Lithium-ion Batteries For UPS Systems

Many of the latest generations of UPS batteries have efficiencies of up to 97%. In contrast, however, the energy storage of UPS systems has remained virtually unchanged over the last 30 years. For the most part, the same lead-acid or VRLA batteries are still used as emergency power storage for uninterruptible power supplies. These function perfectly, too. So far, the batteries used have done their job well: so why should you consider UPS backup battery replacement with lithium-ion batteries?

What is the UPS system？

Uninterruptible power supply or UPS system, it is a process of AC-DC (commonly known as rectification) and then DC-AC (commonly known as inverter). When the city power exists, the rectifier rectifies to charge the battery and at the same time provides DC voltage to the inverter When the mains power fails, the battery pack directly provides direct current (DC) voltage to the inverter to output standard AC power. Depending on the application area, they can be as small as a book or as large as an entire room, uninterruptible power supplies are essential for mission-critical environments! [Uninterruptible Power Supply Guide]

Why should you consider UPS backup battery replacement with lithium-ion batteries?

>> Reduced Operating Costs and CO2 Emissions

VRLA batteries require an ambient temperature of 20°C for optimum use and life. Maintaining or establishing this temperature can be a challenge. For every 10°C above the recommended temperature, the life of a valve-regulated lead-acid battery is cut in half. Lithium-ion batteries are not as sensitive to heat or cold. In this context, this type of energy storage becomes particularly interesting for data centres.

Compared to lead batteries, lithium-ion batteries have more moderate ambient temperature requirements. Elevated temperatures have a much smaller impact on the lifetime of lithium-ion batteries. This has an impact on the cost structure if energy storage can be used for longer periods of time. For example, data centres could be completely free of air conditioning or have it reduced to a certain extent. This not only reduces power consumption but also costs, as well as reduces CO2 emissions.

Higher operating temperatures do not pose a challenge for lithium-ion batteries, which is why they are a good alternative to conventional VRLA batteries. In contrast, lithium-ion batteries can operate at temperatures up to 20°C and above or below 30°C without loss of capacity. An average data centre operates at temperatures of 25°C and above. Since UPS systems can operate without problems in temperatures up to 40°C, this can make air conditioning unnecessary in many European countries (where the air temperature is between 20 and 22°C). This alone can significantly reduce the operating costs of a data centre and at the same time reduce CO2 emissions through lower power consumption.

>> Space-saving with Lithium-ion Batteries

Space-saving is another advantage of lithium-ion batteries. For most data centres, lack of space is not an easy problem to accommodate lead-acid batteries. However, when it comes to expansion, space can become a scarce commodity. Lithium-ion batteries require only a third of the volume of an equivalent VRLA battery block and weigh only a quarter of its weight. This space-saving offers a decisive advantage, especially for small, regional edge data centres.

>> Longer Service Life Offsets Acquisition Costs

Why didn't people switch to lithium-ion batteries a long time ago, when their advantages outweighed their disadvantages? Until now, the high acquisition costs explained the change. However, thanks to further developments, particularly in the automotive industry, prices have fallen significantly in recent years. Even today, lithium-ion batteries are still more expensive than lead-acid batteries. However, the investment pays off again when the doubled service life and lower energy costs are taken into account. By contrast, even lead-acid batteries with a design life of 10 years have to be replaced every seven to eight years. Lithium-ion batteries, on the other hand, have a design life of 13 to 15 years. Contrary to the initial higher investment, this change is worth it in the long run.

>> The Safety of Lithium-ion Technology

In addition to the cost of acquisition, safety issues have also been a reason against conversion in the past. At the same time, however, technology is advancing. The management and inspection of lithium-ion batteries are covered by the IEC 62619 standard. This was specifically designed for control systems for industrial batteries and was introduced more than two years ago.

Lithium-ion batteries are more susceptible to the effects of high temperatures due to overcharging and oxygen being released during the charging process. Therefore, a battery management system (BMS) is required according to IEC 62619. This prevents the organic liquid electrolyte from becoming too hot due to overcharging or undercharging. When the safe voltage range is exceeded, the BMS issues a warning and a compatible UPS system can react. If this is ignored, a second level of warning is connected to a circuit breaker to prevent the battery from being further charged or discharged. This dual level of protection must be implemented and tested to meet the requirements of the IEC 62619 standard.

Every battery, including lead-acid batteries, is potentially dangerous. However, proper handling can minimise the risk. Current lithium-ion technologies are now so safe that they are used in data centres and other critical infrastructure facilities.

>> Types of Lithium-ion Batteries

Lithium-ion batteries are available in different types of materials, the most common being.

• NCM

• LCO

• LMO

• LFP

The material used must be highly stable in any aggregated state. The safest and most reliable is LFP because it does not release oxygen when it decomposes, which greatly reduces the risk of explosion.

What Will The Future Bring?

There is no doubt that in the near future lithium-ion batteries will be used more and more in UPS systems. However, the basis must be compatibility between UPS systems and lithium-ion technology.

Currently, UPS systems in developing countries such as Africa or the Middle East rely mainly on lithium-ion technology. The reliability of the main grid is lower than in countries in Central Europe. Due to the unreliability of the main grid, power outages are almost a daily occurrence. In these cases, UPS systems must intervene several times a day to provide an uninterrupted power supply. The increased use does not put additional pressure on the emergency power storage of lithium-ion batteries. This type of battery is better able to handle continuous on/off cycles than VRLA technology.