Chapter 3. Direct Current Power. MElec-Ch3-1

Transcription

1 Chapter 3 Direct Current Power MElec-Ch3-1

2 Overview Batteries Safety Precautions Marine Storage Battery Charging Systems Battery Utilization MElec-Ch3-2

3 Batteries Cells and Battery Battery Chemistry Primary Cells Secondary Cells Series and Parallel Connections MElec-Ch3-3

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 MElec-Ch3-4

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 MElec-Ch3-5

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 MElec-Ch3-6

7 Series and Parallel Connections + + 6V@ 100 A 6V@ 100 A A - + Series A A A - Parallel A A A Common A Dual Voltage MElec-Ch3-7

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 MElec-Ch3-8

9 Warning Message MElec-Ch3-9

10 Marine Storage Batteries Types Technologies Sizes Marine Battery Ratings Selection, Installation and Maintenance MElec-Ch3-10

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) MElec-Ch3-11

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) MElec-Ch3-12

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 MElec-Ch3-13

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 MElec-Ch3-14

15 Deep-Cycles Gel Battery MElec-Ch3-15

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 MElec-Ch3-16

17 Advantages / Disadvantages Feature Cost Weight Flooded Starting Flooded Deep Cycle Gel AGM Lowest Initial and Highest per Cycle Very Good Initial and per Cycle Lowest per Cycle and Highest Initial Very Good Initial and Excellent per Cycle Lightest per Ah Heaviest per Ah Mounting Upright Upright On side with 10% power loss On side with no power loss Ventilation Low Gasing Gases and Requires Ventilation Very Low to No Gasing Very Low to No Gasing Vibration Resistance Medium Medium High Very High Electrolyte Spillable Spillable and Can Add Water Spillproof and Leakproof Spillproof and Leakproof 25% of Ah capacity 25% of Ah capacity 33% of Ah capacity 33% of Ah capacity n/a approx. 350 approx. 650 approx. 370 Least Sensitive to Overcharging Maximum of 14.1 V Most Sensitive to Overcharging Maximum of 14.6 V Output Amps 50% Capacity Lifetime Cycles Charging (see Table 3-8) Charging Time Good Excellent Best Best Self-Discharge 1 to 3% per month up to 1% per day under 2% per month under 2% per month MElec-Ch3-17

18 Sizes Group Size Amp Hours Typical Size, in. (l x w x h) Weight, lbs. (typical Gel) U x5x x 7 x x 7 x x 7 x D x 9 x D x 11 x MElec-Ch3-18

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 MElec-Ch3-19

20 Battery Ratings by Battery Type Flooded Starting Flooded Deep Cycle Flooded Dual Purpose GEL AGM Starting - Cold Cranking Amps Starting - Reserve Capacity Deep Cycle low A Deep Cycle Life Dual Purpose Capability = Good 0 = Poor Criteria Rating Scale 4 = Best 3 = Excellent 2 = Very Good MElec-Ch3-20

21 Selection, Installation and Service Selection DC Power Requirements Typical 24-hour load Installation Maintenance (Service) Water Cleaning Terminals Winter Lay-up MElec-Ch3-21

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 MElec-Ch3-22

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 MElec-Ch3-23

24 Typical 24-hour Load 12-volt Demand (house battery) Load (in Amperes) Estimated Hours Used Estimated Amp-hours Running Lights Anchor Light Cabin Lights Bilge Pump Fresh Water Pump Refrigerator VHF Radio GPS Receiver Radar TOTALS MElec-Ch3-24

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 MElec-Ch3-25

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 MElec-Ch3-26

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 MElec-Ch3-27

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 MElec-Ch3-28

29 Charging Systems Basic Considerations Degree of Charge Alternators AC Battery Chargers Inverter/Charger Other MElec-Ch3-29

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 MElec-Ch3-30

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 MElec-Ch3-31

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 MElec-Ch3-32

33 Lead-acid 12 volt Voltages Specific Gravity 80º F Open Circuit Voltage 100 % charge 75 % charge 50 % charge 25 % charge Discharged Charging 80º F Bulk Acceptance Float Equilization - Flooded voltage Gel voltage AGM voltage 12.6 to to to to to to to to to to 13.5 Do NOT Equalize 14.4 to to to 13.5 Do NOT Equalize MElec-Ch3-33

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 MElec-Ch3-34

35 Multiple Battery Charging Battery Isolators + + House Battery Starting Battery Engine Driven Alternator #1 + AC Charger #2 + (Two-outputs) - Negative Common MElec-Ch3-35

36 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

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 10 A temperate climate 3 40 A cold, warm or hot climates MElec-Ch3-37

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 MElec-Ch3-38

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 MElec-Ch3-39

40 Battery Utilization Separate Starting and House Battery Switches Battery Monitor Typical 12 volt System MElec-Ch3-40

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 MElec-Ch3-41

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 MElec-Ch3-42

43 Battery Switches to Starter Solenoid to Power Panel SW 3 SW 1 SW 2 F1 + + Starting Battery House Battery Negative Common MElec-Ch3-43

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 MElec-Ch3-44

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 MElec-Ch3-45

46 Typical 12 volt Diagram DC Power Panel #12 Bilge Pump F2 Float Switch #12 Brown SW4 CB1 V #16 SW5 #16 #8 #12 #4 Red A Alternator + - #10 Starter SW2 SW3 S Diesel Engine 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

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 MElec-Ch3-47