A UPS system can protect from several power anomalies, ranging from a complete power outage to minor transients that could damage your critical equipment. (See our blog article on the Nine Power Anomalies that a UPS can cover.) While modern UPS units are more complex than they used to be, the heart of your UPS is still in the batteries.
As a service organization, we receive hundreds of questions each year about batteries, and we’ve compiled a list of the top eight that we often hear from our clients.
1. What types of batteries are available? – While there are several types of batteries on the UPS market today, including wet cell and lithium-ion, valve-regulated lead acid (VRLA) batteries are by far the most common battery. Often known as sealed or maintenance free batteries, VRLA batteries are contained typically in a polypropylene casing that prevents leaking or sloshing of fluid. Because water cannot be added to the battery, they are considered “maintenance free”. However, routine testing and inspection is still vital to ensure your batteries are in good health.
2. How long should my batteries last? – The IEEE specifies the “end of useful life” for a UPS battery is the point at which it can no longer supply 80% of its rated capacity, typically measured in ampere-hours. Once your battery has reached this point, the aging process can quickly accelerate and it should be replaced.
3. My UPS has been in storage, should I be worried about battery health? – When batteries are kept in storage, without charge, their life expectancy can decrease significantly. A lead-acid battery will “self – discharge” and permanent loss of capacity can occur as soon as 6 months. Should you need to store your batteries temporarily, it is important to discuss a charging regimen with your UPS service provider to ensure your battery’s health.
4. What is a hot-swappable battery? – Some UPS systems are designed to allow for removal of a battery module without the need to open the battery breaker or placing the UPS into a bypass state. These types of batteries are considered “hot-swappable”. It is important to understand the risk of removing a hot swappable battery prior to service; make sure to check with your service provider to understand the impact to your critical loads.
5. Why do batteries fail? – Batteries can be susceptible to many kinds of failures but some of the most common reasons might include:
- High Temperatures – heat is by far one of the most common causes for premature failure. In fact, for every 8.3°C (15°F) above 25°C (77°F), the battery is exposed to on a consistent basis, it can shorten that battery’s life by 50%.
- Inaccurate float charge voltage
- Age or lack of maintenance
- Loose inter-cell connections or faulty installation
- Loss of electrolyte as a result of a cracked or faulty case
6. I’ve heard of thermal runaway, what is it?- Thermal runaway occurs when heat, generated internally, builds in the battery and exceeds the battery’s ability to dissipate that heat. Since heat accelerates gas dissipation, thermal failure can quickly escalate, feeding on itself, resulting in damaged casings, explosion or fire. Thermal runaway can occur for many reasons but most often in batteries that are old, poorly maintained or due to improper float voltages.
7. Can I ensure my UPS Batteries will hold in the event of a power outage?– Proper maintenance by a qualified field technician can help identify poor battery conditions and help you determine your level of risk. In addition, installing redundant strings of batteries can help minimize the possibility of load loss should you experience battery failure. Lastly, ensure that your batteries are replaced at regular intervals. Neglect is often the main reason for load loss from battery failure.
8. What is done during a battery maintenance visit? – A complete visual inspection is important; is there bulging or abnormal casings? However, a good service technician should go beyond visuals to measure battery health. Battery maintenance should include individual load testing to determine impedance, measuring AC ripple and voltage, cleaning and inspection of terminal connections, re-torquing if necessary and verifying inter-cell links.