FAQs - Extended Runtime UPS

A lead acid battery should recharge to 80% capacity within 24hours in order to hold sufficient charge and runtime for the next power outage or interruption. The 80% rule applies as the charging characteristics for lead acid batteries is non-linear and the batteries will require a longer period on trickle or float charge to reach 100% of recharged capacity.

Uninterruptible power supplies include automatic battery testing which is completed every 24hours but this only tests the viability of the complete battery set. Each battery set is made up of battery strings and battery blocks. The individual battery blocks should be tested once a year during a preventative maintenance visit by an engineer qualified to work with DC voltages. The testing can be made with a suitable handheld battery tester using inductance and/or impedance testing. A fixed individual battery monitoring system is a more expensive solution but would provide 24/7 monitoring for each individual battery block and battery string. Battery testing at the block level helps to identify batteries that may be ageing more rapidly than others within the string and so assist with planning replacement before any detriment to the overall battery capacity.

The lead acid batteries used in a UPS system are general valve regulated lead acid (VRLA) batteries and maintenance free. Single phase systems tend to use 5year design life batteries requiring 3-4 year replacement. Three phase UPS mostly use 10year design life batteries which tend to need replacement around years 7-8.