12 volt marine electrics mike litzkow. introduction my background plan –start with some problems...
TRANSCRIPT
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
• 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?
Basics of Electricity
• Voltage, Current, and Resistance
• Ohm’s law
• Watt’s law
• Wire size
1 Volt1 Ohm
Basic Electrical Circuit
Battery
Resistance
•Starter motor
•Nav lights
•Radio
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
Parallel Circuits
Starter motor Nav Lights Radio
Starter motor Nav Lights Radio
Parallel circuits on your boat can (usually) beThought of as simpler individual circuits
Basic Electrical Faults
BatteryResistance
(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)
ShortCircuit
1 Volt1 Ohm
Open Circuit
Volts, Ohms, and Amps
BatteryResistance
(load)
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
1 Volt1 Ohm
1 Ampere
I - current (Amperes)
V - electromotive force (Volts)
R - resistance (Ohms)
Ohm’s Law
R
VI
1 Volt1 Ohm
1 Amp
Current isdirectly proportionial to voltage andinversely proportional to resistance
Alternative Forms of Ohm’s Law
R
VI IRV
I
VR
Voltage, current, and resistance in a circuit are fundamentally related
If we know any two of them, we can easily calculate the other
Watt’s Law
VIP
1 Volt1 Ohm
1 Amp
Power isdirectly proportionial to voltage anddirectly 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
Alternative Forms of Watt’s Law
I
PV
V
PI
Voltage, current, and power in a circuit are fundamentally related
If we know any two of them, we can easily calculate the other
VIP
RIP 2R
VP
2
These come from combining Watt’s law with Ohm’s law
Choosing a Light Bulb
Perko 170 Series Navigation Lights12 V0.83 A
1. Take old bulb to hardware store and match physical form2. New bulb must be 12 Volts3. How many Watts should new bulb be? Why is this important?
VIP Remember Watt’s Law
The Power is 12 X 0.83 or approximately 10 Watts
Alternative method: measure currentin bulb that’s still working
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
Coffee Pot - Continued
Marinco15 Amp rated10 Amp fused
Seafit15 Amp rated
Watt’s law deals with power, but these devices are rated by the currentthey can safely handle.
Using alternative form of Watt’s lawI = 130 Watts / 12 VoltsI = 11 Amps
V
PI
Measuring Equipment
Built-in analog meter(not very accurate) Built-in digital meters
(probably accurate)
Hand-held digitalmulti-meter ($40)
Lighter plug volt meter( $18)
Hand-held digitla multi-meterwith current clamp ($154)
Physical Components
Battery
Starter
Alternator
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
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
If your 12V battery is really at 12V,you’re in trouble!
Alternator Testing
Automotive Type Alternator– 13.8 to 14.2 volts with engine
running above idleMarine Alternator
– Voltage may be higher or lower, but should always be above battery’s rest voltage
Quick System Test
1. Attach digital volt meter
2. Check rest voltage – should be 12.6
3. Disable engine from starting– Crank 15 seconds– Voltage should remain at 9.6 or above
4. Switch batteries and repeat steps 2 & 3
5. Start engine and check charging voltage– Should be 13.8 to 14.2 (auto type alternator)
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.
Race Chicago to Macinac – 4 days
Original Estimage
Device Draw Comments
Computer 4.0 8A supply operating at 1/2 capacity
Cabin light 1.0 Avg 1 light on 1/2 the time
Depth Sounder 0.5 Runs continuously
Knotmeter 0.1 Runs continuously
Wind Instruments 0.1 Runs continuously
Nav Lights 1.5 3 lights 1A each on 1/2 time
VHF Radio 1.5 Runs continuously
Subtotal 8.7 Amp hours per hour of operation
Daily Total 208.8 Amp hours per day of operation
Race Total 835.2 Assuming race completed in 4 days
Capacity Needed 2784.0 Maximum draw down 30%
Capacity Available 300.0 3 batteries of 100 AH each
Try again…Revised Estimate`
Device Draw Comments
Computer 0.4 Computer on standby except 6 min / hr
Cabin light 0.2 1 light 2 hrs/day (flashlights rest of time)
Depth Sounder 0.5 Runs continuously
Knotmeter 0.1 Runs continuously
Wind Instruments 0.1 Runs continuously
Nav Lights 1.3 3 lights 1A each on 10 hrs/day
VHF Radio 0.1 2 hrs/day - monitor with handheld rest of time
Subtotal 2.6 Amp hours per hour of operation
Daily Total 63.4 Amp hours per day of operation
Race Total 253.6 Assuming race completed in 4 days
Capacity Needed 317.0 Maximum draw down 80%
Capacity Available 400.0 4 batteries of 100 AH each
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.