UPS Battery Backup Times

Extended runtime UPS battery backup times from 1kVA to 100kVA using plug-in battery packs, external battery cabinets and stands. The tables include line interactive and online UPS with plug-in DC sockets or hardwired DC terminals for additional battery packs.

UPS Battery Sizing Formula

The general formula for calculating the runtime available from a UPS battery is: (10 x Battery Ah) / Load Watts. The Ah (Ampere-hour) of a battery is the amount of energy (charge) stored in a battery. The Ah measures the rate of electron flow to allow 1 Amp (ampere) to flow for 1 hour.

The load measured in Watts is referred to as the Real Power and is the total Watt load placed on the uninterruptible power supply. A load may also be measured in VA (Volts x Amps) or kVA. VA measures the Apparent Power.

Real Power and Apparent Power are related by Power Factor. Where power factor (pF) is equal to Unity (1), Apparent Power = Real Power i.e. 1000VA = 1000W. If the power factor is 0.9, then 1000VA * 0.9 = 900W.

If a 250W load is placed on a 1000VA UPS with a 12Ah battery, then (10 × 12)= 120 / 250 = 0.48 hours x 60 = approximately 29 minutes.

The calculation is an approximate value because battery discharge curves are non-linear. UPS systems use complex algorithms to determine the runtime available for a set Ah battery size connected and the measure load placed upon them. This information can be read on the front panel LCD or remotely via an SNMP Ethernet/IP connection using remote UPS monitoring software.

For a specific runtime application and battery Ah sizing, please contact our projects team.

CertaUPS C3000R Tower/Rackmount Line Interactive 1-3kVA Single Phase UPS

CertaUPS C450R Tower/Rackmount Online 1-3kVA Single Phase UPS

CertaUPS C650 Floor Standing Online 6-10kVA Single Phase (1/1) UPS

CertaUPS C650R Rackmount Online 6-10kVA Single Phase (1/1) UPS

CertaUPS C750 Floor Standing Online 10-20kVA 1/1, 3/1 or 3/3 UPS

Note* this battery pack may require build on site by the SRE installations team.

CertaUPS C750R Rackmount Online 10-20kVA 1/1, 3/1 or 3/3 UPS

On application

Borri Ingenio Plus UPS up to 30-100kVA 3 Phase

• Note requires on-site battery build.

Plug-in Battery Extension Packs

Some line interactive and on-line UPS have a rear panel DC battery extension socket. This type of UPS is designed to use a plug-in battery extension pack to increase the amount of battery runtime available at a specific load. The UPS may allow for additional battery packs to be ‘daisy-chain’ connected to further increase the backup time. The battery will either be charged by DC (direct current) charger built-into the UPS or the plug-in battery pack may have its own built-in AC/DC charger. Where the battery extension pack has a plug-in charger it will require connection to an AC (alternating current) mains power supply.

Plug-in Battery Extension Cartridges

Modular UPS may be installed with plug-in battery extension cartridges. These are self-contained slide-in trays housing a battery string. The battery string is generally made up from small Ah-rated batteries. When these require battery replacement, the cartridge can either be completely replaced or refurbished onsite with replacement UPS battery or battery kits.

Hardwired Battery Cabinets and Stands

For some single phase UPS with runtimes up to 7-8 hours or more and for three phase UPS, extended battery runtimes are provided in external battery extension cabinets or on open or closed (cladded) stands. For operational safety, battery testing and maintenance battery transition boxes (BTBs) may be used for multiple battery strings and each cabinet/string will be fuse/circuit breaker isolated.

UPS Battery Calculations

The ideal recharge time for a valve regulated lead acid (VRLA) UPS battery is to 80% within 24hours. Please contact our projects team if you need more assistance in the selection of the right long runtime UPS backup power application.