I have what I believe is a pretty simple setup.

Two battery banks, a diesel engine with two alternators, various DC
powered devices (lights, starter, electronics) a generator. I don't use
the generator, the PO used it, but all my devices are DC powered.
Currently I don't have a charger, the batteries charge off of the
alternators when I am underway.

This is what I am thinking about for my winter project.

1) replace both battery banks, they are not holding a charge.

2) install a battery charger. I would like to be able to charge the
batteries while
a) hooked up to shore power
b) running the generator
c) while engine is running.

But I don't need/want any AC power. I am not adverse to AC power, I
just don't need any.

So,
any suggestions on make/model of charger?
any references to documents/diagrams?