Design and Implementation of a Costly Battery Management System for Electric Vehicle

Abstract

The importance of Electric Vehicle (EV) is increasing day by day due to the destruction of fossil fuels reserves and the damage caused by internal combustion engine vehicles working with fossil fuels to the environment. The necessary electrical energy of the electric motor used to ensure the movement of the EV is generally provided by the batteries. Efficient and reliable use of EV's is directly related to the use of batteries. For this reason, it requires the use of a BMS that monitors and controls the status of the batteries used as energy sources. In this study, the Battery Management System (BMS) was designed based on the passive cell balancing method for the 20 cell battery pack to be used in electric vehicles, and a three cell BMS application was implemented. Using Li-ion batteries, a PCB in the central BMS structure, which can passively balance the 20 serial battery cells in the design, and which can also determine the SoC of the batteries, has been designed and the actual working condition of the hardware circuit has been tested. In the SoC calculation, the "terminal voltage" method was applied. This method is based on terminal voltage level decrease occurring in the battery due to internal impedances when the battery is discharged. In the design of the BMS pcb, the central BMS system was preferred and the pcb was made simple by using SMD components, the size was reduced and the cost was reduced.
In the BMS pcb made as prototype, there are overvoltage, undervoltage and temperature protections for battery cells. Also, in order to maximum efficiency in battery cells, passive balancing system is applied during the charging of the cells. SoC of each of the battery cells were calculated with BMS and SoH estimates were made. The specified properties of the realized BMS have been tested and proved by the experimental results obtained that the BMS has been operating successfully. In addition, improvements in design speed, size, cost and ease of installation have been achieved by using the passive balancing system in BMS design.

Keywords

• Battery Management System
• SoC
• SoH
• Li-ion

Elektrikli Araç İçin Düşük Maliyetli Bir Batarya Yönetim Sistemi Tasarımı ve Gerçekleştirilmesi

Öz

Fosil yakıt kaynaklarının yakında tükenecek olması ve bu yakıtlarla çalışan içten yanmalı motorlu araçların çevreye verdikleri zararlar nedeniyle Elektrikli Araç (EA)’ların önemi gün geçtikçe artmaktadır. EA’nın hareketinin sağlanabilmesi için kullanılan elektrik motorunun ihtiyaç duyduğu elektrik enerjisi genel olarak bataryalar tarafından sağlanmaktadır. EA’ların verimli ve güvenilir bir şekilde çalıştırılması bataryaların kullanımıyla doğrudan ilişkilidir. Bu durum, enerji kaynağı olarak kullanılan bataryaların durumlarını takip ve kontrol eden bir BYS’nin kullanılmasını zorunlu kılmaktadır. Bu çalışmada, elektrikli araçlarda kullanmak amacıyla 20 hücreli batarya paketi için pasif hücre dengeleme metodu temel alınarak Batarya Yönetim Sistemi (BYS) tasarlanmış ve üç hücreli BYS uygulaması gerçekleştirilmiştir. Li-ion bataryalar kullanılarak tasarımda 20 adet seri batarya hücresinin dengelenmesini pasif şekilde yapabilecek; aşırı gerilim, düşük gerilim ve sıcaklık koruması olan ve ayrıca bataryaların SoC’larını belirleyebilen, merkezi BYS yapısında bir kartın tasarımı gerçekleştirilmiş ve donanımsal devrenin gerçek çalışma durumu test edilmiştir. SoC hesaplamasında “terminal gerilimi” yöntemi uygulanmıştır. Bu yöntem, batarya boşalırken iç empedanslar nedeniyle bataryada meydana gelen terminal gerilim düşümüne dayanmaktadır. BYS kartının tasarımında merkezi BYS sistemi tercih edilmiş ve SMD devre elemanları kullanılarak kartın sade olması sağlanmış, boyutu küçültülmüş ve maliyeti düşürülmüştür. Prototip olarak yapılan BYS kartında batarya hücreleri için aşırı gerilim, düşük gerilim ve sıcaklık korumaları mevcuttur. Ayrıca batarya hücrelerinde azami verim alınabilmesi amacıyla hücrelerin dolumu esnasında pasif dengeleme sistemi uygulanmaktadır. BYS ile batarya hücrelerinin her birinin SoC’ları hesaplanmış ve SoH kestirimleri yapılmıştır. Gerçekleştirilmiş olan BYS’nin belirtilen özellikleri test edilmiş ve sisteminin başarılı bir şekilde çalıştığı elde edilen deneysel sonuçlar aracılığı ile ispatlanmıştır. Ayrıca, BYS tasarımında pasif dengeleme sistemi kullanılarak tasarım hızı, boyutu ile maliyet ve kurulum kolaylığı açısından iyileştirmeler sağlanmıştır.

Anahtar Kelimeler

• Batarya Yönetim Sistemi
• SoC
• SoH
• Li-ion

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