Battery UPS ...
https://www.howtogeek.com/161479/how-to-select-a-battery-backup-for-your-computer/https://www.apc.com/us/en/support/product-support/ups-buying-guide-for-selecting-a-battery-backup-sy...https://www.cyberpowersystems.com/blog/buying-guides/choosing-a-ups/https://powerquality.eaton.com/thoughtleadership/choosing-ups/size-a-ups.aspThere's all sorts of calculators and guidelines and stuff like that online, mostly provided of course by the makers and vendors who sell UPS units.
Some are engineered much better than others, some are cheap garbage. Stick with recognized brands, avoid generic Alibaba products, read a few reviews before spending $$$.
Short version is that it's a competitive and saturated market so products basically price themselves and you basically get exactly what you paid for. Figure out how many Watts your system pulls, multiply by how long you want to run the system off battery, that's the size of the battery (in W
⋅h, kW
⋅h, etc) you should get. Strictly speaking, a battery backup needs to be able to sustain "peak" power for maybe 5 mins at most, long enough to halt whatever you're doing on the computer and gracefully shut down without risking any hardware damage or data loss, etc ... realistically, you won't want to keep paying ever-inflated prices for more unless you're running a mission-critical server or something.
I would never run a computer without UPS and never recommend anyone else does so. It pays for itself over time, not only as an emergency fallback during sudden power loss events but also as a "power conditioner" which smooths out all those jagged spikes and ripples and noise ... adds to overall stability, reliability, and longevity of all the (expensive) hardware plugged into it downstream.
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