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VRLA (Valve Regulated Lead Acid) UPS Batteries: When Should They Be Replaced?

Given the importance of VRLA batteries for UPS systems, it’s no wonder that many people question when they should be replaced, or how long they normally last while in service.

Batteries are the weak link in any UPS system, so it is crucial that they get tested and replaced at the appropriate time.

Failure to do so could result in dropping a load (when a UPS fails to support the critical load due to bad batteries.) Battery fires have resulted from thermal runaway because replacements were not performed when recommended! Not something anyone wants to deal with.

What is the average lifespan of a VRLA Battery?

Most batteries used in average UPS systems have about a five-year lifespan under good conditions, which includes regular maintenance, keeping temperature at 77’F or less, and limited discharges.

A few battery models even have a ten to twenty-year lifespan, which include the GNB Absolyte and the Ensersys DDm series.

Be aware though, while some manufacturers state their batteries are rated for ten years, we often find that five years is where they start to break down. That’s why it is important to have your batteries tested at regular maintenance intervals.

For modular and smaller UPS systems, such as a desktop UPS, we recommend replacing the batteries every three years due to lack of ventilation inside the modules.

What Causes VRLA Batteries to Fail?

All VRLA batteries become less reliable as they approach end-of-life, and even more so after.

Factors such as over temperature exposures, high room temperatures, lots of discharges, and lack of maintenance all reduce reliability and life span.

The chance of battery failure is even greater if they have experienced any kind of overheating conditions at any point in their life. If the temperature in the room is high or unstable, battery life can be dramatically reduced.

To put this in perspective, VRLA batteries must be kept below 77 degrees Fahrenheit, preferably at a stable room temperature.

Every degree above 77 will progressively diminish battery life span. In the past, Unified Power has replaced batteries that tested bad after only 50% of expected lifespan, when they were kept in a consistent 85 degree environment.

Replacing UPS Batteries

UPS batteries should, of course, be replaced sooner if they test bad or marginal, which is why we encourage regular testing, especially near end of life.

Please remember that in a single string setup, just one bad battery takes the entire string out, eliminating any backup time the Uninterruptible Power Supply may provide.

And with multiple string configurations, a bad battery in any one string will take out that string, which results in less backup time and loss of some or all redundancy.

To sum up:

  • Typical VRLA batteries in large UPS should be replaced after 5 years; depending on how they test & type of battery, it may be less time.
  • Batteries contained in closed modules or small UPS should be replaced every three years or less.
  • All batteries should be replaced if they test at 80% or less of rated backup time as part of a full discharge test.

We hope this has been informative and if you should have any other questions, we encourage you to reach out to us at any time.

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