The forecasted lifespan of the valve-regulated lead-acid (VRLA) battery in an APC by Schneider Electric UPS is 3 to 5 years under recommended conditions; however, this life expectancy will fluctuate greatly depending on the following factors. Being proactive and aware of these characteristics and conditions will ensure you maximize the life expectancy of your battery and are prepared for any imminent power failures.
When installing a UPS, the user should determine where to install the unit to best provide power protection of the IT equipment in the room. It is recommended that the UPS be installed in a temperature controlled environment similar to the intended application. The UPS should not be placed near open windows or areas that contain high amounts of moisture; and the environment should be free of excessive dust and corrosive fumes. Do not operate the UPS where the temperature and humidity are outside the specified limits. The ventilation openings at the front, side or rear of the unit must not be blocked. Further discussion on cooling strategies can be found in White Paper 68, “Cooling Strategies for IT Wiring Closets and Small Rooms”.
Most single-phase UPS batteries are classified as “maintenance free” which leads many users to feel that monitoring and maintaining UPS batteries is unnecessary, however this is not the case. A maintenance-free battery only refers to the fact that these batteries do not require any replacement fluid, therefore understanding how to properly care for and monitor batteries is essential.
All batteries have a rated capacity which is determined based on specified conditions. The rated capacity of a UPS battery is based on an ambient temperature of 25°C (77°F). Operating the UPS under these conditions will maximize the life of the UPS and result in optimal performance. While a UPS will continue to operate in varying temperatures, it is important to note that this will likely result in diminishing the performance and lifespan of your battery. A general rule to remember is that for every 8.3°C (15°F) above the ambient temperature of 25°C (77°F), the life of the battery will be reduced by 50 percent. Therefore, keeping a UPS at a comfortable temperature is crucial to maximizing UPS life and capabilities.
When a power failure occurs, the UPS will automatically switch to battery power to provide the attached equipment (load) energy. Once utility power has been restored the UPS battery will automatically recharge to prepare for the next power outage, a process known as the discharge cycle. The chemistry of a VRLA battery, like the one used in a single phase UPS, dictates that a battery can only undergo so many discharge/recharge cycles before it reaches the end of its usable life, and must be replaced.
At installation a battery is at 100 percent of its rated capacity, however each discharge and subsequent recharge will slightly decrease the relative capacity of a battery. The length of the discharge cycle will determine by how much a battery’s capacity is reduced. While cycling is a necessary part of UPS operation, being aware of the cycling frequency will help to predict the life of a UPS.
A battery is determined to require a replacement when it has reached the end of its useful life, which is defined as when it can no longer supply 80% of its rated capacity. When the battery reaches this aforementioned point, the degradation process speeds up, and a replacement battery is needed. It is important to note that while the useful life of a battery is defined as losing 20% or more of its rated capacity, the effects on actual UPS runtime can be much greater.
Proactive UPS owners may seek to purchase a replacement battery before one is necessary in order to avoid the potential consequences of downtime. While this is an acceptable and even recommended practice, there are a few important factors to consider when placing your UPS battery into storage.
Inevitably, an unused battery will experience a life cycle decrease. Lead-acid batteries like the ones used in UPS units experience automatic self-discharge, therefore it is recommended that a battery in storage be charged every 3 to 4 months. Failing to maintain your UPS battery’s charge will result in permanent loss of capacity within 18 and 30 months.
If you are unwilling or unable to charge your battery while in storage, it is recommended the battery be stored at 50°F (10°C) or less. Doing so will slow the degradation cycle of the battery, and help to maximize its life expectancy.
UPSs and their associated batteries are designed to be durable and dependable; however maximizing the life of your device requires proper care from the user. Most users are aware that batteries will eventually need replacement, however many overlook the importance of the battery’s maintenance. Temperature, and cycling frequency are the two characteristics that should be most closely monitored, however the importance of periodic inspections, placement, and storage cannot be overlooked.
Batteries that last the longest, and provide the best performance are consistently the ones that are being provided the best management and care. Providing optimal oversight to for your UPS battery should be simple; just make sure you understand the factors discussed and that your plan is simple, consistent and proactive in nature.