeholder’s

requirements.

The standardized control module below, is the control module used for the parallel module

with CAN gateway and Series modules with can Gateway.

FIGURE 19: CONTROL MODULE PROPOSED STANDARD [63]

It uses SPI bus to communicate with modules, connected in series or parallel or both. Then it

communicates via CAN bus toward the BMS.

For safety issues, each module has a fuse, that protects the cells from overcharging, and

external short circuits, control module is protected by an isolator.

41


Each module must have a standardized CLC chip (for instance an LTC6802s) with a 12 cell

entry located on the battery module for more accuracy. This CLC chip communicate data via

connectors and appropriate fusing located at the surface of the module toward the BMS.

Number of CLC required is proportional to the number of the cells inside the module.

Stakeholder impact:


o Manufacturers:

Ø Rather series connection of modules than parallel one: these is another

drawback on the standardized Tesla model S, as it uses parallel module

configuration. This increases cost and manufacturability of the BMS/interface

and the power consumption. [64]

o First and Second users:

Ø Power consumption affects cost for users.

o Second user:

Ø High accuracy of the system increase accuracy of SOH estimation. Hence,

increases reliability of modules sent for second use.

7.3 Module to car (or pack) Interface

Mechanical fittings must ideally be made with the same material used for packaging, with

regards to manufacturing and recycling purposes. It should be a simple and easy design, that

ease assembly and disassembly of the modules from the battery pack. Welding is proposed as

a low-cost and easier alternative to bolts and nuts, as the process requires less material (Lower

weight and size), however it makes the disassembly process and repurposing for second life

harder. The study then considers the use of clip fixings instead, which is commonly uses in

42


simple and non-durable designs. Clip fixings are machined directly on the module package.

The number of clips used increases with higher weight and sizes of the module.

Clip fixings must be present on all the faces that have a direct contact with the battery pack, in

order to provide stability. If there is only one interface between the module and the battery (for

instance modules located in the middle), larger clip fixings must be used. Impact on

stakeholders are:


o Manufacturers:

Ø Ease of assembling and disassembling, cost reduction due to clip fixing instead

of bolts and nuts, in along term basis.

o Recyclers:

Ø Reduce amount of material needed to recycle, which reduce cost of recycling

7.4 Packaging material standard

The ideal of passive materials standardization is to use one unique material that fits all the

external features and packaging of the module. This significantly reduce costs of

manufacturing and recycling the battery pack, hence impacting on the all overall costs of the

battery.

Module Packaging main objective is protection of the cells. Many safety issues related to Li-

ion are explosion and fire ignition due to poor packaging. The module packaging should meet

the same requirement as the whole battery packaging, that are settled by NEMA and IEC IP

standards, that are respectively settled for stationary systems and automotive application.

Combining their specifications, the packaging requirement are listed below:

1) The material must be able to sustain high mechanical forces abuses

2) The material must also be electrically safe; therefore, an isolate material is required.

43


3) Material should have a high resistance to vapour and liquid corrosion, as the cooling

method used is liquid cooling.

4) The material used must have a melting point higher than the Battery maximum

running temperature, in order to avoid melting.

5) Protect from physical intrusion (dust, liquid…)

6) The volume, weight and cost of material should also be important factor to consider,

as they will affect final performance and cost of the battery.

A good standard should meet the 4 first requirements and provide a fair balance between the

parameters listed in the fifth point, and this would be a glass fibre composite material. This

material is commonly used for module scale sizes enclosure, or slightly bigger such as some

HEV Battery packs. According to modulus diagrams, [65] glass fibre composites have higher

yield strength and lower density than metals (steel). They have a high thermal melting point

above 100°C and they have 0 thermal conductivity and low electrical conductivity.

Impact on stakeholders:


o First and second user:

Ø High reliability, durability and safety of the packaging, but high cost incurred.

o Manufacturers:

Ø Hard machinability and high material costs

8 Cost Analysis

Cost-benefit analysis is related to time gain thanks to ease of assembly and disassembly,

featured on the standardized BTMS, Module/Module interface and car/module interface.

Increased reliability and durability, decrease threat of warranty, thus cost related to risks.

44


Cost savings made in the upper supply-chain, at the battery manufacturer level, positively

impact on the rest of the stakeholders, as long as negative cost impact, such as the parallel

layout of modules, which negatively impact the manufacturing cost of the car.

Issues related to cost-assessment is that few quantifications are made, as it requires more data

that are OEMs property, with limited accessibility

Cost related to Academic and research staff: 45 minutes’ average per week spend by

project supervisor (meetings only, time for responding e-mail and correcting templates is not

taken in account), 14 weeks in total, plus 1-hour interview with academic researcher. Cost

per hour is £50, which gives a total of £575.

Cost related to student research: An average of 8 hours per week consecrated by the author,

for a total of 23 weeks (including bank holidays). Cost per hour is £15, which gives a total of

£2760. Therefore, the total project cost is 2760+575= £3335.

9 Recommendation for future work

The main issue encountered in this study wad the limited data accessibility on each car model

and the trading-off between different features that affects different stakeholder’s requirements,

regarding electrical, thermal system, interface and packaging standardisation.

Recommendation for further work includes:

v Setting an order of priority for stakeholder’s requirement, with regard to each feature

that is attempted to standardize. This allows a better selection, when it comes to trade-

offs.

v Table of interactions between different stakeholder’s requirements.

v Accuracy of data: Dismantle a set of different car models batteries. Test and record

their characteristics directly.

45


v More accessible data on each car model: Detailed information on each stage of the

design process for each car model: Bill of material, CAD&CAM files, risk assessment

and costs specification, are useful to increase the accuracy of the study and the cost

benefit analysis.

v Standard should always be updated, whenever a validated improvement in one area of

the battery is made. In facts, researchers seek to lighter, safer and more performant

batteries. New chemistries are developed such as Li-S and Lithium-air, that in a short

term basis may be validated. Therefore, the standard rules need to be reviewed.

An attempt of standardizing the battery cell format is available on Appendix C in section 12.2.

10 Conclusion

This study highlights an overall positive aspect regarding ethics and costs on standardizing the

external features of a BEV module. In fact, most of the positive impact noticed are for second

users and recyclers. With regard to circular economy, standardisation has then a positive impact

in enhancing this concept. However, some concession at the top of the battery life-chain are

done, with regard to manufacturability, cost and performance, which are balanced by other

positive aspect of standardisation such as circular economy. Issues related to this study are

mainly quantitative, as many of the impacts on stakeholders are noticed but hard to quantify,

especially with regard to cost. Another possible study would be to quantify the cost impact on

stakeholders of each proposes standard.

46


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12 Appendices

12.1 Appendix A: Acceleration and Range theory [66]

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12.2 Appendix B: Standardization of the Cell Format

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12.3 Appendix C: List of Tables for electrical standardization [67], [68]

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