The difference between online, off-line and line-interactive UPSs is also evident in the topologies' battery lifespans. It's important to note that battery lifespan is affected by a number of different factors, including frequency of use and extremely cold or hot environments. Although a lead-acid (VRLA) UPS battery is typically rated for a three- to five-year lifespan, frequent transfers to battery and high ambient temperatures can reduce expected battery life and increase the need for recurrent battery changes.
Because standby UPSs often switch to the battery when installed in environments with poor utility voltage, battery replacement may be required more frequently than if using a line-interactive UPS. The more the voltage fluctuates, the more the offline UPS resorts to the battery.
In line-interactive UPSs, the use of an automatic voltage regulation (AVR) transformer to correct abnormal voltages prevents excessive battery use during undervoltage and overvoltage conditions. Some line-interactive UPSs also feature a more advanced battery charging and management scheme than standby UPSs such as Eaton's ABM technology, which helps extend battery life and provides early warning of battery failure. In addition, certain line-interactive UPSs are able to provide longer runtime with the addition of external battery packs.
Online UPSs only draw power from the batteries only when the utility voltage is extremely low, high or when a complete power loss occurs, which may decrease the need for costly and frequent battery replacements. Most online models have similar battery management schemes as higher-end line-interactive units, which further extends battery life. Additionally, an online UPS can provide long periods of runtime by adding extra battery packs like some line-interactive designs.