Data center backup power is a crucial element to uptime and availability. During an outage, Uninterruptible power supplies (UPSes) enable the switch from utility power to backup generator power. But there is a relatively unreliable and expensive variable to most UPSes: batteries.
"Simply stated, batteries represent three evils: They are big, they are expensive, and they are expendable," said Pete Sacco, the president of Franklin Lakes, N.J.-based engineering firm PTS Data Center Solutions. "Anything you can do to prolong the life of your batteries will indeed extend the availability of your data center."
So here are four ways that data center facility managers can extend the life of their UPS batteries.
Buy the right UPS battery for your data center
In most data centers, UPSes are designed to fully discharge the battery source within 20 minutes. This is called high-rate discharge. High-rate batteries have thinner plates and more plates than lower-rate batteries, but as a result high-rate batteries can lead to a shorter lifespan.
There are many other factors in buying UPS batteries, such as the life expectancy, voltage, front or top access, flag post or inserted post, and other considerations. For example, a small format valve regulated lead acid (VRLA) battery has a relatively low first cost but lower reliability. Meanwhile, a nickel cadmium (NiCd) battery has the best reliability and longest service life, but the first cost can be four times as much as other batteries.
Data center managers must also be aware of potential manufacturing problems such as faulty post seal design and internal connection problems.
Install, operate and maintain batteries correctly
Incorrect installation can lead to shortened battery life, as can improper maintenance. Good maintenance means giving the batteries well ventilated air that is as close as possible to 77 degrees Fahrenheit, and making sure that all batteries in the string are getting air within 3 degrees Fahrenheit to ensure that some of the batteries don't age more quickly than others.
Why? Mixing batteries of different ages or internal resistances can prompt batteries to die more quickly. Regular inspections of the batteries can unveil problems such as loose intercell connections and damaged post seals, which can lead to corrosion and even fires.
Data center managers should also be aware of the battery's discharge status as well. A fully or nearly fully discharged battery that isn't recharged within 48 hours can lead to damage. Overdischarging a battery can cause recharge problems, and excessive discharging -- for example, if a data center does weekly testing of its backup systems that includes battery cycling -- can reduce battery life.
Monitor the UPS batteries' capacity
When the internal resistance of a battery rises due to normal aging factors such as corrosion, and when it has increased by as little as 30%, it's time to replace them. This is most often measured through capacity testing, as most manufacturers say that when a battery drops to 80% of its original capacity, it's cooked.
Consider using flywheel UPS in conjunction with battery UPS
When flywheel UPSes are installed alongside battery UPSes, the flywheels can often handle the shorter power outages that happen more often and can prevent the batteries from cycling.
Art Smith, the chief engineer at KEYE-TV, a CBS affiliate in Austin, said his Active Power flywheels have helped extend battery life by two years.
"I wanted the flywheel to filter out the 'dirty power,' those little power blips and spikes," he said. "The batteries would filter those spikes out -- I understand that -- but if you hit the batteries with those spikes, it's bad for them. It will kill the battery life."