How is generator battery charged on an 82 FC?

[davidkerryedwards]

My one year old battery on the generator was discharged enough to not turn over
the motor
this spring. I could start the generator by pushing the button that connects
house and
generator batteries. I assumed it was low from sitting all winter but after
driving about 75
miles, battery is still weak. I assumed the main engine alternator would charge
the generator
battery. Is this assumption mistaken? Is the generator battery only charged
from 110 volts?
It doesn't seem likely that a battery would fail in just one year (although not
altogether out of
the question).

Kerry
82 Fc 35
Denver