Performance estimation of a cell-to-cell-type active balancing circuit for lithium-ion battery systems

Abstract

Active charge balancing is an approved technique to implement more energy-efficient and eco-friendly lithium-ion battery systems. The theoretical analysis presented in this paper provides a method to estimate the benefits of a cell-to-cell-type active charge balancing circuit in comparison to a passive balancing solution concerning energy savings and capacity gain. The calculation's variable parameters are the battery system configuration and the cell capacity distribution properties. Their validity is limited to applications with normally distributed cell capacities, limited maximum and minimum cell capacity and full cycle usage. The losses related to passive balancing in an nSmP battery system are calculated as well as the overall energy savings achievable with cell-to-cell based active balancing. The capacity gain factor of an actively balanced battery system related to a passive one is found to be in a range between 1.06 and 1.01 depending on the cell parameters and the system configuration. The derived formulas are verified by numeric simulations. Based on the results, several options are identified to increase the energy efficiency of conventional passive balancing systems. The findings can be used during the design process of new battery systems or to analyze and optimize any existing lithium-ion battery system.

Characteristics of Battery Management Systems of Electric Vehicles with Consideration of the Active and Passive Cell Balancing Process

“…Current sensors in EVs should measure currents ranging from from milliamperes to 1000 Amperes and should also be able to capture fast current changes. Current sensors should also have good immunity against EMI noise and small offsets, especially for low current measurements [14,31].…”

Analysis of an Active Charge Balancing Method Based on a Single Nonisolated DC/DC Converter

“…depending on the cell and system parameters. A general theoretical analysis of active balancing performance is available in [22]. There, equations as a function of cell number, efficiency and capacity distribution are given for active balancing circuits.…”

“…The numerical simulations were done in MATLAB. The cell capacity values are normally distributed numbers as a function of the chosen cell parameters (see TABLE II) as it is explained in [22]. The intention of the authors is to simulate the battery cell capacity distribution as realistic as possible.…”

A Novel Non-Isolated Active Charge Balancing Architecture for Lithium-Ion Batteries

“…As shown in [12], active balancing can increase the usable capacity of a battery system during the discharging process by 1% to 6%, depending on the cell and system parameters. In a comparison presented in [2] the cell-to-cell topology shows superior performance compared to any other active balancing methods in terms of balancing speed and efficiency.…”