Published on Wednesday, Nov 9 2011 by
Uninterruptible Power Supply (UPS) systems are fundamental to any data center. Their key role is to maintain a secure electrical supply if the mains fails or exceeds acceptable limits.
At the core of any UPS system is its batteries. With growing concerns about 'green' technologies for data centers, selecting the right UPS battery configuration and regular battery maintenance are some of the ways to ensure optimised system performance and improved power efficiencies.
Battery configuration choices to optimise UPS reliability
It is vital to identify the needs of the user and design a configuration that meets their budget and space requirements, while still offering the highest levels of resilience possible.
The 'serial' string configuration, where identical battery blocks are wired 'end-to-end' to form the UPS battery, may be simple and economical, but does not offer redundancy as one battery failure will disable the whole string.
The alternative is multiple, parallel battery strings, which uses a combination of two or more serial strings, with each string containing the same number of blocks. This modular UPS configuration offers two benefits. Firstly, it increases the resilience of the battery bank so that a single faulty battery will not cause all of the batteries to be unavailable to the UPS; and secondly to provide longer battery autonomy during a mains failure.
In mission critical applications such as data centers, where cost is a secondary consideration, each parallel UPS module warrants its own, separately fused, paralleled battery configuration.
Modular UPS can easily be incremented or decremented to efficiently match changing power requirements of data centres, making it a sustainable power solution.
Battery maintenance to minimize system failure
Lead-acid batteries remain the technology of choice for most UPS systems. As a rule, UPSs use either Open-Vented or Valve Regulated Lead Acid (VRLA) battery types. Of these, VRLA has become the favoured choice because it is more environmentally friendly and has lower routine maintenance requirements. Also, VRLA’s safe and self-contained construction allows more flexibility in storage and use; battery location within server rooms and office environments as well as separate battery rooms becomes possible.
The battery represents a significant proportion of the total cost of a UPS, making battery care and management of paramount importance, especially as improper care and management of batteries is the number one cause of system downtime.
Effective battery maintenance starts with managing ambient temperature. While many UPS and standby power systems automatically test their batteries, nothing beats a visual inspection and on-site testing. Your UPS supplier should provide on-site testing to assess and report on the performance and suitability of the battery set.
Visual checks of the batteries, their terminals and connections for corrosion, cracks, leaks, swellings and dirt should also be performed, and connections tightened if necessary. More detailed assessment of battery condition and future life is currently gained using battery impedance testing. Impedance testing is relatively easy, does not discharge the batteries, and if regularly conducted can track battery condition and accurately predict end of operational life.
Implementing a preventative maintenance plan for your UPS system will ensure a wide range of potential issues are caught before they turn into more serious problems. More importantly, an effective preventive maintenance plan will help minimise downtime, and improve your overall ROI by extending the lifespan of critical power equipment.
A robust power protection strategy is critical to successful data centre operations. The combination of a modular UPS configuration and a sound battery maintenance plan should allow for maximum possible energy efficiency, while minimising capital and space costs throughout the life of the installation.