Power-Loss Playbook

peira.dev · FT-09 · the bad night

Runtime calculators tell you how many minutes you have. They don't tell you the part that actually matters: in what order things go down, whether that sequence fits inside the battery, and what order to bring them back. Work it out now, not by torchlight.

What's on the UPS

MachineRoleWattsStop (s)Shuts down

The battery

volts × amp-hours, on the battery label
wait before acting on a blip
never plan to use the last of it
capacity fades whether you watch or not

The sequence

Shutdown — power is out

Boot — power is back

Runtime here is an estimate, not a measurement — real batteries sag under load and fade with age, which is why the reserve and age factors are in the maths and why you should test it once with a real pull of the plug. A Peira Labs field tool · peira.dev.