For data centers, few things rival the importance of ensuring service reliability 24-7. Without this consistency, the day-to-day operations of countless critical sectors — from telecommunications to emergency medical services — can be severely disrupted, risking individuals’ safety and hampering economic growth.
This underlines why data centers are cautious about protecting their assets, and why choosing the right uninterruptible power supply (UPS) system is particularly important. To ensure that these systems can support the data center’s needs at any time, they require the best battery technology to power them.
Lead-acid batteries have a long history as the default choice, but the proliferation of new innovations and technologies has changed this in recent years. Now, data center operators have the option of choosing between a variety of battery chemistries, each of which comes with unique advantages.
When analyzing what battery type is best for their data center workflow, managers should keep in mind these key components:
The physical size of a UPS system plays a significant role in the layout and internal organization of data centers. Out of the commercial battery varieties, lead-acid has the largest footprint: it possesses the lowest power density, and therefore requires significantly more space than lithium-ion or nickel zinc (NiZn) technology to accommodate the same amount of storage. While this doesn’t pose a challenge for every facility, it does mean that lead-acid batteries are poorly suited for modular facilities, as well as for data centers in expensive urban areas. In comparison, NiZn batteries use up to 65% less linear footprint and thus allow modular builders and construction teams to better optimize their buildouts.
Cost inevitably plays a decisive role in selecting the right battery type. It’s important for data center managers to factor both capital expenditures and long-term operational costs into their investment decision.
Lead-acid batteries have the distinct advantage of being the lowest upfront-cost option on the market. They do, however, require regular maintenance to preserve their average 5-year lifespan. Though an attractive option because of their low initial capital cost, lead-acid batteries are the most expensive to operate in the long run — an important consideration for data center managers.
On the other hand, lithium-ion and NiZn batteries have a higher upfront cost but have a longer life and require less maintenance once installed. For example, by lowering operating expenses (OpEx), NiZn solutions reduce ownership costs by up to 28% over lead-acid based UPS products across the total UPS useful life.
The environmental impact of data centers has gained increasing attention in recent years as businesses face growing pressures from investors, consumers, and regulatory agencies to integrate sustainability into their operations. A third-party expert analysis was conducted to assess the sustainability of various battery chemistries. The study compared factors such as GHG emissions, water footprint, energy use footprint, and volatile organic compounds. The study also provides GHG Protocol Scope 3 level emissions analysis. This information helps data center operators make sustainability one of the top factors in picking a technology – the best choice for both the environment and their company’s reputation.
Unfortunately, the very UPS system meant to prevent an outage too often causes one; accounting for 37% of data center outages, on-site power failure is still the most common cause of significant data center outages. The majority of these on-site outages (53%) are caused by UPS failure and often cost over $100,000 to repair.
One distinct reliability advantage is the ability to sustain battery discharge despite failure of an individual battery cell. In a UPS system, individual batteries are connected in a serial string (with multiple strings often paralleled) to support the required system voltage, power output, and run time. When a lead-acid or lithium-ion cell fails, it creates a high impedance or an open circuit that halts battery string operation. One single cell could be the difference between having the backup capacity needed or none at all, leaving the data center at unnecessary risk. Unlike lead-acid and lithium-ion, NiZn cells remain conductive when weak or depleted, allowing for continuous string operation and uninterrupted uptime.
The safety of data center workers and equipment is paramount when choosing batteries. Selecting a battery type that’s inherently non-flammable removes significant risks and makes the data center safer. For example, cell-level testing with the UL 9540A test method has revealed that NiZn batteries do not exhibit thermal runaway and are non-flammable, making them a safe choice for data centers and their workers alike.
Whichever battery type they choose, data center operators can help ensure their batteries’ safety by having them adhere to the National Fire Protection Association (NFPA) 1 (National Fire Code), the NFPA 855 standard, and the International Code Council’s (ICC) International Fire Code (IFC) 2021. These standards list both the installation safety rules for energy storage systems and testing procedures for batteries.
As the number of options on the market grows, choosing the storage technology best suited for your data center has major impacts on cost, energy efficiency, sustainability, and safety. That’s why the Institute of Electrical and Electronics Engineers’ (IEEE’s) 1679 document family helps users, integrators, and servicing organizations compare traditional stationary battery technologies with newer, advanced technologies. These documents guide the user to select the best battery type for their needs. If you’re considering an energy storage purchase, the IEEE 1679-2020 document and its child documents (IEEE 1679.1, 1679.2, 1679.3 and 1679.4) are invaluable tools.
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