A ton of money and electrical energy is invested in UPSs by datacentre operators to keep their sensitive ICT equipment safe from blackouts and power disturbances. UPSs work by storing power taken from an energy source when the mains supply is good.
This power is delivered back to the critical load through UPS in case the mains either fails or goes over acceptable limits. Sometimes, these are used to provide sustained power to a system to keep it operational for an extended period of time. Typically, a UPS is needed to provide short-term support to either allow for proper and safe shutdown of critical load, or till another power source such as a generators comes online. A good idea for any company is to look into ups battery replacement to ensure all angles of security are protected.
The initial purchase price of VRLA batteries is lower as they are just half the price of corresponding lithium ion batteries. VRLA batteries are better than open vented type batteries as these are safer and environmentally friendly, and also require less routine maintenance.
One of their limitations is the increase in impedance over a period of time which reduces power capacity. The impedance can also increase abruptly in case of overcharging. This is why, it is important to regularly check these batteries for failing cells or a fixed battery monitoring system should be installed for regular checking.
The performance of these batteries vary with temperature and it is important to keep them in a temperature controlled environment. If these batteries are kept operational at a temperature that is substantially above the recommended levels of 20°C, it will lead to irreversible damage. Its life expectancy goes down by half with each increase of 10 C in the average operating temperature.
On the other hand, lower temperatures do not have any sizeable impact on service life but it negatively affects performance. As far as the service life of VRLA battery is concerned, it depends a lot on the ambient temperature and number of discharge cycles. Consequently, a VRLA battery with a 5 year design life may last anywhere from 3 to 4 years whereas a 10 year battery might work for 7 to 8 years.
Lithium Ion Batteries
Lithium ion batteries offer a number of advantages over VRLA batteries. These have a longer service life and you can expect them to keep performing for 12 to 15 years but they are also expensive. They also have an advantage in terms of size and weight as they are up to 60% lighter and 70% smaller, and can keep performing reliably at much higher temperatures as compared to VRLA batteries.
The lithium-ion batteries that are specifically created for UPS applications prioritise safety over power density which is different from the lithium ion batteries meant for mobile phones as those batteries might cause combustion problems. This extra emphasis on safety means that the lithium ion batteries can be packed inside a UPS enclosure without the need to have a separate battery room with environmental conditioning. Regular maintenance is still needed for lithium ion batteries but the procedures are simpler and maintenance-free intervals are longer as compared to VRLA batteries.
The improved performance of lithium-ion batteries is due to their chemistry as the chemical processes in these batteries are fewer in number and much simpler as compared to VRLA batteries. When a lead acid cell battery is charged or discharged, it leads to dissolution of the active materials which are then rebuilt in the electrode structures. In this chemical process, the sulphuric acid electrolyte is also involved and as a result of the chemical reaction, water gets decomposed to oxygen and hydrogen. There are a lot of side reactions that lead to wastage of energy.
There is no denying that VRLA batteries will remain popular as they have proven reliable and the initial purchase price is low. However, lithium-ion batteries have emerged as a competitive TCO offering with reduced maintenance and longer life.
These also take less space which is another incentive for data centre owners. Also, no specially designed temperature maintained rooms are required for Li-ion batteries. A further drop in prices can provide further impetus to lithium-ion batteries. There is another advantage of lithium-ion UPS operations being safer as compared to VRLA batteries due to prioritising safety over maximising power density.