Transcript Chapter 3 Direct Current Power MElec-Ch3 - 1 Overview • • • • • Batteries Safety Precautions Marine Storage Battery Charging Systems Battery Utilization MElec-Ch3 - 2

Chapter 3
Direct Current
Power
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Overview
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Batteries
Safety Precautions
Marine Storage Battery
Charging Systems
Battery Utilization
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Batteries
• Cells and Battery
• Battery Chemistry
 Primary Cells
 Secondary Cells
• Series and Parallel Connections
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Cells and Batteries
• Cells generates DC by chemical reaction
 Two dissimilar electrodes (conductors)
 Immersed in electrolyte (current carrying solution)
 Voltage function of electrode material
• Difference on the Galvanic Scale
• Covered in Chapter 5
• Battery
 Group of cells connected together
 Classes – Primary and Secondary
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Primary Cells
• Primary cells can not be recharged
 Chemical process is not reversible
 aka “Dry Cell”
• Common chemistries
 Zinc-carbon
 Alkaline (zinc and manganese oxide)
• Use
 Flashlights
 Portable radios
• Nominal voltage 1.5 VDC
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Secondary Cells
• Secondary Cells can be recharged
 Reversible chemical reaction
 aka “rechargable”
• Common chemistries
 Lead-acid (2.1 VDC)
 Nickel-cadmium (1.2 VDC)
 Nickel-metal hydride (1.2 VDC)
• Use
 Cars and Boats
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Series and Parallel Connections
+
+
6V@
100 A
6V@
100 A
-
-
12 V @
100 A
-
+
12 V @
50 A
Series
-
+
+
12 V @
50 A
12 V @
50 A
-
Parallel
12 V @
100 A
+
24 V @
50 A
12 V @
50 A
Common
12 V @
100 A
-
Dual Voltage
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Safety Precautions
• Lead-Acid batteries
 May produce explosive gases
 Contain acid
 Battery acid & seawater produce Chlorine Gas
• Charge batteries in well-ventilated area
 Keep sparks, flames and cigarettes away
• Wear eye, face and hand protection
 Baking Soda is effective neutralizing solution
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Warning Message
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Marine Storage Batteries
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Types
Technologies
Sizes
Marine Battery Ratings
Selection, Installation and Maintenance
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Types
• Starting battery
 Large amount of current
for very short time
 Not fuse protected
• Deep-Cycle battery
 Power for many hours
 Can be discharged to 50% capacity
 Protected by large (200 to 400A) fuse
• Dual-Purpose battery
 Large plates (like starting)
 Thick plates (like deep-cycle)
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Technologies
• Flooded
 Sometimes called “flooded” or “free-vented”
• Gelled Electrolyte (Gel)
 Also called Valve-Regulated Lead Acid (VRLA)
• Absorbed Glass Mat (AGM)
 Also called Valve-Regulated Lead Acid (VRLA)
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Flooded
• Traditional marine battery
 Electrolyte is water-diluted sulfuric acid
 Electrodes are lead
 Free vented – charging gases escape
• Advantages
 Low initial cost
 Good deep-cycle performance
• Disadvantages
 Spillable electrolyte
 High self-discharge rate
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Gelled Electrolyte (Gel)
• Gelled Electrolyte
 Electrolyte is a gel
• Mixture of sulfuric acid, fumed silica & phosphoric acid
 Pressure-relief vents (charging gases can’t escape)
• Advantages
 Spillproof / leakproof (can be used in any orientation)
 Lowest cost per cycle
 Low self discharge rate
• Disadvantages
 High initial cost
 Can be damaged, if charged at wet cell rate
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Deep-Cycles Gel Battery
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Absorbed Glass Mat (AGM)
• Designed for military aircraft
 Use matted glass fibers between plates
• Advantages
 Spillproof / leakproof (can be used in any orientation)
 Most shock and vibration resistant
• Disadvantages
 Capable of fewer discharge cycles
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Advantages / Disadvantages
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Sizes
Group Size
Amp Hours
Typical Size, in.
(l x w x h)
Weight, lbs.
(typical Gel)
U1
30 - 40
8x5x7
23
24
70 - 85
11 x 7 x 10
54
27
85 - 105
13 x 7 x 10
63
31
95 - 125
13 x 7 x 10
72
4D
180 - 215
21 x 9 x 10
130
8D
225 - 255
21 x 11 x 10
161
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Battery Ratings
• Ampere-hour (Ah) – Storage capacity
• Open Circuit Voltage (V) – Battery at rest
• Starting batteries
 Cold Cranking Amps (CCA) – 30 sec at 0 F
 Marine Cranking Amps (MCA) – 30 sec at 32 F
 Reserve Capacity (RC) – minutes of 25 A at 80 F
• Deep-cycle batteries
 Rated Capacity – Amp-hours for 20 hr at 80 F
 Deep Cycle Capacity
• Ability to provide small amounts of current over time
• Ability to withstand long, deep discharges
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Battery Ratings by Battery Type
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Selection, Installation and Service
• Selection
 DC Power Requirements
 Typical 24-hour load
• Installation
• Maintenance (Service)
 Water
 Cleaning Terminals
 Winter Lay-up
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Selection
• Starting Battery replacement
 Same Group Size and MCA
 Initial Cost or Life Cycle Cost?
• Flooded – Less expensive to buy
• House (Deep-cycle) Battery replacement
 Consider increased capability
• Double battery life if depth of discharge only 25%
 Initial Cost or Life Cycle Cost?
• Gel - Capable or more discharge cycles
• Ratios (Battery size to largest expected load)
 Flooded – 4 to 1
 Gel and AGM – 3 to 1
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DC Power Requirements
• What source of DC power?
 Powerboat normally powered off an alternator
 Sailboats normally powered off House Battery
 If anchored – Generator or House Battery?
• How often between battery charging?
• Limit depth of discharge to 50%
 For minimal charging time - Limit depth to 35%
 Battery life cut in half, if discharge to 75%
• Following table gives typical DC power demands
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Typical 24-hour Load
Load
(in Amperes)
Estimated
Hours Used
Estimated
Amp-hours
Running Lights
Anchor Light
Cabin Lights
3.0
0.6
3.6
2
10
6
6.0
6.0
21.6
Bilge Pump
Fresh Water Pump
Refrigerator
8.0
7.0
5.7
0.5
1
8
4.0
7.0
45.6
VHF Radio
GPS Receiver
Radar
1.0
0.8
3.0
8
8
8
8.0
6.4
24.0
12-volt Demand
(house battery)
TOTALS
32.7
128.6
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Installation
• Flooded batteries require
 Vented battery compartment
 Easy access to add water
• All batteries
 Should be in acid-resistant box
 Secured with insulated cover
 Starting battery located near engine
 Don’t mix battery age in a battery bank
 Don’t mix battery chemistry in battery bank
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Maintenance (Service)
• Flooded-cell require distilled water
 Rapid loss in single cell indicates bad battery
 Rapid loss in all cells indicates
high charging voltage
• Never force open or add water to Gel or AGM
• Clean and tighten terminals twice a year
 Use special battery tools (illustrated on next slide)
 Can remove corrosion with Baking Soda solution
• Don’t get solution into battery fill ports
 Apply battery “grease” to terminals
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Battery Tools
• Dirty or loose battery terminals can materially
reduce the energy available from a battery
• Use proper battery tools to prevent damage to
battery
Battery Terminal
Puller
Battery Terminal
Cleaner
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Winter Lay-up
• Fully charge and service before winter lay-up
 Flooded batteries should be equalized
• Disconnect negative battery terminal cable
• Flooded deep-cycle should be charged every
50 days
• Gel and AGM should be charged every 6
months
 Also flooded starting
• Continuous trickle charge not recommended
 Unless have automatic cutoff
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Charging Systems
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Basic Considerations
Degree of Charge
Alternators
AC Battery Chargers
Inverter/Charger
Other
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Basic Considerations
• Charging requires more charge (in amp-hours)
than removed
 Flooded 115 to 120%
 VRLA 105 to 114%
• Phases
 Bulk at 20 to 40% of battery's capacity
• Continues until 75% full
 Acceptance charging rate is steadily reduced
• Continues until accepted current equals 2% capacity
 Float current is only 0.1 to 0.2 Amps
• Maintenance, not charging
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Basic Considerations - 2
• Proper Charging Voltage depends on
 Temperature (table on slide 33 based on 80 F)
• Higher temperatures require lower voltage
 Battery Chemistry
 Table gives charging voltage by phase & chemistry
• Flooded-cell Equalization
 Prevents “sulfation”
 Recommended every 20 to 50 cycles
 Over charge, after acceptance phase, to dissolve lead
sulfate crystals on battery’s plates
 High voltage may damage electronic equipment
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Degree of Charge
• Flooded cell with hydrometer (most accurate)
• Gel and AGM with volt meter
 Can also use volt meter on flooded cell
• Next slide gives voltages for rested batteries
 Not charged or discharged for 24 hours
 Can also bleed off surface charge
• Use large light bulb for several minutes
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Lead-acid 12 volt Voltages
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Alternators
• Alternator converts AC to DC with diodes
 Don’t disconnect battery while alternator running
• “Zap-Stop” ® will protect diodes from damage
• Alternator sized at 25-40% of battery capacity
• Charging Diodes (Isolators)
 Permit charging of two batteries
 Have approx 0.6 to 0.7 voltage drop
• Increase alternator voltage for correct
voltage at battery
 Illustrated on next slide
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Multiple Battery Charging
Battery
Isolators
+
+
House
Battery
-
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-
-
+
Starting
Battery
Engine
Driven
Alternator
#1 + AC Charger
#2 +
(Two-outputs)
-
Negative Common
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AC Battery Chargers
• Basic charger (not recommended)
 Single output voltage
 Can’t do bulk, acceptance, and float charging
 Can’t handle multiple chemistries
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AC Battery Chargers - 2
• SCR multi-stage (recommended)
 Three phase charger (bulk, acceptance & float)
• Also will do equalization
 Independent multiple outputs
• Independent setting for Flooded, Gel and AGM
• Independent as to phase
 Best for Deep-Cycle
2 outputs @ 10 A
temperate climate
3 outputs @ 40 A
cold, warm or hot climates
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Inverters / Chargers
• Charger converts 120 VAC to DC
• Inverter converts 12 VDC to 120 VAC
 More on inverters in Chapter 4 on AC
• Advantages
 Lighter & cheaper than separate systems
2Kw inverter
100A charger
3-stage
multiple batteries
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Other
• Solar Panels
 Low power output
 Requires controller or
regulator
• Wind Generator
 Ideal wind of 5 to 30 Kt
 Should be feathered or
stopped at over 35 Kt
 More power than solar
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Battery Utilization
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Separate Starting and House
Battery Switches
Battery Monitor
Typical 12 volt System
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Starting and House Batteries
• Two battery banks are recommended
 Starting – Large amount of current for short period
• Half of breakdowns are – engine won’t crank
 House – Sustained power over long period of time
• Discharge limited to 50%
• Old concept was “Off-1-Both-2” battery switch
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Battery Switches
• Battery switches (current thinking)
 Dedicated “Off-On” switch for each battery
• Each battery charged separately
• Prevents weaker battery discharging stronger one
• When need extra current to crank engine
 Close switch #3 to parallel both batteries
• Switch must be opened after engine is started
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Battery Switches
to Starter
Solenoid
to Power
Panel
SW 3
SW 1
SW 2
F1
+
+
Starting
Battery
House
Battery
-
-
-
Negative Common
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Battery Monitors
• Battery Monitors keep track of
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

How much energy stored in battery
How much energy has been removed
How much energy is left in battery
Time remaining at current discharge rate
• Sophisticated, computer based device
• Voltmeter only provides current status
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Typical 12-volt System
• Next slide illustrates
 Starting and House battery
• Charged by alternator and charging diodes
• Charged by two output, three stage battery
charger
• Dedicated “Off-On” switches for each battery
• Separate battery paralleling switch
 Wires are color coded with size shown
• Note bilge pump wiring
– Fuse in negative lead
– Pump operated by either float switch
or panel switch
 Uses voltmeter to determine battery charge
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Typical 12 volt Diagram
DC
Power
Panel
#12
Bilge
Pump
#12 Brown
Float
Switch
F2
SW4
CB1
V
#16
SW5
#16
#12
#8
#4 Red
#10
+
A
Alternator
Diesel
Engine
Starter
SW2
SW3
S
-
3 Stage
Battery
Charger
Battery
Isolator
(Diodes)
#10 Orange
#8
#12 Brown
SW1
#4
+Starting
Battery
#10
#4 Black (or Yellow)
F1
+ House
Battery
-
#10
-
#4
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Summary
• Types of Marine Batteries
 Flooded-cell, Gel and AGM
 Starting, Deep-cycle and Dual-purpose
• Charge batteries in three phases
 Bulk, Acceptance and Float
 and if lead-acid, periodically equalize
• Keep binding posts & cables clamps clean
• Recommend battery charger / inverter
• Independent battery banks recommended
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