Battery Charge Control for Emergency Back Up Systems

Malhar Bhatt,  Prof. W. G. Hurley

For many years, intensive research has been undertaken to increase the life of valve-regulated lead-acid (VRLA) batteries. The chemical composition of the VRLA battery is different from the flooded lead-acid battery. While offering its unique advantages, the VRLA battery is also prone to overcharging as the electrolyte in this battery is in an absorbed form. Overcharging results in excessive temperature within the battery, which degrades the chemical composition of the electrolyte. While charging, when the battery reaches the full state-of charge, the energy being supplied to the battery is no longer consumed in the charge reaction but is dissipated as heat within the battery. At this point the oxygen recombination cycles accelerates, which leads to temperature rise inside the battery. State-of-the-art control technology is required to control the charging of the battery, reduce the grid corrosion and prevent the battery going into thermal runaway. This project investigates the charging strategies for VRLA batteries in standby applications. Charging techniques such as 'Intermittent Charging' where the battery is charged intermittently on a periodic basis, decreases the continuous overcharge which arises in the case of conventional float charging. But the charging regime to be used in an intermittent charging is a great dilemma to ensure the full recharge of the battery. A new technique termed 'Interrupted Charge Control' (ICC) for standby applications is presented followed by the design of power converter and the microcontroller that governs the charging algorithm.

Start date: 1st of September 2001. This project has been completed.

Project collaborators: Convertec Ltd

Project Publications

Journal
M. Bhatt, W. G. Hurley, W. Wölfle, "A New Approach to Intermittent Charging of Valve-Regulated Lead-Acid Batteries in Standby Applications", IEEE Transactions on Industrial Electronics, vol. 52, no. 5, pp. 1337-1342 (Also Proceedings of the 34th IEEE Power Electronics Specialists Conference, PESC'03, Acapulco, Mexico, vol. 2, pp. 895-900, June 2003), October 2005.

Conference
M. Bhatt, W. Wölfle, W. G. Hurley, "Ladung und Ladungserhatung bei Blei Akkumulatoren fuer Standby-Anwendungen durch geregelte Ladeunterbrechung und Pulsstromsteuerung", Proceedings of the Desing&Elektronik Entwicklerforum, Batterien, Ladenkonzepte & Stromversorgungsdesign, Munich, Germany, March 2004.
M. Bhatt, W. G. Hurley, W. Wölfle, "Battery Charge Control for Emergency Back-Up Systems", Proceedings of the 37th Universities Power Engineering Conference, UPEC 37, Staffordshire University, pp. 411-415, September 2002.

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