Originally Posted by Matt sachs
The engines alternator
will only supply the cranking battery
much like the setup in an automobile, and either a high output alternator
or a seperate gen set will be used on the house bank.
If this is crazy, I hope some will let me know....
Fitting two alternators on the main engine
and using one for the sart battery
and second high capacity alternator for the house battery is OK. A very simple and KISS system. The high output alternator will supply the house batteries needs.
If you only have one alternator on the main engine
I would not dedicate this to just to the start battery. The start battery uses very little AHRs and the alternator will be not doing anything most of the time when it could usefully be charging
the house bank.
There are lots of ways of diverting the alternator output between the start and house banks. A VSR is the common system. It's a shame to have the alternator doing nothing most of the time.
Have a system in place so that the engine can be started by the house bank. The start battery will fail sooner or later, no matter what you do, sometimes reasonably rapidly.
In summary the main engine needs to able to charge both the start and house batteries. This can be done with two alternators, or splitting the charge of a single
alternator as is done successfully in most boats.
To not have the main engine charging
the house battery is crazy