Wednesday, May 15, 2013

How Long Can My UPS (Uninterrupted Power Supply) Battery Last?


What is "end of useful life"? The IEEE defines "end of useful life" for a UPS battery as being the point when it can no longer supply 80 percent of its rated capacity in ampere-hours (AH). Because the relationship between amp-hours and load protection time is not linear, a 20% reduction in capacity results in a much greater reduction in protection time. For example, a UPS battery that supports a full load for 15 minutes when new, will support the same load for only about 8 minutes when it reaches its defined "end of life". When your battery reaches 80 percent of its rated capacity, the aging process accelerates and the battery should be replaced. 
Which factors contribute most to end-of-life for UPS batteries? In North America, Western Europe and similar countries, positive grid corrosion has been the most common end-of-life factor for UPS batteries. This is a result of the normal aging process due to UPS battery chemistry (regardless of battery cycling) and involves the gradual breakdown of the inner wires of the positive grid within the battery. 
In other areas, cycling is often the major contributing factor, due to very unpredictable utility power. 
How do I make sure that my UPS batteries are maintained and serviced properly? With proper maintenance, battery life can be predicted and replacements scheduled without interrupting your operations. These are IEEE and OEM recommendations for general maintenance: 
Comprehensive maintenance programs with a monthly inspection, and more rigorous quarterly and annual checks. Re-torquing all connections, as required Load testing Cleaning the battery area, as required What about my smaller UPS? Does this information to small units? Yes, this information applies to all UPS batteries. It is also important to understand that battery warranty does not necessarily equal battery life and the estimated range for battery life is five to eight years. 
Are Maintenance Free batteries maintenance free? Though sealed batteries are sometimes called "maintenance free," they still require scheduled maintenance and service. The term "maintenance free" refers to the fact that they do not require fluid. Preventive maintenance is the key to maximizing your UPS battery service life. 
What about the disposal of batteries? It is imperative that your service technicians adhere to EPA guidelines for the disposal of all UPS batteries. Remember, it is the owner's responsibility (and liability) to make sure these guidelines are followed.