In service experience of VRLA batteries used for bulk powering of telecommunications equipment in outside plant

Some years ago there was a significant change in the power requirements for outside plant which lead to the bulk powering of telecommunications equipment. Bulk powering has substantially increased the number of power equipment alternatives for both power conversion and energy storage and the need for more compact installations has increased. This has lead to the development of new battery configurations to further optimise energy density, reduce the space utilized and facilitate installation and maintenance. Two particular types of bulk power installation using VRLA batteries developed by FIAMM are described. The effects of ambient temperature, the number of parallel strings, temperature compensation and battery spacing are described in relation to recently gathered data on field service based on a surveillance programme of full discharge testing. The batteries all used absorptive glass mat separators and state-of-the-art electrochemical designs and are well-adapted to the required duty cycle. The batteries have been installed in remote terminals that are now environmentally controlled but were not controlled for more than half the period in service. Tests have been carried out after several years in service and are reported in detail. The overall results show good behaviour after 6 to 7 years of actual service and the design fife of the cells will be readily achieved. Installation design is a key factor and the relation between battery design and configuration at monobloc level with the total battery is considered. Further tests are ongoing and the data generated by this study will serve to demonstrate the effectiveness as well as pointing to improvements of these battery types and configurations in service in an outside plant environment.