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12 Volt Marine Electrics

12 Volt Marine Electrics. Mike Litzkow. Introduction. My background Plan Start with some problems Learn stuff that will be useful in solving those problems Try to apply what we’ve learned to solve the problems. Problems.

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12 Volt Marine Electrics

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  1. 12 Volt Marine Electrics Mike Litzkow

  2. Introduction • My background • Plan • Start with some problems • Learn stuff that will be useful in solving those problems • Try to apply what we’ve learned to solve the problems

  3. Problems • Can I replace my navigation light bulb with one from a hardware store? • Can my lighter plug power my coffee pot? • Are my starter, alternator, battery working? • Why doesn’t my engine start? • How long will my batteries last?

  4. Basics of Electricity • Voltage, Current, and Resistance • Ohm’s law • Watt’s law • Wire size

  5. Basic Electrical Circuit • Resistance • Starter motor • Nav lights • Radio Battery Electrons leave the negative pole of the battery, flow through the resistance, and return to the positive pole of the battery Electrons always have to flow in a complete circuit

  6. Parallel Circuits Parallel circuits on your boat can (usually) be Thought of as simpler individual circuits

  7. Open Circuit Short Circuit Basic Electrical Faults Battery Resistance (load) Short circuit – electrons can flow through the circuit without reaching the resistance (wire overheats, danger of fire) Open circuit – electrons don’t have complete path (nothing happens)

  8. Volts, Ohms, and Amps Resistance (load) Battery A flow rate of 6.24 X 1018 electrons per second is an electrical current of 1 Ampere (Amp) Electrical pressure is required to make the electrons flow through the resistance. This pressure is measured in Volts The resistance is measured in Ohms 1 Volt will push 1 Amp of current through 1 Ohm of resistance

  9. Ohm’s Law Current is directly proportionial to voltage and inversely proportional to resistance I - current (Amperes) V - electromotive force (Volts) R - resistance (Ohms)

  10. Alternative Forms of Ohm’s Law Voltage, current, and resistance in a circuit are fundamentally related If we know any two of them, we can easily calculate the other

  11. Watt’s Law Power is directly proportionial to voltage and directly proportional to current P - power (Watts) V - electromotive force (Volts) I - current (Amperes) Note: these are the same Watts as in a 100 Watt light bulb

  12. These come from combining Watt’s law with Ohm’s law Alternative Forms of Watt’s Law Voltage, current, and power in a circuit are fundamentally related If we know any two of them, we can easily calculate the other

  13. Perko 170 Series Navigation Lights 12 V 0.83 A Remember Watt’s Law The Power is 12 X 0.83 or approximately 10 Watts Choosing a Light Bulb • Take old bulb to hardware store and match physical form • New bulb must be 12 Volts • How many Watts should new bulb be? Why is this important? Alternative method: measure current in bulb that’s still working

  14. MarinePro Coffee Pot • Brews Fresh Hot Coffee in Minutes • See-Through Water Gauge (Easy to Make Just the Right Amount of Coffee). • Thermo Glass Carafe with Stay-Cool, Sure-Grip Handle. • Auto-Shutoff. • Plugs directly into your 12-Volt cigarette lighter. • Uses Standard #2 Cone Filters (Note: 2 Filters are included, along with a coffee scoop). • 6' of Power Cord. • 130 Watts • CE Certified

  15. Using alternative form of Watt’s law I = 130 Watts / 12 Volts I = 11 Amps Coffee Pot - Continued Seafit 15 Amp rated Marinco 15 Amp rated 10 Amp fused Watt’s law deals with power, but these devices are rated by the current they can safely handle.

  16. Hand-held digital multi-meter ($40) Built-in analog meter (not very accurate) Built-in digital meters (probably accurate) Hand-held digitla multi-meter with current clamp ($154) Measuring Equipment Lighter plug volt meter ( $18)

  17. Physical Components Starter Battery Alternator

  18. Battery, Starter, and Alternator • Battery • Stores energy and provides it to starter when needed • Starter • Uses energy from battery to crank the motor • Alternator • Generates electricity to recharge the battery afterwards

  19. If your 12V battery is really at 12V,you’re in trouble! Battery Testing • Rest Voltage • 12.6 – Full charge • 12.4 – ¾ charge • 12.2 – ½ charge • 12.0 – ¼ charge • Capacity • Load to ½ cold cranking amps • Hold for 15 seconds • Voltage should remain above 9.6

  20. Alternator Testing Automotive Type Alternator • 13.8 to 14.2 volts with engine running above idle Marine Alternator • Voltage may be higher or lower, but should always be above battery’s rest voltage

  21. Quick System Test • Attach digital volt meter • Check rest voltage – should be 12.6 • Disable engine from starting • Crank 15 seconds • Voltage should remain at 9.6 or above • Switch batteries and repeat steps 2 & 3 • Start engine and check charging voltage • Should be 13.8 to 14.2 (auto type alternator)

  22. Battery Capacity Calculations • Add up the current draw of all devices you want to use (or measure) • Multiply by number of hours or service you need • Result is in Amp hours. • Should be less than 30% of Amp hour rating of battery. Otherwise you will significantly shorten it’s life.

  23. Race Chicago to Macinac – 4 days

  24. Try again… Alternative 1Buy 200 AH batteries at$250 each Alternative 2Buy LED tri-color lightusing 1/2 A - $300. Reduces 1.3A avgdraw to 0.2A.

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