UPS Battery Temperature Life Calculator

Exponentially: each 10 K above the 25 °C reference halves expected life, and each 10 K below roughly doubles it (the battery-industry rule (IEEE 1188 guidance, Eurobat) that VRLA float life halves roughly every 8–10 K above 25 °C — this tool uses 10 K; some makers state 8.3 K). A sustained 20 K overshoot quarters the life — which is why a 'small' cooling problem is never small over the years.

Both appear in reputable sources: chemistry and construction vary, and makers quote 7.8–10 K halving intervals. The difference matters less than the discipline: measure the real average temperature at the batteries (top of cabinet, not the wall thermostat), apply YOUR maker's figure if stated (edit the reference-life field accordingly), and budget replacements on the computed life rather than the brochure life. At typical tropical sites either constant tells the same story — cool the room.

It is the engineering linearisation of the Arrhenius equation over the normal operating window, adopted by the relevant standards because it matches test data well within ±20–30 °C of the reference. Far outside that window (or where a different failure mechanism takes over, e.g. mechanical wear) the rule loses authority — treat extreme extrapolations as indicative only.

The hot-spot (the hottest point of the insulation/material), because chemistry happens at the hottest spot. If you can only measure surface or ambient, add the typical rise for your equipment class — datasheets usually state hot-spot rise over ambient at rated load — and remember intermittent peaks age the asset during the peak hours, not the average.