Why Are Lithium Batteries Better? Comparing Lithium-Ion To Lead Acid

Many energy storage technologies are available in the stationary power market. However, lead-acid and lithium-ion (Li-ion) batteries are the most commonly used options for powering IT and data center hardware, such as uninterruptible power supplies (UPSs). Lithium-ion UPSs are the better choice for today’s data center. Although more expensive than lead-acid batteries, lithium-ion batteries are considered twice as cost-efficient in the long run due to their longer lifespan and higher efficiency.

How Does a Lead-Acid Battery Work?

A lead-acid battery consists of two electrodes in an electrolyte of sulfuric acid. The positive electrode comprises particles of metallic lead oxide, while the negative electrode is connected to a grid of metallic lead. This type of battery is divided into three categories: sealed, valve-regulated (VRLA), and flooded lead-acid batteries.

VRLA batteries are much safer than conventional “flooded” lead-acid batteries. Flooded batteries require sufficient electrolyte fluid to keep the plates fully submerged, which means you have to fill them regularly with distilled water. They need to remain upright to prevent leakage and require a ventilated environment due to gas created during cycling. Even if proper precautions are taken, acid spillage is possible.

That’s why VRLA batteries were invented. In a VRLA battery, electrolyte loss is significantly reduced because oxygen from the positive plates migrates to the negative plates and is reduced to water. Internal pressure is relieved by venting excess gases via the valve. As a result, VRLA batteries are smaller, require less maintenance, need less ventilation, and can operate in any orientation with little risk of acid leakage.

Valve Regulated Lead-Acid Battery vs. Sealed Lead-Acid Battery

Valve-regulated batteries are technically just sealed batteries that have a valve mechanism allowing for the safe discharge of gas (like hydrogen and oxygen) in the case of excessive internal pressure build-up during charging.

How Does a Lithium-Ion Battery Work?

A lithium-ion (Li-ion) battery comprises cells in which lithium ions travel via an electrolyte from the negative to the positive electrode during discharge and in the opposite direction when charging. Lithium-ion cells use an added lithium compound at the positive electrode and usually graphite at the negative electrode. Various manufacturers use different combinations of chemicals for the positive electrode. The two primary types use lithium iron phosphate (LFP) or nickel, cobalt, and manganese (NCM).

What Is the Difference Between Lead-Acid and Lithium Batteries?

The most notable difference between lead-acid and lithium-ion batteries is that the capacity of a lithium-ion battery is independent of its discharge rate. Lithium-ion batteries also have a higher discharge rate than lead batteries, even at cold temperatures. They deliver a constant amount of power throughout the cycle, while lead-acid batteries start strong and dissipate later.

Lithium-ion batteries have a shorter charge time than lead-acid batteries and perform better at high temperatures. There is no memory effect, which means that lithium-ion batteries do not need to be fully discharged before they are charged again. Li-ion batteries can manage hundreds of charge and discharge cycles with minimum impact on the battery's capacity.

Additionally, lithium-ion batteries have a very high energy density — they can store up to six times the energy of a VRLA battery. As a result, lithium-ion batteries are considerably lighter than VRLA batteries of equivalent capacity. However, with greater energy density comes a greater safety risk should the battery overheat and go into “thermal runaway.” That’s why it’s important to ensure you get best-in-class safety features like a battery management system (BMS) when purchasing lithium-ion batteries.

On top of all this, lithium-ion batteries are considered more environmentally friendly than lead acid. They require fewer raw materials to achieve the same energy storage, and the processing of the materials is less energy-intensive. They can even help companies attain LEED certification.

Why Should You Choose Lithium-Ion Batteries over Lead-Acid?

The properties listed in this table provide a helpful comparison between the two types of batteries. Users must know their requirements before buying.

Lead-Acid vs. Lithium-Ion Battery Comparison

Special Factors to Consider

Any electrical device, including a UPS, can create electromagnetic interference (EMI) in the data center. EMI, which includes radio frequency (RF) interference, can significantly impact the performance of IT equipment. It’s important to employ RF shielding materials to effectively block RF interference to keep your equipment running as expected.

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