Marine Electrical Systemson

Auxiliary Sailboats

Topics To Discuss

• Major AC and DC electrical systems typically found on small to medium size auxiliary sailboats.

• Tools and supplies needed to install or repair those systems.

• Troubleshooting techniques for common problems.

• Safety

Nomenclature

• AC – Alternating Current (120 volts AC)

• DC – Direct Current (12 volts DC)

• V – voltage - volts

• I – current – amperage or amps

• R – resistance - ohms

AC Systems

AC Systems & Components

• Shore Power Connection

• AC Electrical Panel

• Cabin Outlets

• Battery Charger

• Inverter / Chargers

• Hot Water Heater

• Galvanic Isolator

Shore Power Connection

Shore Power Cables

AC Panel

• Sometimes separate but often integrated with the DC Panel.

• AC Main circuit breaker - 30 amp.

• Individual load circuit breakers - 15 amp.

• Reverse Polarity Indicator – warning when neutral line is not at ground potential.

AC Only Panels

Integrated AC / DC Electrical Panel

Reverse AC Polarity Problem• AC circuit breakers are single pole which means

they only disconnect hot wire.• If polarity is reversed then neutral is hot and not

switched.• If neutral is tied to the metal case of an

appliance then there is a shock hazard.• Reverse polarity indicator will not function if

ground is missing.• Always best to disconnect shore power cord

when working on AC systems.

Reverse Polarity Indicator Circuit

AC Outlets Same as those in your house – 120 volts 15 amps

Battery Charger

• Typically provides 10 to 50 amps of charging current depending on manufacture and model.

• Normally has charge state indicators but often mounted where they cannot be seen.

• Better models provide 3 charge stages; bulk, absorption, and float.

Battery Chargers

20 amps max 50 amps max

Inverter / Charger

• At the dock charges the both house and starting batteries.

• Away from the dock provides 120 Volts AC from the house battery.

• Usually include automatic transfer switch for AC loads.

• Available battery charging current and AC power output depends on size.

Inverter / Chargers

Hot Water Heater

• Typically 120 Volts, 1500 watts, 12.5 amps

• Can be round or rectangular, horizontal, or vertical.

• Often include a heat exchanger that uses engine coolant to heat water when under power.

Hot Water Heaters

Galvanic Isolator

Bonding (Grounding) System

Galvanic Isolator• Not really an AC system but is connected in the

AC line.• Isolator prevents low voltage DC path in shore

power ground wire.• Engine, metal through hulls, prop and shaft are

often all electrically connected or bonded together and connected to boat ground.

• Zincs attached to shaft and bonding system are sacrificial anodes to prevent corrosion of bronze prop and through hulls

• Common shore power ground will provide conduction path to other boats and dock with potential corrosion problem.

Galvanic Isolator

DC Systems

DC Systems

• Main Battery Switch

• DC Panel

• Batteries

• Engine Alternator

• Engine Starting Motor

• Typical Loads

Main Battery Switch

• All major connections to batteries go through this switch.

• Exceptions are battery chargers and auto bilge pumps

• Allows selection of Battery 1, Battery 2, Both or Off (None)

Main Battery Switch

DC Panel

• Sometime separate but often integrated with the AC Panel.

• Usually has a MAIN DC circuit breaker.

• Circuit breakers for individual loads.

• DC Voltmeters and Ammeters.

DC Only Panels

AC / DC Electrical Panel

Typical DC Loads

• Starter Motor• Lights• VHF Radio• Instruments (Depth, Speed, Wind)• GPS – Chart Plotter• Auto Pilot• Stereo• Water Pressure Pump

Batteries

Batteries

• Lead, Lead Dioxide, Sulfuric Acid• Normally 12 Volts DC, sometimes two 6 volt

batteries connected in series for 12 volts.• Sometimes grouped in parallel for higher current. • 12 volt battery constructed of 6 individual cells that

are two volts each.• Types: Starting, Deep Cycle, and

Marine/Hybrid/Dual Purpose• Construction: Wet Cell, Gell Cell, AGM (Absorbed

Glass Mat)

Series / Parallel Configurations

Two 6 Volt Batteries in Series

Two 12 volt batteries in parallel

Starting Battery

• Designed for high current - short duration use.• Large number of thin plates for maximum

surface area.• May last for thousands of 2% to 5% of capacity

discharges.• However, if deep cycled the thin plates will

quickly be consumed and fall to the bottom of the cells.

• Will generally fail after 30 to 150 deep cycles of 20% to 80% depending on design.

Deep Cycle

• Designed to be discharged down to as much as 80% of capacity.

• Thicker plates than a starting battery.

• Fewer thicker plates mean less surface area and therefore less current capability.

• However, Deep Cycle batteries can still be used for starting if large enough.

Marine / Hybrid / Dual Purpose

• Designed as a compromise between Starting and Deep Cycle.

• Some Marine batteries are actually Deep Cycle.

• In some hybrid designs plates are composed of lead sponge but coarser than true Starting batteries.

• Often hard to tell what it is without opening the case which is not an option.

Wet / Flooded Cell Batteries

• Most common and usually least expensive.• Can be designed for starting, deep cycle or

hybrid use.• Liquid electrolyte so mounting is important, must

be mounted horizontally.• May vent hydrogen and oxygen generated by

electrolysis at end of charge or if overcharged.• Cases need to be vented.• Electrolyte level must be monitored and topped

up periodically.

Gel Cell Batteries

• Normally designed for deep cycle applications.• A thickening agent immobilizes the electrolyte.• Valve-regulated design means batteries are sealed

so mounting is not critical.• However, if overcharge hydrogen and oxygen will

escape through valves.• Since batteries are sealed and cannot be refilled

with electrolyte charging is more critical.• Gel cells use slightly lower charging voltages than

wet cells and thus the set-points for charging equipment have to be adjusted

AGM, (Absorbed Glass Mat) Batteries

• Normally designed for deep cycle applications.• Liquid electrolyte.• Uses a fiberglass like separator to hold the electrolyte in place

by capillary action. • Physical bond between the separator fibers, the lead plates,

and the container make AGMs spill-proof and the most vibration and impact resistant lead-acid batteries.

• Valve-regulated, sealed, so electrolyte cannot be replaced.• Small amounts of hydrogen and oxygen will be trapped and

recombine. Large amounts will vent.• AGMs use almost the same voltage set-points as flooded

cells and thus can be used as drop-in replacements for flooded cells.

Flooded Electrolyte Batteries

AGM Batteries

Gel Cell Batteries

Lead Acid Battery State of ChargeAfter 3 hour rest

State of Charge 12 Volt battery Volts per Cell

100% 12.7 2.12

90% 12.5 2.08

80% 12.42 2.07

70% 12.32 2.05

60% 12.2 2.03

50% 12.06 2.01

40% 11.9 1.98

30% 11.75 1.96

20% 11.58 1.93

10% 11.31 1.89

0 10.5 1.75

Why Batteries Fail

• Leaving batteries in a discharged state which leads to Lead Sulfation.

• Deep discharging a Starting Battery which damages the plates.

• Excessive vibration and shock damaging the plates.

• Long term sulfation due to normal battery use.

Lead Sulfation• When batteries are discharged amorphous lead

sulfate is formed on the plates. • If recharged soon the lead sulfate is easily

converted back to lead, lead dioxide, and sulfuric acid.

• However, if the battery is left in a discharged state too long the lead sulfate will convert to a crystalline form and will not convert back to lead, etc., during normal charging.

• This process will eventually coat the plates with non-conductive crystalline lead sulfate and kill the battery.

Lead Acid Battery Charge Stages

• Bulk – Charge current is set to maximum safe rate batteries will accept until voltage rises to near (80-90%) full charge level. Voltages at this stage typically range from 10.5 volts to 15 volts.

• Absorption - Voltage remains constant and current gradually tapers off as internal resistance increases during charging. It is during this stage that the charger puts out maximum voltage. Voltages at this stage are typically around 14.2 to 15.5 volts.

• Float - After batteries reach full charge, charging voltage is reduced to a lower level (typically 12.8 to 13.2) to reduce gassing and prolong battery life.

Lead acid Battery Charge Curves

Battery Maintenance

• Keep correct electrolyte level using only distilled water. (Wet cells only)

• Keep terminals clean.

• Keep batteries dry, especially the top.

• Make sure charging levels are correct.

• Keep batteries fully charged.

Battery Safety Issues• Batteries contain sulfuric acid which can cause eye

and skin burns and damage clothes.• A charging battery may contain significant amounts

of hydrogen which could explode if ignited.• Batteries can source hundreds of amps of current

and can melt jewelry around your finger or arm.Therefore:• DO - wear safety glasses and protective clothing.• DON’T - wear rings, bracelets or expensive clothes.• DON’T – allow sparks or flames near batteries,

especially when they are charging.

Engine Electrical Systems

Engine Alternator• Basically the same as the one in your car.• Provides current to charge batteries and operate

equipment, 40 to 100 amps.• Usually has an internal voltage regulator but

high end ones have an external regulator.• High current load requires significant force to

turn alternator so keeping belt tight is important.• Output voltage varies depending on model and

voltage regulator specifications. Range is 13.0 Vdc to 14.6 Vdc which presents an issue for proper battery charging.

Marine Engine Alternators

Yanmar 2/3 QM

Yanmar 2/3 QM

Starting Motor & Solenoid

• Solenoid – relay that switches high current to starter motor, typically draws around 10 amps.

• Starting motor may require 100 amps or more.

• Starting motor circuit requires very large gauge wires to minimize voltage drop and therefore power loss.

Starting Motor & Solenoid

Yanmar Starter Motors

Installation

Repair

Troubleshooting

Installation & Repair

• Tools

• Supplies

• Ohms Law / DC Power

• Wire Size Relative to Load

• Wire Terminals

• Wire Insulation Stripping

Tools

• Book: Boatowner’s Mechanical & Electrical Manual by Nigel Calder

• AC/DC Multimeter

• Assorted flat blade and phillips screw drivers

• Assorted pliers and cutters

• Adjustable, open and box end wrenches

• Wire stripper and terminal crimper

Repair and Installation Materials

• Wire

• Wire Terminals

• Electrical tape

• Shrink tubing

• Tie raps

Ohms Law

I = V/R, V=I*R, R = V/I

What is the voltage drop in a wire with a resistance of 1 ohm carrying 10 amps of current?

V = I*R = 1*10 = 10 volts

DC Power

P = V*I, V=P/I, I = P/V

What is the current for a 12 watt light bulb connected to a 12 volt battery?

I = P/V = 12/12 = 1 Amp

Wire Gauge for 3% Voltage Drop (Critical Loads)

Current (Amps)

5 10 15 20 25 30 40 50 60 70 80 90 100

Length (Feet) Wire Gauge (AWG)

10' 18 14 12 12 10 10 8 8 6 6 6 4 4

15' 16 12 10 10 8 8 6 6 4 4 4 2 2

20' 14 12 10 8 8 6 6 4 4 4 2 2 2

25' 14 10 8 8 6 6 4 4 2 2 2 1 1

30' 12 10 8 6 6 4 4 2 2 2 1 1/0 1/0

40' 12 8 6 6 4 4 2 2 1 1/0 1/0 2/0 2/0

50' 10 8 6 4 4 2 2 1 1/0 1/0 2/0 3/0 3/0

60' 10 6 6 4 2 2 1 1/0 2/0 1/0 3/0 3/0 4/0

Wire Gauge for 10% Voltage Drop (Non-Critical Loads)

Current (Amps)

5 10 15 20 25 30 40 50 60 70 80 90 100

Length (Feet) Wire Gauge (AWG)

10' 18 18 18 16 16 14 14 12 10 8 8 6 6

15' 18 18 16 16 14 14 12 12 10 8 8 6 6

20' 18 16 16 14 12 12 10 10 8 8 8 6 6

25' 18 16 14 12 12 10 10 8 8 8 6 6 6

30' 18 16 14 12 10 10 8 8 8 6 6 6 4

40' 16 14 12 10 10 8 8 6 6 6 4 4 4

50' 16 12 10 10 8 8 6 6 4 4 4 4 2

60' 16 12 10 8 8 8 6 4 4 4 2 2 2

Wire Diameter versus Gauge

AWG Diameter (inches) AWG Diameter (inches)

OOOO 0.46 8 0.1285

OOO 0.4096 9 0.1144

OO 0.3648 10 0.1019

0 0.3249 11 0.0907

1 0.2893 12 0.0808

2 0.2576 13 0.072

3 0.2294 14 0.0641

4 0.2043 15 0.0571

5 0.1819 16 0.0508

6 0.162 17 0.0453

7 0.1443 18 0.0403

Wire & Wire Terminals

• Should always use stranded wire not solid. Marine environment exposes wire to shock and vibration which could fracture solid wire.

• Tinned stranded provides much better corrosion protection than bare copper.

• Use crimped on terminal to make connection.• Use proper tool to crimp on terminal.• Use pull test after crimping to insure proper

crimp.• If you can pull the terminal off by hand, the crimp

is poor.

Marine Grade Wire – Tinned Stranded Copper

Tinned stranded copper wire.

Corroded copper wire.

Clean copper wire

Wire Terminals

Wire Insulation Stripping

• Do it right, use a wire stripping tool.

• If possible avoid using side cutters or a knife which will nick the wire and cause strands to break off.

• Strip off only enough insulation to crimp on the terminal.

Wire Strippers

Wire Terminal Examples

Excellent crimp on small terminal. Notice the slight extension of wire beyond the crimp.

Heavy gauge wire terminals. Sealing heat shrink tubing was used. Notice the small amount of sealing compound to the left of the tubing. This should be a water tight connection with maximum corrosion resistance.

VHF Radio Antenna Coax Cable

Coax cable has center conductor, spacer, shield, and outside sheath or cover.

Spacing between conductor is critical.

Should not be bent to small radius as this will change spacing of conductor and reduce signal.

For marine applications both center conductor and shield should be tinned copper.

Best connectors require special tools for installation but there are tool-less versions.

Shrink Tubing, Tie Wraps, Electrical Tape

Trouble Shooting & Installation

• Basics

• Light doesn’t work.

• VHF Radio doesn’t work.

• Batteries don’t charge.

• Engine won’t turn over.

• Bilge Pump Installation

Trouble Shooting Basics

One of four possible problems• Intermittent connection• Open connection (Blown fuse or open

breaker)• Reverse connection• Short (Usually includes a blown fuse or open

breaker)

Light Doesn’t Work

1. Verify battery is on, main breaker is on and load breaker is on.

2. If there is a fuse instead of a breaker remove and check for continuity.

3. Remove light bulb, do visual check or test bulb for resistance, should be less than 100 ohms.

4. Test voltage at socket pins, be careful not to short test leads together or to metal case.

5. Open up panel and check for voltage on both sides of circuit breaker.

6. If everything checks OK then problem is in wiring.

VHF Radio Doesn’t Work

1. Verify battery is on, main breaker is on and load breaker is on.

2. If there is a fuse instead of a breaker remove and check for continuity.

3. Make sure unit is turned on, volume is up and squelch is off. Select weather channel.

4. Make sure antenna coax connector is attached.5. Remove power connector and test for 12 volts.6. Remove antenna coax connector and check for short

between center conductor and shield.7. If you have static but no signal connect an external

antenna. This can be just a piece of wire stuck into the center of the connector.

Batteries Don’t Charge

• Measure voltage across batteries with all loads off, engine off, and battery charger off. Should be approximately 12.7 volts for a fully charged battery. (See battery charge state chart.)

• If possible start engine and check battery voltage, should be greater and increasing with maximum of approximately 13.8 volts. If not then alternator problem.

• Turn on battery charger and check battery voltage. Should be greater and increasing with maximum of approximately 14.4 volts. If not then battery charger problem.

• If battery voltage increases with either engine running or battery charger on, then batteries will charge. Batteries may not hold a charge if they are old or damaged.

Bilge Pump Installation

• Rule – Mate RM750A 750 GPH• Current at 13.6 Vdc is 3.1 amps• Want as much output as possible so this is

a critical application.• From wire size table 16 gauge is a good

choice.• If automatic operation is desired wire

directly to battery or battery switch with in-line fuse.

Safety

Causes of Fires Started On Board *AC and DC wiring/appliance  55%

– DC shorts/wiring - 30%– DC engine voltage regulator - 12%– AC appliance/heater - 4%– Shore power - 4%– AC wiring/panel - 2%– DC battery charger - 2%– AC power surge - 1%

* (Source – Boat US Blog – Data not verified)

Post Class Recommendations

• Get a copy of Nigel Calder’s book and read it cover to cover.

• Sign up for a boat team to get hands on experience.