Uninterruptable Power Supply and Battery Technology: Change Is Now

Stay Informed

When it comes to data communications, one of the most critical infrastructure elements is the uninterruptible power supply (UPS), especially when it comes to distributed IT, data centers, or network closets.

UPS equipment can help protect your datacom hardware against damage from unexpected power failures, surges, or unclean power. UPS devices provide power backup to your systems, and the UPS battery ensures that there are no interruptions between your systems and the main power supply.

Let’s explore the world of UPS and, more specifically, focus on key questions you should be asking about the changes in UPS battery technology. While UPS technology has been with us for decades, battery technology is rapidly evolving. It is no longer one size fits all.

Change is happening. Change is now.

The Role of a UPS

UPS equipment safeguards your critical infrastructure. When incoming utility power drops below or rises above safe voltage levels, the UPS switches to DC battery power and then inverts it to AC power to run connected equipment. UPS batteries are a critical component of any UPS.

Overview of UPS Batteries

When it comes to UPS, there have been two main battery types:

  • Legacy valve-regulated lead-acid (VRLA)
  • Relatively new lithium-ion

Lithium-ion UPS represents a significant progression in UPS battery technology, which has been dominated by lead-acid batteries for decades. Because lithium-ion batteries offer an 8-10-year lifespan — as opposed to their lead-acid counterparts, which generally need to be replaced every three to five years — the technology offers several advantages.

Important Questions Regarding UPS Battery Technology

What are the primary benefits of switching to lithium-ion UPS batteries?

The most common reason cited is the significantly longer service life. Lithium-ion also provides a greater cycle life — the number of charge/discharge cycles ranges into the thousands for larger three-phase UPS, versus approximately 500 for VRLA batteries — as well as a longer warranty. Small single-phase lithium-ion UPS will not typically exhibit the thousands of full discharge cycles sometimes advertised for lithium-ion cells in perfect conditions. However, they do offer two to three times longer life than their lead-acid battery counterparts, and the lighter weight and smaller footprint are additional benefits.

In addition, IT professionals can easily deploy lithium-ion UPS without the maintenance and refresh challenges of those utilizing lead-acid. The extended battery life provided by lithium-ion enables users to align their UPS refresh cycles with the rest of the IT stack, saving time and money spent on labor and replacement batteries. Furthermore, lithium-ion UPS boasts a “set it and forget it” value proposition, which is especially conducive at sites where UPS protects critical network operations, yet IT resources are not extensive.

Lithium-ion batteries versus VRLA – is there a downside?

The primary downside is that because the technology is so new, many manufacturers have limited experience in UPS applications. However, this is changing rapidly, with successful deployments now exceeding four years.

What about fire risk with lithium-ion versus VRLA battery technology?

While any battery has the potential to catch fire if abused, lithium-ion does have a reputation for more dramatic “thermal events.” However, in UPS applications, the presence of a battery management system (BMS) — which controls charge rate, voltage, and temperature — makes lithium-ion batteries less likely to enter thermal runaway than traditional UPS batteries.

If the battery and its packaging are designed to dissipate more heat than can be created on overcharge, the battery cannot go into thermal runaway. All UPS vendors and battery vendors are ensuring that this is the case for lithium-ion products.

Have lithium-ion UPS experienced any battery failures or fires?

The presence of a BMS has been instrumental in the detection and mitigation of any anomalies. While there have been cases of individual batteries failing to retain a charge, these rare instances were not thermal-related and occurred only after the batteries were abused in a lab with stress testing.

Are lithium-ion batteries more expensive?

Yes, they vary from slightly more expensive than good quality VRLA, to two times more expensive, especially when shipping costs and commissioning services are considered. However, it is important to note that when vendors start shipping battery cabinets pre-loaded with batteries, the shipping costs for lithium-ion batteries should be slightly less than VRLA batteries.

Are there different recharge rates between lithium-ion and VRLA batteries?

Lithium-ion batteries can be recharged significantly faster than traditional UPS batteries; however, keep in mind that the manufacturers limit the amount of battery charge current that the UPS can supply. During recharge, the BMS monitors not only voltage levels, but also the temperature of the cells. In this manner, the system will automatically limit the charge if a cell gets too warm, which can potentially lengthen the recharge time. In general, the VRLA rule-of-thumb of “10 times the discharge time to 90 percent capacity” may not apply to single- or three-phase lithium-ion UPS batteries.

What is the shelf life of lithium-ion batteries before they need to be checked or charged?

A good rule of thumb if the battery modules are connected, i.e. installed in a cabinet, the storage time is six months at 25 degrees Celsius; however, it is always recommended to recharge every six months. This is due to parasitic losses from the BMS. If the battery modules are not connected (either power or communication connections), then the storage time is one year at 25 degrees C.

Can lithium-ion be mixed with other types of batteries (e.g., VRLA)?

No, lithium-ion cannot be put in series or parallel with other types of batteries.

Do lithium-ion batteries have recycling and/or disposal issues?

Lithium-ion batteries are disposable. However, various recycling options are expected soon. Recycling is preferred, and several national recycling agencies may be able to assist. Learn more about your recycling options for lithium-ion batteries.


While UPS technology has been around for multiple decades, UPS battery technology is rapidly changing. We explored and compared the two main UPS battery types – the legacy VRLA and the more recent lithium-ion battery. We addressed and compared significant issues from a benefit versus a downside perspective. We looked at comparisons of cost, fire risk, recharge rates, and many other key issues.

The bottom line is that while it seems like the UPS has always been around, the battery technology that powers the UPS is rapidly evolving, leading to longer-lasting and better UPS battery solutions. Lithium-ion batteries are here to stay and will ultimately lead to better, safer, and more cost-effective UPS solutions.

Make sure the manufacturer you approach to fulfill your UPS needs has the long-term industry knowledge, experience, and partnerships you can count on to help you make the right choices today and tomorrow.

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Value-added benefits:

  • Performance – 2-3 times longer battery lifespan
  • Resiliency – Three times faster recharge
  • Safety – Onboard battery management system (BMS)
  • Intelligence – BMS provides up-to-date insight into battery performance
  • Installation – 40 percent lighter than comparable lead-acid UPS
  • Confidence – 5-year all-inclusive warranty (electronics and battery)


Call your local WESCO representative to learn more about Eaton power solutions today.

The opinions expressed in this piece are solely Eaton's. They do not necessarily represent WESCO’s views.