OceanFlyer Grand Banks 49' Classic Operating Manual page 40

4G2: DC Batteries
The batteries on this boat are not just one, big all-purpose battery. To have redundancy, there
are actually several "banks" of batteries assigned different tasks.
A "starting bank" of two batteries — one for each engine — are used for engine starting. That
way, we won't run it down playing the stereo, for instance, and then be unable to start an engine. This
battery is charged by the engine alternators when running, or by the
battery charger if it is on when there is shore power or the generator is
running.
A second bank of batteries is called "the house battery".
Connected to this bank are the inverter, all the pumps, interior and
exterior lights, horns, navigation and radio gear, etc. It is charged by
the alternators on the engines and, when there is shore power or the
generator is running, by the inverter or a charger if it is on (see "Battery
Switches" section 4G4 below.).
A battery operates the bow thruster.
And two separate batteries are used exclusively for starting the generators which can charge
them all. What redundancy!
Since a battery works by making electricity through a chemical reaction, one component of
which is water, we need to be sure the batteries have water in them; this battery servicing is normally
done routinely every few weeks by the boat's owner or charter company.
4G3: DC Battery Chargers
The vessel is equipped with two 12-volt battery
chargers that can charge the starting batteries:
Charger #1 charges the engine starting
battery, while charger #2 charges the
generator battery.
Normally these are "ON".
When they are needed, the chargers are switched on by operating their
breakers in the 120-volt circuit breaker panel.
Section 4F: Electrical Systems, DC 4.16
Chargers are to starboard in the E/R.
The house battery boxes
The battery chargers have
meters to right of the
lower helm that show the
current being sent by
them to the batteries.