I replaced my alternator 3times and bought a new.

I replaced my alternator 3times and bought a new battery alternators all failed draining my batery what draws rhat much power and cause a alternator go bad aand drain battery after installing a alternator that passed a dianostic check I checked all the fuses and wiring followed the main alternator wires none bad my battery was fully charged at 12.6 with engine running its at 13.6 after a few blocks it drops to 11.7 then I park it take another drive it was 11.7 two blocks till home dropped to 8.11 park it check reading again it was 7.07 not enough to crank it over my alternator went bad battery didnt charge I dont see any wires visible thats arcing or exposed I checked the alternator while engine running and battery the alternator got a different reading then battery no sign of increasing voltage battery read lowerer11.6 and alternator was reading 11.8 till it drained the BATTERY