How data center operators choose the right battery

Date:Mar 29, 2019

Lead-acid batteries

Today, lead-acid batteries are still popular because of their proven track record of reliability. They are the most economical choice for large-scale applications, with excellent performance and efficiency, low internal impedance, high tolerance to improper handling, and high procurement costs.

The electrolyte used in the lead-acid battery includes water and sulfuric acid, and a plate composed of sponge lead (negative electrode) and lead oxide (anode). The main lead-acid battery types are valve-regulated lead-acid batteries (VRLA), also known as "sealed" or "maintenance-free" batteries.

Valve-regulated lead-acid batteries (VRLA) are sealed, but have a valve that discharges internally accumulated gas into the atmosphere. Normal maintenance is usually not required and no water is added because the hydrogen released during charging will recombine with oxygen internally to form water. There are two main types of valve-regulated lead-acid batteries (VRLA) on the market, the difference being the electrolyte mixture: the electrolyte of the glass microfiber separator (AGM) battery is kept in the highly porous microfiber glass separator; and the electrolyte of the gel battery The gel consists of a mixture of sulfuric acid and silica.

UPS power supplies typically use AGM-type hermetic valve-regulated lead-acid batteries (VRLA) because of its low internal resistance, high specific power and efficiency, low self-discharge rate, and low procurement costs. Glass microfiber separator (AGM) batteries charge faster and provide high currents for short periods of time.

The plates of the flooded lead-acid battery are immersed in an acidic electrolyte. Since there is no seal, the hydrogen generated during operation will be directly discharged into the environment, and the ventilation system must be more powerful than the sealed valve-regulated lead-acid battery (VRLA). In most cases, the battery pack is housed in a dedicated room. Rich liquid lead-acid batteries must be kept upright and require manual filling of the water level.

They have a longer life and higher reliability than sealed valve-regulated lead-acid batteries (VRLA). The lead-acid battery battery compartment must be maintained at a reasonably constant temperature (20-25 ° C) to avoid shortening the service life or even causing damage.

Lithium Ion Battery

In a lithium ion battery, the "cathode" is typically a metal oxide and the anode is typically porous carbon graphite. Both are immersed in a liquid electrolyte made of a lithium salt and an organic solvent.

Lithium-ion batteries can be reduced to six types: lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium manganese cobalt oxide (NMC), lithium iron phosphate (LFP), nickel cobalt alumina ( NCA), lithium titanium oxide (LTO). The choice between these batteries depends on several factors, and accurate comparisons are not possible because many aspects such as mechanical, cell size and active material mixing play an important role in performance.

In data center environments, lithium-ion batteries are becoming an increasingly attractive alternative to lead-acid batteries, where power availability is a top priority and lithium-ion batteries offer higher reliability than lead-acid battery solutions. Sex. Not only is each individual battery itself safer and more stable, but each battery module has an electronic controller that continuously checks for any signs of performance change.

The temperature, current, voltage, and state of charge of each battery are monitored at the cabinet level to provide a clear picture of current battery status and predict future uptime and performance. Lithium-ion batteries can be charged faster than lead-acid batteries, providing more discharge/recharge cycles than lead-acid batteries and providing higher power density and efficiency, especially at high discharge rates. This eliminates over-utilization of the battery while reducing the space required for battery installation. Although the initial purchase price of lead-acid batteries is lower, the life of lithium-ion batteries is at least twice that of lead-acid batteries of the same specification, thus reducing the overall investment cost. It also reduces the labor costs associated with battery disassembly and replacement. Lithium-ion batteries generate less waste heat, which reduces cooling costs and reduces the carbon footprint.

Nickel-cadmium batteries

Nickel-cadmium battery electrodes include nickel hydroxide (positive plate) and cadmium hydroxide (negative plate). Nickel-cadmium batteries have a long working life (up to 20 years) and can handle extreme temperatures (-20 ° C to 40 ° C). They also have a high cycle life and are well tolerated for deep discharges. Other benefits associated with low internal resistance provide high power density and fast charging capability. Nickel-cadmium batteries provide long storage times and are highly protected against improper handling.

However, the cost of nickel-cadmium batteries is much higher than that of conventional sealed valve-regulated lead-acid batteries (VRLA). In addition, since both nickel and cadmium are toxic, the battery handling/recycling process is costly. Nickel-cadmium batteries also need to be serviced by adding water, especially in high cycle applications, or at high charging rates for certain charging methods.

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