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Chapter 3

Chapter 3. Direct Current Power. Overview. Batteries Safety Precautions Marine Storage Battery Charging Systems Battery Utilization. Batteries. Cells and Battery Battery Chemistry Primary Cells Secondary Cells Series and Parallel Connections. Cells and Batteries.

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Chapter 3

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  1. Chapter 3 Direct Current Power

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

  3. Batteries • Cells and Battery • Battery Chemistry • Primary Cells • Secondary Cells • Series and Parallel Connections

  4. 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

  5. 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

  6. 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

  7. Series and Parallel Connections + + 12 V @ 100 A 6 V @ 100 A 6 V @ 100 A - - - 24 V @ 50 A Series + + 12 V @ 50 A 12 V @ 100 A 12 V @ 50 A - - + + Common 12 V @ 100 A 12 V @ 50 A 12 V @ 50 A - - Parallel Dual Voltage

  8. 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

  9. Warning Message

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

  11. 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)

  12. 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)

  13. 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

  14. 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

  15. Deep-Cycles Gel Battery

  16. 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

  17. Advantages / Disadvantages

  18. Sizes

  19. 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

  20. Battery Ratings by Battery Type

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

  22. 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

  23. 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

  24. Typical 24-hour Load

  25. 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

  26. 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

  27. 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

  28. 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

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

  30. 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

  31. 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

  32. 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

  33. Lead-acid 12 volt Voltages

  34. 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

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

  36. AC Battery Chargers • Basic charger (not recommended) • Single output voltage • Can’t do bulk, acceptance, and float charging • Can’t handle multiple chemistries

  37. 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

  38. 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

  39. 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

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

  41. 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

  42. 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

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

  44. 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

  45. 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

  46. Typical 12 volt Diagram DC Power Panel #12 Bilge Pump F2 #12 Brown Float Switch #12 Brown SW4 V SW5 #16 CB1 3 Stage Battery Charger Battery Isolator (Diodes) #10 Orange #16 #12 #8 #4 Red #10 #8 SW2 + SW3 A S - SW1 F1 Alternator Starter Diesel Engine #4 + + Starting Battery House Battery #10 #10 - - #4 Black (or Yellow) #4

  47. 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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