Typical store-bought Uninterrupted Power Supplies (UPS’s) last just long enough to save whatever you were working on when the power cut out. This video shows how to hack a weak UPS and make it into a monster power source that will keep your computer and monitor running for up to two days!
https://www.youtube.com/watch?v=jX1OQZ1B6m0
Depending on your level of technical expertise, this great hack doesn’t present much of a challenge, or cost even. Even using just one deep-cycle battery could conceivably give you several hours of use with a modern PC with an efficient power supply.
As for making something that will work for up to 48 hours, as per the title of the video: you’d have to follow the Asian guy’s tips for figuring out the amperage you’d need, based on your PC (and other peripherals) and buy the appropriate number of car/marine batteries.
If you’re the type who lives in utter fear of wires and electrical power, this hack isn’t for you. I’m going to be building my own this weekend with an old UPS with a dead battery, and a single marine battery. I’ll post back in the comments with an update, but don’t foresee any problems.
Please come back and share your experience if you decide to build one of your own!
