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Batteries, UPS

10 Things You Need To Know About UPS Batteries

While undeniably the heart of any uninterruptible power system (UPS), batteries unfortunately are also the most vulnerable aspect. In fact, battery failure consistently ranks among the most common causes of load loss. Understanding how to properly maintain and manage UPS batteries is not only instrumental to extending their service life but can also help thwart costly downtime. Bolster your battery knowledge with these 10 truths:

1. All batteries will experience an “end of useful life”The IEEE defines a UPS battery’s “end of useful life” as the point when it can no longer supply 80 percent of its rated capacity in ampere-hours. At this stage, the aging process accelerates and you should replace the battery. Although the average lifespan for VRLA batteries is three to five years, actual life can vary dramatically due to environmental conditions, the number of discharge cycles and the amount of maintenance received.

2. Batteries die for a variety of reasons – Among the most common causes of battery failure are high or uneven temperatures; inaccurate float charge voltage; loose inter-cell links or connections; loss of electrolyte due to damage or drying out; lack of maintenance; and aging.

3. VRLA and VLA are the two most common types of UPS batteries – Valve-regulated lead acid (VRLA) batteries, also known as sealed or maintenance-free, are batteries that have been encased to prevent any liquid from leaking. Vented Lead Acid (VLA), also known as flooded or wet cell, are comprised of a hard enclosure, lead plates and an electrolyte that allows the flow of current. Don’t miss our next blog, which will explore both of these battery types in much greater detail.

4. Different UPS systems use different batteries – While basic battery technology — and the risks to battery life — remain the same regardless of UPS size, there are some differences between applications. Smaller UPS’s (250VA to 3kVA range) typically contain a single VRLA battery, while the use of wet-cell batteries becomes much more common in bigger systems.

5. Your UPS maintenance plan should cover the batteries, too – A solid, comprehensive service plan will include both the UPS components and the batteries. Regularly scheduled preventive maintenance visits allow trained technicians to inspect, test, calibrate and upgrade battery components, ensuring factory-specified performance and longevity.

6. The battery type will dictate maintenance requirements – The type of batteries will impact which maintenance tasks need to be performed and their frequency, with wet cell batteries requiring more maintenance than VRLA. However, even batteries that claim to be “maintenance-free” still need regular inspection, cleaning and testing.

7. Stored batteries require attention, too – If UPS batteries sit unused with no charging routine, their life will decrease. Due to the self-discharge characteristics of lead-acid batteries, it is recommended that they be charged every three to four months when in storage to avoid permanent loss of capacity (which will occur between 18 and 30 months). To prolong shelf life without charging, store batteries at 10°C (50°F) or less.

8. There is a difference between hot-swappable and user-replaceable batteries – Batteries can be both hot-swappable and user-replaceable. Hot-swappable batteries are able to be changed out while the UPS is running. User-replaceable batteries, which are generally found in smaller UPS’s, indicates that no special tools or training is needed to replace them.

9. A battery’s discharge rating is key to measuring performance – Batteries are generally rated for more than 100 discharges and recharges. However, many will display a marked decline in charging capacity after as few as 10 discharges. The lower the charge that the battery can accept, the less runtime it is able to deliver. Be sure to look for batteries with a high-rate design that sustains stable performance for a long service term.

10. Thermal runaway can have explosive consequences – Often occurring without any warning signs, thermal runaway takes place when the heat generated in a lead-acid cell exceeds its ability to dissipate it. Typically caused by overcharging, excessive charging, internal physical damage, internal short circuit or a hot environment, thermal runaway can result in an explosion, especially in sealed cells.

Batteries, UPS

Knowledge is Power: Understanding UPS battery options

When it comes to the batteries within uninterruptible power systems (UPSs), one size doesn’t fit all.

In fact, for decades, most smaller standby systems have used sealed VRLA batteries, while larger double-conversion systems have typically relied on flooded-cell VLA batteries.

There’s also a relative newcomer to the family, as lithium-ion has joined the two decades-old siblings. Here, we break down the UPS battery family tree:

1. Valve Regulated Lead Acid (VRLA). Commonly referred to as sealed lead-acid (SLA) or maintenance-free, VRLA batteries are the most common type of UPS battery.

Lower upfront costs, relative safety, easy availability and minimal maintenance are the primary advantages of this battery. However, deeming VRLA batteries “maintenance-free” is slightly inaccurate, as they still require regular cleaning and testing.

On the downside, sealed batteries have a short lifespan of about 3 to 7 years. The term ‘valve regulated’ represents the manner in which gas is released from a VRLA battery; if pressure becomes too great, a valve will vent the gas.

Because heat is detrimental to this type of battery, their optimal environment is a dry, temperature-controlled area of 77 degrees or lower.

It is important to note that since water cannot be added to most VRLA batteries, anything that increases the rate of evaporation or water loss — such as temperature or heat from the charging current — will subsequently reduce the life of the battery.

a. Absorbent glass mat (AGM). AGM batteries are a subtype of VRLA batteries. In AGM batteries the electrolyte is held in woven glass fiber mats.
This design allows for flexibility of design, improved self-discharge rates, and a wider operational temperature range.
b. Gel Cell. The second VRLA subtype. Originally conceived during the early 1930s for use in portable electronics early gel cells were less likely to leak when handled roughly.
A modern gel cell uses an electrolyte mixture usually comprised of sulfuric acid mixed with pyrogenic silica resulting in a gel like substance.
Gel cells are known for increased tolerance to vibration, as well as allowing for the lower cost 1-12 Amp hour range VRLA batteries found in smaller UPS systems.

2. Vented Lead Acid (VLA). Also known as flooded or wet cell batteries, VLA not only boast exceptional reliability, but an average lifespan of 20 years.

Composed of thick, lead-based plates flooded with electrolyte acid, these batteries typically have higher upfront costs than their VRLA counterparts, as well as pose a number of safety concerns.

As a result, they require regular maintenance and careful handling because their liquid is corrosive and can be set off by forceful movement.

Wet cell batteries should only be used in areas with proper ventilation and must be adequately protected against vibration and shaking due to the possibility of liquid spilling. In addition, they are prone to damage in extreme climates as the water inside can evaporate or freeze.

Even though wet cell batteries require more maintenance and are more expensive to replace, they are a highly reliable power source for double-conversion UPSs.

3. Lithium-ion. The new kid on the block when it comes to UPS applications, lithium-ion batteries have matured significantly in recent years, both in their design and range of potential uses.

Lithium-ion creates a safe and stable alternative battery option for UPSs, with benefits that include longer lifespan, weight reduction, smaller footprint and expanded warranty coverage.

While originally deployed as battery cabinets in three-phase UPS installations, there are now smaller single-phase lithium-powered UPSs on the market.

Although this type of battery tends to be more expensive than the other two options — which is expected to change as adoption rates become more widespread — lithium-ion batteries offer lower long term operational expenses since they last longer.

While each of the three types of UPS battery has its own set of advantages and disadvantages, it is important to understand your options — not to mention, how to best manage and maintain them.

One battery pitfall to avoid at all costs is thermal runaway, a topic we explored in our last blog.


5 Steps To Prevent Thermal Runaway

When it comes to ailments that affect batteries in uninterruptible power systems (UPS’s), few have the capacity to spark disaster like thermal runaway.

Occurring most often in valve-regulated lead acid (VRLA) batteries, this potentially hazardous condition is created when the rate of internal heat being generated exceeds the rate at which it can be expelled.

Ultimately, the increasing temperature dries out battery cells until the container softens, breaks and melts, triggering a range of possible catastrophes — from load failure and costly unplanned downtime to electrical fires, exploding batteries and the release of toxic chemicals.

Although thermal runaway clearly has the capacity to evolve into a true disaster, the good news is, it is unlikely to occur if just a few simple rules are followed.

Above all else, heed the old adage “an ounce of prevention is worth a pound of cure.” To that end, be sure to:

1. Keep cool — Because heat is one of the primary factors that leads to thermal runaway, it is critical to maintain the temperature of the battery environment at 77°F or below.

The second factor related to thermal runaway is the charge current. As the battery heats up, the internal resistance to the charging current is lowered, which allows more current and in turn, creates more heat.

Once thermal runaway begins, it cannot stop itself; the only cure is to remove and replace the batteries.

2. Trust the experts — Performing regularly scheduled preventative maintenance on the UPS and batteries in instrumental in avoiding thermal runaway.

During a PM visit, technicians can spot problematic batteries or cells before they fail, as well as adjust the charging voltage and current to ensure batteries are not overcharged.

In addition, while VRLA batteries are often deemed “maintenance-free,” they still require regular cleaning, checking and testing by trained professionals.

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3. Replace the batteries — Some VRLA batteries may be pro-rated up to 10 years, but in reality, their average life expectancy generally falls between 5 to 7 years.

All UPS batteries have a rated capacity that is based on specified conditions, and any variation from these guidelines can alter the battery’s performance, shorten its expected life and lead to conditions such as thermal runaway.

To be safe, experts recommend replacing batteries when they reach 5 years.

4. Monitor your environment — Although battery monitoring systems have historically been more prevalent in higher cost, wet-cell installations, the fact is, thermal runaway is more common in VRLA battery strings.

With an array of offerings available for lead-acid battery applications, a monitoring system will record the voltage and temperature of every jar, saving data so it can be reviewed to establish trends.

A monitoring system can also identify if a particular jar has abnormal conditions, enabling it to be isolated and replaced long before thermal runaway has the chance to rear its ugly head.

Laboratory tests by battery vendors have shown that it takes hours or days for thermal runaway to be self-sustaining.

5. Be aware — While routine service calls, regular battery replacement and a monitoring system go a long way toward avoiding thermal runaway, don’t forget the value of simply keeping your eyes open and ears on the ground.

Visually inspect batteries for signs of corrosion or other defects, and keep your ears pealed for any unusual rattling or other sounds coming from the UPS.

By adhering to these simple guidelines, you can significantly reduce the likelihood of thermal runaway running away with your critical load!

Still have questions? Get a response immediately.

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Maintenance, UPS

Recommended UPS Maintenance Schedule

You tender a request for vacation weeks or even months in advance; highlight upcoming appointments on the calendar; and share your daily availability with everyone in the organization — right down to the hour. But are you devoting the same level of care and planning to your UPS maintenance schedule?

If you aren’t sure exactly what needs to be done and when, you’re not alone. Yet it’s important to understand that a UPS is not a device you can simply stick in a corner and forget. An effective maintenance strategy — targeting both the overall UPS and its batteries —is critical to your system’s ongoing reliability and performance. The type of batteries will also determine the level and frequency of service; for instance, most smaller UPS’s use sealed batteries that require little maintenance, while other models utilize flooded-cell batteries that require monthly attention.

While some basic maintenance tasks — such as visual inspections — can be performed by in-house staff, the majority of service necessitates a trained technician from a professional service organization, both for the expertise required and also to ensure personnel safety. Here is an overview of our recommended UPS maintenance schedule:

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At least once a month, assign a competent staff member to:

  • Conduct a visual inspection of the UPS, making sure the overall environment is clean and free of dust and debris
  • Inspect and test the room’s ventilation system to ensure its proper operation
  • Inspect batteries for proper electrolyte levels and signs of leaks
  • If a battery monitoring system is in place, review the results
  • Measure the ambient temperature
  • Measure the battery float charging current
  • If a generator is part of the building’s emergency-power system and feeds the UPS, it should be tested monthly


On a quarterly basis, it is important for a qualified service technician to:

  • Visually inspect equipment for loose connections, burned insulation or any other signs of wear
  • Measure the voltage of each cell or battery block
  • Measure the ambient temperature and negative-post temperature of at least 10 percent of the cells or battery blocks (if possible, check all cells)


Twice a year, a trained technician should:

  • Inspect and repair battery connections as needed, since loose or dirty connections can cause a buildup of heat at the battery terminals — decreasing system capacity, reducing battery life and creating potential fire hazards
  • Visually check for liquid contamination from batteries and capacitors
  • Clean and vacuum UPS equipment enclosures
  • Test the UPS’s overall operation


During this important yearly checkup, depending on your equipment type and requirements, expect a technician to:

  • Take the system offline and inspect its components for signs of corrosion and heat damage
  • Conduct thermal scans on electrical connections using a diagnostic tool that identifies hot spots invisible to the human eye
  • Load-test the battery bank to determine its capacity, which may require disconnecting the UPS from its power source and allowing the batteries to supply power to the connected load
  • Remove dirt and dust from UPS components
  • Measure and check the torque of all connections, re-torqueing any power connections as needed
  • Provide a complete operational test of the system, including a monitored battery-rundown test to determine if any battery strings or cells are near the end of their useful lives, an AC ripple current and interconnecting cable resistance testing
  • For flooded-cell batteries, the technician should:
    • Inspect terminals for signs of corrosion and accumulation of dirt
    • Measure and record the voltage and current of the entire bank
    • Measure and record the voltage for each individual cell and test their electrolytes
    • Record and log measurements to track battery performance

Still have questions? Get a response immediately.

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Maintenance, UPS

10 Truths About UPS Maintenance

Research has repeatedly proven that regular maintenance of uninterruptible power systems (UPSs) is one of the most successful and cost-effective tactics to ensuring their ongoing optimal performance. For optimal results, be advised of the following 10 certainties when it comes to your service approach:

1. UPS components will eventually fail. Yes, even the highest quality UPS operating at the optimal temperature in an environment with perfectly clean power will nonetheless fail at some point.

All UPS’s have certain finite components — such as batteries, capacitors and fans — that simply wear out from normal use. That’s why…

2. You need to schedule maintenance. And by schedule, we mean put it in ink, on the calendar, well in advance.

Studies have shown that the mean time between failures (MTBF) is more than 20 times better for UPSs that receive preventive maintenance (PM) twice a year compared to those that don’t.

Yet PMs can’t be left to chance, especially considering the potential costs of downtime.

Sticking to a predetermined timetable of regular maintenance activities helps ensure your UPS will perform as expected when you need it most (to find out exactly what should be completed on a quarterly, semi-annual and annual basis, be sure to check out our next blog).

3. Preventive maintenance improves ROI. Regular, pre-scheduled UPS maintenance can easily pay for itself by preventing unplanned downtime events.

This can be attributed to the fact that a trained technician has the ability to detect and repair a plethora of issues — from battery or capacitor failures to clogged air filters to outdated firmware — before they become significant and costly issues.

4. Batteries require their own care. As the most vulnerable part of a UPS, batteries are among the leading causes of load loss.

Understanding how to properly maintain and manage UPS batteries will not only help extend their overall service life, but also reduce costly downtime (we have an upcoming blog covering this topic, as well!).

Need help deciding on a UPS? Get a free site assessment!

Click above to get started or call 240.772.1710 for instant help.

5. It’s always safety first. When it comes to electrical power, one teeny blooper can result in serious injury or even death.

With that in mind, it’s critical that safety remains your No. 1 priority when performing any type of service on a UPS.

Be sure to observe all manufacturer recommendations, pay close attention to your facility’s implementation details, and always adhere to standard safety guidelines.

6. You don’t have to be a UPS whiz. Many, if not most aspects of UPS maintenance, are best left to those who are intimately familiar with the devices.

For instance, considering that the voltage inside a UPS system registers at a lethal level, it is completely understandable (and justified) to allocate funds for a professional service organization.

Don’t risk lives.

7. Know who you’re going to call. If a UPS problem does arise, quick response can mean the difference between inconvenience and disaster.

During an emergency, don’t be left scrambling to find a service technician.

Instead, right now, while everything is still performing perfectly, identify a reputable service provider that will be available when you need them — even if that ends up being two in the morning.

Keep all numbers for maintenance and repair in a readily accessible, well-known location.

8. Stop, look and listen. Even if you leave primary UPS maintenance up to the professionals, you can still complete basic inspections yourself.

For example, regularly examine the area around the UPS to make sure there are no obstructions or operating warnings on the panel.

Visually inspect the batteries for signs of corrosion or other defects, and keep your ears pealed for any unusual rattling or other sounds coming from the UPS.

9. Retain records. Be sure to maintain records of all maintenance performed on the UPS, including cleanings, repairs and replacements.

This documentation can help down the line when planning for equipment replacement, additional maintenance needs, or troubleshooting if an issue arises.

Just like your contact numbers, keep records in a handy spot.

10. Don’t throw away your UPS documentation. It’s always wise to consult the manufacturer’s documentation for recommendations for your specific unit.

This paperwork is also likely to include an overview of the type of maintenance that should be performed on the UPS at specific intervals.

Consider these guidelines to be the minimum approach; when it comes to UPS preventive maintenance, more is always better.

Still have questions? Get a response immediately.

Click above to get started or call 240.772.1710 for instant help.

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