Re: Battery keeps going flat ??
this may be stating the obvious, but when you test the voltage at the alternator, how are you testing it ?
for a proper test, switch on EVERYTHING. lights, fog lights, heated screen, blower/aircon,wipers etc, whatever you can switch on. then test the voltage. it's not uncommon for alternators to put out a good charge at idle, or with some revs, but fail completely under load. if the alternator is good, i'd still expect to see over 13v minimum with everything on.
in these cold, dark months your car probably spends more time with these things on than without ?
bear in mind too that as a battery nears the end of it's life, once it's been run flat a couple of times, this speeds up the process.
if everything's fine, then, like mave says, check for current leakage, i had this problem once on a capri, after doing the test, and pulling fuses, the problem was eventually traced to a faulty relay.
you're never alone with schizophrenia.
1992 alfa 75 2.0 twinspark l.e. (one of the last) now sadly departed
1971 mercury cougar. 302c.i., lightly tuned
1995 volvo 850 t-5 240 bhp the new toy !