T&T: Alternators

[John Leroy]

Thanks to all who have responded to my previous posts. I have  
received a lot of invaluable information.

My project is a Monk 36 with a Cummins 220 that currently has the  
original 63 amp Bosch K-1 alternator driven with a non toothed  
serpentine belt.

I'm planning on adding a Mastervolt Mass Combi 2kw inverter with the  
Masterlink MICC remote control panel. Does anyone have any opinion   
of this unit as compared to the Prosine?

I'm planning on two 8D batteries in parallel for the house bank.

While the rated amp hours of the two 8Ds would be 250  amp hours  
each, the 20 hour amp-hour rating would be only 220 amp hours.
Assuming an acceptance rate of 25% of that, each battery could accept  
about 55 amps, for a total of 110 amps for the two batteries.

If I am cruising at 1400 rpm, with a pulley ratio of 2:1, the  
alternator would be turning at 1800 rpm. It looks like the Ballmar  
94-165 puts out about 125 amps which would work.

I talked to Cummins and it looks like the max we could put on to  
replace the 63 amp Bosch K-1  alternator would be the 100 amp Ballmar  
94-100  alternator which  would produce maybe 75  amps at that rpm,  
which is not enough.

I thought of adding a 100 amp alternator, but I believe the existing  
alternator is internally regulated and it would not do to mix that  
with the new externally regulated alternator.

It might be possible to modify the existing alternator by opening it  
up and cutting the internal excitation lead, and adding an external  
one, but probably the better course of action would be to change out  
the existing 63 amp for a 100 externally regulated alternator and add  
an identical 100 amp externally regulated alternator with an  
additional pulley. I think there are regulators built to control two  
alternators.

It would be nice if someone had stock brackets to install the new  
alternator.

Then the outputs of the two alternators and the inverter could be led  
to the house bank with combiners to the start battery and perhaps the  
genset start battery.

Another route would be to retain the stock alternator and route it to  
the engine start battery only, and not combine it with the house  
bank, and add a 165 with two belts and new bracket for the house  
bank. A switch could then be used to use the house bank for start in  
the event the start battery got flattened.

Does anyone have any comments? I would think someone has had a  
similar project, and I'd like to not re-invent the wheel if possible :).

Regards to all,
John LeRoy
Pensacola, FL