Data Center Backup Power: Unlocking Shorter UPS Runtimes

As businesses increasingly rely on digital infrastructure, uptime is everything; even a brief power outage can have severe consequences. Uninterruptible Power Supply (UPS) systems are the first defense against downtime, ensuring continuous power flow. Recent advancements in generator technology and power architecture have enabled faster automatic failover processes, creating the opportunity for reduced UPS battery runtimes. Data centers that once relied on 30-minute runtimes are now embracing runtimes of under five minutes – and now, many are aiming for three-minute runtimes.

This race to reduce UPS runtime has made traditional battery technologies, like lead-acid, struggle to deliver short-term power cost-effectively. Short-term, high-power applications require batteries with both high power density – the ability to release vast amounts of power over a short time – and high discharge rates. However, lead-acid batteries have a relatively low energy density, which forces data centers to purchase and deploy more of them to handle the required load. 

Meanwhile, some alternatives like lithium-ion batteries are constrained by lower discharge rates due to their risk of thermal runaway. The built-in safety mechanisms of lithium-ion battery management systems (BMS) trigger automatic shutdowns if the discharge current exceeds preset thresholds. While this safeguard helps prevent battery fires, it also effectively cripples the UPS system when it's needed most. And in both lithium and lead-acid batteries, a single failed cell blocks the current flow from surrounding cells, creating an open circuit that can bring down the entire battery string in an outage.

To compensate for these shortcomings, data centers have long resorted to oversizing their battery banks. By purchasing more cabinets than strictly necessary, they aim to ensure an adequate power supply during failover events. However, this approach comes at a steep cost – both in upfront expenses, and in valuable floor space that could otherwise be used for revenue-generating servers. These challenges are prompting operators to explore innovative solutions, like nickel-zinc batteries, to optimize their backup power systems.

Combining high power density with high discharge rates, nickel-zinc batteries bring a new level of reliability, safety, and cost-effectiveness to short-term high-power applications. Nickel-zinc batteries provide three times the power density of lead-acid and twice the carrying capability of lithium-ion batteries. Their added reliability stems from nickel-zinc battery cells’ ability to transmit power from the rest of the string, even if an individual cell is weak or depleted. This sets them apart from lead-acid and lithium-ion batteries – in which a single weak or depleted cell cripples the entire string – and ensures that the UPS system remains operational during vital seconds of failover.

In addition, nickel-zinc batteries don’t need the safety controls that constrain lithium chemistries. Since they’re incapable of thermal runaway, their BMS are designed to maintain optimal performance during rapid bursts of energy discharge, without the risk of automatic shutdowns. Their robust design enables them to deliver the vast amounts of short-term power needed to seamlessly bridge the gap between utility power loss and generator startup.

Combining greater reliability with greater power density and a high discharge rate, nickel-zinc technology empowers data centers to right-size their battery banks by eliminating the need for – and cost of – extra batteries to shore up system reliability. For instance, a typical 1MW UPS design with a 3-minute runtime target would require six or more lead-acid battery cabinets, and five or more lithium-ion battery cabinets. Meanwhile, nickel-zinc batteries can comfortably meet the same requirement with just three cabinets. By reclaiming this valuable floor space, data centers can allocate more room for revenue-generating equipment such as servers. And with fewer battery cabinets to purchase, install, and maintain, operators can benefit from significant upfront and operational savings – especially considering nickel-zinc batteries’ 15+ year lifespan and low maintenance needs.

As an added benefit, nickel-zinc batteries are also more sustainable than lithium-ion or lead-acid batteries. Their lifetime greenhouse gas emissions are four times lower than lead-acid batteries, and six times lower than lithium-ion batteries. As data centers and clients come under growing scrutiny for their carbon footprint, nickel-zinc batteries allow operators to offer their clients reduced Scope 3 emissions and compliance with stricter environmental standards.

As UPS runtimes continue to shrink, it’s crucial to choose a battery that consistently delivers vast short-term power during these critical moments. Nickel-zinc batteries provide the reliability and safety that data centers need to navigate the challenges of short-duration discharge, along with cost-saving efficiencies. By harnessing the potential of advanced battery technologies like nickel-zinc, operators can have confidence that their UPS systems will perform flawlessly when called upon and deliver unparalleled levels of performance, reliability, and efficiency.