Boat Electrical Systems Terry Sparks Commander USN Retired
Agenda • Why learn Electricity? • What is Electricity? • What is DC? • Overview of Boat DC systems • The Breaker Panel • Battery Types • 20 Minute Break • Charging Systems • Battery Loading • Safety
Why learn Electricity? • Install equipment without cost for service • Installing equipment without fires • What size fuse do I need for equipment? • Impact of new device on battery last? • Battery size to sail to Catalina? • Can I use an existing circuit breaker? • Other questions can be answered with a little knowledge.
What is Electricity • Electricity is: • Electrons being pushed through a conductive material such as wire or metal by a voltage source. • The limiting of electron flow is as a result of the resistance , the opposition to current flow. • The energy delivered or used by a device is called power.
What is Electricity • Typical Electrical Terms • Voltage in Volts (V, E) • Current in Amps (A, I) • Resistance in Ohms (Ω) • Power in Watts (P)
What is DC • DC stands for “Direct Current” • Direct Current - current/electrons flows only in one direction through a wire and an electrical device. • DC electric energy is supplied by your battery(s) • Devices used for charging batteries provide DC
Electrical Heat is Energy/Power Current -->>>>> - + V Heater/Resistance (Opposition to Flow) Battery Common point Water Flow -->>>>> Spray Energy P P Sprinkler is Opposition to flow Common point earth & atmosphere
Calculations Electrical Work Done Heat / Energy/Power Current -->>>>> - + V Heater/Resistance (Opposition to Flow) Battery Common point Voltage in Volts = Current X Resistance = I X R Current in Amps= Voltage/Resistance = V/R Resistance in Ohms= Voltage/Current = V/I Power in Watts= Voltage X Current = V X I
Voltage and Power Circles V P I R I V
Example 1 • For a 25Watt bulb, what is the smallest fuse we can install? The 25 Watts is at the rated voltage of 12.6 Volts So the current is P/V 25W/12.6V = 1.98 Amps (approximately 2 amp fuse) P I V
Example 2 • When we turn the battery charger on the 2 A fuse blows: • With the charger on the voltage may go to 14.5V? R=V/I so for a 25W component at 12.6V From before we found it I ~ 2A V V So then the resistance is V/I or 12.6V/2A = 6.3 ohms At the new Voltage of 14.5 Volts: 14.5V/6.3 ohms = 2.3A Yep! The fuse would blow so it needs to be at least a 2.5A. I I R R
Your Turn! • My new radio says it draws 2 A. • What is the Power? • What is the Resistance? V P I R I V
Overview of Boat DC systems DC Panel VHF Radio To Boat Ground Battery Charger Fuse Or Fuse FM Radio To 2nd battery Battery Select Switch Navigation Lights - + Battery Boat Ground (Metal things)
Fuses Required? • All devices should have a fuse or circuit breaker on a 12 Volt power feed. • Batteries and Battery chargers. • Devices connected directly to a battery • A fused must also be installed within seven inches of the battery connection. • Charging can be through battery selector switch. • Still needs fuse on output of charger. • Charging to Battery directly requires 2 fuses.
The Breaker Panel • Frequently two sections, DC and AC • Breakers should be DC rated for current and voltage • The current/wire size to be connected to the breaker. • A 20 amp breaker connected to at least #12 wire • A 15 amp breaker connected to at least #14 wire • Long runs of wire should have the next larger size • Items connected to the wire should be less than the breaker • Use Marine stranded/tinned wire only
Battery Types Typical on Boats • Three classes of Batteries • Starting Batteries need lots of current available • Recommend a 1000 MCA battery • Low cost units • Also hook to thrusters and anchor windless
Battery Types Typical on Boats • Three classes of Batteries (cont.) • House Batteries • High Amp-hour rating • Designed to draw smaller currents for long periods • Needs to be capable of many charging cycles • Dual Purpose • Good for Power Boaters • OK for House Current. • OK for Starting Currents • Not as good if planning a lot of anchoring.
Battery Types Typical on Boats • Starting batteries • Starting batteries start engines, not for deep discharge use. • Many thin plates = maximum surface area, and maximum current output. • Repeated deep discharges will result in capacity loss and ultimately in premature failure • A common Misconception: • Starting batteries should be kept on float charge. • Float will encourage corrosion on the electrodes • Result in premature failure. • Starting batteries should be kept open-circuit but charged at least once every two weeks to prevent sulfation.
Battery Types Typical on Boats • Deep cycle batteries • Specially designed deep-cycle cells are much less susceptible to degradation due to cycling • Required for applications where the batteries are regularly discharged • Such as boat house batteries • Batteries have thicker plates • Can deliver less peak current • Can withstand frequent Discharging and Charging.
Battery Types Typical on Boats • Marine Dual Purpose batteries • Are something of a compromise between the two types • Able to be discharged to a greater degree than starting batteries • But discharged less than a deep cycle batteries.
Battery Types Typical on Boats • Lead Acid • Similar to the ones in most cars • Contains water and acid • Can Leak if turned upside Down • More maintenance • Requires water to be added • Terminals must be cleaned
Battery Types Typical on Boats • Lead Acid • Voltage per cell when charged is 2.1V • So 6 cells in a 12 Volt Battery is 12.6 Volts (when charged) • Golf Cart Batteries have 3 Cells or 6.3 Volts • High Capacity batteries, great for House Batteries • Most Charging cycles of any battery
Battery Voltages to think About • Open-circuit at full charged: 12.6 V to 12.8 V • Open-circuit at full discharged: 11.8 V to 12.0 V Time to charge • Battery is at ½ power ~ 12.2V Open Circuit. • After full charge • Terminal voltage will drop quickly to 13.2 V and then slowly to 12.6 V.
Battery Voltages to think About • Equalization charging for flooded lead acids only • 15 V+ for no more than 2 hours once a month. • (I do 30-45 minutes every month) • When all cells have equal specific gravity done. • Battery temperature must be monitored. • Make sure water level still good when complete • Gassing (Hydrogen Gas) threshold: 14.4 V • At 15V make sure ventilation is good
Battery Types Typical on Boats • Gel Cell • The acid is mixed with a silica fume creating a gel-like electrolyte. • Eliminates the electrolyte evaporation • Can be mounted in any position • Requires special setup on most chargers • The least forgiving of the battery types
Battery Types Typical on Boats • AGM (Absorbed Glass Mat) • Electrolyte is absorbed into a mat of fine glass fibers • Can be mounted in any position • Sealed and glass mat protects plates from shorting out with vibration • Most forgiving of all batteries for both Charge and discharge. • Clearly the best battery for boats, but also the most expensive
20 Minute Break 11 19 18 17 16 15 14 13 12 10 1 9 8 7 6 5 4 3 2 0 Time to get back to Class
Charging Systems • Types • Alternator on the Engine • Shore Power or generator via a Battery charger • Solar Cells • Wind Generator • Water Wheel
Charging Multiple Batteries Two engines one battery Two engines two banks One engine two banks One engine two or 3 banks (~0.7V drop on these devices)
Charging Levels * Precise (±0.05 V) float voltage is critical to longevity; too low sulfation is almost as bad as too high corrosion and electrolyte loss
Multi-Stage Charging Solar/Wind • Longest Life on Batteries • Multi-Stage Charger • Bulk Charge • A constant high current to initially charge the battery • Absorption • Constant Voltage Charge to top off the battery • Float Charge • Keeps enough voltage on the battery such that loads requesting current end up coming from the charger instead of the battery. Keeps the battery fully charged. Alternator
Multi-Stage Charging • Equalize to get longest Life - Lead Acid Batteries • Selectable Equalizing Charge • Used as maintenance feature about once a month to knock off the material built up on the plates • Result in an un-balanced charge per cell. • Will significantly extend the life of your Lead Acid Cells • 15 V+ for no more than 2 hours once a month. • When all cells have equal specific gravity it is complete. Hydrometer/ Battery Tester
Alternator on the Engine • Factory Alternators typically do not provide 3 or 4 charging stages • Can reduce battery life • Alternators with an external regulator control typically do provide 3 or 4 charging stages. • Will Provide Maximum Battery Life
Battery Loading • Sailors worry about loading more than power boaters • When we are under sail they are draining the battery. • Conservation through the use of LEDS is like adding another power source. • DC lights draw about 2 Amps Similar LEDs 0.2A • 2 Amp-hours vs. 0.2 amp-hours (See Table next Slide)
Battery Loading • When you anchor over night, it is important to have enough energy (Amp-hours) to: • Provide cabin lights • Anchor light all night • Start the engine the next morning. • An Isolated battery used only for starting is a smart choose • Watch a DVD, maybe “Captain Ron”
Better Battery switch design • The Battery one, Battery two, and both switches are the worst way to control battery connection possible. • Putting the switch in both when a battery is low drains the good battery • Will equalize both batteries to a lesser charge • Go through off to other battery • Charging may remain an issue • Having the switch in both provides for no backup. • Not a good solution for a sailboats or trollers • May work ok for power boats • Still a poor solution
Better Battery switch design • A better solution is 3 single switches. • One for House Battery – On/Off • One for Engine starting – On/Off • One that cross connects the load to the other load circuit. • West Marine has a replacement module to make it simple to convert (See diagram next page)
Ties Loads together not Batteries Operation A better solution • To energize the house supply engage S2 • To start the Engine Engage S1 • If Starting Battery is Low! • Disengage S1 • Engage S3 with S2 Still engaged • To use the Starting Battery on the House • Disengage S2 • Engage S3 with S1 Still engaged • S1, S2, & S3 engaged equals the “Both” position on a traditional Battery Selector Switch. • All three should not be engaged as with the “Both” position, the charged battery will discharge to the un-charged battery. Both/Bypass S3 To Metering and Charging devices House S2 S1 To Metering and Charging devices To Starter 1-many12V Deep Cycle Batteries** Number Based on AH required. Starting Battery With High Cranking Current ** Banks of (2) 6 volt Golf cart batteries in series May provide the most charging cycles and hence longest life. Ships DC Ground
Available as Replacement for 1, 2, both Switch BLUE SEA SYSTEMS Battery Switch/DC Circuit Panel WM Model #: 163233 Manuf. Part #: 8080
Safety • Tips • Important to ensure boat does not burn! • Smaller wires connected to the battery must be fused • Voltages out of Chargers must be fused • Worm wires means to much current • Warn wires can result in shorts
Safety • Tips • Cheap crimp connectors can result in poor and possibly arcing connections (Or Intermittent operation) • Shrink tube over connectors or use connectors that shrink • Use Crimping tool • If you solder connectors, make sure the solder does not wick up into the wire. • Connectors without insulator on end • Solder at connection only Apply Solder Here