How Much Battery Runtime Do You Need?

To meet customer needs of continued operations during power outages, Eaton 9910 UPS solutions offer options that can extend battery (autonomy) runtimes beyond 60 minutes. In today's 7x24 business environment, continued availability along with application and safety considerations must be taken into account and estimated when calculating UPS battery (autonomy) runtimes.

For example, a typical battery (autonomy) runtime is 15 minutes. The recommended formula used to calculate runtime is:

Runtime (calculated in minutes) = business + system application shutdown + safety
Example   Minutes
Business needs = 5
System (application) shutdown = 6
Safety margin = 4
Total battery (autonomy) runtime required = 15

Business needs: Approximately 80% of power outages are less than 5 minutes in duration. Using 5 minutes will ensure that if the typical power outage is less than 5 minutes, the application will not start a premature or unrecoverable shutdown. In the EXAMPLE, 5 minutes is used.

System shutdown: The National Power Laboratory (1990-1995) Power Quality Report indicates there may be consecutive power outages before power continuity is fully restored. By doubling the system/application time, you allow for two consecutive power outages to occur while providing an adequate reserve of battery runtime to initiate a safe system shutdown during the second power outage. In the EXAMPLE, it takes the application 3 minutes to shut down. Doubling (multiplied by two) the shutdown time results in 6 minutes.

Safety margin: Allows for natural battery charge cycles, temperature variations and aging. Also take into account variations in business needs. In the EXAMPLE, 4 minutes is used.

Find the correct UPS model then select the runtime required. If the power consumption of the equipment to be protected is unknown, use the maximum load (watts) number given for the UPS.

For example, if the load requires less than 2,100 Wattsand the runtime is 15 minutes, a valid UPS will be the P30 with one Extended Battery Module (EBM) providing 25 minutes of battery backup (autonomy) runtime at the P30 maximum capacity of 2,100 watts. NOTE: The runtime is total (standard internal batteries and optional EBMs), not additive.

Table A. Battery (autonomy) runtime table

Battery (autonomy) runtime in Minutes
UPS Model Maximum Watts Supported Standard (Internal) Battery +1 EBM +2 EBMs +3 EBMs +4 EBMs EBM Feature
P14 950 5 EBMs not available None


1,050 8 37 70 106 144 6605

Battery Information:
Battery (autonomy) runtimes stated in the above table are for new, fully charged, and full Watt (or kilo-Watt) load. Battery backup times are dependent on Watt load.

Batteries should be charged for 24 hours upon receipt of the initial unit. Batteries typically need less than 24 hours of recharging after an extended outage to reach the fully stated run times.

Extended Battery Module:
EBMs are options which are external to the UPS. Some are line-up and match, e.g. same physical size as UPS (FC’s 6604, 6605, 6607, 6640 and 6641). Some are cabinets (FC 6635 and 6636) that are similar in physical size as UPS. Consider space requirements of EBM when conducting physical planning for tower (desk-side) or rack-mount installations.

Standard battery is the battery included internally with the UPS.