What to choose accessories for UPS?

Question

Uninterruptable power source

There is a desire to assemble a UPS for 400-600 W in a custom case.
I don’t consider the option with used UPS, because. This is still used and may have hidden defects.
Can you tell me which parts to buy?
The problem is that I can not form the request correctly.
"Board for UPS" or "UPS controller" in Google give out the wrong thing.
Help with links or names of components.

Answer 1

Go to a computer shop and order a board from scratch. They will send you. Well, or ruin a new donor