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When Should You Replace Your UPS Batteries?

As the heart of any uninterruptible power supply (UPS), the batteries inside the unit represent the most critical component to ensuring continuous uptime. However, it is well documented that batteries are also the most vulnerable element in a UPS system. In fact, research shows that up to 20 percent of all UPS failures can be attributed to bad batteries, and battery failure ranks as the leading cause of load loss and system downtime during a power outage.

While there are steps you can take to help extend battery lifespan, all UPS batteries will eventually require replacement, regardless of the UPS manufacturer. Understanding how often batteries need to be replaced and recognizing the signs that it is time to replace them will go a long way toward helping you avoid unexpected downtime.

Different Types of UPS Batteries

Historically, there were two types of UPS batteries: valve-regulated lead-acid (VRLA) and vented lead-acid (VLA), also commonly referred to as flooded cell or wet cell. But in 2016, a third alternative was introduced to the UPS market, lithium-ion. Although initially quite expensive and only available in limited UPS models, lithium-ion is now much more widely available from most leading manufacturers.

Regardless of how or where a UPS is deployed, all batteries have a limited lifespan. Even UPS batteries that are well cared for will nonetheless require replacement at some point. This is due to the fact that they are electrochemical energy storage devices that convert chemical energy into the electrical energy UPSs use to operate, and over time the chemicals deplete.

Batteries will generally experience a slow degradation of capacity until they reach 80 percent of their initial rating, at which point they begin to fail much faster. Batteries also reach end of life much quicker when operating in less ideal environments, such as those that don’t maintain an ambient temperature of 77°F, or where recurrent power problems cause batteries to cycle frequently. Battery life can also be significantly reduced if an organization doesn’t engage in regular service and maintenance, which are essential to ensuring ongoing UPS reliability.

So how often do you replace UPS batteries? As a general rule, large UPS units tend to run for 15 or 20 years, while smaller models usually last 10 or more. Therefore, if batteries are approaching the end of their useful life, and the UPS still has years of life remaining, replacing your batteries makes sense from a return on investment (ROI) standpoint, as well as to avoid unexpected and costly downtime.

6 Signs Your UPS Batteries May Need Replacing

Preventing battery failure is key to ensuring that your connected systems stay up and running at all times. While batteries often display signs of impending failure, it is also possible for them to fail without any warning, leaving your critical load unprotected.

Potential early warning signs include:

  1. Low battery alarm: Most battery backup systems include a low battery alarm that will alert you before the battery dies. The UPS performs periodic self-tests, then sends a signal when the battery is approaching end of life, generally through an indicator light or alarm sound. UPSs that include a monitoring system may also send email or text alerts.
  2. Preventive maintenance (PM) findings: Engaging in regular service enables trained technicians to inspect batteries, identify problems, and assess and compare battery readings to ensure your UPS remains in proper operating order. Technicians can then provide expert advice on how to maintain ongoing battery health, as well as recommend when replacing the batteries is the best option.      
  3. Early discharge: Another sign that you should consider replacing your UPS batteries is if they are taking longer to charge and/or self-discharge earlier than usual.
  4. Unusual behavior: When batteries are approaching the end of their useful life, they often begin to display symptoms such as repeating alarms, flashing panel lights and abnormal terminal displays, indicating that replacement is warranted.
  5. Old age: Because manufacturers include a date stamp on batteries, you can always tell their exact age. However, as previously noted, battery lifespan can vary significantly based on environmental and other factors. In most cases, you can expect VRLA UPS batteries to last a maximum of three to four years. To prevent failure and costly downtime, it is wise to proactively replace batteries that are approaching this age. 
  6. Shorting out: When your battery system can no longer supply at least 80 percent of its rated capacity, it is a strong indicator that the battery needs to be replaced. Typically, when it reaches this percentage, the aging process will accelerate very rapidly, leaving the battery vulnerable to immediate failure.

Why Preventive Maintenance is the Optimal Approach to Battery Replacement

Routine preventive maintenance has been shown to be one of the most successful and cost-effective ways to ensure the longevity and reliability of your UPS batteries. This proactive approach monitors ongoing battery health through regular checkups, helping to ensure that batteries will continue to operate at peak performance. Without scheduled preventive maintenance, there is no way to mitigate the possibility of battery failure, leaving your equipment vulnerable to downtime.

Replacing a string of batteries within a large UPS, or the internal battery in a smaller model, costs significantly less than investing in a new UPS. This proactive approach is also considerably less than the unfavorable and expensive consequences of unplanned downtime. It’s important to note that it is quite risky to wait for a sign of impending failure before opting to replace your UPS batteries.

When the UPS sounds a low battery alarm or displays another sign of battery illness, you may not have ample time to schedule a service call and obtain the necessary replacement batteries before the battery dies. Even worse, sometimes batteries fail without any warning at all ── and if that moment coincides with a surge, outage or other power quality issue, your critical load will be unprotected.

Depending on the UPS, battery replacement can be a complex endeavor and is best left to trained technicians. If your UPS battery displays any of the warning signals outlined above, it is important for a professional to confirm the issue and if needed, replace the batteries. In some instances, the naked eye can even determine if a battery needs to be replaced, as changes in physical appearance can be indicators of a short, overcharging or a simple lack of proper maintenance. Cracks in the plastic, bulging casings, broken terminals, leaking and discoloration are all signs that the batteries should be replaced.

In a larger UPS system, a single faulty battery doesn’t necessarily require the entire battery string to be changed. However, a dying battery can affect others on the string, causing them to fail prematurely. Before changing the battery, trained technicians can identify the bad unit and test the health of the entire string down to the cell level to determine if additional strain from the faulty battery has damaged any of the others.

Replace Your UPS Batteries with Unified Power

Regardless of your UPS type, size or application, replacing your batteries is a necessary aspect to maintaining the unit. Engaging in routine PMs will help extend battery lifespan, prevent costly downtime, and ultimately save time and money. As a national provider of critical power equipment and services, Unified Power offers a comprehensive range of battery services, including full and partial replacement, load bank testing, and removal and recycling.

We also stock replacement UPS batteries for all major manufacturers, like Eaton and Mitsubishi, as well as miscellaneous hardware to ensure reliable connections. All services are performed by our expertly trained technicians in accordance with IEEE and other safety standards. An affordable alternative to original equipment manufacturers, Unified Power customers typically save 20% on their maintenance agreements.

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