# Marine AC and DC Electrical Systems

```MARINE AC AND DC
ELECTRICAL SYSTEMS
SEMINAR
BY
Topics
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Electrical Basics
Wire Sizing and Connections
Circuit Protection
Batteries
Battery Charging Systems
– Battery Chargers
– Alternators
– Solar and Wind
Topics
• Battery Monitors
• Inverters
• AC Systems
• Grounding Systems
• American Boat & Yacht Council, Inc. (ABYC) develops the
consensus safety standards for the design, construction, equipage,
maintenance, and repair of small craft. The development of uniform
standards is the basis for industry-wide comparisons of products and
performance.
• ABYC standards are minimum requirements for a safe design,
construction and repair. Boaters should insist that builders, repairers
and installers use these ABYC standards as a minimum. Their boating
experience will be enhanced and the image of the marine industry
justifiably improved..
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• Q:What is the most common problem on a
boat?
• A:The most common problem on a boat is
the failure of it’s electrical system.
• Q:What causes most boat fires?
• A:Most boat fires are directly related to a
faulty electrical system
Electrical Basics
• Ohms law
• Ohms Law is a mathematical equation that shows
the relationship between Voltage, Current and
Resistance in an electrical circuit. It is stated as:
V=IxR
R=V/I
I=V/R
• Where
 V = Voltage
 I = Current
 R = Resistance
A SUMMARY OF WHAT THE MATH MEANS
(Which assumes the Unmentioned Value stays Constant)
• If voltage increases, there will be an increase in current flow (amps)
• If resistance (OHMS) increases Amperage will decrease
• In all circuits, voltage is lost as it travels through the circuit. This is
referred to as VOLTAGE DROP.
– Things Which Add Resistance To A Circuit:
• Long wire runs to a load and back to the power source
• Inadequate wire diameter (AWG Size)
• Wire Type, (Material, # of Strands)
• Loose or Corroded Connections
• Remember, the primary by-product of excessive resistance is
heat!
Wattage
Amps (current flow)
x
Volts (system voltage)
=
Watts (power, either production or
consumption)
What size wire do I need?
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DC WIRE SIZING
Blue Sea Circuit Wizard
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•
Marine Tinned Primary Wire
• Constructed to American Wire
Gauge standards, AWG wire is up
to twelve percent larger than the
equivalent SAE wire sizes. AWG
wire provides a greater current
capacity when compared to SAE
gauge wire.
• Marine Tinned Wire and Cables
are manufactured from tin coated
copper strands for maximum
protection against corrosion,
electrolysis and resists fatigue due
to vibration and flexing.
• Rated at 600 volts and 105
degrees C, the heavy duty
insulation is resistant to heat and
abrasion. Exceeds all UL1426, US
Coast Guard Charterboat (CFR
title 46) and ABYC standards.
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AND TOOLS
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ABYC E-11
• All conductors shall be supported and/or
clamped at least every 18 inches to relieve
strain on connections.
Like this
Not This
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Circuit Protection
What is circuit protection?
•
Circuit protection is the intentional installation of a "weak link" in an
electrical circuit. This is a fuse or circuit breaker, referred to here as a
circuit protection device.
Circuit Protection
What is the Circuit protection against?
• Prevention of wire conductor overheating and
resulting burning of the wire insulation is the primary
reason to install a fuse or circuit breaker. In some
cases they are also installed to protect electrical or
electronic equipment from damage.
How does fire start in an electrical circuit?
• Fire results when too much amperage travels
through a wire. Amperage is electron flow through a
conductor. If too much amperage flows through a
wire, enough heat can be generated to melt and
burn the wire insulation or surrounding materials.
No Circuit Protection
If you have electrical problems and
this, then you needn't look much
farther for the source of the
problem.
Unfortunately this is seen to often
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Circuit Protection
•
What wires need to have Circuit Protection installed?
•
The ideal answer is that every wire in the boat needs to be protected by a fuse
or a circuit breaker. The Circuit Protection Device must be correctly sized to the
wire it protects. As wires branch away from the batteries or other power source
and become progressively lighter, smaller CPDs must be installed at the
beginning of each wiring run.
•
ABYC Standards exempt wiring between the batteries, the main battery switch
and the starter motor. It is not that these wires do not require CPDs, but that it is
often not practical to provide such protection. The diagram below shows where
ABYC standards for CPD placement. Measurements are maximum lengths
between the point of connection and the CPD. All 7" dimensions may be
increased to 40" if the conductor is enclosed in a sheath or enclosure in addition
to the wire insulation.
Circuit Protection
BATTERIES
Ampere Hour Rating (Reference Rating)
• This is the number of amps which a battery can deliver for a
20-hour period. This test is also referred to as the 20-hour
rate. The larger the ampere hour rating, the more power the
battery can deliver over time.
Marine Cranking Amps (MCA)
• This is the number of amps a battery can deliver at 32
degrees fahrenheit for 30 seconds, and maintain at least a
voltage of 1.2 volts per cell. This differs from cold cranking
amps which are measured at 0 degrees fahrenheit.
Reserve Capacity (RC)
• This is the time, in minutes, for which a battery will deliver
25 amperes at 80 degrees fahrenheit. This represents the
time which the battery will continue to operate essential
accessories in the event of alternator or generator failure
or while the key is off.
Batteries
• What happens to volts and
amps?
• Combining batteries in series
multiplies voltage, capacity
(Amp Hours) is unchanged
(equivalent to the rating for
one of the batteries in the
series)
• Combining batteries in
parallel multiplies the
amperage
• Only combine batteries of
like kind and vintage
Starter battery
The starter battery has
many thin plates in
parallel to achieve low
resistance with high
surface area. The starter
battery does not allow
deep cycling.
Deep-cycle battery
The deep-cycle battery has thick plates for
improved cycling abilities. The deep-cycle
battery generally allows about 300 cycles.
Depth of Discharge
Starter Battery
Deep-cycle Battery
100%
50%
30%
12–15 cycles
100–120 cycles
130–150 cycles
150–200 cycles
400–500 cycles
1,000 and more cycles
Inexpensive and simple to manufacture; low cost per watt-hour
Low self-discharge; lowest among rechargeable batteries
High specific power, capable of high discharge currents
Good low and high temperature performance
Low specific energy; poor weight-to-energy ratio
Slow charge; fully saturated charge takes 14-16 hours
Must be stored in charged condition to prevent sulfation
Limitations Limited cycle life; repeated deep-cycling reduces battery life
Flooded version requires watering
Transportation restrictions on the flooded type
Not environmentally friendly
AGM Batteries
Spill-proof through acid encapsulation in matting technology
High specific power, low internal resistance, responsive to load
Up to 5 times faster charge than with flooded technology
Advantages Better cycle life than with flooded systems
Water retention (oxygen and hydrogen combine to produce water)
Vibration resistance due to sandwich construction
Stands up well to cold temperature
Higher manufacturing cost than flooded (but cheaper than gel)
Sensitive to overcharging (gel has tighter tolerances than AGM)
Capacity has gradual decline (gel has a performance dome)
Limitations
Low specific energy
Must be stored in charged condition (less critical than flooded)
Not environmentally friendly (has less electrolyte, lead that flooded)
Charging Characteristics
How long will they last ?
Battery Chargers
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Ferroresonant Chargers
• The better chargers
work ok on wet cell
batteries
• Do not do a good job
on AGM and Gel
batteries
• May cause premature
battery failure because
of constant
overcharging
If you have one, replace it
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Three Stage Battery Charger
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Battery Charger Wiring
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Alternators
• Internal or external regulators
• In automotive type alternators, current for the alternator is supplied by
an internal regulator, which drives the alternator to a specific voltage
value (usually about 14.1 volts), which works great for a starting
battery, just like the one in your car.
• Deep cycle and sealed gel and AGM marine batteries require a more
complex program of charging voltages to achieve their optimal charge.
Multi-stage external voltage regulators, like the Balmar Max Charge
and ARS-5 enable the alternator to vary charging voltages, based on the
battery’s temperature, chemistry (flooded, gel or AGM types) and level
of discharge, to ensure that batteries are recharged quickly and safely.
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SMART REGULATORS
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Alternators
• The Rule of thumb is that the alternator
output in amps should not be less than 25%
of the battery capacity in amp hours for
lead batteries and 40% for AGM.
• You can figure 1 hp draw per 25 amps (12
volt) at maximum output.
Belt Type
Belt Width
Highest
Recommended
Output
Single Vee
3/8
3.5
80A @ 12V, 30A
@ 24V
Single Vee
1/2
4.5
110A @ 12V, 45A
@ 24V
Dual Vee
1/2
12
310A @ 12V,
220A @ 24V
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Charging Multiple Battery Banks
The Battery Isolator
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IT’S IMPORTANT TO REMEMBER
THAT IF A BATTERY ISOLATOR IS
INSTALLED, VOLTAGE SENSING FOR
THE ALTERNATOR MUST BE DONE
AT THE BATTERIES, OR AT LEAST ON
THE BATTERY SIDE OF THE
ISOLATOR.
THIS IS DUE TO THE INHERENT 0.7 V
LOSS THROUGH THE ISOLATOR
DIODES.
ALSO, ISOLATORS MUST BE RATED
FOR THE MAXIMUM ALTERNATOR
AMPERAGE OUTPUT
Battery Isolators are made with two
or more silicon diodes that act like
check valves. The diodes will pass
current from the charging source to
the batteries, but will not pass current
backward from one battery to the
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other or back to the charging source.
A Better Way
BATTERY COMBINERS
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Automatically combines battery banks
during the charging cycle and isolates
under discharge
Ignition protected - safe for installation
aboard gasoline-powered boats
Activates from any charging source alternators, battery chargers, or solar
panels
Requires circuit protection device at
batteries
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The ACR has two parts:
A relay – a switch that is activated by an
electrically powered magnetic coil.
An electronic circuit that senses the voltage
level of the boat’s batteries and signals the
relay switch:
Closed when voltage is high (the ACR’s
COMBINE voltage)
Open when voltage is lower (the ACR’s
UNDERVOLTAGE voltage)
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Battery Combiner Diagram
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Effect of Solar and Wind Energy
on Marine Battery Charging
How do you know if your
batteries are properly charged?
Battery Monitors
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Electrical Specifications
Voltage Measurement
0 - 35.0 VDC (+/-0.01 V resolution)
Current Measurement
-500 - 500 A
Amp-Hour Measurement
High range +/- 200 - 1,999 Ah (1 hour
resolution)
Battery Capacity Range
200 - 2000 Ah
gauge
the status of your battery bank
• Displays voltage, current, consumed
amphours and remaining battery
capacity
• Secondary battery bank voltage
monitoring
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What they tell you
INVERTERS
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A-25.5 REQUIREMENTS - IN GENERAL
A-25.5.1 If the inverter also serves as a battery charger, it shall also meet the requirements of ABYC A-20, Battery Charging Devices.
NOTE: An inverter incorporating a battery charging circuit that meets UL 458, Power Converters/Inverters and Power Converter/Inverter Systems for Land Vehicles and Marine
Crafts, and Supplement SA, Marine Power Converters/Inverters and Power Converter/Inverter Systems, need not meet UL 1236 as referenced in ABYC A-20, Battery Charging
Devices.
A-25.5.2 Output voltage and frequency shall be in accordance with ABYC E-8, Alternating Current (AC) Electrical Systems On Boats.
EXCEPTION: Inverters dedicated to supply power to only a specific piece of equipment.
A-25.5.3 All marine power inverters shall meet the applicable requirements of UL 458, Power Converters/Inverters and Power Converter/Inverter Systems for Land Vehicles and
Marine Crafts, and Supplement SA, Marine Power Converters/Inverters and Power Converter/Inverter Systems.
A-25.5.4 Power inverters shall be automatically controlled to provide frequency and voltage regulation compatible with section 27 of UL 1248, Engine-Generator Assemblies for
Use in Recreational Vehicles.
A-25.5.5 Power inverters shall provide isolation of the AC output from the DC supply circuit.
A-25.5.6 Integral inverter receptacle shall be protected by an integral GFCI device in accordance with ABYC E-8, Alternating Current (AC) Electrical Systems On Boats. The
receptacle is to be used only with cord connected loads.
A-25.5.7 A visible means (e.g., voltmeter or lamp) of determining that the inverter is "on line" and/or in "stand-by" mode shall be provided at the main electrical distribution
panel.
A-25.5.8 A warning label shall be provided at the main electrical panel to indicate that the electrical system includes an inverter. See A-25.10.1.
A-25.5.9 Grommets, bushings, or other means shall be provided to prevent chafing of wires passing through the inverter case.
A-25.5.10 Safety signs and labels shall comply with ABYC T-5, Safety Signs and Labels, and shall contain at least the following informational elements:
A-25.5.10.1 The signal word for the hazard intensity level; and
A-25.5.10.2 the nature of the hazard; and
A-25.5.10.3 the consequences that can result if the instructions to avoid the hazard are not followed; and
A-25.5.10.4 instructions on how to avoid the hazard.
A-25.6 INSTALLATION AND LOCATION
A-25.6.1 The installation and protection of electrical wiring associated with inverters shall comply with ABYC standards ABYC E-8, Alternating Current (AC) Electrical
Systems on Boats, and ABYC E-9, Direct Current (DC) Electrical Systems On Boats.
A-25.6.2 Inverters shall be installed:
A-25.6.2.1 in a ventilated, dry, accessible location; and
A-25.6.2.2 where the ambient temperature will not exceed 122°F (50°C); and
A-25.6.2.3 away from heat sources, such as dry engine exhaust and other heat producing devices.
A-25.6.3 Inverters shall not be installed directly over batteries.
A-25.6.4 Inverter controls shall be readily accessible.
A-25.6.5 Inverters shall be located so that hinged covers and access plates can be opened.
A-25.6.6 Inverters shall be securely fastened to bulkheads or other vessel structural parts.
A-25.6.7 When mounted, the base of the inverter shall be at least two feet above normal bilge water, or protected so it is not subject to bilge splash.
A-25.6.8 The installer shall provide physical protection from falling objects or drippage unless such provision is integral to the inverter.
A-25.6.9 Overcurrent protection in the DC input circuit shall comply with the requirements of ABYC E-9. This protection is intended to protect the wiring in the DC circuit.
NOTE: See ABYC E-9 for battery switch requirements.
A-25.6.10 If ground fault circuit interruption is provided in the output of the inverter, the ground fault interrupter shall not be located in a compartment requiring ignition
protection, unless it is ignition protected as provided in SAE J-1171 or UL 1500.
A-25.6.11 An inverter that does not have an integral ground fault protection device and is installed so that GFCI protection is required by ABYC E-8, shall have the required
GFCI device(s) specified by the inverter manufacturer as to GFCI manufacturer and model number.
NOTE: Harmonic distortion of the AC output waveform from some inverters may affect the operation of some GFCI devices.
A-25.6.12 Power inverters installed in spaces requiring ignition protection shall meet the ignition protection requirements of SAE J1171 or UL 1500. See A-25.10.2 for labeling
requirements.
NOTE: For information on spaces requiring ignition protected equipment see 33 CFR 183.410; ABYC A-1, Marine Liquefied Petroleum Gas (LPG) Systems; ABYC A-22,
Marine Compressed Natural Gas (CNG) Systems; ABYC E-8, Alternating Current (AC) Electrical Systems On Boats; ABYC E-9, Direct Current (DC) Electrical Systems On
Boats; and ABYC H-24, Gasoline Fuel Systems.
A-25.6.13 A means to achieve strain relief shall be installed within six inches of the case unless a strain relief method is integral with the case for wiring passing through.
A-25.7 AC WIRING CONNECTIONS
A-25.7.1 ABYC E-8, Alternating Current (AC) Electrical Systems On Boats, requires a grounded neutral system. The neutral for AC power sources shall be grounded only at the
following points:
A-25.7.1.1 The shore power neutral is grounded through the shore power cable and shall not be grounded on board the boat.
A-25.7.1.2 The inverter output neutral shall be grounded at the inverter.
A-25.7.1.2.1 The inverter/charger output neutral shall be grounded at the inverter/charger.
AC Systems
Galvanic Isolators
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What is a galvanic isolator and why should my shore power system have
one?
•
A galvanic isolator is a device used to block low voltage DC currents coming on board
your boat on the shore power ground wire. These currents could cause corrosion to your
underwater metals; through hulls, propeller, shaft etc.
•
Boats in a marina plugged into shore power all act as a giant battery. They are all
connected together by the green shore power ground wire, which is (or should be)
connected to their DC grounds, engine block, and bonded underwater metals. (Required
by ABYC If the boats are in salt water then that forms an electrolyte and the dissimilar
metals connected together act as a battery, causing corrosion.
GALVANIC ISOLATOR
OLD STYLE ISOLATOR
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•
DUE TO THE INHERENT
VOLTAGE DROP THAT OCCURS
ACROSS A DIODE – TYPICALLY
0.6 V TO 0.7 V –
GALVANIC ISOLATORS CAN BE
USED TO EFFECTIVELY BLOCK
GALVANIC CURRENTS UP OT
ABOUT 1.4 V. BY PUTTING TWO
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DIODES IN SERIES
Fail Safe Galvanic Isolators
• Fail-safe construction featuring
Fail-Safe Plus™ and Fail-Safe
Max™ technology
• Certified to ABYC A-28 July
2008 publication
• No monitoring system required
• Highest AC fault current ratings
available
• Ignition protected
• Maintenance-free solid-state
design
• Rated for high levels of lightning
current
• Very low DC leakage current49
allowed
Grounding System
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Multiple Roles of the Grounding System
Prevent electrical shock hazard to people on board
– In the event of an electrical fault in a AC appliance it is
essential to provide a reliable path for this fault current back to
the source of power, not through the person coming into contact
with the device
Prevent stray current corrosion
– Equalize voltage potentials among dissimilar metal objects
exposed to seawater.
Bonding systems – and cathodic protection (properly sized and
placed anodes)
Lightning Protection
Note : The AC Ground buss (green wire) is connected to the DC
Negative Buss
Grounding System
Electric Shock
Drowning
Good
Ground
Broken
Ground
Effects of a Lightning Strike
Lightning Grounding
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Connect a AWG 4 battery cable from the base of your aluminum mast to the
nearest keel bolt from external ballast. If you have internal ballast, you should
install a lightning ground plate. One square foot is recommended for use in salt
water; fresh water requires much more. Do not rely on a thru-hull or a sintered
bronze radio ground (e.g. Dynaplate) for use as a lightning ground.
•
For additional comfort, also run a 6 AWG wire from your keel bolt or ground plate
to the upper shroud chainplates, and to your headstay chainplate. Don't bother
with the backstay if it is interrupted with antenna insulators. Have each of the
cables that are used for lightning ground wires lead as directly as possible to the
same keel bolt, with any necessary bends being smooth and gradual.
•
Given that you have grounded your mast solidly to the ocean, your mast will be at
exactly the same electric potential as the ocean. There is no chance that you
can dissipate the charge between the ocean and the atmosphere, so don't bother
with a static dissipater at the masthead. Wire "bottle brush" static dissipaters
may be useful to dissipate seagulls.
Recommended Books
Boatowner’s Mechanical and Electrical Manual, third edition
Nigel Calder
Maintain, repair, and improve a boat’s essential systems. A comprehensive
guide to electrical, mechanical, and propulsion systems.
Sailboat Electrical Systems: Improvement, Wiring and Repair
Don Casey
A basic treatment for recreational sailboats and powerboats. A good book
for maintenance and repair.
Sailboat Electrics Simplified
Don Casey
How to install wiring, make good, safe connections, match you battery
bank and alternator to your needs, troubleshoot problems quickly, and 55
avoid shore power problems.
Recommended Books
• Powerboater’s Guide to Electrical Systems: Maintenance,
Troubleshooting and Improvements, second edition
Ed Sherman
Focused on power cruisers, the author is a recognized authority on
electrical practice and is well respected by boat builders and marine
electricians.
• Advanced Marine Electrics and Electronics Troubleshooting
Ed Sherman
Targeted at trade professionals. Boat builders, installers, electricians
and boatyard owners will want this book for its insight into new tools
and techniques for tracking down problems. The advanced boat owner
will benefit as well.
• Boatowner’s Illustrated – Electrical Handbook, second edition
Charlie Wing
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Great for learning about a boat’s electrical system.
Recommended Web Sites
• Bluesea.com
• ABYC
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SUMMARY
• Each circuit must have its own properly rated
circuit protection device.
• Only the starter motor circuit is exempt from
having a circuit protection device
• Check connections for corrosion, loosening.
• Use marine grade “boat cable”