Battery Power - November/December 2013 - (Page 14)
Feature
Understanding When and Why You Need UPS Battery Replacement
Gregory Ratcliff, Director of Life Cycle
Management Services
Emerson Network Power, Liebert Services
μOhms seen at installation. In order to capture the true baseline
of the replacement battery, a stationary instrument is required.
As organizations become increasingly dependent on data
center systems, there is a need for greater reliability in the critical power system. For many organizations, the IT infrastructure
has evolved into an interdependent business-critical network
that includes data, applications, storage, servers and networking.
A power failure at any point along the network can impact the
entire operation and have serious consequences for the business.
In most cases, the ability to keep critical systems running
through power outages, sags, brownouts, utility spikes or other
unforeseeable power issues is dependent on the reliability of the
Uninterruptible Power Supply (UPS) system. However, the UPS
system is only as reliable as the batteries that support it.
A recent study by Emerson Network Power, Liebert Services on
real-world results of Valve-Regulated Lead-Acid (VRLA) batteries
in the UPS environment along with the company's field experience,
has revealed the following three battery performance realities.
1. Battery life cycles vary far too much to rely on
manufacturer's published life spans and initial resistance
baseline data.
In order to get the most accurate resistance baseline measurements of the thousands of VRLA batteries in the study, Liebert
Services chose to use stationary resistance instruments. Battery
voltage-type monitors are an alternative popular methodology,
as are float-current and temperature-only monitors that may be
installed for alarming purposes. However, these systems do not
provide an indication of battery health in UPS, highvoltage, high-unit-count implementations.
For the study, the alarm-based systems were considered unsuitable for increasing availability, while resistance methods provided an indicator of battery state
of health data, particularly when data was compared
over the full lifetime of a given unit and compared
against an initial baseline. The stationary instruments
were a necessity due to inexpensively increase the
frequency of measurement and the high degree of
repeatability they afforded. It was important to capture
very accurate unit-specific, situation-specific baseline
resistance and periodic resistance readings.
What Liebert Services found during the analysis
is that initial baseline consideration should begin
90 days after installation. When a new battery is
replaced due to premature failure or cause, often the
initial change in resistance will be downward and
then remain constant. Figure 1 details an example of
a battery change-out occurring after 600 days of life.
Note that this battery's initial baseline resistance will
likely settle near 5250 μOhms, instead of at 5650
14
Battery Power * November/December 2013
Figure 1. Trending results that are typical for 70 ampere-hour
VRLA batteries.
This result was seen with many battery units and has caused
Liebert Services to reject manufacturer-provided baselines. We
found that when a specific unit settles to its running baseline,
the initial variance from the manufacturer's baselines could be
as much as 25 percent. To effectively alert our customers to
imminent battery failure, we recommend they closely monitor
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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
Batteries
Charging Systems
Testing & Monitoring
ICs & Semiconductors
Manufacturing
Components
Industry News
Marketplace
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