1999 Toyota Van BATTERY TEMPERATURE AND CHOCKING SMELL

Hii Sir, I replaced the old battery bcz it started getting too much hot and smelling too bad, the technician told me its the battery dead. Bought a new one and replace, it works untill when the water level went down, then I added distilled water to required level, after operating for some two weeks, the problem started again, too hot and bad smelling out, all these happens after a car has operated continuously for about six hours, PLEASE I AM NOT RED TO REPLACE THE BATTERY AGAIN, IS IT THE ALTERNATOR OR THE BATTERY PROBLEM