The batteries in this UPS lasted less than a year. It was because those battery were "no name" batteries, or because they were connected in series directly to the AC after the transformer? Shouldn't they have a rectifier and condenser before that? It seems that in this way the battery is connected to AC 24/7
As an electrical engineer I would advise you to recycle it. How much did you save buying no brand vs how much is the equipment you connected to it worth? How long would it take you to rebuild the connected equipment if the UPS threw out too much voltage and blew up everything downstream.? In my opinion the risk isn't worth the savings, don't cheap out on power equipment.
Agreed. There are open source UPS projects out there if you want to know what's gone into your design, but be sure you have the time to do this right.
Physics doesn't give a fuck.