Minimization of Circuitry in Large Format Lithium-ion Battery Management Systems

Open Access
Author:
Miller, Jerin Patrick
Graduate Program:
Electrical Engineering
Degree:
Master of Engineering
Document Type:
Master Thesis
Date of Defense:
November 08, 2012
Committee Members:
  • Jeffrey Scott Mayer, Thesis Advisor
  • John Douglas Mitchell, Thesis Advisor
Keywords:
  • BMS
  • Battery Management System
  • Lithium
  • Lithium-ion
Abstract:
Lithium-ion based batteries are the most energy and power dense rechargeable batteries currently available. However, to operate within safety limits battery voltages, currents, and temperatures must be monitored throughout the charge-and-discharge cycle. Battery Management Systems (BMS) monitor, report, or equalize the cell voltages of large packs to ensure operation within safety limits and to maintain balanced cells within the pack. For large Lithium-ion series packs, monitoring two or more cells in series instead of monitoring individual cells can reduce the size, weight, and complexity of a BMS, which is often desirable to strict space, weight, and reliability requirements. Monitoring and balancing every cell is desirable because when the battery pack is charged all of the cells will be charged to the same voltage and if an individual cell dropped below a certain voltage on discharge, the load could be disconnected from the pack. By monitoring multiple cells and controlling the current limits of the pack, a small amount of resolution is lost but the system can still function safely.