Is Your UPS Battery a Fire Risk?
Updated: Oct 22
Picture a small dental office or a corner shop on a busy afternoon. The lights flicker, the power blinks, and from the back closet comes a steady beeping. The UPS has done its job: the computers, phones and card reader kept running. But that closet is warm, the UPS is a few years old, and nobody remembers when its battery was last changed.
Most of the time, nobody thinks about the UPS under the front desk or in the back closet. That's the point of a UPS, but it also means its battery can get old, hot or damaged without anyone noticing.
Large data centers are paying close attention to battery safety right now. In an October 2026 opinion piece for DatacenterDynamics, David Ellis of H2scan argues that the battery room is the biggest safety threat in a modern data center. He writes that when things go wrong there, the cause is almost always lithium-ion batteries, and he quotes the National Fire Protection Association's observation that nearly every notable data center fire in recent years has involved lithium-ion batteries in some way.
A small office isn't a data center, and a single UPS is far smaller than a battery room. But the basics are the same: batteries store a lot of energy, they wear out, and heat makes every problem worse. Here's what small businesses should know.
What's inside a typical small-business UPS
Most desktop and tower UPS units in offices, clinics and shops use sealed lead-acid batteries, also called VRLA or AGM. Some newer and slimmer models use lithium batteries. Both types work well when they're in good shape and kept in a reasonable environment. Both can become a hazard when they're old, damaged, overheated or charged by a faulty unit.
Batteries age, even when you never use them
A UPS battery wears out whether or not the power ever fails. It sits on a constant charge, and over time its chemistry breaks down. Sealed lead-acid batteries slowly dry out inside, especially when they're warm. Lithium batteries lose capacity and can develop internal faults as they age.
An aging battery is more likely to fail when you need it. In rarer cases it can overheat. That's why "it still turns on" isn't the same as "it's healthy."
Swelling and bulging are a stop sign
If a battery case looks puffy, rounded or cracked, or the battery is hard to slide out of the UPS, it's swollen. Swelling usually means heat or overcharging has caused gas to build up inside. A swollen battery should be taken out of service and replaced, not pushed back in or left running.
Lithium cells are a particular concern here. The DCD article explains how a failing lithium-ion cell can heat itself in a chain reaction known as thermal runaway. You don't need to know the chemistry. Just treat any bulging battery as something to deal with right away.
Heat and closets don't mix
Many small businesses tuck the UPS into an IT closet, a cabinet under a reception desk or a corner behind the server shelf. These spots are often warm, with little airflow and boxes stacked close by.
Heat shortens battery life and raises the chance of trouble. A few simple habits help:
Keep vents on the UPS clear and leave space around it.
Don't stack paper, boxes or other equipment on top of it.
If the closet feels warm to you, it's warm for the battery too. Consider better ventilation or cooling.
Keep the UPS off the floor where it might get wet or kicked.
Warning signs to watch for
Call for help, and shut the unit down safely if you can, if you notice any of these:
A sour, rotten-egg or chemical smell near the UPS
A case that feels hot to the touch, not just warm
Bulging, cracks or leaking around the battery
Frequent beeping, a "replace battery" light or a failed self-test
A UPS that switches to battery for no reason or shuts down quickly during a short outage
If you see smoke or flames, leave the area and call 911. Don't try to handle a burning battery yourself.
Why a yearly battery check matters
A UPS can look fine from the outside while its battery is near the end of its life. A yearly check catches problems early, while they're still cheap and simple to fix. A good check looks at the battery's age and physical condition, tests whether it can still carry the load for a short outage, reviews the UPS alarms and event log, and looks at where the unit is installed.
For more on what a UPS does day to day, see how UPS systems keep critical loads online and our guide to home office UPS benefits.
What to do next
Find every UPS in your space, including the small ones under desks.
Check the label or your records for when the battery was installed.
Look for swelling, heat, smells or alarms.
Make sure each unit has airflow and nothing stacked on it.
Plan to replace old or damaged batteries before they fail.
Not sure how old your battery is? Send us your UPS model and we'll help you check its age. Email office@luxena.net or use our Contact page.
Need a hand?
Luxena, LLC offers UPS battery checks and battery replacement for businesses across the Southeast USA, based on availability. Email office@luxena.net, use the request form, or reach us through our Contact page. You can also browse replacement batteries in our shop.
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