Battery chemistries currently available for UPS backup include Lead-Acid, Lithium-ion (Li-ion) and Nickel-Cadmium. There are also non-battery technologies like flywheels and Super-Capacitors.

However, this article focuses on the two types that currently dominate the data centre industry: Lead-Acid, which represent over 90 per cent of the UPS market share, and Li-ion, which is attracting increasing interest due to its purported performance benefits and high visibility through its use in electric vehicles, UPS, Telecom etc. Li-ion is attracting interest through being attributed with performance features superior to traditional Lead-Acid VRLA batteries, which are typically either gel or absorbent glass mat (AGM) designs. Compared to traditional VRLA equivalents, Li-ion offers a high cycle life, together with a significant size and weight reduction. Li-ion batteries also have high charge efficiency, with excellent partial state of charge tolerance – in fact, partial charge is preferred for long cycle life and operation in float conditions at full state of charge is avoided. The self-discharge rate of Li-ion is also low, which results in prolonged shelf life when in storage. Finally, it has well high and low temperature performance, and no gas emissions.

Let’s briefly review the benefits of using lithium iron phosphate batteries for UPS applications.

First, we must consider the reasons lithium batteries are a natural fit for next generation power backup systems where system operation, availability and space constraints must be balanced with cost.

In general, lithium batteries have a higher energy density, resulting in a 50% to 75% reduction in footprint that can be utilized to add servers and other IT equipment in the case of data center’s UPS application or to reduce facility construction costs. Along with their smaller footprint, lithium-battery systems bring a significant reduction in weight, which can also be a major factor into the telecom BTS site design costs.

Lithium iron phosphate batteries also have longer lifespan, which saves on replacement costs and operational disruptions.

KEY CHARACTERISTIC	LEAD-ACID (VRLA)	LITHIUM IRON PHOSPHATE
Energy Density	Low	High
Lifespan	Less	Long
Weight	High	Low
Footprint Required	Large	Small-Moderate
Recharge	Slow	Fast
Maintenance Cost	Moderate	Low
Cooling Required	High	Low-Moderate
Battery Management	External needed	Built-In
Battery Monitoring	Optional	Highly Recommended

Lithium iron phosphate batteries can operate at higher temperatures without sacrificing battery life. VRLA batteries lose 50% of battery life for every 10°C of heat rise. Extended life and lower maintenance reduce operational costs, lowering the total cost of ownership (TCO) over VRLA batteries.

Simply put, these batteries are smaller, lighter, longer-lasting and more efficient than your traditional VRLA UPS batteries.