Battery Power - November/December 2013 - (Page 8)

Feature Li-Ion Battery Technology Delivers High Power for Data Center UPS Installations Stuart Lansburg and Christophe Jehoulet Saft The changing needs of data center developers and operators, combined with the explosion in cloud computing, are driving the demand for high density storage and secure online operations. There are more than half a million data centers in existence today. All together, they suffer 2.8 million hours of downtime each year at a cost of $426 billion. Implementing a high power UPS can reduce significantly this downtime and its associated costs. Energy storage based on high power Li-ion (lithium-ion) battery systems is now emerging as an efficient alternative to traditional lead-acid batteries. This article outlines the specific benefits of Li-ion technology for data center UPS installations and explains how Saft has incorporated them in a new modular system designed for installation in a stand-alone 19-inch rackmountable format. The Intensium Flex system comprises three main modules: * The Synerion module (with Li-ion cells) * The BMM (Battery Management Module) * The MBMM (Master Battery Management Module) When these standard building blocks are assembled together, they enable a UPS or HVDC Li-ion system to be customized to suit voltages from 48 V to 860 V. The Synerion Module Large format industrial Li-ion cells provide both high power capability and high energy density and are also maintenancefree. When Li-ion cells are integrated into systems with electronics that provide redundant safety features, operating features for optimized performance and communication features for application interaction/control, then the overall package is perfectly suited to ensure the high uptime required by data centers. Li-ion battery systems are both light in weight and compact, offering a small installation footprint that allows operators to free up space for other important data center functions. They also provide a long, reliable, maintenance-free and safe operating life that minimizes downtime costs and total cost of ownership (TCO). Saft has more than 15 years of experience in designing, testing and producing Li-ion systems across a wide range of industrial applications. This has now been incorporated in the Intensium Flex system developed specifically for data center UPS or high voltage DC architecture (HVDC). The Synerion module incorporates 14 Li-ion cells and their associated electronics in a 3 RU unit that is 19-inch rack mountable and provides a nominal 48 V. Two different Li-ion cell designs are used according to the application. One is a high power cell for applications requiring up to 15 minutes of autonomy and the second is a medium power cell suited for more than 15 minutes of autonomy. Like traditional batteries, with Li-ion, there is a trade-off between capacity and power when optimizing cell design. The NCA electrochemistry selected for Saft Li-ion cells in industrial standby and renewable energy storage sector applications represents a trade-off between inherent electrochemical safety and superior lifetime performance. The overall safety level of the module is not compromised, however. Redundant safety features are included in the electronics and the cell, starting with the controlled venting feature inside each cell. A modular electronic board called the System Monitoring Unit (SMU) is connected to the cells in a Synerion module. It interconnects the cells and provides monitoring and control functions such as voltage balancing and the detection of the end of charge voltage, end of discharge voltage, an over-temperature condition and under/over safety threshold voltage limit. This information is transmitted over the internal CAN bus to the BMM, which acts as the prime safety control unit. The module, used either as a single module (48 V) or connected in series with several other modules, cannot ever operate alone. It must be connected and managed by a BMM. Systems up to 864 V nominal can be created. Li-Ion System Approach The BMM (Battery Management Module) Li-Ion Advantages Traditionally, the terms 'batteries' or 'battery packs' has been used to describe a string of lead-acid or nickel-based cells connected electrically in series. Usually, they incorporate minimal electronics, such as a current interrupting device (i.e. a fuse). In contrast, when working with Li-ion technology, the cells are only one part of a global system that also includes a fuse added as a redundant safety feature, electronic functions such as monitoring and cell balancing, processors with control algorithms, electrically operated contactors and the ability for bi-directional communication. Therefore, when discussing Li-ion systems with these added functionalities, we refer to modules, rather than batteries or battery packs, to designate the various sub-units. 8 Battery Power * November/December 2013 The BMM module is the brain of the Intensium Flex system that interconnects the power and the communication circuits with the application. This allows it to interrupt the string current (condition when a safety threshold is exceeded) and to communicate between the SMU circuits and the application. Its functions include current measurement, CAN bus and dry contactor signal (potential free contactor) communications, electromechanical contactor control (built-in) and processing of monitored data from the SMU. It provides the first level of safety protection using the primary thresholds (voltage, current and temperature) written in the safety algorithms. Up to 18 Synerion modules (48 V configuration) can be

Table of Contents for the Digital Edition of Battery Power - November/December 2013

Solid-State Battery Developed at CU-Boulder Could Double the Range of Electric Cars
GS Yuasa Batteries Help Power Orbital Science’s Cygnus Spacecraft on Mission to ISS
Li-Ion Battery Technology Delivers High Power for Data Center UPS Installations
Battery Demands for Yesterday, Today and Tomorrow
Understanding When and Why You Need UPS Battery Replacement
Charging Forward: A Resurgence of the EV Movement and the Role Charging Infrastructure Plays in Continuing the Momentum
Charging Systems
Testing & Monitoring
ICs & Semiconductors
Industry News

Battery Power - November/December 2013