This article explains the advantages and disadvantages of using lithium batteries in data centers.

Because there are no economically viable alternatives to VRLA batteries, design engineers have had to accept their drawbacks. However, the situation with lithium-ion batteries has changed in recent years. Until now, uninterruptible power supply (UPS) systems for data centers were not feasible due to the lack of a reasonable balance between price, energy, capacity, safety, and reliability. But thanks to advancements in electric vehicle technology, this problem has been solved. The first lithium-ion battery-powered UPS system was launched in 2016. Now, all major manufacturers use lithium-ion batteries, and this direction is widely recognized as the most promising option. According to Bloomberg New Energy Finance, by 2025, lithium-ion battery solutions will account for 40% of the UPS market used in data centers.

Advantages and disadvantages of lithium batteries

Sometimes, individual modules, or even individual batteries, need to monitor critical performance parameters such as temperature, voltage, and current. Sometimes, a power cabinet or even the entire system can handle this monitoring process. Monitoring is essential to fully control the charging and discharging process and prevent critical heating and irreversible chemical processes. Lithium-ion batteries offer higher energy density (Wh/kg) and higher power density (W/kg). They possess similar energy storage capacity to lead-acid batteries, but weigh less than one-third as much, an advantage that helps reduce the overall system weight by 60-80%.

In recent years, data centers have prioritized increasing their power density due to space constraints and the need for higher operational efficiency. Optimizing available space has become one of the most important tasks for data center owners. Compact lithium-ion batteries can reduce the footprint of uninterruptible power supply (UPS) systems by 50-80%. These batteries charge faster and have a lower self-discharge rate, playing a crucial role during frequent operational interruptions. When idle, lithium-ion batteries lose approximately 1-2% of their charge per month. Their most significant advantage is their long lifespan. Lead-acid batteries have a very short lifespan of only 3 to 6 years, while lithium-ion batteries can last for approximately 10 years. Depending on the chemistry, technology, and temperature, lithium-ion batteries can achieve up to 5,000 charge cycles and require no maintenance, while lead-acid batteries average only 700 charge cycles.

The total cost of ownership (TCO) for lithium-ion batteries is 10 years (the average lifespan of a data center UPS), which is 39% lower than that of lead-acid batteries. While this is an optimistic estimate, it still guarantees at least a 10% saving. The only significant drawback of lithium-ion batteries is the significantly higher initial investment. This is why large data centers have long been pioneers in adopting this new solution. The primary purpose of this facility is to reduce the TCO, rather than short-term profits, even in which case the accumulated cost savings are still considerable. Furthermore, the smaller battery size allows for more efficient use of available space, while reliable monitoring systems ensure superior security and stable performance. Lithium-ion batteries can operate at higher temperatures than VRLA without capacity loss and reduce the load on cooling systems. Of course, there are even single-phase UPS systems equipped with lithium-ion batteries. Application models range from the largest data centers to industrial applications, and finally to small server rooms or even individual racks.

Easy to replace

The most important question that all customers will ultimately ask themselves is: Is now the right time to upgrade their uninterruptible power supply (UPS) system to lithium batteries ? To answer this, the first consideration is the availability of the technology's capacity. New batteries are not compatible with all UPS models, which may require significant hardware and embedded software upgrades. Even at the same nominal voltage, battery charging and discharging characteristics can differ.

In data centers, the typical lifespan of a UPS system is 10-15 years. Lead-acid batteries last 3-6 years, while lithium batteries can last up to 10 years or even longer. Replacing a large number of lead-acid batteries in the early stages of a UPS system's lifespan (before 5 years) demonstrates its effectiveness. However, after switching to lithium batteries, they may still be usable until the end of the UPS system's lifespan. If your UPS system is nearing the middle of its lifespan, the battery lifespan may be even longer, so replacing the batteries in most cases is pointless. At the end of its lifespan, you should consider replacing your entire UPS system with a brand-new lithium battery solution. However, even for older UPS systems, installing expensive batteries remains convenient. You should consider their decreasing price and the ratio of maintenance costs to the cost of a complete replacement.

Forecast and Outlook

While lithium-ion battery-powered UPS systems continue to reduce operating costs and total cost of ownership, most customers still opt for the time-tested VRLA solutions. This can be explained primarily by the fact that lithium-ion batteries offer only long-term advantages. However, this does significantly increase capital costs. In any case, customer investment in innovation continues to grow annually and only increases. For large data centers, the savings can be substantial, thus lithium-ion battery-powered systems will gradually become more prevalent in the enterprise sector. Lithium-ion chemistry also continues to advance. New solutions and technologies will emerge over time, while lithium-ion battery prices will further decrease.