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BTECH's Focus - Predicting Battery Failure
Since it's inception in 1989, BTECH has concentrated
solely on battery monitoring systems and related technology to enable
you to better predict battery failure. Our mission is to bring the
knowledge and experience we have gained remotely monitoring batteries
worldwide to you. Trended battery measurement data from BTECH can
detect impending battery failures before your backup system is affected,
with enough time in advance to replace the failing batteries.
What We Know
Battery reliability is inherently unpredictable and
the reason for 85% of catastrophic UPS failures. Based on information
derived from battery manufacturers and our real-world experience,
we have assembled the following battery performance graph:
BTECH's battery lifecycle graph displays important
relationships between impedance and capacity for VRLA batteries.
Some important points that stand out:
- The baseline impedance, which is measured for each battery in
the string by the BTECH monitoring system after the system has
passed the initial discharge test, roughly equates to 100% capacity
when the battery is new.
- A 30% rise in impedance above the baseline roughly equates
to 80% battery capacity, which is the point at which the IEEE
recommends immediate replacement. Based on recommendations of
a number of battery manufacturers, BTECH has adopted the 30% value
as the critical impedance alarm point - the time for the user
to schedule a service visit to possibly replace the battery. In
reality this number could be 20 or even 50% - but the most important
point here is that once the battery goes "on the curve"
it is in it's failure mode.
- The behavior of the battery after this 80% capacity point is
reached is unpredictable, making the time from the 80% point to
outright failure, as displayed on the graph as "t",
indefinable. BTECH recommends scheduling a service call and replacement
immediately to protect your battery system.
- Because the behavior of VRLA batteries has been demonstrated
by BTECH to be unpredictable, capacity remaining or time remaining
functions built into current UPS systems or competitive monitoring
systems are inherently inaccurate. BTECH believes it is technically
impossible to provide accurate time-remaining data for battery
systems that are less than 100% healthy.
- The only way to ensure the integrity of your VRLA battery system
is to replace the failing battery in the string when the impedance
rises 30%, when the data from BTECH's monitoring system tells
you.
- A typical two-week impedance failure from one of our customers
is shown in the impedance vs. time graph below. The yellow diamonds
represent weekly measurements. The corresponding voltage vs.time
curve is shown below. It is important to note that voltage is
often not the leading indicator of failure for most battery types.
Impedance of one 12V Battery vs. Time in a 40
Unit (480v) String
Voltage of a 12V Battery vs. Time in a 40 Unit
(480v) String
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