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 one battery (located
alongside the port engine) is
used for starting the
engines only
. 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 port engine
alternator when this engine is running, and by any other charging source through the battery combiner
there is charging voltage, or by the stand-alone charger if shore power or the generator is running and
it is turned on (this last case is rare).
Also on the port side outboard of the engine is the generator starting battery. It is charged only
by the generator or, if there is shore power and it is turned “on”, the battery charger (this is rare).
A third bank of two batteries is called “the house battery”, located outboard of the starboard
engine. Connected to this are all the pumps, interior and exterior lights, horns, navigation and radio
gear, etc. (“the house”), and the starboard engine starter. This bank is charged by the alternator on
the starboard engine; when there is shore power or the generator is running, by the inverter if it is on;
when the port engine is running, by the port engine’s alternator through the battery combiner; or, if on,
the battery charger.
If necessary, (but only in emergencies) you can switch the battery switch in the forward engine
room panel to “parallel”, so that both starting and house banks are connected together! This way, we
can be virtually positive that our engines will start. Normally, however, we leave this switch in the non-
paralleled position so the systems are independent.
Note: If it takes more than two attempts to start an engine, turn off its sea water
valve to avoid water-locking the engine until it starts.
What redundancy!
4G3: DC Battery Chargers
The vessel is equipped with a 12-volt battery charger, the original unit installed by Grand Banks
when the boat was manufactured. It charges all the batteries, although normally the inverter is the
primary battery charger, charging the house batteries.
The charger is switched on by its breaker in the 120-volt circuit breaker panel.
On Patos, the Inverter is the primary battery charger! Do not turn the “Battery
Charger” breaker on unless the inverter has failed, or the generator battery is
dead! Normally use the Inverter only to charge the batteries!
House batteries outboard of the starboard engine are in the white
boxes.
Section 4G: Electrical Systems, DC 4.13