Uninterruptible Power Supply (UPS) systems give backup power during outages. They are vital in data centers, hospitals, offices, and homes with critical electronics. Every UPS relies on a battery to store and deliver energy when the main power fails. You need to understand the battery types to choose the right system for your needs, budget, and environment. In this post, we’ll explore three main types of UPS batteries to help you decide which one fits best.
Lead-Acid UPS Batteries
Lead-Acid batteries are known for their reliability when used in a UPS, and that alone has made them a popular choice of UPS battery for quite a while. They are also the most economical choice when weight is not a concern, like in large power applications. Their cost-effectiveness combines with high tolerance and low internal impedance for a smart battery choice.
Lead-Acid batteries come in two different types:
Valve Regulated (VRLA)
This type, also called Sealed Lead-Acid (SLA), appears most often in modern UPS systems. Manufacturers typically design them to last 5 or 10 years. For best performance, store them in a dry, climate-controlled room at 20–25°C.
VRLA batteries are sealed inside a case which has a valve that vents to release gas if internal pressure gets too much, hence the term “valve regulated”.
These batteries are sealed. You can mount them vertically or horizontally. This makes them suitable for battery compartments, rackmount trays, or external cabinets. They require no direct maintenance. You don’t need to top them up with water.
Open Vented (VLA)
Also known as Flooded, these batteries have plates that are flooded with electrolyte acid. They have a long design life (up to 20 years) and are typically used in large installations needing a high ampere-hour (Ah) rating.
Because they aren’t sealed, any hydrogen generated escapes directly into the environment. This means installations using VLA batteries require more powerful ventilation systems and can pose a greater safety hazard.
A VRLA UPS battery uses two main types of electrolyte composition. The first is Absorbed Glass Mat (AGM), which holds the electrolyte in a porous microfiber glass separator. The second is Gel, which combines sulfuric acid and silica to form a thick, gel-like substance.
They can’t be used in cabinets or racks, which means they aren’t suitable for office environments or data centre installations. VLA batteries are also more expensive than the VRLA alternative.
VRLA UPS batteries use two main types of electrolyte composition. The first is Absorbed Glass Mat (AGM), which holds the electrolyte in a porous microfiber glass separator. The second is Gel, which combines sulfuric acid with silica to form a thick, gel-like substance.
AGM technology is the norm for UPS batteries because of its lower cost, lower internal resistance and higher charge/discharge rates.
By comparison, Gel-filled VRLA has a higher internal resistance, which makes it less suitable for high-rate discharging common with UPS applications. It does offer advantages in terms of a wider operating temperature range (-40°C to +55°C) and extended design life.
Nickel-Cadmium UPS Batteries
Formerly a popular choice of telecoms installations, Nickel-Cadmium (NiCd) batteries are still used in locations with very high ambient temperatures. Additionally, they are able to handle a wide ambient temperature range of -20°C to +40°C. They offer the advantage of a 20 year design life, a long life cycle, and tolerance of deep discharges.
But they are more expensive than VRLAs, and the toxic materials with which they are made makes them hard to dispose of. Many countries have outlawed or severely restricted the manufacture and usage of Nickel-Cadmium batteries for this reason.
Lithium-Ion UPS Batteries
Lithium-Ion (Li-Ion) batteries power many electronic devices like laptops and smartphones. They also play a key role in the rise of electric vehicles. Recently, more people are using them in uninterruptible power supplies. These batteries also store energy from renewable sources like wind and solar power.
The advantages of Li-Ion include higher reliability than traditional VRLA/SLA batteries because of built-in battery monitoring and management systems, which check every individual cell for any change in performance.
Another benefit of Lithium-Ion UPS batteries is that they are significantly smaller and lighter because of their significantly higher power density. They also have faster charge times, longer cycles, and at least double the service life compared to VRLA/SLA.
Despite the cost of Li-Ion UPS batteries decreasing over recent years, it is still a far more expensive initial choice than the other options.
However, the longer service life does balance out the higher upfront capital costs. Li-Ion generates less heat and can operate at higher temperatures, meaning they don’t require as much air conditioning, which can reduce cooling costs.
Conclusion
Choosing the right UPS battery depends on factors like application size, budget, maintenance capabilities, and environmental conditions. While VRLA batteries are common for general use, lithium-ion offers a long-term, efficient solution for critical operations. For large-scale or industrial needs, flooded lead-acid or NiCd batteries may be more appropriate.
Evaluate your power needs, space constraints, and maintenance capabilities before selecting a UPS battery type to ensure continuous and reliable power protection.
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