Executive Summary
- Chris Cutler, Riello UPS Business Development Manager – Data Centres, states that it’s time for a rethink of backup power strategies; in this article, he explores the misconceptions around UPS and considers the lithium-ion question.
- Design life and service life are not the same thing. A battery with a 10-year design life won’t provide ten years of full performance because capacity naturally decreases throughout its lifespan.
- Batteries are becoming more of a critical and active factor in infrastructure performance, rather than remaining as a passive part of backup systems to be called upon when things fail.
For all the attention paid to generators, cooling systems, and power distribution infrastructure, one component remains fundamental to data centre resilience: the UPS battery.
Without a healthy battery system, even the most sophisticated uninterruptible power supply becomes incapable of delivering the protection it was designed for. Yet batteries continue to be one of the most misunderstood assets within critical power infrastructure.
Many operators still view batteries as a relatively simple component that can be installed and largely forgotten until replacement becomes necessary. In reality, battery technology is evolving rapidly.
As UK data centres pursue greater energy efficiencies, higher operating temperatures, and more ambitious sustainability targets, battery selection and management are increasingly becoming strategic decisions rather than routine maintenance considerations.
The challenge is no longer simply ensuring batteries work. It is ensuring they continue to perform reliably throughout their operational life while delivering the lowest possible total cost of ownership.
The weak link in data centre resilience?
UPS systems exist for one purpose: to bridge the gap between a power disturbance and the restoration of a stable power source, whether that means a standby generator kicking in or mains supply recovery.
However, a UPS is only as reliable as the batteries supporting it. Indeed, battery-related issues account for the overwhelming majority of UPS failures. Unlike many other components within critical infrastructure, batteries begin deteriorating from the moment they leave the factory. Their performance gradually declines over time, often without any obvious warning signs.
Why battery life isn’t what it seems
One of the most common misconceptions surrounding UPS batteries is the assumption that design life and service life are the same thing.
A battery marketed with a 10-year design life won’t provide ten years of full performance. Capacity naturally decreases throughout its lifespan, with industry guidance generally considering a battery to have reached the end of its service life once capacity falls below 80% of its original rating.
This is one reason why you should replace so-called 10-year batteries after seven or eight years, to build in that contingency or safety net. Similarly, with 5-year batteries, it’s advisable to replace them at year three or four.
Several factors accelerate this decline. Temperature remains the most significant. Traditional lead-acid batteries perform best between 20°C and 25°C. Every 10°C increase above this range can dramatically reduce lifespan, with some estimates suggesting life is effectively halved.
For data centres, this presents a dilemma. Many operators are raising operating temperatures to improve Power Usage Effectiveness (PUE) and reduce cooling costs. While servers and networking equipment have become more tolerant of warmer environments, batteries remain far less forgiving.
Evolving UPS battery technology
For decades, valve-regulated lead acid (VRLA) batteries have been the default choice for UPS applications.
Their popularity is easy to understand. They are relatively inexpensive, widely available, and have a long track record in mission-critical environments. However, the limitations of traditional VRLA technology are just as apparent as facilities seek greater efficiency and longer asset lifecycles.
In response, manufacturers have invested heavily in newer battery technologies designed to overcome these shortcomings.
Pure lead absorbed glass mat (AGM) batteries have emerged as one of the most significant developments. By using lead with extremely high purity levels, these batteries reduce internal corrosion, generate less heat during charging, and offer greater tolerance to elevated operating temperatures.
For operators, this translates into longer service life, reduced cooling requirements, faster recharge times, and more predictable end-of-life performance.
The technology effectively bridges the gap between conventional lead acid and lithium-ion solutions.
The lithium-ion question
No discussion about modern UPS batteries is complete without considering lithium-ion. Driven by the rapid expansion of electric vehicle manufacturing, lithium-ion costs have fallen considerably, making the technology more viable for data centre environments.
Looking at the advantages, lithium-ion batteries provide substantially higher energy density, allowing operators to achieve equivalent runtime using considerably less floor space. They also tolerate higher operating temperatures, offer longer design lives, and can deliver higher cycle counts than lead-acid alternatives.
For colocation providers and hyperscale operators where space and energy efficiency are at a premium, these benefits are difficult to ignore.
However, there are considerable drawbacks too. Although prices continue to fall, lithium-ion remains a much higher upfront investment. There are also significant concerns surrounding fire safety, battery management systems, and end-of-life recycling too.
While lithium-ion’s operational lifespan can contribute positively to sustainability goals, lead-acid batteries continue to benefit from one of the most mature recycling infrastructures of any industrial technology.
For many organisations, the decision ultimately comes down to balancing capital expenditure against long-term operational savings.
Technology alone is not enough
Choosing the right battery technology is only part of the equation. Even the most advanced battery will experience premature failure if it is poorly managed.
High temperatures, excessive discharge cycles, incorrect charging voltages, and inadequate monitoring can all dramatically shorten operational life. In many cases, batteries fail not because of inherent defects but because small issues remain undetected until they trigger a larger problem.
A single overheating battery can raise the temperature of surrounding cells. One deteriorating battery block can alter charging behaviour across an entire string. Such cascading failures highlight the importance of proactive maintenance.
From reactive maintenance to predictive management
As battery systems become larger and more sophisticated, monitoring technologies are playing an increasingly important role. Traditional visual inspections remain important but provide only a partial picture.
Modern battery monitoring systems can continuously track parameters such as cell voltage, internal resistance, charging current, temperature, and discharge performance. By identifying subtle changes over time, operators can detect early signs of deterioration before they develop into failures.
This shift towards predictive maintenance mirrors broader trends across the sector, where operational decisions are increasingly driven by data rather than fixed maintenance schedules.
A total cost of ownership mindset
Ultimately, the future of UPS battery management is likely to be defined by total cost of ownership rather than upfront purchase price.
Battery procurement decisions increasingly need to account for cooling requirements, maintenance costs, replacement cycles, floor space utilisation, energy efficiency, sustainability objectives and disposal considerations.
For some facilities, traditional and proven VRLA batteries will continue to offer the best value. Others may find pure lead technology provides an attractive balance between performance and affordability.
Meanwhile, lithium-ion will remain an option in applications where space efficiency, long lifespans, and reduced maintenance justify the higher initial investment.
What is becoming increasingly clear is that battery strategy can no longer be treated as an afterthought. As data centres evolve to meet rising demands for efficiency, resilience, and sustainability, batteries are moving from being a passive part of backup power systems to a critical factor in overall infrastructure performance.
In an industry where downtime is measured in reputational damage as well as financial loss, understanding both how batteries age and which technologies are best suited to modern operating environments is almost as important as selecting the UPS itself.
