Battery and Capacitor Replacement Keeps Backup Power Equipment in Good Health

Scott Baer, Marketing Manager-Batteries • Emerson Network Power, Liebert Services

Under the best of conditions, all batteries have a limited life expectancy, dictated by the frequency of battery discharge and recharge. Valve-regulated lead-acid (VRLA) batteries with a five-year design life start to lose capacity or fail within three to five years, and this aging process can be accelerated by any number of factors, including high or improper ambient temperatures, high or low charge voltage, overcharging and over cycling, loose connections and strained battery terminals.

Another factor in the reduction of lifespan is improper or non-existent battery maintenance. As with so many things, being proactive often brings with it more benefits than costs, especially as it pertains to replacing the battery in a data center’s uninterruptible power supply (UPS). Batteries are electrochemical devices that require regular checks to ensure safe and proper operation. As soon as batteries are placed into service, it is important to maintain them with a maintenance program that identifies system anomalies and trends end of life.

Business continuity during an unplanned power outage is dependent on a data center’s power equipment, the UPS and its battery backups. To safeguard backup power systems against unplanned or premature battery failures that could pose a significant risk for mission-critical applications, IT and facility managers should ensure battery maintenance best practices are implemented.

A haphazard approach to maintenance only creates uncertainty regarding system availability, a problem that is avoidable. When establishing routine maintenance protocols, starting with the guidelines from the Institute of Electrical and Electronics Engineers (IEEE) and manufacturers’ schedules is a good way to ensure batteries are properly installed, serviced and/or replaced.

IEEE standards, which pertain to data centers, utilities and other industrial operations, detail recommended frequency of inspections and the items the inspections should cover; how and when capacity or discharge tests should be conducted; and battery replacement criteria. These guidelines for avoiding battery failure can then be supplemented with additional preventive maintenance to support optimal performance.

Once a determination is made that a battery needs to be replaced, time is of the essence. Maintaining a battery spares cabinet equipped with an on-board charger eliminates problems involved with mixing old and new batteries in a string. Spares will be fully charged with a 12-volt DC microprocessor-controlled charger wired to batteries with pluggable connectors. These batteries then age concurrently with the main battery string, making for a stable critical power supply when it is needed.

However, ensuring battery health by itself isn’t the only factor affecting system uptime. UPS systems also contain large banks of both DC electrolytic and AC polymeric film capacitors that degrade with time. The function of capacitors within the UPS is to filter out electrical fluctuations and provide clean power to the equipment being protected. They are not static electrical components that operate in a circuit. Their design life is a mathematical function of manufacturers’ rated voltage, the voltage actually applied, the current running through them, ambient temperature, and thermal resistance. For all practical purposes, estimating service life would be based on manufacturers’ rated voltage combined with the device’s operating temperature.

Over time, even under the most favorable operating conditions, capacitors’ ability to withstand voltage and pressure changes diminishes. Adverse operating conditions like excessive current and heat, along with overwork, can accelerate the process considerably. Capacitor failure modes are hard to predict. Sometimes they fail catastrophically, but most of the time, they simply degrade with age. Aging capacitors can contribute to the degradation of batteries and shorten their useful life. But replacement, with original equipment manufacturer (OEM) parts, will help ensure a longer mean time between failures (MTBF) of the UPS and optimize battery life.

Battery abnormalities that go undetected, or those that are not properly diagnosed and corrected, can have catastrophic consequences in the data center including costly downtime. Along with helping you establish a regular battery maintenance program, a trusted service provider can set up, maintain and integrate an on-site battery spares cabinet. This solution offers IT and facility managers added peace of mind knowing that fully-charged, ready-to-install batteries are on hand.

Additionally, a proactive capacitor replacement program can be established based on equipment age, operating conditions and time of last replacement. However, a replacement program for capacitors based on an experienced service provider’s historical field data is the most reliable way to plan an ideal replacement time, and ensure a healthy backup power system that is able to support business-critical operations when it’s needed.


BaerScott Baer joined Emerson Network Power in 1999 bringing with him extensive experience in both engineering and sales. Currently he is the marketing manager for batteries in North America where he helps customers incorporate best practices regarding the maintenance and replacement of their UPS batteries. A five-year veteran of the US Marine Corps, Baer has a bachelor’s degree in technical management. He is active in several end-user consortiums, including AFCOM and Gartner, where he shares his Data Center Infrastructure Management (DCIM) expertise in pursuit of the common goals of improving data center availability and efficiency.