Ive been told its producing charge but not quite enough to charge the battery, also ive been told the alternator is fairly new.
my 'mechanic' (dodgey back street garage) told me @1000 rpm its 10v and 6000rpm its 12v.
Ive spoken to a few authorized suzuki shops and they advised me its probably the reg/rec and they usually go after 5yrs approx.
Does this help?