[Maurice Johnson]

What brand and model alternator do you presently have? Most case sizes have a range of stators and rotors to provide a wide range of outputs. A lot of my work is on cruising sailboats which have short engine run times, but high DC demands. Companies like Balmar and Amptech can give you an externally regulated Delco-Remy 10SI with anything from 50 to 135 amps. The house battery bank on my sailboat consisting of 4 deep cycle group 31's are kept up by a 10SI which will put out 90 amps at an alternator speed of about 2800rpm. Keep in mind that these outputs do put a good load on the motor, so a good contact area on the alternator pulley is critical, minimum of 90 degrees, if you want to avoid single belt squeal. Marine regulators also "ramp up" slowly to max field current. See the Balmar site. I realise this answer is more marine related, but this DC supply thing is VERY big around boats.