Electric conversion of combustion engine cars - kth .diva

EXAMENSARBETE INOM MASKINTEKNIK, Innovation och design, högskoleingenjör 15 hp SÖDERTÄLJE, SVERIGE 2022

Electric conversion of combustion engine cars

In accordance with Sweden’s laws and used car fleet

Annika Modling Bobby Åbrandt

SKOLAN FÖR INDUSTRIELL TEKNIK OCH MANAGEMENT INSTITUTIONEN FÖR HÅLLBAR PRODUKTIONSUTVECKLING

Electric conversion of combustion engine cars

by

Annika Modling Bobby Åbrandt

Examensarbete TRITA-ITM-EX 2022:353 KTH Industriell teknik och management

Hållbar produktionsutveckling Kvarnbergagatan 12, 151 81 Södertälje

Examensarbete TRITA-ITM-EX 2022:353

Elkonvertering av bilar med förbränningsmotor

Annika Modling

Bobby Åbrandt Godkänt

2022-06-14

Examinator KTH

Mark W Lange

Handledare KTH

Louise Maniette Uppdragsgivare

KTH Företagskontakt/handledare

Sammanfattning Den pågående elektrifieringen av personlig transport är ett av verktygen för att uppnå en hållbar utveckling. I samband med detta stiger bränslepriser och förbud mot dieseldrivna bilar finns numera i flertalet städer. Trots detta är elbilar fortfarande mycket dyra i inköp. Elkonvertering av befintliga (begagnade) bilar kan vara både ekonomiskt och ekologiskt gynnsamt då resultatet blir en cirkulär ekonomi och minskat behov av fossila bränslen, samtidigt som bilägaren ej behöver betala för dyrt bränsle. Detta examensarbete kartlägger möjligheterna och utmaningarna kring elkonvertering av en begagnad bil med förbränningsmotor som alternativ för att köpa en ny elektrisk bil. Konverteringen skall vara ett DIY-projekt som kan genomföras av alla som har kapaciteten att lära sig de färdigheter som krävs samt har finansiella möjlighten att äga en bil. Delar av eller hela arbetet kan även lämnas bort till en mekanisk verkstad om byggaren saknar kunskap eller utrustningen för att genomföra projektet. Att utföra en sådan konvertering visar sig vara högst modulärt där val av bil eller komponenter behöver fattas utifrån budget, tid och kunskap. Kolborst-DC motorer erbjuder pålitlighet till ett lågt pris men har förhållandevis låg verkningsgrad. Trefas AC motorer innebär högre kostnad men erbjuder högre effektivitet och mer effekt. De batterier som bedöms lämpliga för konverteringen är bly-syra batterier och litium-jonbatterier. Även här skiljer sig kostnad och prestanda. Bly-syra batterier är robusta och innebär lägre kostnad, men har låg energidensitet och resulterar i hög vikt. De lämpar sig därför för mindre bilar med kort räckvidd. Litium-jonbatterier, som används kommersiellt i dagens elbilar, har hög energidensitet och lägre vikt. De är dock ett mer kostsamt alternativ och kräver cellövervakning för att förhindra potentiellt haveri. Bilen kommer behövas registreras som ombyggt fordon för att lagligt kunna brukas i Sverige. Viktigt är att bilens ursprungliga totalvikt ej överskrids, varför en bil med låg tjänstevikt och hög maxlast är att föredra som utgångspunkt för konverteringen.

Nyckelord Elkonvertering, förbränningsmotor, elmotor, litiumjon, blysyra, DIY, begagnat, cirkulär process

Bachelor of Science Thesis TRITA-ITM-EX 2022:353

Electric conversion of combustion engine cars

Annika Modling

Bobby Åbrandt Approved

2022-06-14 Examiner KTH

Mark W Lange Supervisor KTH

Louise Maniette Commissioner

KTH Contact person at company

Abstract The electrification of personal transport vehicles is one of the strategies to counteract global warming and dependance on fossil fuels. Diesel powered cars are already prohibited in several big cities and the prices for fuel are constantly climbing. Even so, electric cars are still a premium that not everyone can afford as they could an older ICE-car. This means that there can be a gap in the near future were the Swedish working- and middle class can neither afford a new EV nor refuel their combustion engine car. This thesis investigates the possibilities and challenges of electric conversion of an existing, (used) combustion engine car as an alternative to buying a new electric car. The conversion is meant to be a DIY-project that can be carried out by anyone with the capacity to learn all the skills necessary and with sufficient funds to own a car in the first place. Parts of or the whole project can be outsourced to machine shops or similar, if there are areas where knowledge or equipment of the builder are insufficient. This type of conversion proves to be highly modular where the selection of both car and components depends on budget, time, and knowledge. Brushed DC motors offer reliability at a low cost, but with relatively low efficiency. A three-phase induction motor will be a more costly option, but with the benefit of higher efficiency and power. The batteries that are deemed appropriate for the conversion are lead-acid and lithium-ion batteries. Lead-acid batteries are robust and have a low cost. Their low energy density will however result in a higher weight making this type of battery best suited for a small car with short range. Lithium-ion batteries, which are used in commercial EVs, have a high energy density and lower weight. They come at a high cost however, and they require individual monitoring of the cells’ voltage to prevent potential failure. The converted car will have to be registered as a modified vehicle in order to legally be used in Sweden. The original total weight of the car cannot be exceeded during the conversion and because of this, a car with low curb weight and high max load is preferable as a starting point. Key-words Electric conversion, combustion engine, electric motor, lithium-ion, lead-acid, DIY, second hand

Table of contents

1 Introduction 1

1.1 Background 1

1.2 Purpose 2

1.3 Objectives 3

1.4 Methodology 3

1.5 Delimitations 4

2 Laws and regulations 5

2.1 Type approval 5

2.2 Modified vehicle 6

2.3 Curb weight, max load and axle load 6

2.4 Towing capacity 6

2.5 Registration and tax 6

2.6 Inspection 7

2.7 Documentation 8

3 Exploring context 8

3.1 Target group 8

3.2 Scenario: How are cars being used? 9

3.3 Functional /system analysis of a car 10

4 Market analysis 11

4.1 Prices for new electric vehicles 12

4.2 Available kits for electric conversion 12

4.3 What are the most popular cars in Sweden? 13

4.4 What are the most popular used cars? 13

4.5 Number of vehicles legally registered today 14

5 Vehicle evaluation 14

5.1 Criteria for vehicle evaluation 14

5.2 Evaluation of the three models 16

6 Primary components and infrastructure 18

6.1 Electric motors 18

6.2 Batteries 21

6.3 Energy requirements 23

6.4 Converter / Inverter (Traction system) 25

6.5 Controller 26

6.6 BMS 26

6.7 Charger 27

6.8 Coupling & Adapter plate 28

6.9 Battery temperature 29

6.10 Wiring 29

7 Auxiliary functions 30

7.1 The 12 Volt system 30

7.2 Power steering 31

7.3 Power brakes 31

7.4 Cabin heat 32

8 Result and analysis 32

8.1 Laws 32

8.2 Target group 33

8.3 Market analysis 33

8.4 Electric motors 34

8.5 Batteries 35

8.6 Components to support new electric drivetrain 36

8.7 Replacements for auxiliary functions 37

8.8 Affordable and expensive solution 37

8.9 Rendering 41

8.10 Documentation 42

9 Conclusion 43

9.1 Evaluation of the project 43

9.2 Recommendations for further studies 44

Glossary

AC - Alternating current

BMS - Battery management system

BLDC - Brushless DC motor

Curb weight - vehicle weight with all liquids needed for operation, a full tank of fueland a 75kg driver but without any passengers or cargo

DC - Direct current

European car classifications / market segments (Wikipedia, 2022)

A segment / City car

B segment / Supermini / Subcompact

C segment / Small family / Compact

D segment / Large family / Mid-size

E segment / Executive / Full-size

F segment / Luxury saloon / Full-size luxury

EV - Electric vehicle

HV - High voltage, traction battery system

ICE- Internal combustion engine

PMSM - Permanent magnet synchronous motor

SCB - Swedish government agency operating responsible for producing officialstatistics for decision-making, debate and research

SFRO - A Swedish organization whose guidelines help car enthusiasts registermodified vehicles

Total weight - Gross vehicle weight - maximum operating mass including allpassengers and cargo. It is the sum of the curb weight and load capacity

WLTP - Worldwide harmonized light vehicles test procedure

Electric conversion of combustion engine cars

1 Introduction

1.1 Background

The electrification of personal transport vehicles is one of the strategies to counteractglobal warming and dependency on fossil fuels. Diesel powered cars are alreadyprohibited in several big cities and the prices for fuel are constantly climbing. Evenso, electric cars have long waiting lists and are still a premium and not everyone canafford them as they could an older ICE-car. This means that there could be a gap inthe near future where the working and middle class will neither be able to fill up theircars nor buy electric vehicles. This gap needs to be filled by more budget friendlycommuting alternatives where the conversion of vehicles may be a reasonablestrategy, this project is going to explore possibilities for that.

Converting cars also helps in the transition to a more circular economy; instead ofrelying on consumption of finite resources to produce new products, the lifespan ofexisting products is extended as much as possible. Products are shared, repaired,reused, remanufactured and lastly recycled (European commission, 2019). Thisproject represents an example for the remanufacture step of a circular economy.Instead of disposing of outdated cars with internal combustion engines and thenproducing new electrically powered vehicles this project makes use of the existingcar fleet and extends its lifetime.

With the rise of social media there are more and more resources available online forall kinds of people to learn about all different kinds of disciplines. Social media unitesenthusiasts with professionals of all fields making the DIY community bigger and freelearning more accessible than ever. Because of this, projects like the EV conversionare now available and doable for a wide variety of people who could not have fulfilleda project of this magnitude earlier.

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Fig. 1: Circular economy model

1.2 Purpose

The purpose of this thesis project is to research the possibilities and challengesregarding electric conversion of used cars for personal day-to-day use.

To reach the defined purpose different aspects have to be considered;

● The internal combustion engine provides more than just locomotion.Substitutes will therefore be needed to be addressed in order to maintain keyfunctions that are engine-powered such as power steering, power brakes, andheat.

● The laws and regulations surrounding conversion will be researched whichmeans that the results will only be guaranteed to be applicable in Sweden.The customer needs, such as range and car size will therefore be based onthe needs of a Swedish citizen.

● Based on the conducted research different options for the conversion ofpopular models in sweden will be proposed and different technical solutions atvarying price points will be outlined. The report will be a study on thechallenges to overcome during the conversion (whether they are practical orlegal) rather than a step by step guide.

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1.3 Objectives

Several objectives will need to be fulfilled to define a project with the right depth;

● The laws and regulations that apply for car modifications must be studied andfollowed

● The requirements of the target group (mainly car size and range) must beidentified in order to produce relevant results

● The most popular car models in Sweden will be researched to get anunderstanding for customer needs

● Different types of electric motors and batteries will be evaluated

● An overview of the components needed to support the new electric drivetrainwill be supplied

● Replacements for auxiliary functions previously provided by the combustionengine will be found

● Two suggested combinations of components will be exemplified, one is themost affordable and one is more expensive

● A visual representation of a suggested solution kit will be rendered

1.4 Methodology

Fig. 2: A representation of the structure of the project, showing the hierarchy that dictates the choices that are made

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At the base of the project are the laws and regulations surrounding the modificationof vehicles. To get a better understanding of the laws relevant to this project andregulations limiting conversion a literature study will be performed in addition to aninterview with SFRO, a Swedish organization whose guidelines help car enthusiastsregister modified vehicles

To define a target group, a literature and market study will be conducted. This togather relevant information about the customers’ needs and wants as well astechnical requirements and features that are non negotiable in cars used in a dailycommuting. A typical scenario describing how the target group uses their car in adaily setting will be created to be able to suggest appropriate technical solutions.

An interview with the Swedish agency for statistics (SCB) will be conducted to gatherinformation about the supply of used cars.

Components and technical solutions will be specified based on laws and regulationsas well as the target groups minimum requirements. Data from specific car modelswill be used to describe an example conversion; the selection of relevant vehicleswill be made based on customer needs as well as supply on the market.

Concepts will be visualized through evaluation matrices, morphological charts, andrendered images.

An iterative approach will be used throughout the project where there is no linearpath. An estimation will then be made, and the plausibility/results assessed.

1.5 Delimitations

● The proposed process will be based on Swedish laws, regulations, andcustomer demands and the results will therefore only be guaranteed to berepeatable in Sweden.

● The impact on the electrical grid as a result of increased volume of electricvehicles will not be taken into consideration.

● Calculations of driving range will be based on a number of assumptions andcan therefore only be seen as an approximation. This is because drivingrange is a complex study that is normally tested through WLTP.

● For the selected cars to be relevant, they need to have a level of reliabilitywhile still being fairly easy to work on. Therefore, the project’s market analysiswill use model years 2000-2010 as a starting point.

● The project will cover how to fulfill the minimum requirements (technical andcomfort) for daily commuting and will therefore not necessarily reach the

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performance or elegance of features and function the donor car originallyprovided.

● For the car models, a general approach will be taken and small differences indata between different model and engine configurations will not beconsidered.

● The conversion should be available for a variety of people in addition toexperienced tradespeople and automotive workshops. As such, advancedtechnical solutions will be avoided where possible.

● Furthermore, continuous advancements in motor- and battery technologymake the subject of EV conversion dynamic in nature. As such, it is of morevalue to explore and map the relevant options, rather than aiming for one“perfect” solution. Because of this, components will be specified as type andnot as specific articles.

● Only battery electric vehicle (BEV) conversion is considered. Hybrid vehiclesand hydrogen electric vehicles will not be explored in this report.

2 Laws and regulations

There are laws and regulations that dictate the modification of vehicles. The subjectof EV conversion is relatively new in the eyes of the law. Because of this uncertaintyfactor, the project started off with a literature study of the legal framework to makesure no work was done that ultimately turns out to not be eligible. Beyond that, emailcontact was established with Gustav Ulander, an expert at SFRO, to validate theresearched material.

2.1 Type approval

Since 1998, all cars sold in the EU are type approved. This means that a car isapproved in that exact state with those specific components. This law allows for carsto be sold everywhere in the EU, bypassing any national regulations. The downsideis that cars can not (legitimately) be altered afterhand, not even a new set of wheels.

In Sweden, cars are subject to mandatory inspection every 14 months (Besiktning),and so even small modifications that could fly under the radar can be detected andcause driving prohibition until restored to original.This would make it practicallyimpossible to execute an electric conversion or any other type of extensivemodification within this legal framework.

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2.2 Modified vehicle

To allow for more freedom in modifying a car (in this case electric conversion), it canbe registered as a “modified vehicle”. This is done by turning to an organization suchas SFRO, which consists of various experts in the area. They have their ownrequirements on vehicles that bypass the type approval. Within this classification, thebuilder is free to change not only physical parts but also vehicle data such as curbweight (tjänstevikt) power output, et cetera (Ulander, 2022).

Historically, there has been a minimum extent to which the car needs to be alteredfor it to be accepted in the modified category. Recently however, SFRO came to anagreement with the Swedish transport agency that EV conversion is exempt fromthis requirement, and that EV conversion alone is considered enough. As with anytype of engine swap, a registration inspection is needed before the car is allowed tobe used on the streets (Ulander, 2022).

2.3 Curb weight, max load and axle load

Even if the curb weight can be altered, the total weight of the car can not beexceeded. For instance, if the batteries weigh too much then the amount ofpassengers allowed in the car can be reduced, as with the luggage capacity.

Furthermore, there are maximum load ratings for the respective axles on a car.These can not be exceeded unless upgrades are done to parts like brakes andsuspension, to compensate for the extra weight. It is possible that these needupgrading even if the car is kept within the maximum load ratings, if the vehicledynamics is deemed unstable (Ulander, 2022).

2.4 Towing capacity

The towing capacity is tested by SFRO and an assessment is made whether theoriginal capacity can be kept or if it should be altered. This is done from case to case(Ulander, 2022).

2.5 Registration and tax

If the car is relatively new (with Co2 based taxing) then the tax will be replaced by abase tax of 360 SEK annually. In the case of older cars (that have a weight basedtax) there are not yet any guidelines on how the tax figure is decided, as there havebeen very few of those registrations (Ulander, 2022).

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2.6 Inspection

Apart from general guidelines provided by SFRO when doing an EV conversion, thefollowing items are checked during a registration inspection, before the vehicle canlegally be used in traffic (Hoffman and Ulander, 2022):

● Energy storage○ What type of battery cell?○ Is there a monitoring system?○ Are the high voltage components protected from touch?○ Is there monitoring and protection from short-circuiting?○ Is there technical operational data for voltage, current, etc?

● Power-electronics○ Passive discharge of capacitance down to less than 60V DC in under 5

minutes○ Technical operational data such as voltage, current, etc

● Electric motor○ Technical operational data such as maximum voltage, current, power

and rpm○ Is there temperature monitoring?

● Wiring○ Correct dimensions○ Correct color on wiring related to traction system○ Properly anchored to prevent wear○ No wires may be places over sharp edges

● Warning signs and text○ Where danger is prevalent

● Documentation○ Is there a wiring diagram, function diagram and simple system

description? For rescue personnel to be able to power down thevehicle

● Brake system○ Measuring of (under) pressure (if vacuum servo), measuring of servo

effect○ Measuring of brake performance

● Steering○ Functional test of power steering (if applicable)

This list can be used as overall guidelines while building the vehicle. It is also usefulas consultation before the official inspection.

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2.7 Documentation

Documentation of the build must include a wiring diagram and a simple functiondiagram with an accompanying system description. These help rescue-personnel toknow where to cut power in case of emergency and are examined during inspection(Hoffman and Ulander, 2022).

3 Exploring context

To understand what kind of expectations the converted vehicle is going to need tomeet, the target group has to be defined. A scenario describing the typical usage ofa car in Sweden will help narrow down the technical requirements and an analysis ofvehicle functions will help prioritize features for technical solutions.

3.1 Target group

The premise of this project is to help speed up the electric conversion of the vehiclefleet in Sweden, the target group of the project is therefore aimed to be as large andinclusive as possible.

As a starting point, a target group is defined and summarized in fig. 3, this only as anindication of who could execute a project as the EV conversion. The bottom line ofthe project is however, that almost anyone should be able to execute it if they investthe time and research needed or seek help with problems they cannot solvethemselves. Because of this the only real limitations to the target group are mentaland physical capability as well as sufficient income to own a car and the target groupdescribed below is only an example.

Fig. 3: Summary of the target group

The target group is defined as (but not strictly limited too) people who are betweenthe ages where it is physically possible for them to execute the conversion which

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could be between 24 and 62. They should also have the mental capacity to acquirethe needed knowledge. With the internet connecting the world’s DIY communitiesand the world being in a state of open source, all knowledge required for the buildcan be found, with numerous people uploading detailed content of their EVconversions. Technically adept people and especially experts in electronics will havean advantage however, not least in better estimating the challenge.

When it comes to family status the project is suitable for both single households,couples and, as 32% of households in Sweden include one-three children, evensmaller families (Boverket, 2020). Both apartment and house are appropriate livingspaces for the target group as long access to charging is granted.

People performing this conversion are recommended to have high school or highereducation as a fair amount of research and learning will be needed to complete theproject. The profession is not as important but people having hands-on careers suchas mechanics or carpenters will have an advantage grasping the practical bits of theconversion. The motive behind the execution of this project can be economical,environmental, and / or personal interest in the topic.

3.2 Scenario: How are cars being used?

Fig. 4: Scenario for car usage

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The car is used mainly for daily commuting for an average driving distance of 11,000km per year or 30 km per day (Melkersson, 2021). With this average daily drivingdistance in Sweden, a range of 100km should be sufficient to support the daily use ofthe car with daily charging. Typically cars are used for commuting from and to theworkplace as well as doing everyday tasks such as driving children to school, goingto the gym or other hobbies as well as grocery shopping. All those needs should becovered with the converted car. Alternatively the converted EV can be a second carin the household which would result in lowered demands on driving distance andcargo capacity as the first car can cover long distance traveling or heavytransportations.

3.3 Functional /system analysis of a car

The concept of a car was divided into primary and secondary functions (see fig.5).Primary functions are directly related to actually moving the car, while secondaryfunctions represent the supporting features.

The conversion will focus on the essential functions, but if the comfort andconvenience categories can be maintained in the process, they will be.

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Fig. 5 : Functional / system analysis of a car

4 Market analysis

The goal of a market analysis is to understand the supply and price of electricvehicles and conversion kits. To be able to select appropriate models to exemplifyelectric conversion it is important to understand the customer demands and supply ofvehicles on the Swedish market, therefore, different sources will be analyzed to findthe most popular models every year, both new and second hand. And to understandthe supply of each model in Sweden the amount of registered vehicles will bequantified.

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4.1 Prices for new electric vehicles

Electric vehicles are gaining popularity and car manufacturers are steadily expandingtheir electric vehicle fleets. In the smaller vehicle classes such as the A- and B-segment there is a quite extensive supply of new vehicles on the market. The mostaffordable model in this segment is the Fiat 500e with a starting price of 260,000SEK (Söderholm, 2020). Other vehicles in this segment are the Peugeot e208, theMini Cooper se, or the Opel Corsa with an average price of around 400,000 SEK(Automobiles Peugeot, 2022; BMW Northern Europe AB, 2022; Opel AutomobileGmbH, 2022).

Volkswagen and Renault are examples of manufacturers that offer electric vehiclesin the C segment, starting at around 400,000 SEK (Volkswagen, 2022; RN NordicAB, 2022).

The larger and full sized vehicles that are available for purchase now are Tesla'sModel 3 and Model S which have a starting point of 500,000 SEK and 900,000 SEKrespectively (Tesla, 2022). There are even several crossover SUV models in the Dsegment that are fully electric such as the VW ID6 and the Audi Q5 e-tron. Otherwagons in the D and E segments such as Volkswagen Passat, Volvo V60 or BMW 5series are commonly not fully electric but rather feature hybrid drive trains.

4.2 Available kits for electric conversion

In the market for conversion kits there are a couple different options such as modelbased kits, universal kits, and even some concepts for “minimal” conversion at amore moderate price tag.

There are manufacturers such as EV West that offer kits tailored to specific carmodels (EV West, 2022). Those kits are available for older, rarer models that are notvery common in Sweden making this option more tailored towards car enthusiastsrather than customers looking to cover daily commuting.

Other manufacturers such as EV Europe offer universal kits where the customer canchoose different components based on their needs making this option highlycustomisable to different models . These complete universal kits range from about16-30 thousand dollars (excl. taxes) depending on capacity, brand of components,and different charging kits (EV Europe, 2022). Converting a used vehicle with one ofthese kits is, depending on configurations and selection of vehicle, is not going togive much of an economical advantage over buying a brand new EV.

A concept for “minimal” conversion was introduced by french company transitionone. Transition one offers a service to convert customers' own vehicles into EVs .

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These low budget conversions start at around 5,000€ and are designed for urbanuse. Conversion is done in a minimal fashion keeping as many of the cars originalfeatures and only replacing the combustion engine and its secondary functions whilefor example keeping the original gear box. This French based company mainlyfocuses on the French market where smaller vehicles in the A and B segments arepopular (Fully Charged Show, 2022).

The company has produced two prototypes but have about a year of developmentleft. Once production ready this companys’ conversions will feature a 15kWh batteryfor 100km urban use taking advantage of regenerative braking and the fuel gaugeshows charging level. The original gearbox will be kept where the lower gears areused for (uphill) starts, gear 3 and 4 for urban use, and higher gears for highwaydriving. The concept is based on individual approval by model, mostly of smaller carsthat are in high demand in the french market. Transition one does not convertvehicles themselves but rather delivers kits and teaches existing garages that willconvert vehicles locally (Fully Charged Show, 2022).

4.3 What are the most popular cars in Sweden?

The Volvo V70 was the most sold vehicle most years between 2005 and 2011. Insecond and third place most years were the Volkswagen Passat or Golf. Otherpopular models in the early 2000s and 2010s were the Saab 9-3 and 9-5, the VolvoV50, and the BMW 3 series (Rabe, 2008; Bäcklund, 2010; Vikström, 2011; Vikström,2012).

Between 2018 and 2021 (after the discontinuation of the V70) models like the V90and V60 can be found at the top, with the passat and Golf still being popular. Otherpopular models are smaller SUVs such as the Volvo XC40 and XC60 or theVolkswagen Tiguan (Rabe, 2019; Bilmodeller.se, no date; Nilsson, 2022).

These statistics show clearly that large cars have been the most demanded inSweden for a long time with almost all of the most popular models being wagons orSUVs in the D or E segment and some in the C segment. Beyond vehicle size andcargo capacity another important factor when Swedish citizens buy a vehicle issafety (Rabe, 2020).

4.4 What are the most popular used cars?

In 2021 the most popular used cars in Sweden were V70, Passat and Golf whichwere also the most sold new vehicles in 2010 (Redaktionen Stordåhd, 2022).

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4.5 Number of vehicles legally registered today

To get an idea of the supply of used vehicles of the three most popular models, theamount of registered vehicles between 2000 and -10 was researched. To be able tofind the most recent data on the Swedish vehicle fleet an interview with SCB wasconducted via mail (Heldert, 2022).

Volvo V70 (2000-2010) 172 398 st

Volkswagen Golf (2000-2010) 71 812st

Volkswagen Passat (2000-2010) 38 504 st

Not only was the V70 the most sold car for most of its model years, it is even still ahighly demanded used car and there is a very large amount of them available today.

5 Vehicle evaluation

5.1 Criteria for vehicle evaluation

A number of criteria has been identified for evaluating how appropriate the threemodels are for conversion. These are: supply, weight, cargo space, and safety.

The first criterion is the supply of the vehicle. Since the aim of the project is to coveran as large as possible target group, it is important that the suggested cars of choiceare greatly available and within a reasonable price range.

The popularity of a car also dictates the number of aftermarket- and used parts,which helps in keeping an older car rolling. As with the available parts, theaccumulated knowledge of a car increases with popularity. Since this EV conversionis built on a great amount of information gathering, the DIY community can help bothin the conversion and in the basic maintenance of the car.

Secondly, there are a number of weights that are relevant to vehicle selection suchas the curb weight and max load. In terms of the curb weight it is preferable to find a

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model with a low curb weight to minimize the amount of batteries needed to movethe car for the defined (but loose) goal of 100 km.

Beyond a low curb weight another criterion for vehicle selection is the max load ofthe model. To be able to accommodate the amount of batteries needed to achievethe desired range a high max load is of advantage. The total weight of the modifiedcar must, as previously stated, not be changed in the conversion process. Therefore,a high max load is desirable to maintain cargo capacity and the ability to transportpassengers even after a heavy battery pack has been fitted.

As the car is primarily used in daily commuting and not long distance hauling, theavailable cargo space is not necessarily a priority from a luggage perspective. Itdoes however provide more flexibility in battery placement without the need forreconstruction of the car’s body. All while maintaining room for passengers.

As safety is proven to be top priority when a Swedish citizen choses car (Rabe,2020), it is an important assessment criteria. Independent crash tests are conductedby organizations such as euro-ncap with the criteria: driver protection, passengerprotection, pedestrian protection, and safety assistance. There is a caveat whencomparing crash test ratings though, as the ratings are based on performancecompared to cars in the same segment (ANCAP, 2022) and the three cars beingevaluated are in different segments.

Apart from crash testing, there is a maneuver test called “moose test” introduced bythe car magazine Teknikens värld. It consists of a quick swerve into the oncominglane, before turning back into the right lane. This simulates evading a moose on acountry road and the speed at which this maneuver can be safely carried outdetermines the result. The cars being tested are loaded to max spec, and thereforethis test can be an indication of whether or not the vehicle suspension needs to beupgraded to accommodate the extra weight (Rabe, 2021).

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5.2 Evaluation of the three models

Fig. 6: Spreadsheet summarizing appropriate car models

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Fig. 7: Evaluation of strengths and weakness of the chosen car models

Advantages of the Volkswagen Golf are its safety rating, low curb weight, and highmax load. Downfalls are the weaker moose test rating that could mean that anumber of modifications to the suspension could be needed to improve drivingdynamics at high loads.

The Volkswagen Passat carries more cargo space than the golf, and has slightlybetter maneuverability when fully loaded according to the moose test. It doeshowever score lower in pedestrian safety. It is slightly lighter than the V70 but withsimilar cargo capacity (weight).

The Volvo V70 scores high in maneuverability, luggage space and supply but has thehighest curb weight and a lower pedestrian safety.

Although the Volvo scores highest based on the criteria that are set up, the marginsare small. Because of that all three models are exceptional candidates for an EVconversion and a selection can be made individually by each builder based onpersonal preference and needs.

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6 Primary components and infrastructure

The primary function of the internal combustion engine is to provide locomotion forthe car. During the electric conversion the combustion engine is going to be replacedby an electric motor. Beyond the combustion engine, other major components ofsignificant weight that will be removed before conversion are exhaust system,radiator and coolant, as well as fuel tank.

In this chapter, appropriate motor types will be compared to each other. To supplythis new electric motor with energy, a battery pack will be needed and appropriatebattery types will also be compared in this chapter. Lastly, a number of supportingcomponents will be needed to create an infrastructure for the traction (drive) systemwhich will likewise be discussed in this chapter.

6.1 Electric motors

Electric motors differ from combustion engines in several ways. Electric motors candeliver more power than they are rated for during a limited period of time, forexample under heavy acceleration. They also deliver their power and peak powerover a larger range than ICE:s, so a 100 kW electric motor effectively offers morepower than a 100 kW combustion engine over its RPM range. This is evident whenlooking at the area under the power curves of a given electric motor and combustionengine.

The combustion engine produces no torque at the bottom of the band (fig.8). Itinstead increases with engine speed, with the power curve following. The powerdecreases right after its peak as the torque decreases significantly in relation toengine speed.

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Fig. 8: Example of typical engine power and torque curves for an ICE (generic) (Fernie, 2016)

The electric motor, in this case a permanent magnet synchronous motor, producesits maximum torque from 0 rpm (blue curve, fig.9). The power curve (black) is theneffectively increasing with engine speed before leveling out and then decreasing atthe top of the band as the torque decreases.

Different electric motors will have relatively different curves and power bands, butthey generally share the ability to produce torque without the need of engine speed.

Fig. 9: Motor graph of electric motor (Hyper 9D - PMSM) (Electrogenic Ltd, 022).

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There are two main categories of electric motors, AC and DC;

AC motors use alternating current to turn its shaft. They generally allow for a highpower output, partly because they can utilize three-phase electric power (GainesvilleIndustrial Electric Co, 2022). They also allow for regenerative braking which isfavorable when trying to maximize range in an EV. They require no “service”, andthey can maintain a sustainable temperature during prolonged high loading. Thedownside is that they can be more expensive, and require more advanced controllingthan DC motors.

DC motors on the other hand use direct current. In their simplest form they areinexpensive and only need a two-lead wire to turn (positive and negative leads).They produce high amounts of torque at low RPMs.

There is a variety of electric motors, some more applicable in EVs than others.Mainly four types of motors were chosen to be studied, as they seemed to fit withinthe parameters of the conversion. This was based on what is used by carmanufacturers, in other DIY conversions and what is commercially available).

The motors chosen were; brushed DC motors, brushless DC motors (BLDC), ACinduction motors, and permanent magnet synchronous motors (PMSM).

Both permanent magnet DC motors and permanent magnet synchronousmotors (AC) are highly efficient but rely on rare earth metals to create the magneticfield. Since they are limited in torque to the strength of the magnets they are more fitfor small, light cars than big, heavy ones (The Engineering Post, 2022). As for themagnets, research is being conducted to eventually replace the rare neodymium withferritic materials, although these motors are not yet as power dense (Eriksson andEklund, 2021).

A brushed DC motor is the (relatively) least efficient of the listed motors. It doeshowever have a high starting torque, and the simple construction and infrastructuremakes it an affordable and accessible option. It is how many DIY conversions startoff (Maguire, 2018). It loses torque and efficiency at high speed, but if the gearbox iskept in place, the motor can be kept in a rpm range that is the most beneficial.Allegedly, the heat created at the commutator can be a cause for concern, andshould be monitored. These are rarely used in production vehicles.

An AC induction motor is widely used in commercial EVs as it is powerful, efficient,and allows for energy recovery in the form of brake regeneration (The EngineeringPost, 2022). Since there are no brushes that wear down against a commutator, it is,like the permanent magnet motors, “maintenance free”. The downside is that itrequires an inverter circuit to turn the battery’s DC power to AC. It is also dependenton hall sensors and fine programming to run properly, increasing both complexityand cost to some degree.

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6.2 Batteries

There are a handful of different battery types with different attributes and price pointsthat are appropriate for use in electric vehicles.

Lead-acid batteries consist of sulfuric acid and water mixture acting as theelectrolyte and an anode and cathode covered in lead. Common types of lead-acidbatteries include flooded batteries, AGM (absorbent glass fiber) and gel batteries. Inflooded lead batteries the electrolyte is its (high-density) liquid form which creates arisk for leakage. In AGM batteries glass fiber is soaked in the electrolyte eliminatingthe risk for leakage. These batteries are extremely resistant to vibration andmaintenance free. Gel batteries are the most advanced type of lead-acid batterieswith tolerance for high temperatures, shock, vibration and over discharging (Hoffmanand Ulander, 2022).

Lead-acid batteries are commonly used in ICE cars to power the starter, ignitionsystem and other electrical components. A standard car battery has 12 Volts andconsists of 6 cells with 2.1 Volts each. These batteries generally have a lifespan of400-600 charging cycles (Hoffman and Ulander, 2022).

Advantages of this battery type is that they are cheap, easy to produce and recycle,and do not need any monitoring (Petrovich, Chesky, 2019). They do however have arelatively small capacity with significant bulk and weight only providing around 35-40Wh/kg. Another disadvantage of lead-acid batteries is that they do not holdconsistent voltage over the whole charging cycle making the motor less powerful asthe battery discharges (Chian et al. 2019).

Nickel-cadmium batteries were earlier used in electric vehicles as they areinexpensive, reliable, and have a long lifespan of around 500-1000 charging cycles(Petrovich and Chesky, 2019). With a power density of 40-60 Wh/kg they have anadvantage over lead-acid batteries but are inferior to other more modern batterytypes.

A disadvantage of these batteries is that they suffer from “memory effect” thoughwhere maximum storage capacity depletes due to crystallization if the batteries arenot being charged properly. This battery type is now prohibited due to cadmiumtoxicity (Petrovich and Chesky, 2019).

Nickel-metal hydride batteries have a power density of 60-120 Wh/kg and alifespan of 500-1000 charging cycles. They are more expensive than nickel-cadmiumbatteries but still rather affordable. They are suitable for use in electric vehicles asthey are reliable and have a large range of operating temperatures and were

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frequently used in electric vehicles until the breakthrough of the lithium ion battery(Petrovich and Chesky, 2019).

Disadvantages of this battery type include that they self discharge quickly which canbe an issue if the vehicle is parked for a prolonged period of time. They need precisecontrol of the recharging process making their usage more complex than otherbatteries.

ZEBRA batteries, or sodium-nickel-chloride batteries, are molten salt batteries witha storage density of roughly 115 Wh/kg and a long lifespan of several thousandcycles.

Problematic with this battery type is the high operation temperature of around 300°Cthat is required. The battery therefore requires preheating prior to usage after an EVis parked for extended periods of time (especially in cold weather) which is energyconsuming. Therefore the ZEBRA battery is more suitable for EVs that are beingused consistently, for example in public transport, and rather inappropriate for dailycommuting (Chian et al. 2019).

Lithium-ion batteries are commonly used in EV today. There is a large variety ofchemical compositions and properties of lithium ion batteries on the marketdepending on the manufacturer of the battery (Chian et al. 2019). Generally thisbattery type has a long life span of 400-1200 cycles and greater energy density thanthe other types with 100-265 Wh/kg. They also hold a quite consistent voltage overtheir discharging cycle (fig. 10). Lithium ion batteries are highly reactive and thusrequire suitable packaging and precise control of the recharging process (Petrovichand Chesky, 2019). These batteries have a high cost but are attractive in the marketbecause of their high energy density.

Fig. 10: Discharge curves of Li-ion and Pb-batteries (Zwerfcat, no date)

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Several of the described battery types can be considered inappropriate for the use inan EV for daily commuting. Nickel-cadmium batteries’ toxicity, nickel-metal hydridebatteries’ quick self discharge, and ZEBRA batteries’ high operating temperaturemake those battery types hard to use for this project. The two appropriate batterytypes that can be considered are lead acid and lithium ion batteries.

6.3 Energy requirements

To approximate the amount of batteries needed to power the converted vehicle ahandful of calculations were executed. The Volvo V70 was used as an example asthis is the heaviest of the chosen models and is therefore going to need the mostbatteries.

The calculated driving range of stock electric vehicles is based on driving cycles withdifferent amounts of accelerations, hills, braking and more which makes it hard tocalculate the energy consumption the Volvo would have. As a starting point forapproximations, a table over energy consumption for different car models wasstudied; this showed that large vehicles like 7-seat SUV and full size vans have aconsumption between 0,27 and 0,295 kW/km. Cars in the same segment as the V70have a consumption between 0,19 and 0,21 kW/km (EV Database, 2022).

Those tests are however made without taking auxiliary functions such as lights andheat into consideration, and with a beneficial ambient temperature of 23 degrees(Hampel, 2022). Because of that and the fact that the Volvo, depending on how thebuilder configures their car, might not be as efficient as actual EVs (potentially higherweight and lack of brake-regen etc). The approximation of energy consumption wastherefore set to the highest end of the spectrum 0,3 kW/km. This means that theVolvo would need a battery capacity of 30 kWh to reach the range goal of 100 km.

Based on the now assumed energy consumption, the required amount in bothvolume and weight of each of the two appropriate battery types was calculated. Todo this a commercially available lead acid battery and lithium ion module werechosen (fig. 11). The lead acid battery is of average capacity, whereas the Li-ionmodule consists of higher quality cells.

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Fig. 11: The two batteries chosen as an example

The results of the calculations on required batteries can be seen in the table below.

Battery type Volume (for 30 kWh) Weight (for 30 kWh)

Biltema lead-acid battery 309,6 liters 710 kg

Tesla 86,3 liters 140 kg

To summarize these findings a visual representation of required battery amounts ismade. For this the two types of batteries should be visually comparable. Therefore,the required volume of lithium-ion batteries is represented by the dimensions of thelead-acid battery. The volumetric and weight comparison between the chosenlithium-ion and lead-acid batteries are visualized in fig. 12 below. This represents theapproximate amount of batteries needed to give the Volvo a range of 100 km.

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Fig. 12: Volumetric and weight comparison between lead-acid and lithium-ion batteries

As a reference point the same calculations were executed for the smallest of thethree car models; the Volkswagen Golf. First the energy consumption wasapproximated based on the aforementioned table. According to this, vehicles in thesame segment as the Golf have an energy consumption of around 0,165 kWh/km.Assuming once again that the converted Golf is going to be less efficient than stockEVs, an energy consumption of 0.2 kWh/km is approximated. The curb weight of theGolf is around ⅔ of the curb weight of the Volvo so an energy consumption that is ⅓lower seems appropriate.

This means for 100 km of driving range the Golf would need 17,5 lead-acid batteriesweighing around 474 kg or 3,75 lithium ion modules which weigh around 94 kg.

6.4 Converter / Inverter (Traction system)

Depending on the voltage of the battery pack and motor/controller, a DC/DCconverter may be needed in the HV battery system to get the correct input voltage tothe controller and then motor. If the battery voltage is matched with the controller

If an AC motor is chosen, an inverter will be needed to take the battery’s DC powerand turn it into AC, and vice versa when using regenerative braking.

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6.5 Controller

Regardless of what motor type is being used, a controller will be needed to adjustthe speed of the motor (and therefore vehicle). A potentiometer that registers theangle of the gas pedal can be used as input for the controller, which then providesthe motor with the requested amount of power.

If a brushed DC motor is used then the simplest form of controller can be used. Thisis because the brush/commutator interface is effectively a built-in position sensorcircuit, and the only flow into the system is voltage and current.

Brushless DC motors (BLDC), Permanent magnet synchronous motor (PMSM) andInduction AC motors are all dependent on feedback from the rotor’s position sensorsthat tell the controller what set of windings to magnetize. This is not entirely unlike acombustion engine that needs a crankshaft position sensor in order to fire the rightcylinder at the right time.

The controller needs to be sized according to the motor in order to deliver enoughpower

6.6 BMS

All battery cells will differ in capacity to some degree. This means that each cell willbe fully charged and discharged at a different rate. The battery module’s voltage willtherefore drop to below working voltage and require charging as soon as the cell withthe least capacity is discharged even if other cells in the module still carry charge.Discharging the battery cell further will cause deep discharge, resulting in additionalwear.

The real problem with unbalanced cells however, is during charging. The batterieswith more capacity will be taking all the excess energy that the lower capacity cellcannot hold which can result in damage and potentially a fiery explosion.

Lithium-ion batteries therefore require a battery management- and cell balancingsystem (illustrated in fig. 13). This essentially means that the voltage of each cell isindividually monitored and charged accordingly. This reduces risk of catastrophicfailure, improves longevity and ensures all the energy stored in the batteries can beutilized.

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Fig. 13: Battery management system: The C battery (left picture) will become overcharged as it reaches full charge before theother two cells. It is then at risk. The B battery (right picture) will instead be deep-discharged as the electric consumer tries todraw more energy out of the battery pack.

6.7 Charger

The relevant types of chargers are:

● The Type 2 charger is the most common charger on modern EVs and is foundon most public charging stations. It is rated at 70A at 1-phase and 63A at3-phase. It is standard in the EU (Sandberg, 2019).

● The CCS (Combined Charging System) combines the type 2 interface withtwo additional large pins that can be used for DC fast charging (Sandberg,2019).

● Onboard charger with 230V Shuko or 400V connector

Fig. 14: Charger types

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The primary goal of the conversion is to allow for daily driving. This means that thepurpose of the car is not necessarily long trips. However, if the battery and chargingsystem are designed appropriately it is possible to make the car compatible withpublic charging stations in addition to 230V wall sockets. Since the array of chargingstations available in Sweden is extensive, this would make it possible to take theconverted vehicle on longer journeys if the trip is properly planned.

An example of a company that follows the same philosophy is Zero EV; theirstandpoint is that it is more worthwhile to build an EV with as little battery capacity aspossible to account for daily driving, and instead making fast charging available forthe “rare” occasions of long trips (Zero EV, 2021). This way, both money and weightof the car can be saved. They also sell a kit for installing a CCS charging socket thatenables this.

Therefore a CCS charger can be a worthwhile investment. It contains the ubiquitoustype 2 socket, which means the car can be charged at most public stations, at one’sworkplace and so on. It also has the two DC-pins that allow for fast charging, makingit possible to take the car on longer journeys.

If one wants to go the cheapest route however, it is possible to mount an onboardcharger that fits the battery and have a standard 230V or 400V connector to plug inwherever there is a power outlet.

6.8 Coupling & Adapter plate

A coupling will be needed to transfer power from the motor to the transmission. Thiscan be done by getting a coupling that fits the motor’s shaft and welding the splinedsection of the car’s original clutch to it. If the person performing the conversion lacksthe means to weld, the work can be performed by a machine shop.

Apart from power transfer, the motor also needs to be bolted to the gearbox. This isgenerally done by machining an adapter plate with respective bolt patterns for themotor and the gearbox. This is possible to do with an angle grinder and drill press. Itis important to get the alignment correct however, and cutting thick materials withhome tools can be non trivial. Again, this can be outsourced to a machine shop withthe ability to use CNC and water cutting.

The plate in image 15 is made from 20 mm aluminum that came from the scrap binof a machine shop, helping to keep the cost down (Maguire, 2018)

This type of adapter plate follows the same concept as conventional engine swaps.

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Fig. 15: Adapter plate

6.9 Battery temperature

Lithium-ion batteries need to be kept between certain temperatures in order to fullywork. The range of operating temperatures for a specific battery pack is specified ona datasheet. Teslas 5,3 kWh battery module for instance has a dischargetemperature range of -20 to 60°C, a charging temperature range of 0 to 45°C, and astorage temperature range of -20 to 50°C (Stealth EV, 2022).

Batteries do not respond well to extreme cold, even when not in use. So in coldercountries like Sweden where temperature can get far below 0°C, some type ofbattery heating system is recommended. For this, a resistive heating elementcombined with a temperature sensor is sufficient. Not only can the temperaturesensor be used for battery heating, it also monitors the battery for overheating andcan cut off power supply if the battery is at risk.

6.10 Wiring

The guidelines for wiring in an EV conversion are similar to other types of electricalinstallations (Hoffman and Ulander, 2022).

● The wires must be protected from wearing against sharp edges. This meansthat any wiring that goes through a hole in a panel needs a cable gland orgrommet

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● There should be a master switch that when turned off leaves the high voltagesystem without power, for service as an example. In addition, an emergencystop switch should be installed and sit close to where the driver is

● Wires should be correctly dimensioned and follow a color scheme, forexample orange wires should be used for the HV system

● No HV components may be exposed for touch in order to avoid electrocution

7 Auxiliary functions

There are a number of systems in a car that are directly dependent on thecombustion engine but not related to movement of the car; those are defined asauxiliary functions. To sustain those functions different solutions have to be found.

7.1 The 12 Volt system

The 12 Volt system in a car is powered by an alternator that is directly connected tothe combustion engine. The alternator is a type of electric generator that convertsthe mechanical energy produced in the combustion engine into electrical energy topower the 12 Volt system and charge the battery. The battery (typically lead acid)powers the ignition system (no longer required) and the alternator then powers allthe electric appliances like headlights, radio and computers, windshield wipers, andpower windows and seats.

According to SFRO, it is highly recommended for EV converted vehicles that the 12Vsystem is separate from the electric drivetrain (Hoffman; Ulander, 2022). As theinternal combustion engine is removed in the conversion process an alternative wayof powering the 12 Volt system is needed. This can be accomplished with a DC/DCconverter that converts the high voltage of the main battery pack into 12 Volts tocharge the lead acid battery.

As an example: The V70 typically has an alternator with 115A current and 14Vvoltage. This means that the chosen DC/DC converter needs to supply at least 1500Watts of 12V output power.

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7.2 Power steering

Power steering is based on hydraulics where a pumped fluid multiplies the steeringforce applied by the driver. In power steering there is a mechanical connectionbetween the steering wheel and the linkage that steers the wheels (this is not thecase in electric steering). The power steering system consists of a gerotor / pumptypically driven by combustion engine and an actuator in the form of a hydrauliccylinder.

To maintain the power steering in a car while removing the engine, there are twoviable options;

● Keep hydraulic power steering and replace the engine driven (belt driven)pump with a 12V electric hydraulic pump. The most cost effective way to dothis is to find an electric power steering pump with a reservoir used fromanother car.

● Install electric power steering. Here an electric motor provides assistance insteering (instead of a hydraulic system). In this case the hydraulic cylinder isreplaced by an electric motor. The power to the actuator is controlled by thepower steering system.

Installing electric power steering requires major modifications to the steering systemwhich is time consuming and expensive. If an electric pump is used the steeringsystem does not need to be modified any further making this option more timeefficient and economical.

7.3 Power brakes

Power brakes are based on hydraulics where a pumped fluid multiplies the brakingforce applied by the driver. The vacuum booster pulls air out of the booster chamberwith a pump or other vacuum source, typically the combustion engine's intakemanifold. The vacuum booster multiplies the force applied by the driver and deliversit to the master cylinder, from there it is distributed to the four brake calipers.

To maintain the power brakes in a car while removing the engine, there are a handfulof viable options (Hoffman and Ulander, 2022);

● Keep hydraulic power brakes and replace the engine's vacuum with a 12Velectric vacuum pump and a vacuum reservoir (popular in EV community)

● Remove the vacuum booster and brake pedal ratio

● Remove the vacuum booster and replace the master cylinder

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Installing an electric vacuum pump to supply the braking system with vacuum is theeasiest way to sustain the function of the brakes. Adjusting the pedal ratio orreplacing the master cylinder require more knowledge of the braking system and aretherefore more advanced options.

7.4 Cabin heat

The heating system in a car utilizes the heat that is developed in the combustionengine to heat the cabin of the car. Here, a water pump that is directly connected tothe combustion engine is responsible for passenger compartment heating. Thesystem works like a heat exchanger with the water circulating between thecombustion engine, the radiator, and the heater core.

To maintain the ability to heat the passenger compartment in a car after removing theengine, the following options can be considered:

● Keep the heating core and install an electric water heating system.

● Replace heating core with a ceramic element (PTC heater) and install anadditional contactor DC. In moderate climates a 1500W ceramic elementshould be sufficient but a bigger element might be needed in colder climates.

● Install portable interior heater

The simplest heating solution would be installing a portable heater, this can be donequickly and at a low price but is most likely not going to be a permanent solution. Amore advanced technical solution is installing a PTC heater, this includes moreadvanced conversion but has the advantage of being able to use the cars originalfans for more efficient heating.

8 Result and analysis

The results of the studies show that the EV conversion is a highly modular build andmany choices need to be made by the person doing it. Listed below is a summary ofthe research on the proposed conversion.

8.1 Laws

The result of the law studies indicates that the model year and make of the carshould have little impact on the end result from a legal perspective. This is becausethe car will be registered as “modified” and a new set of rules will apply.

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The main legal limitation appears to be weight limit, since the total weight of the carcan not be exceeded during the conversion. It is also important that the car handlesand brakes sufficiently, even if the total weight has not been exceeded.

8.2 Target group

The bottom line of the project is that almost anyone should be able to execute theconversion if they invest the time and research needed or seek help with problemsthey cannot solve themselves. Because of this the only real limitations to the targetgroup are mental and physical capability as well as sufficient income to own a car.

While selecting and purchasing vehicles, Swedish citizens prioritize safety makingsafety test ratings a priority during the market analysis and vehicle evaluation. Theaverage daily driving distance in Sweden is 30km, the example conversion willtherefore have a target range of 100km.

8.3 Market analysis

Most popular are three classes of cars; station wagons and full-size vehicles in theD- and E-segment, midsize cars in the C-segment, and in more recent years small ormidsize SUVs.

There is a supply of electric vehicles in the smaller segments but the prices for bothnew and second-hand vehicles are still high. Likewise fully electric larger cars likeTeslas models and SUVs are expensive. Wagons, which have been popular inSweden for many years, do not seem to be the main focus in electrification for carmanufacturers as these models are mostly hybrid options.

As the options for kits are either too expensive, tailored for the wrong types ofvehicles or only preliminary concepts not ready for production none of these optionsare optimal for the desired result of this project.

Most popular cars in the relevant years were the Volvo V70, the Volkswagen Passatand the Volkswagen Golf; those are even the current most popular second-handcars. All of these three models are appropriate choices for an EV conversion.

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8.4 Electric motors

Fig. 16: Comparison of motor types

All of the four motors described in chapter 6 are well suited for an EV conversion. Itis therefore up to the budget and goals of the builder which motor to go for. Thecheapest and simplest route is to go for a brushed DC motor. The car must beequipped with a motor temperature sensor (Ulander 2022) so if the motor runs hot,this can be monitored and attended to. The BLDC along with the PMSM are highlyefficient, but they can be expensive. They also put additional strain on worldNeodymium production. The AC induction motor is an alternative with its high poweroutput and without need for rare earth materials or brush-replacement.

Once the electric infrastructure in the car is built, with batteries, wiring, andsupporting systems, it is possible to change/upgrade the motor later on.

In order to lower conversion costs motors can be bought used but second hand partswithout warranty will always come with some risk. In order to lower this risk it isrecommended to judge a used motor by age, hours operated and in whatenvironment it has been running. Beyond that, a few steps can be taken to ensuresome degree of reliability. The windings in the motor can be tested for insulation tomake sure there is no internal short-circuiting, as the coating on the wires can weardown. If it is a brushed DC motor, the brushes can be inspected and/or replacedbefore put in the car.

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8.5 Batteries

Fig. 17: Comparison of battery types highlighting the two appropriate types

As previously discussed, the two appropriate battery types to be considered for theproject are lead acid and lithium ion batteries.

Lead acid batteries are easy to use, inexpensive and robust but have a less efficientdischarge curve and are heavy. They are the cheapest way to power the vehicle butwould however weigh so much that no passengers or cargo would be allowed, andthe range would diminish from the sheer weight it needs to haul around. It is howeverpossible as an ultra-cheap short range solution, settling for less capacity, reducingthe weight.

Lithium ion batteries have a high energy content and hold voltage well but are priceyand need precise monitoring. The fastest and safest way is to buy an existing batterypack, either new or from a used EV. They can also be scavenged from oldelectronics (laptops) and after checking their capacity, be used to build a custombattery pack (Garcia, 2014). This can be done at a way lower cost, but requires moreknowledge and time, and might result in a less robust battery pack.

Both types can be appropriate and a selection can be made on a case to case basisdepending on the individual's needs and budget.

The battery is the biggest cost of the Ev conversion. To reduce this cost, usedbatteries can be an alternative to new ones. One of the reasons used batteries can

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be a viable option is that battery packs in electric vehicles can in some cases outlivethe vehicle they were built for. Most manufacturers of electric vehicles sell theirvehicles with a warranty of 7-8 years or 100,000 miles (including the battery pack)(Kia UK, 2022; Volkswagen of America Inc, 2022). According to Tesla's 2019 impactreport their batteries have over 80% of their original capacity after 200,000 mileswhereas vehicles in Europe have an average life time of around 130,000 miles(Tesla, 2020). Based on this, buying a used battery pack in good condition can be aneconomical and sustainable choice for an EV conversion .

8.6 Components to support new electric drivetrain

The components needed to support the new electric drivetrain were researched anddifferent options for each category were visualized in a morphological chart (fig 18).

Fig. 18: Overview of components needed to support the new electric drivetrain

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8.7 Replacements for auxiliary functions

The different options for replacing the previously engine powered auxiliary functionswere likewise visualized in a morphological chart (fig 19).

Fig. 19: Overview of components needed to support auxiliary functions

8.8 Affordable and expensive solution

Lead acid batteries are potentially applicable in a small and lightweight car such asthe Volkswagen Golf. To achieve the aspired 100 km range, roughly 470 kg of Leadacid batteries are needed, being well within the maximum load of 600 kg.

In a large car like the Volvo V70, the required amount of lead acid is around 700 kg,which exceeds the maximum load of the vehicle. Here, a lithium ion battery pack isrecommended if the range of 100 km is desired. There are companies selling usedbatteries with not that many miles on them that have been tested for performancewhich can be a great option to keep the conversion cost down.

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Viable options for the different components are visualized below.

The most cost effective path to select primary components is shown in fig 20. Thissolution should cost around 20-50,000 SEK and will be heavier due to the lead acidbatteries, it will therefore have a shorter range than a vehicle with an equivalentLi-Ion pack.

Fig. 20: Affordable option

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A more technically refined and expensive build is shown in fig 21. This alternative iscloser to that of a production car. This conversion can be executed between 60,000and 200,000 SEK depending on if batteries are purchased as used or not. Thecomponents chosen in this option will give the possibility of regenerative braking aswell as fast-charging.

Fig. 21: Expensive option

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For both the affordable and expensive option, the same secondary components arerecommended as they are the most suitable for the conversion. These solutionssustain the functionality of the car without advanced alterations. They are notnecessarily more expensive than the other options.

Fig. 22: Suitable combination of secondary components

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8.9 Rendering

A visual representation of a suggested solution kit can be seen below (fig. 23). Theincluded components are the “expensive option” that was previously described. Thisconverted car will have a range of around 100 km, an AC induction engine withregenerative braking as well as a lithium-ion battery back that minimizes the weightof the conversion. The V70 in the example is fitted with a CCS charging point whichmakes both standard Type 2 charging as well as fast charging available. The car willtherefore be useful for both daily commuting and (well planned) longer trips aspreviously described. Power brakes and steering will be maintained using vacuumpumps and the original water heating system is replaced with a PTC auxiliary heaterproviding sufficient warmth while being able to use the original infrastructure of fans.

Fig. 23: Example of needed components for converting a Volvo V70

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8.10 Documentation

The aforementioned documentation of the electric conversion must include a wiringdiagram and a simple function diagram with an accompanying system description.(Hoffman and Ulander, 2022).

An example of a wiring diagram for the proposed conversion can be seen in fig. 24. Itis not constructed with a specific pinout since the components are not specified. Itdoes however list the relevant electrical components that are necessary. It should benoted that the high voltage DC/DC converter may not be necessary, and may bereplaced by an inverter should the motor choice be AC instead.

The ground is the car’s chassis, and it is connected to the 12V battery’s negativepole. The traction system is “floating” and therefore not grounded in the car’schassis.

Fig. 24: Wiring diagram

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The proposed function diagram can be seen in fig. 25. It resembles the wiringdiagram but is simplified into function blocks. The color roughly illustrates thedifferent voltage levels of the system. Just like the wiring diagram, it shows how thetraction (HV) system and 12V system are completely separate.

Fig. 25: Function diagram

9 Conclusion

9.1 Evaluation of the project

The three cars that were evaluated and suggested were originally chosen solelybased on popularity, but as they turned out to be good candidates for the conversion,no iteration was deemed as necessary. They can all carry a heavy load whilemaintaining good vehicle dynamics. In the end it is up to the user to define which carbest suits their needs.

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The target group is technically anyone that has an interest in the conversion,whether it be for economical, environmental, or personal reasons. There is noreason why parts of the build can not be outsourced to a machine shop, a competentacquaintance, or similar. It is a balance between time, knowledge and cost.

One should be aware however that the same risk that applies to electric installationin buildings etc, apply when wiring a high voltage electric vehicle. As such, a basicunderstanding of electricity will be vital in order to safely execute the conversion.

The customer base was thoroughly studied in parallel with laws and technicalsolutions. Later on, this turned out not to be essential as the build is highly modular,and everything from car size to range depends on what needs the person doing theconversion has.

As previously stated, the subject of conversion is dynamic in nature, and thetechnical components suggested may in the future be seen as obsolete.Improvements in technology may alter how the components are chosen. Forinstance, BLDC motors may in the future be built on ferritic magnets that can makethe motor more affordable while still being efficient.

As the conversion is intended as (at least partly) a DIY endeavor, sources to thisreport include Youtube videos of individuals who have previously gone through withconversions and their experience. Since content of this sort does not necessarilyfollow the scientific method nor is peer-reviewed, it should be seen as anecdotalevidence. However, by combining results from several sources and including whatprofessional companies that do EV conversions claim, the degree of certainty fallswithin tolerance for this type of build and project.

9.2 Recommendations for further studies

For further studies, it would be relevant to do an economical analysis of doing aconversion compared to buying a used electric vehicle, especially as the amount ofused EVs will most likely increase.

To understand the environmental impact of an EV conversion, a life cycle analysis ofthe car and the relevant components can be performed.

Another relevant area of further studies is an analysis of how the curb weight of theconverted vehicle is impacted by the conversion. Here it is important to analyze howmuch weight is going to be removed with the removal of the original engine andsupporting systems and how much the new solutions would weigh. The placement ofthe new components has to be thoroughly planned as to not exceed the specifiedaxle loads of the vehicle.

44

It should also be stated that the laws regarding electric conversion are still beingupdated, with a book containing new guidelines already being scheduled for release(Ulander, 2022).

45

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