Various Factors Impact UPS Battery Life
There are many factors that influence UPS battery life including freight issues, manufacturing defects, charging issues and maintenance. Unfortunately, there is no neat formula or app on your phone that can predict this precisely. For Data Center Managers and Facility Managers, the most important factors are:
- depth and frequency of discharge
- temperature of the room
For this article, we are going to focus on VRLA batteries. The industry standard for battery life expectancy is 3-5 years.
Maintenance is important for a variety of reasons. At the absolute minimum, you want to keep the battery connections properly torqued and visually inspect the batteries for signs of problems. Having a trained technician perform a full PM on a semi-annual or quarterly basis can provide enough historical data to help predict the end of service life. You might also consider a Battery Monitoring System to provide daily information about the current state of each battery.
Depth and Frequency of Discharge
For the depth and frequency of discharge, I have often heard Eaton Area Service Manager Allen Fowler describe battery output using a loaf of bread. You can have one big long discharge. You can have a lot of short discharges. At the end of the day, the battery is going to discharge and recharge (known as a cycle) only so many times. The UPS will shutdown around 1.7V/cell to try to keep the batteries from discharging to such a low voltage that they cannot be re-used. Minimizing the number of long battery discharges is key to a long battery life.
Lastly, the ambient temperature in the room is a key factor. A chemical reaction is occurring inside the battery and we all remember from Chemistry 101 that heat speeds up a reaction. The faster the reaction, the faster the battery breaks down. Eaton’s Large UPS Battery Handbook states “…for every 8.3°C (15°F) average annual temperature above 25°C (77°F), the life of the battery is reduced by 50 percent”. Heat can also cause a battery to dry out. It is important to note that over-charging can also cause damaging excess heat. Keeping the room 77°F is important to prolonging the life of your batteries.
In summary, maintenance, short discharges and proper ambient temperature are the key ingredients to happy long-lasting batteries. Maintenance and a Battery Monitoring System will help give you the information to know when the right time to replace your batteries is.
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