MJM Yachts 40z Express - Manual (Page 28)

6.0
6.1
ELECTRICAL SYSTEM
GENERAL
The 40z’s electrical system may be more advanced than what you are accustomed to. It
combines DC and AC power in several ways.
Most of the electrical components on your boat use DC power. 12 volt DC power is stored in two
8D House Batteries and two 31G Start Batteries, totaling 700 Ampere Hours of capacity. This
battery capacity is replenished in 3 ways :(1) Alternator output from the engines when running (2)
From 110V 60cyle AC shorepower through the Mastervolt Charger or (3) From the Northern
Lights Generator which outputs 110V 60-cycle power to the charger.
120-volt AC power, typically found in homes, is supplied to the boat in 3 ways: (1) via 1 or 2
shore-power cords plugged into a shoreside receptacle (2) by an optional generator or (3) by
inverting DC power from a battery into AC power through the Mastervolt Inverter. The AC
components aboard your boat include the refrigerator/freezer, cooktop, microwave, some TV
components, the air-conditioning, water heater, inverter, and receptacles (plug in AC equipment).
Both AC and DC electrical power sources are potentially dangerous. Do
not attempt to work on any part of your boat’s electrical system if you are not a qualified
marine electrician.
12 VOLT DC SYSTEM
There are two battery banks on your boat. The house bank consists of (2) 245Ah, absorbed-glass
mat (D8 AGM) batteries. The engine bank consists of two 105Ah Group 31 AGM start batteries
which are also used to run the windlass. Whenever a charging source is present (either from the
battery charger or an engine-driven alternator) both banks are automatically charged. AGM
batteries are essentially no-maintenance.
Do not attempt to open the batteries. Other than keeping them properly charged,
stored, and clean (especially between the terminals), there is virtually nothing you need to do to
them. The battery charger is factory set specifically for AGMs.
If the engine is not running, the batteries can be
charged via the battery charger, which is powered by
AC electricity either from your generator or shore-
power. It is important to read and understand the
inverter/charger manual to be sure that the unit is
functioning as you expect.
Never allow your DC system’s
voltage to fall below 11.2 volts. Sensitive electronics
may fail to function. For this reason, it is advisable
when leaving the boat to turn off all loads, turn off
their respective circuit breakers, and turn off the
main DC battery switches and turn off the inverter.
24 Hour Circuits The only load that remains on
when the battery switches are in the OFF position
are the “24 Hour” circuits (shown at right) which by-
pass the panel circuit breakers and are connected
directly to the batteries.
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CHAPTER 6
BILGE PUMP
BILGE PUMP
BILGE PUMP
HIGH WATER ALRM
STEREO MEM
DVD MEM