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September 3, 2018 | Rob Hirschberg

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What are the Popular Types of Rechargeable Battery Chemistries?

The most popular types of rechargeable battery chemistries include Lead-Acid, Nickel-Cadmium (NiCd), Nickel-Metal Hydride (NiMH), and Lithium ion (Li-on). Here are descriptions of the advantages and disadvantages of each chemistry.


  • Inexpensive

  • High/low drain, moderate energy density

  • Can withstand very High discharge rates with virtually no loss of capacity

  • Moderate rate of self discharge

  • Reputed to suffer from memory effect

  • Environmental hazard due to Cadmium


  • Moderately expensive

  • Moderate energy density

  • Moderate rate of self-discharge

  • Does not suffer from memory effect

  • Environmental hazard due to Lead

Nickel-Metal Hydride

  • Cheap

  • Not usable in higher drain devices

  • Traditional chemistry has high energy density

  • High rate of self-discharge

Lithium Ion

  • Very expensive

  • Very high energy density

  • Very low rate of self discharge

  • Volatile

What are Flooded Acid Batteries?

Flooded lead-acid batteries come in a wide variety of shapes and sizes due to their widespread usage in many industries and applications. They’re the most commonly used batteries on the reserve power (standby) market today because they are reliable and robust against harsh environments. Flooded batteries are 100 percent recyclable.

Flooded batteries do not recombine the hydrogen and oxygen gases to water internally as seen with VRLA batteries; instead, these gases are vented externally. Therefore, ventilation must be considered and properly sized to eliminate the hydrogen gases from the battery area.

Flooded batteries require more maintenance than VRLA batteries. Distilled or deionized water has to be routinely replenished to make up for the lost moisture (hydrogen and oxygen).

What are the Most Common Uses for Flooded Acid Batteries?

Flooded lead-acid batteries are utilized in automobiles, forklifts, uninterruptible power supply (UPS), switchgear, telecommunications, emergency lighting and other applications.

What are Lithium Ion Batteries?

Lithium ion batteries have a very high density compared to other battery technologies today. This means they are suitable for applications that need a high amount of power. Its electrochemistry uses lithium ions as a main component. Lithium ion batteries are low maintenance and don’t require scheduled cycling to increase the battery’s lifespan.

Lithium is the lightest of all metals. It has the greatest electrochemical potential and delivers the highest specific energy per weight. Lithium ion batteries have high nominal cell voltage of 3.60V. Additionally, lithium ion batteries do not suffer from memory effects and their self-discharge rate is less than half that of nickel-based systems. Benefits of Lithium Ion batteries include very high energy density, very light weight, no memory effects, slow self-discharge, low maintenance, and no gassing.

What are the Most Common Uses for Lithium Ion Batteries?

Common uses for lithium ion batteries are in portable devices including laptops, computers, and cameras. Lithium Ion Batteries are starting to be used in standby and emergency backup applications for the telecommunications, cable, and data center industries. Lithium Ion Batteries are also being used in material handling applications such as electric forklifts, pallet jacks, order pickers, reach trucks, and more.

What are the benefits of Lithium Ion Batteries in the Data Center?

Benefits of Lithium Ion batteries include very high energy density, very light weight, no memory effects, slow self-discharge, low maintenance, and no gassing. Lithium-ion batteries tend to have a lower total cost of ownership (TCO) when compared to other battery technologies. One of the reasons the TCO is lower is that lithium-ion batteries last significantly longer than VRLA batteries. 

What are the disadvantages of Lithium Ion Batteries in the Data Center?

Lithium-ion batteries upfront costs are significantly higher than that of VRLA batteries so the initial investment may seem too large for some data centers.

What is a VRLA Battery?

VRLA (Valve-Regulated Lead-Acid) batteries utilize a one-way, pressure-relief valve system to achieve a “recombinant” technology. This means that the oxygen normally produced on the positive plate is absorbed by the negative plate. This suppresses the production of hydrogen at the negative plate. Water (H2O) is produced instead, retaining the moisture within the battery. VRLA batteries never need watering, and should never be opened as this would expose the battery to excess oxygen from the air.

VRLA technology encompasses both gelled electrolyte / gel batteries and absorbed glass mat / AGM batteries.

What are Common Uses of VRLA Batteries?

VRLA batteries are used in a variety of deep cycle and standby / emergency applications. Deep cycle, deep discharge VRLA battery applications include floor scrubbers, wheelchairs, golf carts, personnel carriers, and certain renewable energy applications. Standby and Emergency Backup applications of VRLA batteries include, UPS (uninterrupted power systems), cable / broadband, emergency lighting, telecom, and renewable energy.

Do VRLA Batteries Require Ventilation?

Ventilation allows the VRLA batteries to release potentially dangerous, built-up gasses while keeping necessary electrolytes. These batteries do so through their one-way, pressure-relief valves, which safely allow the release of gasses and excess pressure while also keeping the batteries properly sealed. Too much oxygen leaking into the battery could quickly contaminate and destroy it. All types of VRLA batteries come with pressure-relief valves.

What is an AGM VRLA Battery?

VRLA-AGM type is a recombinant battery. This means that the oxygen evolved at the positive plates will recombine with the hydrogen generated at negative plates generating water and preventing water loss. Absorbed glass mat (AGM) batteries absorb the electrolyte in a fiber-glass mat separator. This causes them to be spill proof, meaning they don’t leak acid like a flooded design if tipped on their side. The glass mats in AGM batteries are wrapped around the positive plate, which helps prevent damage from vibration and extend cycling. AGM battery designs can have over twice the cycle life of a conventional flooded product in the right application. AGM VRLA batteries cost more than flooded batteries, but are less expensive than gel batteries.

What is a GEL VRLA Battery?

A gel battery has the sulfuric acid electrolyte mixed with silica material to form an immobilized gel.  VRLA - Gel batteries are recombinant type and do not need water and emit less gas than VLA (flooded) type lead-acid batteries.  Gel batteries reduce the electrolyte evaporation and spillage that are common to the VLA (flooded) battery.  Gel batteries are considered to have greater resistance to extreme service temperatures.  Although Gel batteries belong to a VRLA category, their construction is similar to VLA (flooded) batteries except for the gelled electrolyte.  A Gel battery’s separator material is generally not an Absorbent Glass Mat, but microporous plastic material.  VRLA Gel Batteries produce less hydrogen than other battery technologies and are maintenance-free.

What are the advantages of VRLA Batteries in the Data Center?

A benefit of VRLA batteries for UPS Systems and Data Centers is that they are maintenance-free. Maintenance-free VRLA batteries save time and reduce the risk of failure from lack of maintenance.  Additionally, VRLA batteries have a high-rate capacity and high charge efficiency.  VRLA battery technology is often cheaper than other battery technologies.

What are the disadvantages of VRLA Batteries in the Data Center?

While an advantage of VRLA batteries is that they are relatively easy and inexpensive to install, a disadvantage is that should something go wrong, they can be damaged through improper installation. Also, VRLA batteries tend to have a shorter life when compared to Lithium Ion batteries.

What are Renewable Energy Batteries?

Renewable energy batteries collect excess energy and store it for when there is no renewable energy available. Renewable Energy batteries are designed to provide high cycling performance and a safe, uninterrupted supply of energy in renewable energy applications. Renewable energy batteries can be used in multiple applications from small off-grid solar to large scale energy storage for commercial solar and wind farms. Many battery technologies are utilized for renewable energy applications including VRLA-AGM, VRLA-Gel, NiCd, and more.

What are Common Uses for Renewable Energy Batteries?

Renewable energy batteries can be used in multiple applications from small off-grid solar to large scale energy storage for commercial solar and wind farms. There are several types of renewable energy. Solar panels collect solar energy, while wind turbines transform wind into mechanical power. Moving water transforms into renewable energy with dams and hydro plants. Whenever there is an excess of this type of energy, renewable energy batteries can store it for future use.

What are Nickel Cadmium Batteries?

Nickel cadmium batteries are rechargeable batteries with a strong ability to conduct energy. Their strong conducting skills allow them to create very high currents, and they can recharge in a short amount of time. Nickel cadmium batteries need regular maintenance to extend their lifespan. They also have memory effect, so they need full discharge cycles to avoid capacity loss.

Ni-Cd cells have a nominal cell potential of 1.2 volts. Ni-Cd batteries have been around since late 1890s. They use nickel oxide hydroxide and metallic cadmium as electrodes. The electrolyte is alkaline – a solution of potassium hydroxide. The specific gravity of Ni-Cd electrolyte doesn’t change during charge & discharge – it retains the ability to transfer ions between cell plates. Compared with other types of rechargeable cells they offer good cycle life and capacity, good performance at low temperatures, and work well at high discharge rates.

What are Common Uses for Nickel Cadmium Batteries?

Nickel cadmium batteries started off as energy sources for two-way radios, professional video cameras, power tools such as drills, and emergency medical equipment. Now, larger ventilated wet cell and valve regulated Ni-Cd batteries are commonly used in reserve power applications such as emergency lighting, standby power, and UPS as well as other applications.

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