I think I will buy one later but I need to know some things before buying like how much time does it still work without break in normal temperature and in hot temp also ? I wonder if it will be bad after a time or something like that operating in a bad electricity ? My main use of the UPS will be protection of the bad electricity. also there is many brands like APC, repotic and sollatek which is the best ?
The answer to all your questions is: it depends! - Usually, any known brand UPS is capable of working for decades. It's the batteries that fail. For example, if you are constantly having power failures maybe your battery needs to be replaced after only 6 months because lead acid batteries don't like full discharges. I've seen UPS working on places that have huge AC motors that cause a spike on the voltage and the UPS kicks in hundreds of times a day and they still work after years! - UPS are designed for 24/7 operation under bad electricity, but they can only work on battery power for some minutes. You need to check how many batteries does the UPS have. More = better. Also you need to make sure that you buy the correct "VA" rating. Don't buy a 2000VA UPS if you are only using a low power pc and don't buy a 500VA ups and power a high end workstation. - Most of my costumers use APC ups. They have excellent build quality, but they aren't cheap.