Search

U završnom radu opisane su osnovne strukture baterija, njihove podjele i potreba razvoja sustava za balansiranje ćelija. Primjerima su prikazani bitni parametri baterija kao što su C- rate, stanje napunjenosti, kapacitet i uzroci smanjivanja dostupnog kapaciteta. Navedeni su razlozi zbog kojih dolazi do neuravnoteženosti ćelija i prikazane su određene topologije koje se koriste za balansiranje ćelija. Topologija bazirana na zapornom pretvaraču je detaljno opisana u radu. Tijekom testiranja dolazi do neispravnosti makete i predloženi su postupci nadogradnje sustava. This final project describes basic structure of batteries, their classification and the need for development of Battery Management Systems. Parameters such as C-rate, SoC, capacity and the reasons for capacity degradation are described in various examples. Reasons for cell imbalance are also described and the project contains an overview of cell balancing methods for L-ion batteries. Method based on single transfomer with Flyback was used in making a model on which the testing was done. During the testing the model faced a malfunction and certain suggestions for future upgrades are made.

U ovome radu opisana je važnost BMS-a kao sustava koji omogućava sigurno i optimalno iskorištavanje energije iz baterija. Ukratko je opisana povijest baterije, vrste baterija te njihove prednosti i nedostatci. Prikazana je karakteristika punjenja, odnosno pražnjenja litij ionskih baterija čime je opisan glavni problem koji BMS rješava. Predstavljene su pasivna i aktivna metoda balansiranja baterija s naglaskom na pasivnu zbog njene česte uporabe. Dan je uvid u sklopovlje potrebno za izradu BMS-a te je dan opis koda koji je napisan za potrebe ovog završnog rada. Kod se nalazi na mikroupravljaču i upravlja BMS-om. Na kraju se predstavlja moguće buduće rješenje postojećih problema. This thesis describes the importance of the battery management system (BMS), which ensures safe and optimal use of energy from batteries. It contains a short history of the battery, type of the battery with its advantages and disadvantages, so as the charging, i.e., discharging characteristics of the lithium-ion battery, describing the main problem solved with the BMS. Passive and active methods of battery balancing are also described, with a focus on the passive one because of its common use. Insight into hardware necessary for the making of the BMS is also described so as the code written for the purpose of the thesis. The code is located on a microcontroller and controls the BMS. Possible solution of the existing problems is presented in the end.

Tehnologija proizvodnje baterija na principu litijevih iona je do danas dosta sazrela. Baterije ove vrste su najučinkovitije, lako se pune, imaju najveću gustoću energije i daju najveću struju. Ta spoznaja, zajedno sa razvojem učinske elektronike i sustava upravljanja elektromotornim pogonima omogućila je razvoj električnih automobila koji se zbog visoke cijene komponenata, prvenstveno baterija, još uvijek sramežljivo pojavljuju na tržištu. Jedan od problema koji su vezani uz baterije je nejednakost u naponima ćelija. Zbog toga se ukupni kapacitet baterije smanjuje, povećavaju se opterećenja drugih ćelija što uzrokuje smanjenje životnog vijeka baterije. Znanstvenici su predložili povelik broj sustava balansiranja ćelija, a ovisno o traženim specifikacijama odabire se onaj najbolji. Ovaj rad donosi detaljan pregled sustava balansiranja, a zbog jednostavnosti i niske cijene odabrana je metoda upravljivih otpornika (eng. shunting resistor). Testiranjem sustava dobiveni su dobri rezultati te se ova metoda preporuča ako nema potrebe za dvosmjernim režimom rada. Nowadays, the Lithium Ion technology for battery production process is getting more mature. These kind of batteries are the most efficient ones, they can be easily charged, have maximum energy density, and give maximum current. That knowledge, together with development of power electronics and electric machines control systems, enabled the development of the newest car form – an electric one. Nevertheless, because of its expensive components, especially batteries, they cannot be seen on our streets yet. One of the problems associated with batteries is cell imbalance. That causes battery pack capacity to decrease and shortage of battery lifespan. Thus, scientists have proposed a considerable amount of cell balancing systems, and depending of demanded specifications a best one is chosen. This master thesis brings detailed perspective of cell balancing systems together with their pros and cons. Because of its simplicity and low cost, a shunting resistor method has been selected. Tests have showed good results so that makes shunting resistor method the best choice, unless bidirectional regime is required.

U ovom zavržnom radu bilo je potrebno upoznati se s karakteristikama LiFeMnPO4 baterija. To je učinjeno na način da se baterija, sastavljena od četiri ćelije, punila i praznila konstantom strujom od 20, 30 , 40 i 90 A. Mjerenja su se izvodila pomoću akvizicijske kartice, a podaci su se pratili i zapisivali na računalu pomoću programa u LavVIEW-u. Konačne karakteristike su dobivene pomoću Matlaba. Poslije je bilo potrebno steći uvid u postojeće sustave punjenja i balansiranja navedenih baterija. Dan je pregled prednosti i nedostataka nekoliko postojećih sustava i metoda za punjenje i balansiranje. Predložen je modificirani sustav koji uključuje i balansiranje i punjenje baterija te je razrađen na razini ideje. Firstly, it was necessary to get to know characteristics of LiFeMnPO4 batteries in this final thesis. That was realized by charging and discharging the battery, made up of four cells, with constant current of 20, 30, 40 and 90 A. Measurments were done by data acquisition card, and they were being monitored and logged by LabVIEW program. Finally, characteristics were obtained in Matlab. Later, it was necessary to get to know existing charging and cell balancing systems for given batteries. Overview of advandages and disadvantages of several charging and cell balancing systems and methods are given. Modified system was proposed which includes both charging and cell balancing. It was elaborated only on level of idea.