DIY UPS

I want to "hack" my computer into adding a ups. I am pretty sure that switch mode power supplies first step are to convert the ac to dc right? So could I make a "UPS" that just provides 170 volt DC constantly and have a battery connected to that? If the power goes out, everything just runs off the battery because its all connected.

I have many things I want to plug into it, that all are just switch mode PSUs. I'm just wondering if this is plausible because I just put together a somewhat expensive pc and cannot just kill the new 50-60 dollar PSU.

Do I understand this correctly? You want to build a UPS that runs on the mains voltage and will likely kill your computer and possibly injure you in the process. And you are not able to supply even a schematic of your proposed device, but ask strangers to help you with such a project? All to save a bit of money that will cost many times what a real, commercial UPS will cost. I don't think so.

Paul

As your trying to protect an expensive PC I would go the little extra to buy a proper UPS. The size/cost depends on how much power you draw for all your devices and how long it needs to power them for without mains supply.

170V???
Where did that come from?

UPS units usually supply "household" AC voltage, 115VAC 60Hz or 220 VAC 50 Hz, depending on where you live. The power either comes directly from the house wiring, or from the battery if the household power fails.

You can often get UPS units very cheaply at computer recycling and thrift shops. The rechargeable batteries eventually fail and although they are easy to replace, people just throw the entire UPS out.

A commercial UPS will usually also have a feature that when, after an extended power failure, the batteries become nearly exhausted, a signal is sent to the connected PC . This signal is interpreted by an application (maybe one supplied by the UPS manufacturer) to begin a graceful shutdown of the PC. This minimises the risk of storage corruption etc. It would be good to duplicate that feature in your project.

NoraTheDoggo:
I want to "hack" my computer into adding a ups. I am pretty sure that switch mode power supplies first step are to convert the ac to dc right? So could I make a "UPS" that just provides 170 volt DC constantly and have a battery connected to that? If the power goes out, everything just runs off the battery because its all connected.

I have many things I want to plug into it, that all are just switch mode PSUs. I'm just wondering if this is plausible because I just put together a somewhat expensive pc and cannot just kill the new 50-60 dollar PSU.

Absolutely NOT.
Bad idea!
You will endup electrocuted and possibly destroy your expensive PC.