Chapter 3 Direct Current Power 1 Overview

Chapter 3 Direct Current Power 1

Overview • • • Batteries Safety Precautions Marine Storage Battery Charging Systems Battery Utilization 2

Batteries • Cells and Battery • Battery Chemistry § Primary Cells § Secondary Cells • Series and Parallel Connections 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 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 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 6

Series and Parallel Connections + + 6 V@ 100 A - - 12 V @ 100 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 7

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 8

Warning Message 9

Marine Storage Batteries • • • Types Technologies Sizes Marine Battery Ratings Selection, Installation and Maintenance 10

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 400 A) fuse • Dual-Purpose battery § Large plates (like starting) § Thick plates (like deep-cycle) 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) 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 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 14

Deep-Cycles Gel Battery 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 16

Advantages / Disadvantages 17

Sizes 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 19

Battery Ratings by Battery Type 20

Selection, Installation and Service • Selection § DC Power Requirements § Typical 24 -hour load • Installation • Maintenance (Service) § Water § Cleaning Terminals § Winter Lay-up 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 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 23

Typical 24 -hour Load 24

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 25

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 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 27

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 28

Charging Systems • • • Basic Considerations Degree of Charge Alternators AC Battery Chargers Inverter/Charger Other 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 30

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 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 32

Lead-acid 12 volt Voltages 33

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 34

Multiple Battery Charging Battery Isolators + + - - - + Starting Battery House Battery - Engine Driven Alternator #1 + AC Charger #2 + (Two-outputs) - Negative Common 35

AC Battery Chargers • Basic charger (not recommended) § Single output voltage § Can’t do bulk, acceptance, and float charging § Can’t handle multiple chemistries 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 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 2 Kw inverter 100 A charger 3 -stage multiple batteries 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 39

Battery Utilization • • Separate Starting and House Battery Switches Battery Monitor Typical 12 volt System 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 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 42

Battery Switches to Starter Solenoid to Power Panel SW 3 SW 1 SW 2 F 1 + + Starting Battery - - House Battery - Negative Common 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 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 45

Typical 12 volt Diagram DC Power Panel #12 Bilge Pump F 2 Float Switch #12 Brown SW 4 CB 1 V #16 SW 5 #16 #8 #12 #4 Red A Alternator + - #10 Starter SW 2 SW 3 S Diesel Engine 3 Stage Battery Charger Battery Isolator (Diodes) #10 Orange #8 #12 Brown SW 1 + Starting Battery #10 #4 Black (or Yellow) F 1 #4 + - House Battery #10 - #4 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 47