Lithium-Ion Batteries and the Data Center
2016 brought with it bad press for the lithium ion battery industry. The industry was tarnished by two high profile and well publicized failures that again questioned the battery technology’s safety. First there were the hover boards. After failures were reported leading up to the 2015 holiday season, 500,000 hover boards were eventually recalled in July of 2016. Next there was the Samsung Galaxy Note 7. Phones were exploding in pockets and devices were confiscated at airports as Samsung struggled to find a solution. Ultimately, Samsung recalled and canceled their flagship product as rivals Apple and Google looked to capitalize.
These high profile lithium ion battery failures were just the latest, coming on the heels of battery failures grounding the Boeing 787 Dreamliner fleet or the occasional laptop battery failure, among others. At the same time the battery technology has become ubiquitous, used in everything from consumer electronics and power tools, to medical devices and electric vehicles. Lithium-Ion has become the battery of choice for many applications due to its high specific energy (energy per weight and size), high capacity, long cycle life and extended shelf life. However, despite these advantages, Lithium Ion batteries have not replaced the lead-acid battery as the preferred energy storage system for Uninterruptible Power System (UPS) applications. The reason for this is its high initial cost, concerns about its relative safety compared to the alternatives and a shortage of standards, codes and regulations for central battery plant applications.
Types of Lithium Ion Batteries
The term lithium ion (Li-ion) is a catch-all for a half dozen or more different types of batteries containing the lithium ion. The earliest batteries using lithium were found to be too unstable, especially during charge operation. “The inherent instability of lithium metal, shifted research to a non-metallic solution using lithium ions.” Born out of this research was Sony’s commercialized battery using lithium ions in 1991. “Although lower in specific energy than lithium-metal, Li-ion is safer, provided the voltage and currents limits are being respected.” (Source: Battery University). Since then researchers have worked with different chemistries to develop batteries with varying performance characteristics for different applications. These battery types are summarized in the table below (Source: Battery University, BU-216: Summary Table of Lithium-based Batteries)
Cost, Controls and Safety
The types of Li-Ion batteries used in UPS applications are Lithium Iron Phosphate (LFP) and Lithium Titanate (LTO). The cost of Li-Ion batteries are still 1.5 to 3 times the cost of VRLAs for UPS applications, however this cost difference has been trending down (Source: Schneider Electric: FAQ for Using Lithium-Ion Batteries with a UPS, Patrick Donovan, Martin Zacho). Vertiv (formerly Emerson Network Power) sites a similar cost premium for their Li-Ion battery UPS. While the costs continue to decrease, manufacturers hope to sell the advantages of Li-Ion batteries, including a higher power density, which means less space for the same amount of power, a longer life, lower weight and higher ambient operating temperatures. Despite the higher cost compared to traditional lead-acid batteries, manufacturers say that Li-Ion should prove to have a lower total cost of ownership because it will last longer and take up less space.
The Li-Ion battery cost can be attributed in part to its manufacturing process and integral battery monitoring and protection. As it turns out, both of these factors are related to the overall safety of Li-Ion batteries. “Battery manufacturers strive to minimize the presence of microscopic metal particles; however, complex assembly techniques make the elimination of all metallic dust a challenge.” These particles can result in internal shorts, leading to fires or explosions. Newer, higher performing batteries with ever thinner separators are more susceptible to impurities. A high standard of quality control from a reputable manufacturer is of utmost importance. Generally, the technology is safe and improving but, the sheer number of batteries, which can be used in all kinds of products and applications, means a small percentage are sometimes sourced from low cost providers lacking adequate quality control. Even reputable manufactures can have a “bad batch” that may lead to failure. To manage quality, “most major Li-ion cell manufacturer x-ray every single cell as part of automated quality control [while] software examines anomalies” but such careful manufacturing practices come at a cost. (Source: Battery University, BU-304a Safety Concerns with Li-ion).
In addition to quality manufacturing processes, Li-ion batteries require internal and external protections for safe operation. Internal safeguards include built in current surge protection, pressure sensitive circuit interrupters, safety vents and temperature sensitive ion-flow inhibitors. External protection includes overvoltage and overcurrent protection. The larger the battery string the more complex, and costly, the protection circuit becomes. While the external protection is a safeguard from overcharging or excessive discharge it does not protect against an internal short due to microscopic particles as mentioned above.
The manufacturing process and integral protection and controls of Li-Ion batteries are considerably more complex than lead-acid batteries. These complexities contribute to the overall cost premium of Li-Ion batteries. Using the electric vehicle Li-ion battery as a barometer, it’s not unreasonable to expect that these costs will decrease over time as manufacturers leverage economies of scale and improve their processes to achieve higher quality and overall safety.
Li-Ion Batteries and the Data Center
Despite the high initial cost or safety concerns, Li-Ion are finding their way into data centers. While some UPS manufacturers are reluctant to publicly embrace the technology, two manufacturers, Schneider and Vertiv, offer a Li-Ion battery option for their UPSs. Vertiv says the Samsung Li-Ion battery they use has been successfully applied to large UPS systems in Asia for several years now. Adoption by U.S. customers is still slow in coming but Vertiv announced their first large scale deployment last August at a Forsythe data center in Elk Grove Village, Ill. In fact, Forsythe has reportedly been using the beta Vertiv Li-Ion UPS battery on one side of a redundant 300kVA UPS system since 2015 (Source: Data Center Frontier, Lithium-Ion UPS System Comes to the Data Center, Rich Miller).
In other news, cloud scale data center builder/operator Microsoft has deployed lithium-ion batteries made for portable power tools in their open compute server power supplies. Each server gets a Li-Ion battery pack that Microsoft calls Local Energy Storage (LES), replacing a central UPS/battery system with a distributed architecture. Cloud operators can do things a little different than the typical enterprise or Co-Lo data center but nonetheless it demonstrates the growing awareness and acceptance of Li-Ion battery technology.
Li-Ion batteries are being used by early adopters who are forging ahead before standards, codes and guideline are established. Battery experts we trust have a wait and see attitude and want to see more developments in battery string protection, control and monitoring. With central code authorities having yet to weigh in, deployments must be approved by local jurisdictions. To date, there is very little written about Li-Ion stored energy applications in industry, let alone in data centers. In fact, standards from NFPA and FM Global only address Li-Ion warehouse storage facilities and their adequate fire protection. However, the next code cycles will likely address Li-Ion UPS applications if their costs continue to decrease, fueling customer demand. In the risk adverse environment of data centers, we recommend watching the developments closely, keeping tabs on new codes and standards and reviewing it with your insurance underwriter before acting. The technology does look promising but we are waiting for a larger install base before giving it our full support.