Page 32 - Energize Issue 1 2023

TECHNICAL

The 2005 paper given at Battcon Some have stated that they believe warranty is just a marketing game. Given the
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attempted to explain difficulties with way in which the 20-year warranty came into being and how it has been implemented
warranty and detailed expected results over time, it is understandable how the warranty could be viewed that way. It may help
for VRLA cells, but it is important to keep to understand if we look at the typical failure characteristics of a lead acid battery. The
in mind that most expected life estimates curve characteristic below in Figure 2 is considered by many to show the typical failure
are based upon floating a battery at a characteristic of a lead-acid battery over time.
constant temperature for a specified As can be seen in Figures 2 and 3, the failure characteristics resemble a bathtub
period of time devoid of any external diagram. Initial failures can be caught within a reasonably short period of time. While most
variables except cycling. initial failures can be considered the result of manufacturing defect, shipping, storage
and manner of installation can contribute to initial failures. Random failures are typically,
What does this say about although not always, determined by operational conditions and more closely associated
warranty? with “stress factors”. 18
In O’Donnell’s 2005 Battcon paper a As batteries age, however, the “stress factors” play a much more significant role in the
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suggestion was made that manufacturers actual service life achieved, although quality of manufacturing materials and processes will
and the IEEE Stationary Battery certainly aid or hinder the final result.
Committee consider drafting a more In the final analysis, however, the attention to proper maintenance will have the
realistic approach to equating service life biggest influence on achieving the desired lifetime result. This can be shown by the
against design life and adopting a different following graph in Figure 3
approach to warranty. Thus, proving a battery is defective is not always easy given the variables described
As can be seen, the difficulties lie in above. A more realistic approach to warranty would be beneficial. 19
the fact that design life and service life are
not synonymous. And warranty is in fact Conclusion: What can we learn from this?
only a guarantee against manufacturing First, warranty provisions must be separated from design life and service life. Further,
defect. A warranty statement can only service life must be differentiated from design life. Battery manufacturers could do
assure a user that if he follows accepted a better job in defining the parameters and characteristics used to state design life,
and documented maintenance practices
as outlined by the manufacturer, the
battery (or cell) is warranted against
manufacturing defect for a specific period
of time.
Some battery manufacturers also have
a stipulation that cycling of a stationary
battery is confined to a finite number of
cycles and exceeding that number will
void the warranty. Other manufacturers
place a stipulation on temperature. For
instance, one manufacturer states that if
the average ambient temperature exceeds
80°F, the warranty is void. Another states
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as a Condition and Limitation, “The yearly
ambient temperature in the area of use in Figure 2
any year may not exceed 25°C. 16
Due to the extreme variables that can
affect service life, most manufacturers
limit their full warranty to a specific period
of time, e.g. 12 months, 24 months or up
to 60 months after date of manufacture.
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Most permit a 90-day window beyond
the date of manufacture to allow time
for transit and installation. Although it
is common in North America to offer
a twenty-year warranty, determinants
such as stress factors and other variables
can make the validity of the warranty
questionable after a given number of
years. Figure 3

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