Chapter 3 Direct Current Power MElec-Ch3 - 1 Overview • • • • • Batteries Safety Precautions Marine Storage Battery Charging Systems Battery Utilization MElec-Ch3 - 2
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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
MElec-Ch3 - 1
Overview
•
•
•
•
•
Batteries
Safety Precautions
Marine Storage Battery
Charging Systems
Battery Utilization
MElec-Ch3 - 2
Batteries
• Cells and Battery
• Battery Chemistry
Primary Cells
Secondary Cells
• Series and Parallel Connections
MElec-Ch3 - 3
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
MElec-Ch3 - 4
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
MElec-Ch3 - 5
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
MElec-Ch3 - 6
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
MElec-Ch3 - 9
Marine Storage Batteries
•
•
•
•
•
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)
MElec-Ch3 - 11
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)
MElec-Ch3 - 12
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
MElec-Ch3 - 13
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
MElec-Ch3 - 15
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
MElec-Ch3 - 18
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
MElec-Ch3 - 19
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
MElec-Ch3 - 21
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
MElec-Ch3 - 22
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
MElec-Ch3 - 23
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
MElec-Ch3 - 26
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
MElec-Ch3 - 28
Charging Systems
•
•
•
•
•
•
Basic Considerations
Degree of Charge
Alternators
AC Battery Chargers
Inverter/Charger
Other
MElec-Ch3 - 29
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
MElec-Ch3 - 31
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
MElec-Ch3 - 32
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
-
-
-
-
+
Starting
Battery
Engine
Driven
Alternator
#1 + AC Charger
#2 +
(Two-outputs)
-
Negative Common
MElec-Ch3 - 35
AC Battery Chargers
• Basic charger (not recommended)
Single output voltage
Can’t do bulk, acceptance, and float charging
Can’t handle multiple chemistries
MElec-Ch3 - 36
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
MElec-Ch3 - 37
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
MElec-Ch3 - 38
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
MElec-Ch3 - 39
Battery Utilization
•
•
•
•
Separate Starting and House
Battery Switches
Battery Monitor
Typical 12 volt System
MElec-Ch3 - 40
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
MElec-Ch3 - 41
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
MElec-Ch3 - 42
Battery Switches
to Starter
Solenoid
to Power
Panel
SW 3
SW 1
SW 2
F1
+
+
Starting
Battery
House
Battery
-
-
-
Negative Common
MElec-Ch3 - 43
Battery Monitors
• Battery Monitors keep track of
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
MElec-Ch3 - 44
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
MElec-Ch3 - 45
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
MElec-Ch3 - 46
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
MElec-Ch3 - 47