Sähköajoneuvojen akusto ja kestoikä

Abstract

Tämän opinnäytetyön aiheena on sähköautojen akustojen kestävyys ja kapasiteetin lasku.Työn tarkoituksena on selvittää, miten sähköautojen akkukapasiteetti laskee ja mitkä eri tekijät siihen vaikuttavat.Työ on toteutettu kirjallisuusselvityksenä tutkimalla aihetta käsitteleviä internetlähteitä ja kirjallisuutta.

Työssä on käsitelty yleisimmät sähköautoissa käytettävät akkutyypit ja niiden rakenne sekä tarkasteltu yleisesti sähköautojen ja akkujen toimintaa. Samalla on myös selvitetty, mitkä eri tekijät saattavat vaikuttaa akun kapasiteettiin.

Esimerkkiautoiksi valikoituivat kaksi täyssähköautoa: nopeasti ympäri maailmaa suosiotaan nostanut Teslan Model S ja Nissan LEAF.

Työssä huomattiin, että moni asia saattaa vaikuttaa sähköauton akuston kapasiteetin laskuun. Esimerkiksi korkeissa lämpötiloissa tai kovilla pakkasilla akut rasittuvat enemmän ja niiden käyttöikä saattaa lyhentyä. Myös jatkuva pikalatauksen käyttö saattaa syödä kapasiteettia samalla tavalla kuin kuluva aika. Oikein käytettynä ja normaalia latausta käyttävien Teslojen akustojen latauskertoja arvellaan kertyvän jopa yli 800, ennen kuin kapasiteetti laskee niin paljon, että akustojen vaihto on ajankohtaista.

This thesis deals with the lifetimes of electric car batteries, and how much the capacity of the batteries will go down in different cases. The main objective was to find out which cir-cumstances lower the electric car battery capacity. The thesis also takes a look at batte-ries which are used in electric cars now and describes the technical data of these batteries. The batteries which are examined in this thesis are the most common batteries which are used in electric cars, so all the batteries which are available in the electric market are not dealt with. This thesis is based on literature and research work.

First the basics of the electric cars and batteries are presented. After that eight different batteries are introduced which are commonly used in electric cars today. The following topics are presented: operating voltages, how many charge/discharge cycles battery will take, chemical reactions, how well the battery will work in the electric car and the future of the batteries. After that electric cars and how they work are discussed, what the situation of the electric cars in Finland is today, good points to own an electric car, and also the negati-ve points are dealt with.

The first example car, Tesla Model S, is introduced. No data published by Tesla Company about the car battery capacity could be found, and most of the data found about the car had been reported by car owners and researchers. One reason for that maybe that Tesla Mo-del S is just a few years old car model. Because of the quite high price of the car there are not many of them in traffic in Finland, and not yet enough precise information about the bat-tery capacity. However, there are data of Tesla`s driving range, warranty and charging times. The next car which is featured in this thesis is Nissan Leaf. Technical data, driving ranges, and charging times of the car are presented.

It was found that some batteries are more suitable for electric cars than others, and there is no perfect battery because all of them have good and weak points. Some batteries are cheaper to manufacture but often the lifetime of these batteries is shorter than the lifetime of expensive batteries, which means that the capacity of the battery goes down faster. There is no clear conclusion what the main reason for the capacity loss is, but it seems that se-veral factors together drop the capacity, such as not charging and servicing the battery right.