Sajee tronics

  First step you need to remove the buzzer otherwise it will keep making noise and irritating when you are using for long hours. Identify the buzzer and remove it safely using soldering iron and Desolder Sucker. Please refer this article which i already covered for using soldering iron and Desolder Sucker.  https://sajeetronics.blogspot.com/2021/05/soldering-basics-and-smd-soldering-on.html   Replace the 7 or 9 Amp Battery (Originally came with the UPS) with a CAR battery Connect Car battery + and - with the UPS Battery terminal + and - Now UPS will start produce AC voltage from AC out put terminals. But using this solution for long hours is not recommended Because  MOS-FET and Transformer gets heat when it's started DC to AC conversion Process. Normal UPS is designed to Use for 15-20 min only so if you need long hours you need a proper ventilation system inside the UPS.  Fixing a cooler fan To achieve that we need to Fix a cooler fan. But i have seen in the most of the solutions