Alternator not recharging battery

my mazda 232 protg 02 - continually flattens the battery.. I have changed the alternator numerous times but it keeps on killing the battery especially at night times when i'm using the headlights, the alternator stopes working.. i'm not sure if its to do with the relays??
sometimes it makes the radiator very hot -exceeds normal temperature.. I'm confused what is really causing this problems..

I need some answers from this forum..

all opinions shared will be much appreciated..

thanks,
Papzman