Index

Power Distribution Panels for Panache - (3 Versions).

   SECTION 1: DISTRIBUTE POWER   - Battery Location, Wire Mult Batteries, Primary Buss Bars, Earth Ground, Factory Panel, Fuse Panel, Cct Bkr Panel.
   SECTION 2: PANEL COMPONENTS - Components with Sub Circuits, Back Panel, Breaker Panel, Alarm Circuit, Charge Circuit, Panel Meters.
   SECTION 3: USEFUL WIRING INFO - Terminate Wire, Corrosion, AWG, Colour Code, Ampacity, Conductor Size.
   SECTION 4: OBSERVATIONS             - The bottom line.

(To generate electricity go to Tech Tip E01).
 

SECTION 1 - DISTRIBUTE POWER

BATTERY LOCATION - A liquid filled battery should be installed in a water proof battery box with a battery blanket at the bottom to absorb all the electrolyte the battery can hold.  The battery box must be insulated so there is no chance the terminals can be electrically shorted to something.  The battery box must also be vented to the outside to release any explosive hydrogen gas (lighter than air).  These requirements are code.
- Unfortunately the space under Panache's starboard settee is too small to include a battery box but the fibreglass does provide excellent protection.  So in lieu of a battery box I built a wood shelf with fiddles to secure the house/starter AGM battery.  The battery is also secured with a rope that goes through 2 eye straps bolted to the settee wall; 1 eye is even with the bottom of the battery and the other is even with the top of the battery.  The bottom rope goes through a gap under the shelf, then up through a hole across the middle of the battery where the two ends meet in a trucker knot.  Secured as such the battery cannot move when heeled at 90⁰ or bouncing in a rough seaway.  Its not often that an SJ23 is rolled on its side (heeled at 90⁰) but s__t happens so you may as well prepare for it.  The shelf is covered with a battery blanket nestled between the fiddles and the settee is vented.  A major advantages of a sealed AGM battery is, no leaks or hydrogen fumes when being charged.  While an AGM battery should not be discharged below 50%, an Optima AGM can be totally discharged without damage.  Just don't do it often.

While this single AGM battery is very secure and well protected under the starboard settee, if this were a liquid filled battery it would be impossible to check the electrolyte to determine the state of charge.  The battery would have to be tipped to exposed the caps which would invalidate the readings.  Checking electrolyte would be easier if the battery were installed under the cockpit where the boat is also better balanced laterally.  The bigger and heavier the battery, the greater the imbalance.  But then balance is a function of weight distribution of all the goodies stored on the boat.  Compromises again. 
- An alternative location is under the forward berth which would require #1/0 welding cable (minimum) to offset the power loss of the longer cables.  The weight transfer forward and easier access for battery maintenance are advantages.  I wouldn't never install a liquid filled battery under the forward berth.  The bouncing motion will be hard on the plates and likely shorten its life, and the battery box must be ducted into the cabin to vent explosive hydrogen gas.  I hate it when things go boom in the night!  Don't smoke or light a match!

WIRE MULTIPLE BATTERIES for EQUAL CHARGE - Many boats have an engine cranking battery and a deep cycle house battery.  Some have a second house battery to double the storage capacity.  There is a correct and a not so correct way to connect multiple house batteries for equal charging.  While the not so correct way will still work, the correct way balances the voltage across all of them so they are charged equally, ensuring optimum performance and long life.  Equal wire length is especially important for Li batteries that have  a low internal resistance.  When the time comes to connect the house batteries in parallel with the discharged starter battery you can be more assured of having enough power to start the engine.

1 - POWER DISTRIBUTION PANEL FROM THE FACTORY (Panache version 1, 1977) - The factory original power distribution panel is pretty simple, consisting of only three switches.  A later design included a fourth switch for a steaming light (MAST LTS) as shown below.  Anything added to a panel was done by the owner as demonstrated by Randy who replaced the original single pole MAST LTS switch with a dual pole to operate either the anchor or steaming light.  Clever way to improve it without changing the panel.  A schematic was never included in the SJ23 manual as the circuitry consisted of a single battery feed connected to a length of #10 solid wire soldered across the power inputs of the fuses.  The battery return for each load was wired directly to the negative terminal of the battery instead of through the panel.  Not the best method for isolating a trouble but it works.  All in all, pretty simple and I think for this reason, not worth mentioning in the manual.  Back in the 1970s presumably everybody knew something about electricity!  The panel was located on the port side, above the galley stove.  Now there's a recipe for disaster if I ever saw one, sticking your hand over a steaming pot to flip a switch.  I'll grant you it can be done quickly but any dose of steam to the dry electrical contacts will hasten their demise due to corrosion. 

2 - POWER DISTRIBUTION PANEL E/W SWITCHES & FUSES (Panache version 2, 2002) - The factory panel didn't have the capacity to handle the eight circuits I wanted, so I fabricated an electrical panel with switches, fuses and 2 meters.  It was installed at the aft end of the starboard settee directly above the battery for lowest power loss via short wiring.  This location is out of the weather and away from the cook, which is rather important if you think that getting fed is of any significance to your existence on this planet!  The mechanical assembly should be within the capabilities of most handymen with opposing thumbs!  The wiring is fairly straight forward.  If you can't do it, find yourself an electronics "nut".  Many of them are only too willing to help in exchange for a day of sailing.

The aluminum bar protected the switches against accidental operation from a 'sleeping giant' who likes to stretch his legs and sometimes throws gear on the bunk.  This was a lift handle I scrounged from an old telecommunications test set.  The voltmeter at the top of the panel measures battery voltage via the red momentary switch just below it.  The 500MA ammeter below it measures solar panel charge current to confirm operation.  This meter is probably WWII vintage.  The 12VDC accessory outlet at the bottom right corner is fused and usually houses a USB charger.  I occasionally plugged a 300W inverter in it for AC power.  Click here to see the schematic for this panel.   TOP

3 - POWER DISTRIBUTION PANEL E/W CIRCUIT BREAKERS (Panache version 3, 2017) - I pondered long and hard to fabricate a new distribution panel to replace the working fuse panel.  I had the parts and the tools.  I just needed a justification.  That materialized with a recurring intermittent connection on the fuse panel that limited how much power I could draw.  So, the new design included 15 DC circuit breakers, 2 digital panel meters, 1 DC outlet, 1 AC outlet and a tripped breaker alarm.  Then I discovered the retail cost of this panel would cost on the up side of $1200 Ca (2017).  Yikes!  Most of the parts came to me as surplus communications equipment from various sites I worked at.  Deep down I always knew scrounging was a worthwhile endeavour. 

Design criteria and features of this panel:

• A circuit breaker requires slightly less space than a switch/fuse combo making it possible to install more circuits in the same space; in Panache's case from 8 circuits to 15. 
• The contrast of a white breaker lever against a black panel makes it easy to see the on/off status at a glance as evident in the photo.
• The current rating of a breaker is normally sized to protect the wire.  I'm using 15A breakers and carry a spare. 
• The front panel is latched by a couple of brass barrel bolts and flips down on brass hinges for ready access to the back.  There is just enough space behind the panel to prevent wire movement without squishing it.  This "squish" space is very important so the connections are not strained and with enough ventilation to keep it dry.
• The adjacent settee back rest can flip down to access the back panel wiring.  There is sufficient slack in the wiring to slide the back panel sideways a bit for servicing.
• All wiring is labelled showing from/to termination ends of a wire.
• All extra or defective wiring was removed to eliminate clutter and confusion.
• A toggle switch was later added to the panel to direct power to the steaming or deck light.
• An external LED spotlight illuminates the front of the panel nicely for night operation.  It is connected to permanent power to service the wiring with the main power switched off.  I will still need a head light to move around.

There is usually some obstacle that rears its ugly head when developing new hardware and I didn't want to go down the proverbial garden path of having forgotten a circuit, an illogical layout or difficult wiring as with the previous fuse panel.  That's the main reason why I progressed slowly with this upgrade.  The thing about low loss, large gauge wiring is that it can't bend like small gauge can, so planning the component layout was important.

Q - Ever wonder why the new panel is green?
A - Its a lot easier to write on an aluminum panel covered with Frog Tape.  Then if you get it wrong, apply new tape for a new mistake!  It's also great to write a note on. 

Electrical Protection - The primary function of a circuit breaker is to protect the downstream wiring against an electrical short from loose wiring, worn insulation or any other reason you can dream of!  For this reason a breaker is installed at the power source.  Take this seriously if you don't want to experience a fire on the water or on the road.  Fire is nasty stuff.  The secondary function of a circuit breaker is to leave the other circuits operational while a defective one is isolated for service.  To be totally effective each circuit must have its own breaker. 

NOTE 1 - The World Single Pole Magnetic AC/DC Circuit Breaker meets all American Boat and Yacht Council (ABYC) Standards, is UL 1077 Recognized, CSA Certified for Canada, TUV Certified and CE marked for Europe.

Battery Return Wires & Single Point "Grounding" - All loads are wired with their own battery return wire (often mistakenly called a ground wire) terminated on a common negative power buss bar  Never use a metal boat part, mast or toe rail, for a return conductor. 
LOAD RETURN WIRES - With this breaker panel each device has its own battery return wire (usually #10 stranded black) connected to the common negative return buss bar (BB3) on the back panel.  The battery return wire for BB3 is a black #4 weld cable connected to the primary negative buss bar (BB0) which is then connected to the battery negative post.  Connecting them in this order eliminates circulating current in the wiring.  If you don't achieve single point grounding, the laws of chemistry and physics will apply and you won't be happy with the electrical "noise" affecting your electronics! 
EARTH GROUND - At this point in time Panache has a single conductor to bleed off electrical "noise" or static charge from the primary negative buss to the water (earth / ground) using the immersed outboard leg.  So far a sacrificial anode to prevent electrolysis of the aluminum leg is not required but I'm always looking.  I may install a dedicated lightning ground in the future.  More below.

Large Gauge Battery Wires - In Panache's configuration the 12V power is sourced from the battery positive post to the primary buss bars (BB0) and is filtered with 2 ferrite beads to block RF noise from the outboard generator.  Then the power is fed to the secondary buss bars (BB1, BB2), using #4 weld red cable.  Finally the power from the secondary buss bars is connected to each breaker via a #10 stranded red wire.  Each breaker is connected to its load with #10 stranded red or smaller gauge wire.  The very low power devices operate on smaller 16 gauge wire.

Connector Corrosion - A dry metal connection exposed to a humid environment will corrode and deteriorate in a year, or less.  This is basic chemistry and physics, so learn to live with it.  The prevention is to keep oxygen away by coating the connection with a drop of ATF or synthetic oil.  Either oil has the advantage of creeping into an unseen crevice for complete protection and it doesn't wash off.  It is easy to apply and if done sparingly, keeps things clean.  Apply a drop once a year for continued protection.  Alternatively spraying lithium grease or smearing a light coat of synthetic grease on each connection also works but is definitely messy.  Switches and circuit breakers must be operated occasionally to function properly.  The wiping action keeps the contacts clean.  More below. 
 

SECTION 2 - PANEL COMPONENTS

COMPONENTS & SUB CIRCUITS - Electrically the circuit breaker panel is the same as a switch & fuse panel.  Physically it is quite different to incorporate the new hardware and features.  In this system the positive wire is protected (circuit breaker) as close as possible to the source of power to minimize the wiring with power still on which also reduces corrosion on the power distribution wires.  The description of each component below follows the power flowing from the battery to each load, which should make this easier to understand.

• BATTERY - Optima 55AH 12V AGM battery charged by 2 solar panels (sometimes a third) and a 6 amp generator in the outboard.  See Tech Tip E01 for charging the battery.
   
• MAIN DISCONNECT CIRCUIT BREAKER (BKR 0) - 125A circuit breaker (normally on) is installed under the starboard settee.  It is wired between the house/starter battery and the primary buss bars to automatically disconnect all system power in the event of a major electrical short. 
  - Opening this breaker will eliminate all drain on the battery except to the charge controller.
  - The charge controller bypasses BKR 0 as it is wired directly to the battery to maximize charging.
   
• PRIMARY POWER DISTRIBUTION BUSS BARS - Nothing complicated here.  Just a couple of copper bars to securely terminate the battery leads; the starter/generator cables of the outboard and the secondary buss bars.  It the safest way to securely distribute power to the breaker panel.  The power flowing to the secondary the buss bars is filtered by several ferrite beads to block RF voltage spikes from the outboard generator or a PWM solar charge controller that was previously installed. 
  NOTE - Panache's PWM charge controller was replaced by a MPPT charge controller in 2020.  The ferrite beads were left in place to filter any noise from the outboard generator. 
   

• BACK PANEL SECONDARY POWER DISTRIBUTION BUSS BARS, BB1/BB2/BB3/BB4, SW1-3 & TERMINAL STRIPS TS1/TS2 (Back Panel) - The secondary buss bars are located on the back panel (behind starboard settee back rest) to distribute power as follows:
   

  Terminal	BB1	BB2	BB3	BB4	SW1-3	TS1	TS2
  Description	Switched power to circuit breakers.  (transient protected)	Constant power to circuit breakers.  (transient protected)	Load Return for all devices except the inverter and deck wash pump.	Load return for high start current devices; inverter, deck wash pump. (The current bypasses meter M2 so it does not burn out the internal shunt of the meter) and the transient suppressors TVS 1&2.	Switches to manually operate bilge pumps.	Media player & constant power to 3 bilge pumps.	Switched power to the cabin devices.

  Adding a back panel organized the wiring which created a trouble free installation.  The wood panel rests on a vinyl grid to keep it high and dry.  The wires to the breaker panel are intentionally spread loose along the bottom, resting on the same vinyl grid, to make it easy to trace the suspected faulty wire and to prevent cross talk of wires carrying data.  The connectors are not strained or squished together which is more important than you may think.  Labeling makes it easier to find components and to trace wires.
  NOTE - (The power on each positive buss BB1 & BB2 is protected by a P6KE transient voltage suppression (TVS) diode that drains a transient to the battery return buss BB4.  These 2 diodes clamp a transient voltage in nanoseconds, effectively shorting a transient to a maximum of 36VDC before it can rise to a damaging level.  Also see Tech Tip E01)

  The back panel (L to R) showing BB1 switched power buss bar.  BB2 constant power buss bar.  BB3 battery return buss bar.  BB4 battery return buss bar to bypass meter M2 shunt.  S1, S2, S3 bilge pump switches.  TS1 media player (top) & bilge pumps (bottom).  TS2 cabin lights (hidden). 
  NOTE - The labelled wires to each device lay loose along the bottom to easily trace a problematic one. 
  
  
   

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• BREAKER PANEL ( E/W Circuit Breakers, Meters and 12V & 115V Outlets) - The table below approximates a front view of the panel layout.  The bracketed numbers in red denote the measured current drawn by each circuit. 
   

The breaker panel is flipped down to show components on the back.  It may look like a rats nest but each wire was selectively picked, verified and connected during installation to confirm all are correct.  Not all battery wires are red.  It just wasn't practical to replace a perfectly good wire in an installed harness so I just crimped and soldered the correct lug on the end then sealed the end with red heat shrink.  The bundles of wires at the hinge are left loose to prevent flex fatigue.  The two shielded sense wires (grey) from the panel meters (2 green circuit boards) are secured to the white cable standoff post to eliminate fatigue to the delicate panel meter connectors.  The slack in the wire is to permit install or removal of a meter.  (Its a difficult thing to photograph so please excuse the poor lighting).

Each bank of 15A breaker switches below is outlined with pin striping on the front of the panel for quick understanding of switched battery to the left (NORMALLY OFF) and permanent on battery to the right (KEEP ON), with panel meters and toggle switches between.  This is so another guy can find the switch!  I never have this problem myself you understand!  The front panel flips down on two beefy brass hinges to access the wiring behind (shown above) and is secured upright by two brass barrel bolts for operation (below). 

The breaker panel is flipped up and latched with the solar meter (M1) measuring a charge of 17.4V and the load meter (M2) measuring battery voltage of 13V .  This high input voltage measured by the solar meter (M1) is indicative of an MPPT charge controller output.  Each meter can handle 10A.
NOTE - Not all the segments of a panel meter show when photographed with a digital camera since the power to each segment is multiplexed.  To the naked eye they appear fully illuminated and readable.  Its a clever trick to take advantage of the slow response of the human eye while saving power.

This is the panel illuminated at night.  One LED is all it takes.  My cell phone is being charged from the 12V outlet.

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• COMPONENT LAYOUT - Shown below is a component layout of the back panel and the back of the breaker panel showing the major wires.  The alarm, charging, and panel meter circuits are shown below.

• MAIN POWER SWITCH (S0) - A Moeller Marine battery disconnect switch (110A @ 12V) controls power (manual operation) to breakers B1-B11.  This switch is equipped with a removable key to prevent unauthorized use.  The power is switched off when the boat is unattended.  If there were two house batteries in this system I would install an OFF/1/BOTH/2 switch. 
  Note - The power into this panel is filtered by ferrite beads at the primary power buss. 
   
• METER SWITCHES (S1 & S2) - S1 solar charge current.  S2 load discharge current.  Switches are normally off to minimize power drain.
   
• ALARM CUT OFF SWITCH (S3) - Switch is normally on to hear an alarm and off to quiet alarm.
   
• CIRCUIT BREAKERS 1-11 (Fed by Switched Power from Distribution Buss BB1) - These breakers are manually operated to switch power to each load as required.  This bank of similar function breakers is clustered on the left side of the panel.  Some may be left on with the power controlled by a switch on the device.  The life of a breaker is reduced by using it as a switch. 
  Next time a thunderstorm comes your way consider shutting off ALL the circuit breakers to protect the electrical system and devices against an Electromagnetic Pulse (EMP).  Make it a habit to leave the breakers OFF when you leave the boat.
  
  Bkr 1 (Run lights, 15A) - This breaker is sized for 3 incandescent bulbs just in case I have to replace an LED bulb with an incandescent. 
  (If you wish to install an LED tri-light on the mast head as an alternate to the hull mounted running lights then install a single throw double pole switch after BKR 1 to direct power to either set of lights, NOT both.  It is confusing and therefore illegal to illuminate two sets of running lights on a boat.  The double pole switch will eliminate confusion and ensure legal compliance.  It is common to use a tri-light for visibility in deep ocean troughs and the hull lights in a harbour.) 
  Bkr 2 (Steam or deck light, 15A) - This breaker feeds power to switch S4 (single throw double pole), a 2 position switch that directs power to the steam light (up) or deck light (down).  See panel photo above.  There was just enough space to install this adjacent to BKR 2 to make it easy to understand.
  Bkr 3 (Instrument Lights, 15A) - Ritchie Compass, Signet Knotmeter, & Windex.
  Bkr 4 (Auto Pilot, 15A) - Raymarine Tiller Pilot ST2000.
  Bkr 5 (Depth Sounder & GPS, 15A) - Haweye D10DX and Magellan GPS320 Receiver.
  Bkr 6 (Deck Wash Pump, 15A) - 12V Utility Pump.  See Tech Tip E19.
  
  
  Bkr 7 (VHF, 15A) - Standard Horizon Explorer GPS GX1700W. 
  Its useful to install a quick blow fuse on the battery return wire to protect the VHF against an air induced power surge.
  Bkr 8 (Media Player, 15A) - Kenwood KMM-BT315U.
  Bkr 9 (Cabin Power, 15A) - This breaker feeds power to Term Strip 2, from which all cabin power is fed (lights, fan, galley pump).
  
  Bkr 10 (12V Outlet, 15A) - This breaker feeds power to the 12V outlet located at the bottom right corner of the panel. 
  - This style 12V outlet is notorious for having a poor, intermittent connection.  It can have considerable voltage drop & power loss.  As much as I dislike it, there are many devices wired to connect to it so I'm stuck with having to install one.  I installed the best quality I could find.
  - This outlet usually has a USB adapter plugged in it to charge a cell phone.  It may also interfere with the VHF radio.  The quickest way to determine if RF interference is your problem it to shut off the power to the USB adapter.
  - A caution about a low grade USB adapter that radiates RF. 
  
  Bkr 11 (110VAC Outlet, 15A) - This 30A breaker feeds power to a 400W pure sine wave inverter (installed 2024) that supplies 115VAC to the AC outlet located at the bottom right corner of the panel.  A pure sine wave inverter draws ~35% less power from the battery than a modified inverter and sensitive electronics can operate safely from it without burning out.  See NOTE 2 below.  To further reduce power consumption, the cooling fan runs only when required.
  - Since the inverter draws a significant surge current when starting, it will overload the internal shunt in load meter, M2.  Therefore the battery return wire is connected to (BB4-11), bypassing the shunt.  This wire gauge is sufficient to drive the inverter to full output, continuously. 
  - NEVER connect the AC neutral of an inverter to boat ground as it is hazardous.  Leave it isolated.  Panache's inverter draws power only from the battery.  As such it cannot connect to shore power where it may create an unintended hazardous ground path or start electrolysis via the outboard leg (if left in the water).  The electrical path combinations with shore power and adjacent boats can become very complex and difficult to measure. 
  NOTE 2 - The power from a modified sine wave inverter (stepped sine wave) may burn out a device that has an inductive load like a transformer, motor or switching power supply.  But it is safe to connect a resistive load like a soldering iron.  Since a true sine wave inverter draws ~35% less power than a modified one it is a good example of you get what you pay for!
  - Unfortunately I cannot measure the DC current this inverter draws.  But I operated a Dremel Tool for about 30 minutes and the solar panel charge current dropped to ~150MA after only 4 minutes in full sun, having almost restored the charge.  This indicates the inverter drew little power from the battery and/or the solar panels had no problem keeping up to the lower power draw.  This is significantly better operation than my previous stepped sine wave inverter.
  
   
• BREAKERS 12-15 Alarmed (Fed by Constant Power from Distribution Buss BB2) - The power fed to the alarm contacts of the 4 breakers at the top right of the panel comes from buss bar BB2 (constant power), bypassing the main power switch (S0) on the breaker panel.  These breakers are normally left ON.  A breaker goes to alarm state when off. 
  
  Bkr 12 (Solar Panels, 15A) - Controls power from the 2 solar panels on the sliding hatch, and a temporary 3^rd panel wired to the cockpit.
  (Technically I don't need this breaker because the ampacity of the wiring exceeds the power output of the panels.  In Panache's case BKR 12 functions as an on/off switch that has current protection). 
  Bkr 13 (Anchor Light, 15A) - Supplies constant power to the anchor light that switches automatically with darkness.
  Bkr 14 (Media Player Memory, 15A) - Supplies constant power to maintain media player memory configuration.
  Bkr 15 (Bilge Pumps, 15A) - Supplies constant power to operate the 3 bilge pumps automatically via their float switches.  There are also 3 switches on the back panel to test/operate each pump manually.  See Tech Tip E16.
  
  Alarm Circuit - The common contacts of the sealed alarm contacts inside breakers 12-15 are daisy chained together (light black wire drawn through each breaker in diagram) to power a Sonalert (SA) and illuminate the LED if one of the breakers trips or is switched off (alarm condition).  However, the combined alarm signal is wired through an Alarm Cut Off (ACO) switch to silence the thing because there is nothing more irritating and interfering than a loud alarm when trying to isolate a trouble.  The LED draws your eye to the alarm condition, especially at night.
   
• SOLAR CHARGING CIRCUIT - The combined 3A output of the two sliding hatch mounted solar panels are switched through breaker B12 so charging power to the system can be shut off to service the wiring and electronics safely.  A temporary third solar panel can be added to offset high electrical loads while working at the dock.  (To protect a solar charge controller the INPUT POWER MUST be switched off first, then the output power.  Switching the output power off with the input power on may damage the charge controller).  The output is protected with an internal 20A fuse.  The instantaneous voltage and current of the solar power can be verified on meter M1 or the LED display on the charge controller.  While its OK if the charge current exceeds the panel meter rating (10A) for a short time, it is not recommended.  The #10 gauge wires to and from the solar charge controller ensure quick battery charging with clean power for the electronics. 
  NOTE - By convention the exposed contacts of a shunt MUST be installed in the battery return path, so it is at a safe 0V.  This wiring configuration also ensures the meter measures a "steady" DC current if there is a PWM charge controller.  See Tech Tip E01.
• OUTBOARD STARTER / GENERATOR - The outboard starter / generator (6A) is connected directly to the primary buss bars (BB 0) so the starter can draw maximum power from the battery, bypassing the breaker panel.  With the engine running, the generator automatically charges the battery through the Bkr 0.  So far I have not seen it necessary to install a breaker in this circuit for the following reasons: 
  - The momentary starter switch on the outboard is normally open, creating protection. 
  - The generator uses the same wires as the starter and has a diode to prevent reverse current flow. 
  - The main breaker B0 will provide some automatic protection. 
  - If I'm on board I can always unplug the outboard at the transom or switch off the main breaker, B0.
  - If it should prove necessary, I will install an inline automotive fuse. 
   
• DIGITAL PANEL METERS (M1 & M2) - Due to limited space on the front panel I installed two digital panel meters (M1, 10A solar charge current) & (M2, 10A load discharge current).  Both meters have an internal shunt to measure 10A current, freeing up space on the back panel where an external shunt would be installed. 
  - Each meter operates on <20MA at 4.5-30VDC that is sourced from the switched power buss, BB1.  Input power is controlled by toggle switches S1 & S2, when I want to measure the values.  I considered a momentary switch but constant power to these meters frees up my hands if I have to service the system.
  M1 (Solar Charge) - This volt sense is wired to the output of Bkr12 to confirm the presence of solar power. 
  M2 (Load Discharge) - This volt sense is wired to the switched power buss BB1, to measure house battery voltage. 
  NOTE - The battery voltage on M2 may show up to 21V when the outboard generator is charging.  This is not a fault.  These meters show peak voltage, not RMS and the outboard generator sends pulsing DC power to the battery. 
   

  - Meter M1 - A 10A panel meter wired to measure charge voltage & current from all (3) solar panels.  - Meter M2 - A 10A panel meter wired to measure discharge voltage & current to all loads except the inverter.  - Operating Power: 4-28VDC @ <20MA. - Measuring Range: 10A via internal shunt, 200VDC with .08% resolution and 3 decimal place display.  Can be field calibrated.  NOTE - A shunt can measure current in only one direction.  If it is wired backwards some meters can't show a reading and others show an abnormal reading of ~2.2A.  Simply reverse the wires to show the correct reading.  No damage done. A purpose made battery monitor is superior to using a simple volt & ammeter because it can calculate ampere hours consumed (integrating current in & out of battery) and show the state of charge (SoC) of the battery.  EG: Victron BMV-700.

   

  PANEL METER M1 SOLAR CHARGE (Power & Sense Leads)
  M1 LEAD COLOUR & DESCRIPTION	(EXTENSION CABLE, M1)	CONNECTION	FUNCTION
  Rd - Power in	(Rd)	To S1 & BB1 (switched power buss).	Meter power, on/off via S1.
  Bk - Power gnd & sense common	(Gn)	To BB3 (battery return buss).	Meter power, common battery return for all devices except inverter.
  Yl - Sense volts	(Bk)	To BKR12, solar charge controller positive.	Measure solar charge voltage.   (0V when BKR12 is open).
  Bk - Shunt current sense -	Bk	To solar panel, negative.	Measure solar charge current out.
  Rd - Shunt current sense +	Bk	To solar charge controller, negative.	Measure solar charge current in.
  PANEL METER M2 LOAD DISCHARGE (Power & Sense Leads)
  M2 LEAD COLOUR & DESCRIPTION	(EXTENSION CABLE, M2)	CONNECTION	FUNCTION
  Rd - Power in	(Rd)	To S2 & BB1 (switched power buss).	Meter power, on/off via S2.
  Bk - Power gnd & sense common	(Bk)	To BB4 (battery return buss).	Meter power, common battery return for all devices except inverter.
  Yl - Sense volts	(Bk)	To switched power buss, (BB1).	Measure battery voltage.
  Bk - Shunt current sense -	Bk	To BB4.	Measure negative load current out.
  Rd - Shunt current sense +	Rd	To BB3.	Measure positive load current in.
  NOTE - If you replace a defective meter from another manufacturer confirm that the pin assignment at the connectors are identical before you plug the cord into the new meter.  Usually the function stays with the wire colour which might be in a different position on the connector.  You might have to move & splice wires to maintain function.
  SENSE LEAD WIRING - The panel meter sense leads are delicate and too short to reach the back panel.  So I soldered them to an extension cable that has slightly larger gauge wire.  (Don't install a terminal strip next to the meter using mechanical connections.  A panel meter measures extremely low voltages (MV range) and any corrosion in a connection will create a false reading).  The 2 extension cables are also secured to a stand off post to eliminate vibration fatigue at the meter connectors.  See table above to translate the panel meter wire colours to my extension cable colours.  For simplicity the meter schematics above don't show the extension cables.  NOTE - The extension cable leads are labelled by function & location for future service.  You will forget!

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SECTION 3 - USEFUL WIRING INFO, (Warning - Dry Stuff)
 

TERMINATE & PROTECT WIRE from CORROSION - Always terminate low voltage (12VDC) wire with a copper clad (corrosion inhibitor) spade or ring terminal.  The terminal must be crimped to the wire for mechanical strength and soldered for corrosion free electrical continuity.  The purpose of the small opening at the business end of the terminal is to confirm that the strands are inserted to full depth for maximum current carrying capacity.  Apply only enough solder in this hole to cover the bare copper ends and let a bit flow into the barrel of the terminal for improved current flow.  If you overdo the soldering you will make a solid conductor of the strands leading into the terminal, defeating the flex properties of the stranded wire.  Finally, seal the wire behind the terminal with "Liquid Tape" or sealed heat shrink to make a gas tight connection between the wire insulation and the terminal.  This prevents corrosion to maintain the electrical connection.

Terminals come in spade (M or F), fork or ring, with sizes to match the wire gauge.  Which to use depends on the application. 

• FORK - A fork terminal is quicker to install than a ring terminal, but is not as secure.  If the fork comes free from the screw it could create an electrical short.  These terminals are fine to use in a vibration free application on land.  They are not so fine to use on a boat that is inherently prone to movement and vibration!  The style of forked terminal where the ends are turned up a bit to prevent slipping out from under a loose screw head are better.
• RING - A ring terminal stays captive to a loose screw to prevent an electrical short.  On a boat that undergoes pitching and yawing you should use ring terminals for all connections.  Additionally, the complete ring of metal under the screw head creates the highest current carrying capacity and the least potential for loosening. 
• BUTT SPLICE - Butt splices are used to connect two wires together, end to end, but should be installed only where it can be serviced.  A butt splice may create a hidden point of corrosion if it is not sealed from water and air.  If the butt is installed in a really difficult to access place it is best to install a continuous length of wire than to splice two lengths together.  You will forget it is there! 
• CORROSION - Whenever a connector is terminated to a wire it is important to create a gas tight seal over the exposed copper strands between the insulation and the barrel of the connector.  This prevents corrosion from creeping up the cable, under the insulation.  Strip off the correct length of insulation so the insulation presses hard against the back of the terminal.  If you stripped off too much insulation either cut off the excess wire or spread some brush on "Liquid Tape" over the exposed strands.  Make sure it completely seals the back of the terminal to the insulation on the wire. 
  - "Liquid Tape" is a black sticky goop that comes in a small metal can with a brush applicator attached to the inside of the lid.  (It is the same stuff as neoprene glue for a wet suit).  The goop can easily penetrate a hole in insulation to cover the copper strands and keep air or water out.  It has excellent self levelling properties that make it ideal for flowing around the end of a wire to totally seal the surface.  It cures dry in minutes and is an excellent insulator.  Follow up with heat shrink over the dried goop for impact protection.  The best heat shrink has an adhesive on the inside to seal/protect the copper against dampness and air.   It must be shrunk uniformly with a heat gun.  Electrical tape is not as good as heat shrink but if you set a small tie wrap over the last pull of the tape, it prevents unravelling. 
  - The combination of solder and heat shrink creates a moisture and gas proof sealed connection that is unlikely to fail in your life time.  Remember corrosion is slow combustion.  Combustion requires fuel (copper), oxygen (air) and a catalyst (water) to start the reaction.  Eliminate one of the three and the combustion is stopped!  While it is recommended to use tinned copper wire on a boat to prevent corrosion, on Panache I was forced to repair a hybrid of existing wires.  For this reason I gave all my low current exposed copper wires the "Liquid Tape" and sealed heat shrink treatment.  I also applied a light coat of silicon grease (synthetic is OK too) over the exposed connection portion of each #2 power terminal and a drop of ATF on each spade terminal to prevent corrosion.  To date I have experienced no failure. 

All wires that leave the power panel must be secured against movement with lots of tie downs.  It goes without explanation they must be installed in a high area so they stay dry.  Use Velcro straps to bundle the wires together.  Tie-raps are fine on a panel where no movement is expected but on a cable harness in a boat they can cut through the insulation exposing the copper to corrosion or an electrical short.  Using soft Velcro ensures long life of the insulation.  A Velcro strap also has the advantage of being field serviceable without tools.  Bundle the wires loosely.  Twist the wires around each other in the vicinity of the compass.  This breaks up the magnetic field.  If a bundle of wires has to go through a bulkhead then install a rubber grommet in the hole to protect the wire against chafe on a sharp edge. 

• For battery distribution (+12VDC) use red insulated wire (or black wire with red ends).
• For battery return (-12VDC) use black insulated wire.  (This NOT a ground unless it connected to earth).
• Label the panel end of each wire to indicate where the far end of the wire goes to. 
  Label the far end of each wire to indicate which panel switch the wire comes from. 
• Size the wire for a maximum 3% voltage drop under full current. 
• Use #16 or smaller gauge wire for instrument or signal connections. 
• Use #10 to #16 gauge wire for most applications like lights. 
• Use #6 or larger gauge wire for high current consuming loads like the power feed to a fuse panel, battery charging leads, etc. TOP
   

Looking for specifications of marine grade wiring?  http://www.cncphotoalbum.com/doityourself/wiring/wiring.htm 

Conductor Size - Ampacity is the ultimate safe current carrying capacity of the wire before damage occurs to the insulation. without regard to voltage drop. Because the insulation of most SAE wire sizes is not the same as ANCOR. this chart should not be used for other conductor sizes. Use the following two table to find proper wire size to insure adequate performance.

Determine Conductor Size (AWG) for 3% Voltage Drop at 12 Volts - Use 3% voltage drop for any "critical application" affecting the safety of the vessel or its passengers: bilge pumps, navigation lights, electronics, etc.  (2.54 cm = 1")

Determine Conductor Size (AWG) for 10% Voltage Drop at 12 Volts - Use 10% voltage drop for any "non-critical applications like windlasses, cabin lights, etc.

Important!

Length (ft): Determined by measuring the length of the conductor from the positive (+) power source connection to the electrical load and back to the negative (-) power source connection.  Note that the power source connection may be either the battery, buss bar, circuit breaker, or power switch.

Current (amps): Determined by adding the total amps on a circuit.

Conductor size not covered in the tables above may be calculated by using the following formula:

After calculating the Circular Mil Area (CM) use Table B to determine the proper conductor size (The National Fire Protection Agency and USCG require that the next larger conductor be used when the calculated CM area falls between two conductor sizes).

CM = cross Circular Mil area of conductor
K = 10.75 (Constant representing the mil-foot resistance of copper)
I = Current (amps)
L = Length (feet)
E = Voltage drop at load (volts)

For Example...

Q: A bilge pump draws 10 amps.  The positive battery run is 11' from the power panel, including the float switch.  The battery return run (negative) is 10'.  Which size wire to install?

A: Use the formula to calculate the answer:

CM  = 10.75 x 10 (amps) x 21' (feet) / 0.36 (3% of 12V)
CM  = 6.271

Table A shows that 12 AWG wire has a CM area of 6.500 and is the correct choice.  However, SAE wire has a CM area of only 5.833.  Under NFPA and USCG regulations, therefore #10 SAE wire must be used.  TOP
 

SECTION 4 - ON THE WATER OBSERVATIONS

2021 - I resolved the two wiring errors of the meter sense leads and added BB4.  Other than these, the new wiring and the connected devices have operated trouble free.  The breakers and switches function as per the logic of the panel layout.  Other sailors find the panel easier to understand than their own, which actually says a lot.

2023 - Next time a thunderstorm comes your way consider shutting off ALL the circuit breakers to protect the electrical system and devices against an Electromagnetic Pulse (EMP).  Make it a habit to leave the breakers OFF when you leave the boat.
 

(To generate power go to Tech Tip E01).
 

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