Types of UPS Batteries: The Heart of Your UPS System
Your UPS system is one of the most crucial components in your critical power infrastructure, and for your UPS, the batteries are really the “heart” of that system. Even though your UPS needs that heart, batteries are often neglected. In the next few weeks we’ll go into more detail about each type of battery that can be used in a UPS system and the advantages and disadvantages for each type. It should be noted though, that regardless of the batteries you choose, all batteries decrease in their ability to store and deliver power over time. However, if you follow all guidelines for storage, maintenance and usage, eventually you will still have to replace UPS batteries on a schedule to get the best usage out of your UPS.
There are three main types of UPS batteries.
- Valve Regulated Lead Acid (VRLA)
- Flooded Cell or VLA batteries
- Lithium Ion batteries.
Valve Regulated Lead Acid (VRLA)
This battery type is the type most often found in UPS units today. The term valve regulated relates to the way gas is released from the battery. If the gas pressure becomes too great in the battery, a valve will vent when the gas reaches a certain pressure. Water can’t be added to VRLA batteries, so factors that increase evaporation, like ambient temperature and heat from charging current, reduces battery life. VRLA typically have less up-front costs than flooded cell batteries, but they also have a shorter life, about 5 years total. This type of battery also requires less maintenance then the flooded cell battery does. The best environment for VRLA batteries is to be stored at room temperature in a dry, climate controlled room.
Flooded, or Wet Cell
Flooded cell, or VLA batteries, are very reliable, and typically have a 20 year life. The battery is composed of thick, lead-based plates flooded with electrolyte acid. There are more safety measures needed with this type of battery than with VRLA, and they need their own separate battery room due to potential chemical hazards they pose. They also typically have higher upfront costs than other batteries. Due to the capital cost and the hazards they pose, VLA batteries have become less popular to use in recent years. They also have additional maintenance requirements that need to be adhered to, such as being filled only with distilled water, keeping water levels filled correctly and often requiring equalization.
Lithium Ion batteries have matured significantly in their design for a number of uses, such as being used in electric vehicles and, of course, UPS storage. These batteries have the advantage of being both small in size and light weight, and they also have built in battery management and not just monitoring. This manages charge current, voltage, and cell voltage balance, and also adjusts for issues of over temperature by disconnecting single batteries or strings if temperatures rise above safe levels. The battery management can send alarms on the UPS and also notify the battery cabinet monitor. Lithium Ion batteries also have high charge and discharge times, as well as high recharge times. This makes them attractive in non-traditional UPS applications, such as grid sharing and industrial process control support. These batteries also have lower operational expense costs, as they need less frequent replacement, and can operate at higher ambient temperatures. The down side to this type of battery is they can be very expensive compared to the other two options. They typically cost about 40% more to manufacture than Nickel cadmium cells.