How long a battery lasts before you need to replace it is what really matters when it comes to battery lifetime. However, it’s important to understand the different metrics suppliers use to measure lifetime. Of particular importance is service life. This is the estimated time a battery will last before it reaches 80% of its energy capacity, the common definition of end of life for batteries. Service life assumes the battery is operating under “real world” conditions for a stated application and is therefore highly variable. In contrast, calendar life is the estimated time a battery will last if it were to remain trickle charged for its entire life with no power outages at a specified temperature, usually 25°C (77°F). VRLA batteries have a service life in the range of 3-6 years whereas li-ion batteries can have a service life upwards of 10 years (estimated using accelerated life testing). Note that it will be several years before data on actual service life becomes available for newer li-ion batteries, however, some liion batteries offer warranties in the 10 year range as a hedge against the lack of service data.

Both lead acid and lithium-ion batteries will see a degradation in calendar life and cycle life as the temperature rises. However, in general, li-ion service life is less affected by higher temperatures than lead acid. Many of the li-ion batteries being used in UPSs are designed for higher average temperatures (e.g., 40°C/104°F) and are capable of reaching the specified service life at those higher temperatures.

How long a battery lasts before you need to replace it is what really matters when it comes to battery lifetime. However, it’s important to understand the different metrics suppliers use to measure lifetime. Of particular importance is service life. This is the estimated time a battery will last before it reaches 80% of its energy capacity, the common definition of end of life for batteries. Service life assumes the battery is operating under “real world” conditions for a stated application and is therefore highly variable. In contrast, calendar life is the estimated time a battery will last if it were to remain trickle charged for its entire life with no power outages at a specified temperature, usually 25°C (77°F). VRLA batteries have a service life in the range of 3-6 years whereas li-ion batteries can have a service life upwards of 10 years (estimated using accelerated life testing). Note that it will be several years before data on actual service life becomes available for newer li-ion batteries, however, some liion batteries offer warranties in the 10 year range as a hedge against the lack of service data.
 

 

Both lead acid and lithium-ion batteries will see a degradation in calendar life and cycle life as the temperature rises. However, in general, li-ion service life is less affected by higher temperatures than lead acid. Many of the li-ion batteries being used in UPSs are designed for higher average temperatures (e.g., 40°C/104°F) and are capable of reaching the specified service life at those higher temperatures.