backup power batteries and UPS

Backup Power Batteries: What Are The Different Types And When Should They Be Replaced?

The uninterruptible power supply (UPS) is a popular power backup solution which relies on batteries to supply power. Ensure you have continuous power by replacing your batteries when necessary. 

What are the UPS battery types?

When it comes to UPS backup, there are different battery types you will encounter:

1 . Semi Sealed – Lead Calcium Battery

This option of battery has been widely installed in UPS installations. The battery is semi-sealed such that it cannot be filled with electrolyte. It has a specific construction that recycles the gases that return to the cells as electrolyte thus the reference to maintenance free and this prolongs the usable life of the battery. The expected design life of this type of battery is 4 – 5 years. The battery is also fully recyclable.

2. Valve Regulated Lead Acid (VRLA) battery

Most commonly found in UPS backup is the VRLA (also known as the sealed lead-acid or SLA) battery. They are named after the way that gas is released from the battery – valve-regulated. VRLA batteries are a low-maintenance option battery, which has added to their popularity, however, they cannot survive in hot environments as this will reduce the lifespan. This means that, although being low maintenance, these batteries must be housed in a climate-controlled environment which is dry and cool. Anything that increases the rate of evaporation of electrolyte (such as heat from a charging current) will decrease the UPS battery lifespan. The expected design life of these batteries can extend up to 8 – 10 years.

There are two subtypes of VLRA battery, including:

  • Absorbent glass mat (AGM)

This is where the electrolyte is held in woven glass fibre mats, allowing for flexibility of design, improved self-discharge rates, and a wider operational temperature range.

  • Gel Cell

A modern gel cell uses an electrolyte mixture comprised of sulfuric acid mixed with pyrogenic silica resulting in a gel-like substance. Gel cells are tolerant to vibration and are a lower-cost VRLA battery found in smaller UPS systems.

3.Vented Lead Acid (Flooded or Wet Cell) battery

These are an incredibly reliable UPS battery composed of thick, lead-based plates flooded with electrolyte acid. The hazardous chemicals within this backup battery necessitates storage in a separate battery room and they are generally a lot more expensive than VRLA batteries. Storage of VLA batteries also requires proper ventilation with protection against vibration due to the possibility of liquid spillage. These batteries are prone to damage in extreme climates as the water inside can evaporate or freeze. Other maintenance requirements include ensuring distilled water levels are filled correctly and equalisation is maintained. Typical design life can be up to 20 years.

4. Lithium-Ion battery

The latest development in backup power batteries is the introduction of the Lithium-Ion / Iron battery. This requires a built-in battery management system which regulates the charge current, voltage, and cell voltage balance, while also adjusting for issues such as overheating by disconnecting single batteries or strings. The use of these as UPS batteries is not common. The real downside is that these are the most expensive UPS battery option. expected design life can be 15 – 20 years.

When should a UPS battery be replaced?

The battery replacement really depends on the battery type and UPS model you’re using. Some UPS models will conduct regular checks on the battery capacity but, if it doesn’t, you might not know whether the batteries have the capacity to support the connected equipment for the required time. Some UPS units test their batteries every 2 weeks, but this isn’t necessarily a great indicator of the batteries’ capacity. 

Cycle Life of a battery needs to be considered specifically when a battery is in an environment that is likely to have high discharge usage. There are specific batteries and configurations that can be installed to cater for an installation of this nature.

It’s important to replace UPS batteries once they have reached a certain age or you’ll notice a clear reduction in runtime. From the time it is bought, the UPS battery starts losing capacity, slowly at first then gradually picks up the pace until it gets down to approximately 80%, before declining rapidly. The best way to determine your battery capacity is to perform a functional load test rather than relying on the internal battery test of the UPS.

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