Reducing Cell to Cell Variation of Lithium-Ion Battery Packs During Operation

Abstract

In this work, an experimental approach to reduce the variation from cell to cell during battery operation is evaluated to reach a better battery utilization. Numerous theoretical considerations of intelligent battery management systems without long-term experimental validation of their capabilities lead to a gap in the literature, which this work aims to address. For this purpose, the ageing behaviour of two batteries is investigated for almost 1.5 years. One battery is connected to an active balancing battery management system (BMS) and the other to a conventional passive balancing BMS. Important battery parameters, such as capacity and internal resistance, are recorded in each cycle. The battery behaviour is evaluated in detail by observing the voltage difference of the individual cells at the end of discharge and by calculating the amount of charge balanced by the BMS. Significant differences between the BMS systems used are elucidated, which illustrate the advantages of active balancing. In contrast to passive balancing, active balancing can reduce the ageing rate of the battery and achieve better utilization with a more than five times lower voltage spread at end of discharge, a up to 3.1% higher discharge capacity and a 7.7% longer service life.

Aging Determination of Series-Connected Lithium-Ion Cells Independent of Module Design

“…Figure 8 shows that the best cell was additionally discharged for the longest time and the worst cell was supported for the longest time in order to reach the end of discharge voltage. Considering [69], the balancing current was set to 2 A, which allows us to fully balance the battery in the discharging phase. The balancing charges can additionally be used to calculate the capacity of each cell when the balancing was successful and all cells have reached their end of discharge voltage.…”

Average Model of Switched-Energy-Tank Battery Equalizer for Accelerated Performance Assessment

“…Many research efforts have observed the importance of battery equalization for the performance of the series battery string. The equalizing techniques are classified into passive and active methods [10][11][12]. Although passive methods are widely adopted in industrial applications, the energy dissipation scheme suffers from poor equalizing speed and efficiency [13][14][15][16].…”

Yeni Nesil, Modüler ve Akıllı Batarya Yönetim Sistemi

“…2021 yılına gelindiğinde BMS'ler batarya paketi içerisinde yer alan paralel bağlı hücrelerden bir tanesinin arızalı olup olmadığını anlayacak kadar gelişmiş yapay sinir ağlarına sahip olmuştur (Lumertz et al, 2021). Dengeleme konusunda batarya geliştirilen yöntemler batarya dinlenme halindeyken, aktif durumdayken ve çalışırken batarya hücreleri arasındaki denge farkını azaltma çalışmaları yapılmıştır (Ziegler et al, 2021). Şarj ve sağlık durumunu daha doğru tahmin etmek için gelişmiş şarj durumu ve sağlık durumu kestirim algoritmaları üretilmiştir (Singirikonda & Obulesu, 2021).…”