Understanding the Limitations of VRLA UPS Batteries for High-Cycle Applications

When it comes to powering critical systems, selecting the right battery technology can mean the difference between seamless operations and unexpected downtime. While VRLA (Valve-Regulated Lead Acid) batteries are a popular choice for UPS systems, their limitations in high-cycle applications often go unnoticed—until performance begins to degrade. Understanding these limitations is of the utmost importance to ensure that your UPS system operates efficiently and reliably all the time.

More about VRLA Batteries

A UPS battery, specifically a VRLA (Valve-Regulated Lead Acid) battery, is engineered for occasional high-rate, high-power discharges rather than daily cycling. This type of sealed lead-acid battery is typically installed in a float-charge environment, making it unsuitable for any cycling applications. In this blog, we explore the limitations of VRLA UPS batteries in high-cycle scenarios and the long-term impact of daily discharges on battery performance and lifespan.

The Role of VRLA Batteries in UPS Systems

VRLA technology is best suited for a float charge setup, where an occasional full discharge occurs approximately once every six months, maximizing battery life.

Charging Requirements and Partial State of Charge (PSOC) Issues

Any UPS battery needs 72 hours to get to 100% charge. Daily cycling makes it challenging for the battery to reach this level, though most batteries will reach about 90% within 24 hours.

Performing a discharge before the battery reaches 100% charged (known as a Partial State of Charge or PSOC discharge) results in a permanent chemical structure change within the battery. This leads to sulphation of the cell plates, which diminishes performance and results in permanent, irreversible damage that extended charging cannot mitigate.

Impact of Daily Discharging on VRLA Battery Health

Repeated discharging from a PSOC state causes an avalanche effect, where backup time decreases with each additional discharge. As the battery struggles to reach full charge, each discharge cycle further erodes its ability to hold a charge effectively.

Limited Discharge Capacity of VRLA UPS Batteries

A VRLA UPS battery is designed for a limited number of discharges, especially deep discharges (those lasting over 15 to 20 minutes). Frequent deep discharges, like those that happen during multiple daily power outages, draw heavily on the battery’s reserve capacity, accelerating wear to the point it may even need replacement within weeks or months.

When subjected to long or deep discharges, especially at low loads, a VRLA battery will show signs of capacity loss after only 30 to 50 cycles. This capacity loss is due to the fact that a battery is a medium-term consumable product like the fans and capacitors also used in a UPS, and usage dictates service life.

Degradation of Battery Capacity Over Time

Each time a battery is used, it loses some active material from the cell plates. This loss of material reduces the available reaction area for interaction with the acid solution, leading to a gradual and, in some cases, very rapid decline in the battery’s capacity.

The Unsuitability of VRLA Batteries for High-Cycling Applications

Currently, there is no lead technology application for everyday cycling other than lead-carbon batteries, which are only available in limited sizes. There are other options like lithium solutions. Both of these are excessively expensive, with lithium technology not recyclable in Africa and requiring very expensive export in hazardous goods containers when they reach the end of life.  

Some lithium technologies also contain cadmium and selenium. Both are highly toxic substances, adding to the problem of not being recyclable. The majority of these minerals found in the world come out of war-torn central Africa, using child labor, slave labor, and human trafficking, so they also come with a negative moral issue and human rights abuse.

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At Standby Systems, we have highly qualified technical staff in both sales and projects of UPS lead acid batteries in the design, sales, and servicing of all your UPS and battery needs. We can offer any UPS user various options and choices with the technology recommended and perform detailed technical evaluations and sizing.

Read our article: Everything you need to know about UPS batteries in South Africa if you’d like more info.

Our preferred brand for this technology is ELITE batteries, for which we are the sole importer and distribution hub, providing support across Southern and Central Africa. ELITE batteries are available in a range of amp-hour capacities and life expectancies, including cost-effective options with a 3- to 5-year service life, as well as longer-lasting options with life expectancies of 8 to 10 years or even up to 15 years. All these products are designed and manufactured in ISO9001-certified facilities, ensuring the highest quality within their respective classes.

If you’d like us to contact you regarding the right batteries for your specific UPS unit or industry, please leave your contact details on this form, and one of our highly trained technicians will contact you.

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