Hyundai Repair: Electrical system fault, alternator belt, hyundai accent

Question
My 1995 Hyundai Accent 1.5L uses the battery up until it goes completely flat and then the engine stops running.My friend and I tried to put his battery on my car and the car starts up normally and will drive normally until the battery is flat. After starting the engine we disconnected the negative side of the battery and the engine stopped running immediately. But if you do the same with his car, its engine will continue running.What's wrong with my car and how do fix it.

Answer
Your battery isn't being charged by the alternator.  In most cases, this is caused by the alternator itself, requiring the alternator to be replaced.  Other potential, but rare issues include:
-- blown main fuse opening the circuit between the alternator post and the battery's positive terminal
-- alternator belt loose or missing
-- power not applied to alternator in alternator connector.