How much runtime is actually required?
The right runtime starts with the protection objective. Does the UPS only need to bridge brief voltage dips? Does a server need time for an orderly shutdown? Or must a system keep running until a standby supply takes over?
“As long as possible” is not a reliable requirement. Define the response and its timing instead: detect the fault, alert the responsible people, stop applications, secure data and shut systems down safely.
What determines UPS runtime?
With the same battery, a higher connected load results in a shorter backup time. The relationship is not simply linear. A power rating such as 1,500 VA therefore does not translate into a fixed number of minutes.
Battery size, the number of battery modules, efficiency, ambient temperature and the operating condition of the UPS also matter. Long runtimes may require more space and weight and can increase recharge time.
Why does runtime change over time?
Batteries age and lose usable capacity. High temperatures, frequent discharges and unsuitable operating conditions can accelerate this process. A display estimate or brief self-test does not always prove that the planned runtime is still available under the real load.
Critical applications need a suitable maintenance and test concept. It should consider the load and planned response as well as battery condition.
How can runtime be planned?
The actual load and required time window provide the starting point. The ERREPI runtime simulator gives an initial estimate. Critical systems, generator operation, long runtimes or aged batteries should then be checked using the specific operating data.
ERREPI can help determine whether internal batteries are enough, external battery modules are required or a different system and operating concept is more suitable.