When you have a whole stack of devices and appliances that all have an AC to DC adapter and which you’d like to put on an uninterruptable power supply (UPS), you could do the obvious thing and get an off-the-shelf UPS with myriad AC outputs. In the case of a 19″ rack this means wrangling a power strip or two and any combination of differently sized AC/DC adapters into the rack, with questionable efficiency and waste heat dumped into the rack. This is where a DC-only UPS like [Maciej Grela]’s Second Life UPS Mark II provides an interesting alternative.
This is a companion discussion topic for the original entry at https://hackaday.com/2023/12/17/second-life-ups-mark-ii-a-ups-for-low-voltage-dc-applications/