FOCUS on POWER
BATTERIES
say the totalworld ultracapacitor market had generated revenues of $113.1m in 2008 and is likely to reach $381.9m by 2015, so obviously one towatch.We will doubtless see more power storage solutions based on this enter the market over time, driven possibly by green IT style drivers (as these batteries are easily rechargeable due to their basic design).
The bottom line is that there are evolutionary pressures in the battery market that are presenting data center managers with many more options than they had before, but the tried and tested lead acid car battery seems set to be with us for a good while yet.
The battery strings found in data centers, which support three-phase UPS systems typically supplied by Liebert, Powerware, MGE, Pillar andMitsubishi, can have single or multiple 480V cabinets of 40 12-V sealed VRLA batteries or racks of 2V, 4V, 6V or 8V VRLA or Flooded (Wet-Cell) Batteries. It is critical to monitor each battery type, as failure can occur in as little as twoweeks.
The lead acid battery, invented in the 1850s, was itself revolutionised in the 1980s with the introduction of valve regulated lead acid (VRLA) cells. The problem this introduced from the data center manager’s point of view was that itwas no longer straightforward to monitor howmuch they have in them lifewise. The older method – measurement of depth and specific gravity of electrolyte – became impractical with the introduction of VRLA as the cell case is nowsealed, except for a pressure release valve. So a test that doesn’t just measure remaining voltagewas needed and the source resistance or impedance of the cellwas picked as a good indicator of VRLA cell condition, indicating both chemical degradation and physical damage.
This has led to a newclass of battery- monitoring breakthroughs, based on instrumentation (handheld, semi-permanent or permanently connected) that provide electronic data to reliably predict cell failure using‘ohmic’valuemeasurement – ohmic is the preferred termover resistance, impedance and conductance for such ametric.
The optimumbattery-monitoring solution for a UPS installationwould be a system permanentlywired into the battery and capable ofmeasuring both voltage and ohmic value daily. It shouldmeasure voltagemultiple times per day to look for UPS, breaker or cabling errors, and ohmic value daily so you get an earlywarning of impending failure.
Both data sets should be stored for later analysis and having an ability to signal – externally to the facility management system or manager – that a problem either existed orwas imminent is also a desirable feature of any such battery-management system.
A number of firms are on the market with battery-monitoring, including Factstar, IntelliData, Alber, BTMGlobalController and PDI. A firmcalled NDSL in this market and better known by the brand name Cellwatch. Cellwatch comes on a 19”rack or wall-mounted server onWindows running Cellwatch proprietary application for reporting, recording and data analysis, and is also modular to allowreconfiguration or expansion if needed.
The systemworks by measuring voltage and ohmic value on each cell many times per day, and then presents that in graphical formfor historical analysis or trending. It can also compare the data being gathered continuously with high- and low-alarm settings for alarmactivation.
It can be set to measure the temperature of either the battery room ambient or a pilot cell, plus it keeps an eye on discharge current from a battery string in order to compare it with any preset discharge alarmlimit set in software. In the event of a discharge, Cellwatch rapidly records all cell voltage data as the battery discharges for later identification ofweak cells under load.
Btech offers the S5 series battery-monitoring system for larger sites, and the CellQ family of components for smaller battery backup systems, where the requirement for local interpretation of the data is not required (
www.btechinc.com). It measures core battery parameters in real-time, including system voltage, float, charge and discharge current, plus ambient and pilot cell temperatures, and can cover up to 520 individual cells and eight strings per system. Btech claims 4,000 sites use it globally.
Another battery-monitoring solution, from IntelliBatt (
www.intellibatt.com), is based on a proprietary battery design, which claims to have extracted maximum life out of the VRLA approach, but the firmhas also decided to start offering a turnkey battery-monitoring solution to what it sees as a fragmented battery backup power marketplace. The idea, it claims, is to put under one roof (the old one throat to choke approach, as itwere) all the battery maintenance
Keep an eye on them
components – the physical batteries, enclosures, monitoring systems, monitoring service and preventative maintenance.
The IntelliBatt-branded turnkey solution offers the firm’s own-brand batteries with built-in monitoring andweb–based remote monitoring, easy-to-access cabinets, certified technicians and installation , bi-directional secure communication with IntelliBatt’s operations center, is supported by battery expert analysis and reporting, conditions- based versus time-based maintenance, and battery replacement to pre-empt power failure and extend battery life.
“Battery power is often described as the Achilles Heel of the data center since nearly 85% of all UPS failures are caused by battery failure,”explains Steve Cotton, a co-principal at IntelliBatt.
“Our customers must have 100% uptime for their applications to deliver on service level agreements to their customers, which is whywe’ve designed a battery-monitoring solution that closes the loop between data collection and intelligent use of the data collected,”he says.
Installing battery-monitoring systems in your data center effectively makes it possible to assure the batteries will actually run if there is a power outage. It’s a level of securityworth having and also contributes more intelligence to the information-gathering exercise that is a crucial part of making today’s data centers run as efficiently as possible.
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