Today, selecting the right battery for your data center is not a simple task. There are numerous Valve-Regulated (VRLA) and Flooded Lead Acid batteries from which to choose. Now, with the advancements in lithium-ion technology, lithium batteries are becoming a viable option for many data center UPS, ancillary power backup and switchgear applications.

Lithium-ion batteries do offer several advantages over traditional lead-acid batteries, i.e., weight and lifespan, but VRLA battery systems are still found in a majority of data centers and remain a very practical option. How do you choose which battery is right for you?



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Cost is important, but it isn’t everything

There are plenty of factors you need to consider in determining the right battery type. From weighing the pros and cons of the battery technologies to analyzing the asset life of the system the batteries are to support, you need to carefully evaluate each factor. 

Lead acid batteries have been around for over 100 years and can be found in most data center UPS systems. The two types of batteries, VRLA and Flooded, are both the similar from an internal chemistry perspective, except that Flooded batteries require upright orientation, dedicated ventilation and routine maintenance to check and maintain the deep cycle water level.  From a replacement perspective, Flooded batteries have a longer lifespan but do have higher maintenance costs.

Lead acid battery manufacturers have focused on continuous improvements and have implemented new VRLA battery technologies with higher resistance to thermal runaway and less sensitivity to higher operating temperatures.  

Whereas lead-acid has been around for a long-time, lithium-ion battery technology designed for data center applications is relatively new.  Lithium-ion technology is well suited for data center UPS, ancillary power backup and switchgear applications which typically involved temperature-controlled environments, high power density requirements and installations where lightweight, small footprint and low energy consumption are at a premium.  It has many advantages like longer life and more cycle times but at a higher price point.


All lithium-ion batteries are not created equal 

Lithium-ion batteries do offer several advantages over traditional lead-acid batteries, i.e., weight, lifespan. But all lithium-ion batteries are not the same and differ significantly in their chemical makeup. 

Chemistry plays a major role in the function and performance of lithium-ion batteries. The chemical makeup of the lithium-ion battery affects the performance of key attributes such as power density, energy, safety, temperature and lifespan. Given this, lithium-ion battery designs are typically plotted on radar charts that show independent scales of each attribute. These charts provide a visual display of performance that helps when assessing these various characteristics. 

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System application requirements will determine the most suitable balance of performance and therefore most appropriate lithium-ion chemistry.

For example, the Saft Flex’ion battery system is purpose-built using Lithium Iron Phosphate (LFP) which provides the strongest performance on safety and power density. This lithium-ion technology is well suited for Data Center UPS applications which typically involve temperature-controlled environments, high power density requirements and have available space for battery footprint but are still interested in minimizing footprint.

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When to retrofit in an existing UPS

The age of the UPS system can also help determine whether to replace a battery system with VLRAs or retrofit with lithium-ion batteries. If the UPS system is less than 5 years old, a battery replacement using lithium-ion technology will likely reach end-of-life at about the same time as the UPS. Whereas, if the UPS is 5 to10 years old, lithium-ion batteries will most likely outlive the UPS system, therefore a VRLA replacement might be a better option.


Conclusion

One battery technology is not necessarily better than any other. There are many considerations to weigh when selecting the best battery for your application. Several of these are related to chemistry, while others are related to the system the battery supports.  To make the right choice, you have to decide what factors are most important and weigh the pros and cons of each alternative before making a decision.