5 Decision Factors: Choosing your Data Center Battery Bank

White paper by Carrie Goetz, Principal/CTO, StrategITcom

Selecting the most appropriate battery for a data center depends on more than the battery itself and the chemistry it utilizes. The installed location and environment will contribute to battery efficiency.

When selecting batteries for mission-critical operations, the choice is not as simple as cost or preference. There are tangible factors that can vary widely from one room construction to another and one chemistry to another. Some factors to consider are as follows:

1. New build v. retrofit or component replacement

2. Data center size

3. Occupancy environmentals

4. Chemistry and form factors

5. Day Two costs

1. New Build-vs-Retrofit or Component Replacement

Comparing new buildings to retrofitted situations, the room size and environmental systems may dictate your battery selection. Rooms initially sized for smaller battery types or designed with specific features for a single battery type will find retrofitting racks challenging. Accommodating other batteries with the same capacity may be difficult, if not impossible. Conversely, a room designed for larger batteries suits multiple battery chemistries, provided the room's ventilation and air conditioning needs are addressed. It may be cost prohibitive to add HVAC and ventilation. If a new solution requires major retrofitting, costs must be captured in the project.

For new construction, battery decision factors are much more manageable. Organizations can determine battery capacity based on modeled or predicted power demand for the life of the building. That is, at best, a tricky situation. Data centers built 5 years ago likely weren’t factoring in the increase in power required for some of today’s applications. Generative AI is a great example. If one designs for today’s loads, the room is limited to that configuration in perpetuity. Additional capacity will impact all power chain solutions including the UPS, batteries, and other increases. The additional equipment may require new construction or a container solution external to the building. Some facilities opt to design in building blocks, allowing capacity to be added in banks on demand, saving initial battery capital outlay.

The uncertainty about the future of batteries complicates and compounds our decision on room size. Supply chain issues, availability of raw goods used in fabrication, labor pressures, and any number of factors can render the best selection useless for on-time delivery. Having flexibility in the battery room will prove beneficial in the long run. Increasing a 10 x 10 room to a 10 x 20 room doesn’t double construction costs as the end walls remain the same. Floor loading calculations should accommodate the heaviest of chemistries to support future growth without modification.

Some battery systems, like VRLA batteries, can operate without a purpose-built room. While building codes require some form of ventilation, simple ventilation and complex HVAC systems have very different CAPEX and OPEX implications. VRLA batteries are often able to operate in rooms with standard/typical ventilation while nonrecombinant battery chemistries (VLA, NiCd and others) generally require costly secondary ventilation. Savings within the battery room environment can free up project dollars for other facility needs.

2. Data Center Size

The size of the facility and the divisions within it for data halls will help dictate the room size for each battery bank(s). Power density within the white space determines the number of batteries on day one, but of course, we know that loads fluctuate, as will the power requirements for the facility over time. AI is a great example. One search on ChatGPT uses approximately 5x the power of a regular search engine search. Generative AI can use 20-30 times the power of precursor applications. Physical size is one factor, but power density within that same space creates a different set of equations on day one and as the facility grows.

To size battery banks, one needs to know the actual or expected amount of power required and the time necessary for depletion or discharge before generators or other backup power kicks in. Chemistry selection comes into play for recharge cycle times, which vary from one chemistry to another. Battery selection for remote locations may differ from those in a larger-scale facility. Remote locations may have different criteria, such as fewer replacements and faster recharge times due to a lack of resources at the remote site.

From a physical perspective, how the batteries orient within the cabinets, racks, or containers factors into the overall footprint. Racks and connections vary based on the requirements of the battery systems. Some battery systems require proprietary or purpose-built cabinets. Others can be stored in open racks or cabinets. Additional rack space for battery management systems may be necessary.

Some batteries have terminals on top, while others are on front. Sometimes, a simple change like front-facing terminals can increase power density in a given area. It pays to work with battery manufacturers and their experts to help examine all possibilities before the final design. That way, facilities can ensure that overall room size does not limit battery selection. Nimbleness in design may be vital in limiting downtime events.

3. Room Environmental Requirements and Monitoring

Air handling requirements in the room vary with construction. Maintaining thermal requirements within the room helps maintain the battery's useful life and, more importantly, safety requirements. Thermal runaway must be avoided. Some systems require more complicated cooling and battery management systems to safeguard against runaway events. The room may require additional sensors and monitoring for safety, temperature, and fire safety.

Due to the toxicity of fumes, some constructions require more extensive ventilation than others. Off-gassing must be addressed by code and for safety. VRLA batteries provide additional protection as gasses recombine (Pure Lead Max) or are kept internally (other chemistries) under normal operations.

Temperature ranges similarly must be maintained to ensure that thermal runaway, fires, and loss of lifespan don’t occur. Some chemistries require more extensive room-level temperature control than others. For instance, Lithium-ion batteries generate more heat during discharge and charging cycles and, therefore, require HVAC or battery cooling systems. In contrast, FLA and VRLA battery rooms require ventilation but have minimal heat change during charge and discharge cycles.

Fire suppression system mandates vary from one chemistry to another. While smaller data centers will not realize a significant cost delta for battery room fire suppression systems, this is not true for larger facilities. Changing from one chemistry to another may require supplemental or a complete change in fire suppression agents and systems. In some larger facilities, this may render battery chemistry change cost prohibitive.

Fire suppression changes in a live environment are complex at best. Understanding variances between chemistries will allow new facilities to build solutions that can support or be expanded to support multiple constructions with minor upgrades. Training staff and security to monitor battery rooms should be part of any implementation. The battery manufacturers supply fire suppression specifics in compliance with and enforced via codes. It is always advisable to contact local AHJ (authorities having jurisdiction) with questions about codes, as local codes can be more stringent than national codes.

4. Chemistry and Form Factors

As mentioned above, different chemistries fit in different form factors. Batteries have various design size specifications, footprints, and connect in multiple manners. Some battery design features have distinct advantages, not just from one battery type to another. However, even between manufacturers of the same kind of battery, some style features make installation, size demands, and maintenance easier. Nuances between one battery and another will likely impact preferences.

Reconfiguring a battery room for new battery types can be an expensive undertaking. Building a room suitable for larger form factor batteries on day one is far simpler and less costly than trying to stretch a constructed room. It pays to do some front-end engineering to determine how various form factors fit within the space. This simple exercise provides an adaptable room. If a battery room doesn’t require HVAC on day one, space for ducts, returns, and other supporting systems should be considered. The best designs accommodate these areas by leaving these spaces free of obstructions. This practice saves retrofit costs.

5. Day Two Factors

Chemistry considerations are a combination of preference and the room conditions outlined above. All batteries and any battery management system in use requires routine maintenance, updates, and monitoring. Every time someone interfaces with a battery system, human costs contribute to the overall battery system cost. These costs are unavoidable. In a recent study from Uptime Institute, battery failures contributed to roughly 40% of UPS breakdowns within the data center.

Operating ranges and replacement schedules for various battery chemistries

The chart above shows the temperature variances between the different battery constructions. All major data center systems require routine maintenance. Some organizations opt to find battery technologies with the same lifecycle and maintenance requirements as HVAC, chillers, UPS, and other systems.

Organizing these activities creates one outage period for preventative maintenance tasks and component replacements. Every preventative maintenance window introduces risk. The fewer outage windows, the lower the risk. Companies that practice consolidated down windows have enhanced testing capabilities by looping in interfaces between systems with individual system testing.

Summary

In summation, the more we know about various battery sizes, discharge times, lifecycles, and other factors, the easier it is to design a room that doesn’t force a decision towards a single chemistry or manufacturer. In times when capacity increases, the ability to use battery design features to gain space and capacity saves costs, downtime, and capital improvement projects.

Simple features like front mounted terminals instead of top mount saves on clearances and rack height requirements. Nimbleness in design is helpful in the long run by providing multiple options across the entire battery supply chain. For assistance selecting your batteries and designing room requirements, contact your C&D representative.

Author & Data Center Expert Carrie Goetz

Carrie Goetz is Principal/CTO of StrategITcom, and the Amazon bestselling author of “Jumpstart Your Career in Data Centers Featuring Careers for Women, Trades, and Vets in Tech and Data Centers.” Carrie personifies over 40 years of global experience designing, running, and auditing data centers, IT departments, and intelligent buildings.

Among her accolades:

• 2023 Inaugural Lifetime Achievement Award AFCOM/Data Center World

• 2023 BICSI ICT Woman of the Year

• 2022 and 2023 Top 25 Women in Technology by Mission Critical

• 30 Top Most Influential Women in Tech 2021 by CIO Outlook

• Top 10 Most Influential Women in Technology 2020 by Analytics Insight

• Network Computing Inspiration Award finalist 2020

• IMason’s IM100

• 2020 Comptia Women in Leadership Spotlight Finalist.

Carrie is a fractional CTO for multiple companies. She is an international keynote speaker published in 69 countries in over 250 publications. She holds an honorary doctorate in Mission Critical Operations, RCDD/NTS, PSP, CNID, CDCP, CSM-Agile, and AWS CCP and is a Master Infrastructure Mason with 40+ certifications throughout her career.

Carrie served on the WIMCO national education committee and is a long-time participant in the 7x24 Exchange, AFCOM and Data Center Institute board of advisors, Mission Critical Advisory Board, Women in Data Centers, CNet Technical Curriculum Advisory Board, and NEDAS Advisory Board. She is a member of BICSI, Women in BICSI, and an Education committee member, as well as a member of Women Leading Technology Sorority.

Carrie champions STEM education through outreach projects and her podcast series. She holds two patents.