In our industry we often hear, “Why does my 20 year battery only last 12 years?”  Or, “Why does my 10 year battery only last 7 years?”  Well, the answer lies in knowing the difference between battery “Design Life” vs “Service Life” expectations.

Design life is a theoretical calculation based on the life expectancy of the components used to make the cells and from endurance testing under ideal lab conditions.  Service life is established from data acquired for cells installed in real world applications under their actual installed conditions. 

Keep in mind there are parameters that can affect service life such as but not limited to: operating temperature, float voltage, ripple on the dc bus, frequency and depth of discharge, improper or lack of maintenance practices, and type of battery chosen for the application.
Permanent battery monitoring systems and handheld portable battery analyzers that measure and record temperature, voltage, internal ohmic values, and ripple are useful tools for trending these measurement parameters.  Also having a software package that allows you to analyze the trends of these parameters can help predict battery state of health and ensure you get the optimal service life for your investment.