While undeniably the heart of any uninterruptible power system (UPS), batteries unfortunately are also the most vulnerable aspect. In fact, battery failure consistently ranks among the most common causes of load loss. Understanding how to properly maintain and manage UPS batteries is not only instrumental to extending their service life but can also help thwart costly downtime. Bolster your battery knowledge with these 10 truths:
1. All batteries will experience an “end of useful life” – The IEEE defines a UPS battery’s “end of useful life” as the point when it can no longer supply 80 percent of its rated capacity in ampere-hours. At this stage, the aging process accelerates and you should replace the battery. Although the average lifespan for VRLA batteries is three to five years, actual life can vary dramatically due to environmental conditions, the number of discharge cycles and the amount of maintenance received.
2. Batteries die for a variety of reasons – Among the most common causes of battery failure are high or uneven temperatures; inaccurate float charge voltage; loose inter-cell links or connections; loss of electrolyte due to damage or drying out; lack of maintenance; and aging.
3. VRLA and VLA are the two most common types of UPS batteries – Valve-regulated lead acid (VRLA) batteries, also known as sealed or maintenance-free, are batteries that have been encased to prevent any liquid from leaking. Vented Lead Acid (VLA), also known as flooded or wet cell, are comprised of a hard enclosure, lead plates and an electrolyte that allows the flow of current. Don’t miss our next blog, which will explore both of these battery types in much greater detail.
4. Different UPS systems use different batteries – While basic battery technology — and the risks to battery life — remain the same regardless of UPS size, there are some differences between applications. Smaller UPS’s (250VA to 3kVA range) typically contain a single VRLA battery, while the use of wet-cell batteries becomes much more common in bigger systems.
5. Your UPS maintenance plan should cover the batteries, too – A solid, comprehensive service plan will include both the UPS components and the batteries. Regularly scheduled preventive maintenance visits allow trained technicians to inspect, test, calibrate and upgrade battery components, ensuring factory-specified performance and longevity.
6. The battery type will dictate maintenance requirements – The type of batteries will impact which maintenance tasks need to be performed and their frequency, with wet cell batteries requiring more maintenance than VRLA. However, even batteries that claim to be “maintenance-free” still need regular inspection, cleaning and testing.
7. Stored batteries require attention, too – If UPS batteries sit unused with no charging routine, their life will decrease. Due to the self-discharge characteristics of lead-acid batteries, it is recommended that they be charged every three to four months when in storage to avoid permanent loss of capacity (which will occur between 18 and 30 months). To prolong shelf life without charging, store batteries at 10°C (50°F) or less.
8. There is a difference between hot-swappable and user-replaceable batteries – Batteries can be both hot-swappable and user-replaceable. Hot-swappable batteries are able to be changed out while the UPS is running. User-replaceable batteries, which are generally found in smaller UPS’s, indicates that no special tools or training is needed to replace them.
9. A battery’s discharge rating is key to measuring performance – Batteries are generally rated for more than 100 discharges and recharges. However, many will display a marked decline in charging capacity after as few as 10 discharges. The lower the charge that the battery can accept, the less runtime it is able to deliver. Be sure to look for batteries with a high-rate design that sustains stable performance for a long service term.
10. Thermal runaway can have explosive consequences – Often occurring without any warning signs, thermal runaway takes place when the heat generated in a lead-acid cell exceeds its ability to dissipate it. Typically caused by overcharging, excessive charging, internal physical damage, internal short circuit or a hot environment, thermal runaway can result in an explosion, especially in sealed cells.