Charging and balancing system for Li-ion batteries

Kao zadatak ovoga rada postavljeno je ispitivanje karakteristika Li-ion baterija te unaprijeđenje njihovog punjenja postupkom balansiranja. Li-ion baterije su često korištene baterije ponajviše zbog njihovog svojstva velike gustoće energije (Wh/L). Korištene baterije imaju radni raspon od 3,0 do 4,2 V, veliki raspon iznosa struje punjenja (do 300 A), te temperaturni raspon od - 25 °C do + 25 °C. Dodatni postupak ispitivanja karakteristika, osobito ovisnosti kapaciteta baterije o struji punjenja detaljno je opisan u poglavlju 2. Rezultati mjerenja ukazuju na to da kapacitet baterije prilično ovisi i struji punjenja. Preporučljivo je baterije puniti nižom strujom radi dobivanja većeg kapaciteta. U poglavlju 3 opisan je sustav balansiranja napona ćelija. Naime, u svrhu povećanja kapaciteta, osmišljen je sustav kojim bi se zaustavljalo punjene ćelije najvišeg napona sve dok razlika između najvišeg i najnižeg ne postane jednaka unaprijed određenoj vrijednosti. Sustav je fizički ostvaren, te je spreman za daljnje korištenje.The task of this paper was to examine the characteristics of Li-ion battery charging and to improve their process of charging using balancing. Li-ion batteries are often used mostly due to their properties of high energy density (Wh / L). Used batteries have an operating range of 3,0 to 4,2 V, a wide range of value of charging current (300 A), and a temperature range of - 25 °C to + 25 °C. Additional testing of characteristics, especially correlation between capacity and battery charge current is described in Chapter 2. Measurement results indicate that the battery capacity is quite dependent of the charging current. It is advisable to use lower battery charge current in order to obtain a larger capacity. Chapter 3 describes power cells balancing system. The new system, which would increase capacity, was designed. It would use switches to control cell voltages. When the difference between the highest and lowest cell voltage were equal to a predetermined value, the power supply will be cut off for the cell with the highest voltage. The system is physically implemented, and ready for further use