1992 Volvo 940 I'm having major charging problems

Electrical problem
1992 Volvo 940 4 cyl Front Wheel Drive

I have a 1992 volvo 940 GL non turbo Ive replaced my fuel pump bekas it went out then shortly after that the car lost all power mechanic said it was fixed.I had to replace the egr valve so it would pass smog then it stalled out like it had ran out of gas, and drained the battery, I bought 3 used alternators all 3 were putting out only 11.0-11.5 volts, so I replaced the relay switch it worked for a few more days then the car lost all charge again, finally I bought a new alternator and a new battery and it ran for a few more days and did the same thing again. It lost power but took a jump, then it wouldnt even take a jump so I am at a loss as to what it is that could be causing me this problem. Can you diagnose the cause