Optimising the structure of a cascaded modular battery system for enhancing the performance of battery packs

Abstract

The overall performance of battery packs may be affected by imbalances between the series connected cells which is more likely in packs with high number of cells needed to provide a high voltage as needed for example in electric vehicles. In this case, the overall capacity and power capability of the pack are limited by the weakest cell in the stack which results in incomplete utilisation of the pack's capabilities. In traditional centralised battery systems (TCBS), this is addressed by implementing cell active/passive balancing circuitry/techniques which restore some of the pack's energy capability. This paper proposes the use of cascaded modular battery systems (CMBS) to remove the need for extra balancing circuitry and maximises the performance and reliability of a battery system containing unequal matched/aged cells. The analysis is assessing the CMBS overall system efficiency, reliability and weight compared to the TCBS for a design of a 300 V/3.6 kW battery system as a case study.

Keywords

• battery chargers
• electric vehicles
• battery powered vehicles
• battery management systems
• secondary cells
• cascaded modular battery system
• battery packs
• series connected cells
• pack
• high voltage
• power capability
• weakest cell
• traditional centralised battery systems
• cell active/passive balancing circuitry/techniques
• unequal matched/aged cells
• system efficiency
• V/3.6 kW battery system
• voltage 300.0 V
• power 3.6 kW