SJ23 Tech Tip E01, (Updated 2023-10-21) Bob Schimmel


Power up with Solar Energy for Panache.

     SECTION 1: GENERATE POWER - Panel Types, Panel Location, Rigid Panels with Hail Protection, Temporary Panel, Flexible Panels.
     SECTION 2: REGULATE POWER - Charge Controllers, PWM Controller, MPPT Controller, RFI & Damaging Voltage Spikes.
     SECTION 3: STORE POWER          - Battery, Dual Batteries, Discharge Protection.
The bottom line.

(To distribute & use electricity, go to Tech Tip E02). 

CAUTION - It is important to note that Panache's electrical system is a floating ground type with no hard connection to shore power.  However, once the outboard leg touches water it could be considered a grounded system since the negative of the battery is connected to the frame of the outboard.  This must be considered when at a fuel dock or when lightning is within range. 

NOTE - If you install this system on your boat and add a connection for AC shore power, you must add a sacrificial anode to protect the metal in the water.  You should also consider installing an isolation transformer to protect yourself when stepping off the boat due to wrong polarity on shore.  This also makes the boat shock proof for swimmers and prevents galvanic corrosion.  Intermittent grounding can create stray current that is dangerous.  Click here for more info

The nice thing about a solar panel is that it can charge a battery without noise or smelly fumes, so it's definitely the environmental thing to do.  However, it still requires oil to make a panel, but let's set that aside for now.  The general idea here is to make Panache self sufficient for electrical power since there is no dock power on any dock in Alberta and the run time of my outboard equipped with 6A charger is not sufficient to maintain the battery.  So .......

There are three main components of a solar charging system; the solar panel, a solar charge controller and the RV battery to store the juice and operate devices from.  If the components are sized correctly to match the electrical load then you can expect a 5 year service life from the battery as opposed to 2 or 3 years.  It's not uncommon to extend the battery life 50%.  If the hardware and wiring is installed and configured correctly you can expect very low maintenance with dependable power.  However, all systems require occasional maintenance; wash the panel, clean the battery top, check the electrolyte, torque & lube the electrical connections once a year, and monitor the battery charging voltage/current regularly.  The last one verifies the overall system health if you know how much maintenance current your system requires.  You'll learn this with experience. 


SOLAR PANEL TYPES - As of the early 1990s there were two types of solar panels, monocrystalline (rigid) or amorphous (rigid or flexible).  Back then a solar panel was about 10-15% efficient in converting sunlight to electricity.  By 2016 the efficiency was up to 21%.  Some of the more expensive type are constructed with a bypass diode around each cell to be shade tolerant.  If a cell is shaded (not generating voltage) then the power from the illuminated cells (generating voltage) bypass the shaded cell via a diode.  In other words, with one cell switched off the output voltage drops only slightly because the rest keep generating, resulting in more power generated during a day.  Perfect for a sailboat installation with lines casting a moving shadow over the panel.  On a panel that is not equipped with bypass diodes, the output voltage typically drops to half the illuminated voltage.

A monocrystalline solar panel generates the most output power, making it the technology of choice for a boat.  This panel derives its name from the fact that wafer thin slices of black crystals are attached to a sheet in squares.  During panel assembly the crystals are wired together manually and sandwiched between sheets of tempered glass, Lexan or laminated flexible sheet material.  This panel is expensive since it is labour intensive to construct but retains its output performance for life and is therefore the most cost effective.

A polycrystalline solar panel is less efficient than a monocrystalline but costs less.  They are light blue in colour.

An amorphous silicon solar panel (thin film) consists of a thin coating of brown silicon 'painted' on the back of tempered glass or Lexan.  The silicon coating is applied in narrow ribbons for maximum coverage.  The coating is then protected by a backing sheet and sealed at the perimeter with a hermetic sealant and rigid moulding.  If the seal at the perimeter of the two sheets breaks, the wiring corrodes and the panel will soon fail.  They are the least expensive panel to manufacture, being machine produced but loose their emission with time and so has a limited life span.  Its OK to install on a sailboat provided you can add hail protection.

A rigid panel is very delicate so don't ever step on it as it will break, rendering it useless as you pollute the air with obscenities.  Oh well, you can always take it apart to find out what makes it tick!  A flexible panel on the other hand, is very robust as it can usually be stepped on, doesn't leak and can conform to the shape of the deck.  For all out durability you can't match a flexible panel but you pay extra for this robust construction.  At one time all flexible panels were amorphous silicone.  Now monocrystalline flexible panels incorporate very tiny cut crystals, small enough to survive the bending radius of the panel.  This way you have the best of both worlds, flex, strength, power output with long life.  They are the best choice for a sailboat.   TOP

SOLAR PANEL LOCATION - There are several parts to a successful installation:

  1. The very first criteria is that the panel MUST fit in the desired location.  Too big is definitely out of the question.
  2. The mechanical mounting MUST work in all weather conditions.
  3. The desired location should receive lots of exposure to the sun, regardless of which way the boat is pointed.  This is important since even the shadow from a line across the panel will reduce the output power by ~40%, unless its a shade tolerant panel
  4. The panel should be installed away from foot traffic, unless its a flexible panel rated for occasional foot traffic.  Unused deck space is scarce on a sailboat which is where a flexible panel excels.  Besides being strong enough to step on, they can usually withstand hail.
  5. Multiple panels create redundancy.  A panel on either side of the deck generally ensures that at least one of them provides charging current.  Half the charging current is better than none. 
  6. A small panel is easier to install than a large panel.
  7. A panel installed on a dodger, bimini or arch can charge a battery very quickly due to the excellent exposure and can operate cooler.  It can also provide shade for the carbon based life forms below it!  A flexible panel can be secured up there by lacing, zippers, snaps or sometimes sewn to the cloth.  This makes it easy to live with.

If your boat doesn't have a dodger, bimini or arch then the least interfering permanent location on a SJ23 is on the pushpit as shown below.  I rejected this for Panache due to the gusty winds in the anchorage.  My criteria is that the solar panels have to stand up to whatever weather blows through an exposed anchorage, be easy to remove or tilt, survive hail and lastly work while sailing.  But I don't see these two having a problem with their panel and they look like they're having a good time?  The hardware to install a panel on the pushpit has greatly improved over the years so its worth considering again.  All the following installations require creativity to run the wires.

  1. ON TOP OF THE SLIDING HATCH A solar panel installed on top of the hatch is clear of most deck work.  Long ago I made it a practice to NOT step on the sliding hatch so installed a rigid panel here.  A second panel was added to increase the charging current from .5A to 1A.  At least one of the two panels receives sunlight most of the time.  They charge while sailing; an important consideration if you intend to operate an electric autopilot for any length of time.  This configuration gave me sufficient power at the time and I no longer concerned myself with battery drain.  Shown below are the panels mounted on the original wood feet glued to the hatch with Sikaflex.  The panels are at a slight slope so most of the dust washes off.  Every once in a while I gave them a wipe.  They are easy to store for end of season by removing the black center strip.  My next version will be a flexible panel.
  2. CLIPPED TO THE PUSHPIT - I like this spot more and more everyday because the panel is out of the way.  I'm considering it for a temporary third panel on Panache.  A friend has two articulating panels on his pushpit and I'm envious of the charging performance. 
  3. MOUNTED ON THE PUSHPIT - Here is another SJ23 with a pushpit mounted solar panel.
  4. ABOVE THE COCKPIT ON AN ARCH, BIMINI OR DODGER - I like these locations because you get both shade and power from the panel while under way.  No moving parts, an extra hand hold, a place to hang things, clip the back of an awning to, mount cockpit lights and best of all, out of the way.  Its a lot of work to build an arch though.
  5. SOME TEMPORARY LOCATIONS; The following locations work well when the boat is stationary in a slip as you have the option of choosing one that is illuminated.  Failing this, a small articulating panel is beneficial as it is can be pointed to the sun for maximum illumination.  Watch your ammeter as you rotate the panel and lock it at maximum current.  This is very useful to recharge a low battery at anchor. 
    1. Hang from the companionway drop boards.
    2. Hang from a lifeline.
    3. Hang from the pushpit.
    4. Hang from a cabin grab rail. 
    5. Rest against the cockpit backrest.
    6. Lay on the cockpit sole.

Solar panel installations I have seen but rejected for Panache.

  1. ON THE FORWARD HATCH - Probably the least interfering location on a SJ23, but I consider covering the acrylic hatch sacrilegious.  After all, you may as well use plywood for a hatch and never look at the stars from the forward berth!  I did make a concession for a Nicro vent though as I definitely needed ventilation and I can look around it.
  2. ON THE DECK JUST FORWARD OF THE SLIDING HATCHThis spot is fairly well illuminated and is out of the way when sailing.  With a very thin panel the sliding hatch might pass over it.  While you could install a window in the sliding hatch to pass light to the panel, Gene doesn't recommend it since it would weaken the hatch too much.  TOP

Over the years I have "experimented" with the following locations.

  1. ON THE DECK JUST BEHIND THE MAST (Panache version 1, 2002) Panache's original single rigid solar panel was installed in a wood frame mounted flat on the deck behind the mast.  This spot is mostly out of the way when sailing but is often shaded by the mast.  When the boat pitched a lot I quickly discovered it was in the way for reefing or covering the mainsail. 
  2. ON THE SLIDING HATCH (Panache version 2, 2003) - With the addition of my mechanical boom vang the shadow over the panel just behind the mast reduced the output power too much so I moved it to the top of the sliding hatch where it received good illumination and was out of the way of foot traffic.  It worked OK but was soon replaced with version 3 to double the output. 

    TWO RIGID SOLAR PANELS on the SLIDING HATCH (Panache version 3, 2003).
    (Two Coleman 5W panels regulated by several types of linear regulators and finally a Morningstar SG4 PWM charge controller).

    The two rigid solar panels on Panache's sliding hatch were mounted on wood feet glued to the hatch.  Each panel was plugged into the boat wire harness below itself and wired in parallel under the center support.  The wire harness went through a sealed hole at the center of the hatch, then to the aft starboard corner where 2' of slack cable was loosely hung from 2 nylon cable straps.  From there it was plugged into the boat wiring harness at the top of the companionway.  All of this so the panels could be removed for winter or stepping the mast.  Additionally the sliding hatch could be removed for service.

    Fig 1 - Solar panel wood mounting brackets and electrical connectors for each panel.  This was prior to installing hail guard covers.

    Fig 2 - Power cable tightens to almost straight when hatch is open.


    Fig 3 - With the hatch closed the power cable hangs in a loop.  This loop is never in the way, despite what it looks like. 


    The 2' of slack cable accommodates the movement of the sliding hatch.  When the hatch is closed the loop hangs at the aft end of the cabin where it is out of the way.  When the hatch is open the cable is stretched straight along the underside of the companionway, also out of the way.  All the wiring is connectorized to remove the solar panels for winter storage or to service the sliding hatch.  To comply to standards, the panel positive output is the female side of the connector.  I haven't figured out a simpler, more effective technique and it hasn't failed, yet.  TOP


HAIL PROTECTION:  Our lake gets some very nasty thunder storms with golf ball size hail in early to mid summer and I didn't relish the prospect of loosing another panel to those icy demons.   I held off installing hail protection for many years, thinking that panel overheating or filtering sunlight would reduce the charging performance.  Heat is one of the greatest killers of electronics which is the major reason why I did not install a hail cover over the panels for so many years.  It was time to confirm this idea. 
As the temperature of a panel increases the output power is reduced at ~.258 %/0C.  Panel output is rated at 250C (770F) which will drop to ~20% at 300C (900F).  For this reason there should be an air gap behind the panel to cool it or install it against a cooling heat sink.  If the panel is installed at a slope it
self cooling in the sun to reach optimal output.  This also makes it self cleaning in the rain and prevents standing water from creeping into the edge of a rigid panel. 
y experiment proved that a Lexan cover does not reduce the light and there was only a slight temperature increase.  So..... 

NEW MOUNTS & HAIL PROTECTION for RIGID PANELS (Panache version 4, 2010)
(regulated by a Morningstar SG4 PWM controller)

I fabricated 2 removable Lexan covers for the rigid solar panels.  While there are solar panels today that a person can step on and withstand hail, the mounting hardware for my rigid panels was in place so I saw little point in replacing them.  The previous wood corner posts were replaced with the slightly taller UHMW posts shown below.  The solar panels fit in the bottom slot and the 1/8" thick Lexan sheet fits in the top slot.  If I had a C&C machine these posts would have been constructed as one piece, but since I didn't, I made them in layers.  Each layer was cut to exact dimensions, then stacked to make the corner posts you see here.  The top of each post was capped with an aluminum plate (2" square with a corner cut out) to squeeze the layers together uniformly.  This technique worked very well.  Each post is through bolted to the hatch and sealed to the top with butyl rubber.  To secure the Lexan sheet at the middle support I stacked an aluminum spacer (slightly thicker than the Lexan) and an aluminum cap on top of the middle support to create an upper slot.  This last part was amazingly simple and effective.  The Lexan has withstood all winds and hail. 

The outside corner of the solar panel fits in the lower slot of the posts and the center rests in the slot of the middle support.

Solar panels in place ready for the aluminum cap to go over the middle support. 
Note the use of flat head screws on the corner posts so they are smooth on top.
The Lexan cover fits in the upper slot of each post leaving enough space for air flow.
Lexan covers snapped in place to protect the solar panels. 

The fabrication was done, the hardware was installed and the panels produced power again.  And none too soon because another hail storm was only hours away.  Time to get off the boat.  I'm happy to report that the protective Lexan covers stand up to the hail.  The covers can be pushed into the corner posts and popped into place under the center cap by flexing the Lexan up.  Removal is just as easy.  This makes it quick and easy to clean a panel.  As previously tested, there is no loss of charge current due to the transparency of the Lexan.  The Lexan covered solar panels operate at the same temperature as if they were fully exposed.   TOP

There are times when more power is needed to do major surgery on a boat.  I was in that situation when Panache was secured in a new slip that was conveniently close to my truck for tools and parts.  I was not going to pass this up.  The previous owner installed a thru-hole in the aft end of the cockpit foot well.  It wasn't being used so I extended a third charge cable through it with enough slack to position a panel anywhere in the cockpit.  I learned a lot about solar charging by living onboard that week.  When not needed, I simply pushed the cable back in the hole where the excess lay loose under the cockpit.  The hole was then sealed with a bit of neoprene rubber.

TEMPORARY RIGID SOLAR PANEL (Panache version 5, 2020)

- My project was going to take a week and this temporary panel would be useful to generate extra power.  So I decided to protect the back with 1/4" plywood coated with Sikkens Cetol.  While the wind never knocked it over, it is secured with a light line around the winch (not shown).  When not needed, the panel will just fit inside the starboard locker (Tech Tip B19) between the drop boards and the fenders (31.5x13)".  That part was pure fluke.  Not everything I do is engineered to work!
- The third input cable is connected in parallel with the two panels on the sliding hatch.  All solar panels are controlled by BKR 12 from where the combined flow of electrons continue their merry ole journey to the battery, ready for the next demand of juice.

(insert replacement panel info here, 2024) 

Oh Oh - One day during my renovation work I used a day's worth of power ahead of a week of cloudy weather.  I was surprised that the 3 rigid solar panels could not charge the battery in this low light.  "Amazing what you discover when you use the boat daily compared to weekend only."  This low charge rate is not viable for daily cruising when the solar array must maintain the battery charge and/or restore it to full capacity by evening.  It's bad for a battery to not be topped up promptly.  To determine a suitable charge rate I borrowed a 30W panel for a week and the charge controller restored the Optima AGM battery the first day.  Armed with this knowledge I decided to upgrade Panache's solar array and charge controller for 2021.  TOP

FLEXIBLE SOLAR PANELS (Panache version 6, 2021) - When I was working on Panache in her new slip the large single panel above was an improvement but moving shadows and cloudy weather still limited the performance over the course of a day.  This is the primary reason why I replaced the two rigid 5W thin film panels with two 35W flexible shade tolerant panels.

The dimensions of the none-slip area on the sliding hatch is (31x25)" which is perfect to install a couple of (15x24.5)" panels, covering ~90% of the hatch.  So during the winter of 2021 I installed a couple of Go Power! Flex-35 monocrystalline flexible panels equipped with bypass diodes (phew) to maximize efficiency.  It was impractical to make the panels removable for stepping the mast so instead I fashioned a sheet of 1/8" thick plywood to cover them.  Its the simpler solution and cheap insurance.  I hate when things get thumped for a minor foot slip. 

The first job was to restore the sliding hatch.  Clark never intended hardware to be installed on the balsa cored hatch so to protect it I glued the feet that supported the rigid solar panels.  Its amazing how well the Sikaflex held but a chisel and hammer won in the end.  Some acetone and a wire brush on my Dremel Tool removed the stubborn stuff deep down in the non-skid.  A drill bit removed the Sikaflex inside the screw holes which were later filled with G/Flex epoxy to restore the water tightness.  Lastly, I painted the hatch to protect the epoxy and left it to cure for several days.  All good as new.

(Two Go Power! Flex-35 solar panels regulated by a Genasun GV-10-Pb-12V MPPT charge controller).
  • The flexible panels are oriented with the power cables at the forward end of the SJ23 sliding hatch where they can go through the top with an easy, low strain, curve.  I can't emphasize how important low strain will be over the years with exposure to the sun as it minimizes the chance of insulation cracking.  Orienting the power cables forward keeps the end of the sliding hatch clear where I "tend" to lean against it with the heel of the boat.  It is a comfortable place to stand with a nice motion in big waves. 

  • While Go Power! states this panel can be glued in place, I chose to fasten them with machine screws through the corner grommets so I can remove them if required.  I drilled two additional holes through the long sides of the panel to prevent them from fluttering in a side breeze.  Fluttering is a great way to quickly age a flexible panel!  These panels never move.

  • The 1/2" thick hatch has a balsa core that require the screw mounting and cable entry holes to be sealed with epoxy.  The holes were drilled oversize, filled with G/Flex epoxy, the hardened epoxy was drilled out to correct size, screws & cables passed through then sealed with Sikaflex.  No leaks.  See Tech Tip G08 for older techniques. 
    PS:  Installing the cable through the sliding hatch required the removal of the MC4 connectors.

  • The power wires were run under the length of the hatch for cosmetics and weather protection of the terminal strip.  They are wired in parallel at the terminal strip from where the power continues to the batteries via the boat harness.  I previously tested the panels to confirm that steering diodes are not required. 

  • See note below about keeping a solar panel cool.

Fig 1 - Measuring the hatch for two new flexible solar panels. 
            They will be a perfect fit!

Fig 2 - The rigid solar panels were removed and the screw holes filled with epoxy.  The mounting and cable entry holes for the new flexible panels were sealed with epoxy.  Afterwards the surface was painted with 3 coats of acrylic.

The two cable entry holes shown in Fig 2 were drilled at a shallow 150 using a Pocket Hole Drill Guide clamped in position to prevent movement of the drill bit.  The none-skid on the hatch was painted white to protect the epoxy and to match the colour of the solar panels.  The underside of the hatch was also painted white to brighten the cabin and make it easier to clean.  With cables in place (Fig 4) the holes were sealed with silicon sealant and capped with a custom fabricated UHMW clam shell for support and protection.

A final dry fit on Panache confirmed that the bundle of wires and terminal strip can slide freely over the sill through the full sliding distance of the hatch.  Better to be safe than sorry.  On Panache the gap between the bottom of the hatch and the top of the sill is 1 1/8" due to additional 1/8" thick UHMW glider under the hatch rails.  Without the glider the gap is about 3/4".  See Tech Tip B04

Fig 3 - A dry fit for the #10 double jacketed wires.  The natural, easy curve is just the thing for long life in the UV light of the sun.

Fig 4 - The custom UHMW cap over the cable entry hole help to guide he wires and seal the hole.  The #10 wire was formed to this curve to eliminate long term strain.  The orange tagged cable is +.

  • Panel to house wires are connected under the hatch with crimped and sealed lugs, ensuring a zero Ohm connection.

  • Power lugs with dual holes in Fig 5 are used on the terminal strip so they don't loosen, ensuring a zero Ohm connection. 

  • The vacant terminals are reserved to add 2 Schottky diodes, should they become necessary. 

  • This is also where the 28" loop of flexible wires connect to the boat wiring harness on the starboard bulkhead.  The wire loop is covered in a woven nylon sheath to organize the conductors as a unit. 

  • I also replaced the previous smaller boat wiring harness with larger gauge (#10) wire to minimize loss, routing it further away from the VHF radio.

Fig 5 - The panel power leads are sealed at the entry holes and secured along the bottom of the hatch.  The flexible cable to the boat wiring harness is secured with a cable clamp next to the terminal strip.  The cable bundle and terminal strip just clear over the sill at the front. 

Fig 6 - Since the solar panels are not removable, thin plywood may protect them when I work on the deck.  This is a prototype to test feasibility.

- On a sunny February day I pointed the Flex-35 solar panels to the sun and connected them to the AGM battery via a Morningstar SunSaver MPPT charge controller.  The sun was about 200 above the horizon with thin clouds scooting by.  The panels charged the battery at 1-2 amps during overcast and slightly over 3amps during the brief exposure of full sun.  Pretty good considering the low angle of the sun.  The current dropped off to 1 amp during the overcast.  Despite the low light, the battery reached absorption mode after 2 hours on the first day and reached maintenance mode after 2 hours on the second day.  These solar panels do not require full sun.  Their sunlight "acceptance angle" is quite wide and can generate power even on a cloudy day.  The performance improvement going from 2x5 W to 2x35 W is impressive. 

Fig 7 - Top view of solar panels installed on Panache right after they were installed.  Click here for a different view.  Notice that the hatch rails are now white so they stay cooler, minimizing thermal expansion. 


Fig 8 - Flex cable "collapsed" with hatch closed.  The 2 middle terminals pass equal power from the panels, operating the controller in bulk mode during a sunny day.


Fig 9 - Flex cable extended with hatch open.  In either case the flex cable is out of the way.  It is now soft with the sheath covering the wires and looks presentable.



HINT - To test the operation of each solar panel darken one panel with a towel and view the charge current and voltage of the exposed panel on the solar charge meter.  Then cover the other panel and repeat the measurement.  Since these Go Power! Flex-35 panels are equipped with bypass diodes, pulling the towel back slowly reveals the operation of each segment of the panel.


PARTS - Go Power! Flex-35 monocrystalline panel, Schottky diodes below.

REDUCE SOLAR PANEL TEMPERATURE WITH PASSIVE COOLING (2023) - After a typical afternoon of full sun I measured the temperature of Panache's Go Power! GP-FLEX-35 watt solar panels.  55C is a tad warm to lean your arm on!  While most panels have a maximum limit of ~80C, operating at this high temperature reduces the life and output power.  At Panache's latitude (53.30N) and Alberta's intense sun light (due to clean, dry air East of the Rocky Mountains) I want long life with as much charging power as possible from these panels.  So for these reasons I added a 3/16" thick sheet of Coroplast under the panels to create an air gap for passive cooling with the wind.  The air passages are oriented fore/aft, in the direction of the prevailing wind through Panache's slip, light as it is. 

A week after the installation the panel temperature was measured at 48C on a similar sunny afternoon.  I have not measured a higher temperature since, so Coroplast bodes well.  Time will tell if this continues.  So far they seem to produce slightly more power than mounted directly to the sliding hatch.  You have to think creatively when using Coroplast to solve your problem.  A blast of compressed air can clean the channels at the beginning of the season.  Another possibility is a sheet of aluminum resting on spacers under the panels. 

Active Cooling - To further cool the panels, you could install a 12V computer fans on the bottom of the hatch to blow air through the Coroplast or under the aluminum.  The fans would have to be < 1/2" thick to pass through the 3/4" high gap over the sill, be powered directly from each panel, and be thermally switched to shut off when cool.  This has the potential to cool a panel to ~30C.  The bonus is they would improve ventilation through the cabin.  This is a possibility I will leave for the future. 

Coroplast under the Flexible Solar Panels - While Coroplast has impressive compression strength to support the panels, I wouldn't recommend stepping on them.  Installing the Coroplast means NO STEPPING on the panels, which applies to sheet aluminum as well.  This really isn't a problem as I've resigned to not stepping on the sliding hatch a long time ago.  However, I'm impressed with how much weight it can support under my hand.  Yes, it is easy to blow through the channels and you can see light through them as well.  Unfortunately the camera can't show that.  The mounting screws are tightened only just snug so as not to dimple the panel.  This stress could delaminate a panel along with thermal expansion. 

Trimming with a razor knife is amazingly easy.

Cockpit view of trimmed edge.

No Stepping on Panels.

"Installing these solar panels demanded "perfection" since the skipper has been known to steer Panache by the edge of the sliding hatch.  Therefore, the panels were centered on the hatch, parallel with the center line of the boat.  This is a tad difficult since the shape of the non-skid on the sliding hatch is a trapezoid.  Didn't know that huh?.  This work was painstakingly slow; laying out hardware, measuring, determining pros & cons, contemplating (tick tick, tick tick), reaching a final design, measure again, prep, paint, work a bit, epoxy, wait, scrape a bit, paint, repeat, etc.  It turned out to be a perfect "time consuming" project for the first COVID19 winter."   TOP

(Regulating power is about protecting the battery and appliances)

LINEAR REGULATOR (~1980s onward) - A solar regulator must be used to prevent over charging a battery, especially a flooded battery where the electrolyte can be gassed off.  Prior to the 1990s the only choice was a linear regulator.  The silicon steering diodes D1 & D2 were required to prevent discharging the battery at night and to steer the charging current to the battery during the day.  Today the one way path for charge current is accomplished within the electronics of a solar charge controller.

Panache originally had a shunt regulator and I seriously considered a series regulator, thinking it to be superior.  I soon learned the difference is negligible.  This argument can probably be won by the same person who can argue politics over religion!  There are three problems with a linear regulator; it is barely functional with the shade & weather variables on a moving sail boat, it applies very little charge voltage to the battery when the light is weak and the external 1N4007 silicon steering diodes drop the voltage to the battery too much.  So I abandoned my shunt regulator in favour of a MorningStar SunGuard SG-4 PWM charge controller.

A solar "charge controller" is the marketing term used today for what was initially called a "smart" regulator.  The electronics is significantly improved over the original linear regulators to maintain some charge current during the low light of dusk, dawn or shadow.  Some charge controllers have a low voltage disconnect (LVD) feature to cut off the load when the battery voltage is critically low, protecting the battery from permanent discharge damage.  Given equal operating environments, a solar charge controller easily out performs a linear regulator. 

SOLAR PANELS WIRED IN PARALLEL WITH STEERING DIODE - The standing rigging on a sailboat has a habit of blocking sunlight to a solar panel as the boat heels one way and then another.  The hull also turns relative to the sun, thereby casting a moving shadow over the panels.  For these reasons I installed a solar panel on either side of Panache's sliding hatch, so at least one panel is illuminated, most of the time.  They are wired in parallel for maximum charge to the battery and match the open circuit voltage to the controller. 
NOTE - For equal performance, the solar panels and steering diodes must match each other.  One of Panache's panels produced less power than the other due to a steering diode I forgot to remove from the external wiring harness.  Removing it increased the panel output .6V, resulting in a slightly more charge to the battery.  The battery voltage rose from 13.1V to a healthier 13.9V with the panels producing equal power.

  1. Panel with Steering Diode - If your panels are equipped with an internal steering diode (after ~1990s) then you can connect them in parallel sending the combined output to the charge controller input.  All the power will go to the battery.  DO NOT exceed the input power rating of a PWM controller.  It is OK to exceed the input power of an MPPT controller provided you don't exceed Voc.  This was Panache's configuration with the two rigid panels on the sliding hatch. 

    (How to Test a Solar Panel for an Internal Steering Diode - Other than reading the panel documentation or physically seeing the diode, you can use a variable DC power supply e/w current limiting to test your solar panel for the presence of an internal diode.  Darken the panel so the output voltage is 0V as measured with a voltmeter.  Then connect the power supply to the solar panel wires, (+ to + and - to -) with current limiting set to ~100 MA.  Slowly turn up the power supply voltage to 15V while monitoring the current.  If no current flows (only uamps = no current) a diode is present.  If current flows, the panel needs an external Schottky diode wired in series to block current from the other panel.  Never having measured this current I think it would be in the low milliamp range.

  2. Panel Without Steering Diode - If your old (~before 1990s) panels are NOT equipped with an internal steering diode then you must add an external Schottky diode in series with each to prevent the shaded panel (lower output voltage) from absorbing the power from the illuminated panel (higher output voltage).  Wire the combined outputs to the charge controller input as shown at right.  All the power will go to the battery.
    - Select a
    Schottky diode that can handle about 50% more current than the panel can generate.  It must also have a peak inverse voltage (PIV) of >30V.  Its best to mount it on a heat sink where it can dissipate heat.  Connect the leads to a terminal strip for secure connection.  Connecting a diode in "mid-air" to a wire is just asking for trouble.

  3. A Charge Controller for each Panel - The best system performance (most expensive but with redundancy) is a separate charge controller for each panel with the outputs connected in parallel.  No steering diodes are required as each controller performs that function.  The combined power will go to the battery.

  4. Solar Panel(s) with Outboard Generator - A slight variation on this configuration is an outboard motor generator connected in parallel to a single or dual solar panels.  The generator consists of a magnet in the flywheel spinning by a stationery pickup coil.  The coil has a diode in series with it to produce positive pulses (a half wave rectifier) of power, generating ~(5-6)A current.  Connecting the generator in parallel to the solar panel(s) is not a problem since the generator diode also blocks current generated by the solar panels.  The solar controller is the steering diode for the solar panel.  No external diodes are required and the combined power will go to the battery.  

NOTE - There is another reason to install a steering diode in front of each panel.  It can block a higher voltage power spike from damaging a panel.  TOP


SOLAR CHARGE CONTROLLER (PWM or MPPT) - Very much superior to a linear regulator are two types of solar charge controllers; one type uses Pulse Width Modulation (PWM) and the other uses Maximum Power Point Tracking (MPPT). 

PWM - During bulk charging a PWM charge controller applies all the solar panel voltage directly to the battery.  In absorption and maintenance modes a PWM charge controller is essentially a DC to DC converter that charges a large capacitor which is then discharged into the battery in pulses.  This is the mode when a PWM controller has gain over a linear regulator, about 50% more efficient. 
MPPT - An MPPT charge controller is about 15-20% more efficient than a PWM controller, achieving this by continually measuring (tracking) the maximum power point (E & I) of the solar panel to be applied to the battery.  This is a clever technique to transfer the most power, during all 3 charge modes listed below.  Get to know them intimately. 
With either charge controller the output is adjusted automatically in proportion to the solar panel illumination (shade, angle & temperature),
the temperature of the controller & battery, the wiring and finally the battery voltage.


(good technology for sunny weather)
(performs better than PWM, even in cloudy weather)
This mode charges the battery to ~(80-90)%.
The output power of the controller is constant, passing whatever power the panel produces.  This is the mode in which PWM gains nothing. 
- During low morning and evening light it continues to charge extending the charge time, albeit slower.
This mode charges the battery to ~(80-90)%.
The controller continually measures (tracking) the maximum power point of the solar panel to create a current gain, charging the battery to the limiting voltage of the controller set by the type of battery.  This is the mode in which MPPT gains over PWM.
This mode charges the battery to ~(90-98)%.
As the battery voltage rises to the controller limiting voltage, the output changes to DC pulses.  If the charge controller is installed next to the battery the internal temperature compensation can reduce the output to protect the battery.
This mode charges battery to ~(90-98)%.
As the battery voltage rises to the limiting voltage of the
controller, the output is proportionally reduced.  The output is also limited by the temperature of the controller and battery.  There is little current gain in this mode.
When the battery is at full charge ~(98-100)%, the controller output is further reduced to a trickle by reducing the pulse width to maintain battery charge. 
When the battery is at full charge ~(98-100)%, the controller output is further reduced to a trickle to maintain battery charge.
The PWM pulsing action during the absorption and maintenance modes applied to a flooded battery minimize plate sulphation and prevent the electrolyte from gassing off.  This leads to long battery life and health. 
If an MPPT charge controller is configured to charge a liquid filled battery most can automatically perform a monthly equalize charge across all cells.  Other battery types are also maintained for long life and health.

Beyond this, the description of solar panels and charge controllers gets very technical and is beyond the scope of this Tech Tip.  It helps if you understand Ohm's Law, I=E/R.  For a more detailed description of pulse width or power point track charging, go the Morningstar web site.  Learning is a daily exercise that tickles the brain!


PWM SOLAR CHARGE CONTROLLER (2004) - The SunGuard SG-4 PWM charge controller manufactured by Morningstar has an electrical efficiency ~50% greater than a linear regulator.  That's like adding a second solar panel and it costs about $30 Can, (2004).  Good bye linear regulator.  The output is pre-set to 14.1 VDC which is optimized for a flooded, gel or sealed/AGM battery.  It is internally temperature compensated to adjust the output voltage which is OK if it is installed next to the battery.  These features make the SG-4 ideal for a pocket cruiser like a SJ23.  Given the electrical performance, waterproof packaging and reasonable cost I installed an SG-4 controller in 2005 and have had zero issues with it. 
PS: I was considering upgrading to the SunSaver MPPT controller until
I removed the external steering diodes shown in the diagrams above.  Turns out they were redundant since my rigid solar panels were equipped with an internal steering diode.  The battery voltage increased .6V which made me a happy camper.  The SG-4 is equipped with an internal Mosfet that is far more efficient and doesn't reduce the charging voltage to the battery.

  • SIZE - About the size of a 2" cube.

  • TEMPERATURE COMPENSATION - Internal.  For optimal charging locate the controller adjacent to the battery to "sense" battery temperature. 
    Operating range -40C to 60C.

  • CHARGE RATING - 4.5A input from a 12V solar array.  It can handle an array rated at 64W output to charge a 12V battery. 
    DO NOT exceed the input rating of 30 Voc.

  • EQUALIZE CHARGE - Cannot equalize charge a battery.

  • BATTERY SELECTION - The output voltage charge curve is a compromise setting for flooded, gel or sealed/AGM battery types.

  • EFFICIENCY - About 75-80%.

  • CONNECTION - The controller has 4 wires; 2 for solar array input, 2 for battery output.  Ground connection is negative battery.

  • INVERTER - Connect an AC inverter input directly to the battery.  The surge current during start up is too high for a charge controller.

  • Also check out the section on Electrical "Noise" reduction.

PRIMARY BUSS BARS - When I acquired an AGM battery I thought it high time to clean up the hickety potch wiring to the battery under the settee.  This is when I fabricated the primary buss bars for Panache.  Its quite an improvement and a bit of overkill for such a small boat but the electricity doesn't know that!  You can read more about this in Tech Tip E02.  From left to right is quite an improvement.


PANACHE CHARGE WIRING with PWM CHARGE CONTROLLER (2016) - In the diagram below (top view) the DC pulses originating from the SG-4 controller are fed directly to the battery via short, low impedance wires.  This is the desired wiring configuration for a single battery.  The ferrite beads completely attenuate the DC pulses sent to the power panel wires, ensuring clean DC power for the VHF and AM/FM radios. 

  • The A PWM charge controller must be connected directly to the battery and physically close to it so the impedance of the output wires does not attenuate the high frequency charge pulses (PWM).  It should also be installed physically close to the battery so it senses the same temperature as the battery.  Both of these ensure the highest possible charge efficiency while protecting the battery. 
    NOTE - So DO NOT connect the SG-4 controller at the power distribution panel.  Doing so will apply the DC pulses to the boat's wiring harness and the "noise" will be heard on the VHF, AM/FM radio, or other sound system, making them almost unusable due to electrical noise.  The "PWM noise" sounds similar to ignition noise from an outboard engine operating at a constant RPM.  So, assuming your engine didn't radiate ignition "noise" before you installed the controller, a constant pulse rate after the installation is the telltale sign the interfering signal is coming from the controller via the wiring. 
    The solution is to install a ferrite RF noise suppressor bead over each wire that feeds power into the boat's electrical system as shown above.  Most ferrite beads do an excellent job of attenuating PWM & RF interference signals on a wire.  It is usually best to install a ferrite bead close to the
    signal source; battery or battery buss bar.  In an extreme case you may have to install several beads is series or wrap the wire several times through the same bead. 

  • You can find an inexpensive source of ferrite beads in the cable bin at your local electronics recycle centre.  That "bump" on the end of a computer power cable is a ferrite bead.  Cut the cable off at either end of the bead and pull the cable out the hole.  Voila a useable ferrite bead. 

  • CONCLUSION - If you consider the variable light conditions on a moving sailboat, a PWM solar charge controller is an efficient device to charge a battery since it can still charge during low light, is dynamically regulated in proportion to sunlight, the electrolyte does not "boil" off and the pulsing output removes any sulphate crystals from the plates of a flooded battery.  For more detail info on pulse charging technology see Tech Tip E04.  


MPPT SOLAR CHARGE CONTROLLER (2020) - When designing the charging system of an SJ23 the charge controller should be considered first since it relates to system sizing and protects the costly battery by charging it correctly.  Problem is, an MPPT charge controller is a pricey component for a small electrical system like on an SJ23.  It's one of the reasons why I stayed with a PWM charge controller for so many years.  Then in 2020 someone offered me a large solar panel that I just couldn't refuse.  Since the input current had the potential to exceed the 4.5A limit of my PWM charge controller it was time for an upgrade.  So which charge controller to select?

(Either of these charge controllers is an excellent choice for an SJ23 as both are fast tracking and neither transmits RFI)

GENASUN GV-10-Pb-12V - This 10A MPPT charge controller does NOT transmit RFI, is extremely fast tracking, has only 0.9MA of self consumption current, and can recover a dead battery.  It was installed on Panache in Spring 2021 and is wired as per diagram below.
Order from GENASUN Canada  10 year warranty.

MORNINGSTAR MPPT SunSaver - This 15A MPPT charge controller does NOT transmit RFI, is fast tracking and has LVD.  The low voltage disconnect is a feature that is just a tad important if you have electric start with a single battery.
Order from an authorized solar supply store.  5 year warranty.

SIZE - (5.5 x 2.5 x 1.2)".

SIZE - (6 x 2.5 x 1)".

RATING - 10A at 34Voc max (140W) input from a solar panel.
(It's OK to oversize the solar array as the extra capacity can maintain the day time charge current during marginal light).

RATING - 15A at 75Voc max (200W) input from a solar panel. 
(It's OK to oversize the solar array as the extra capacity can maintain the day time charge current during marginal light).

EFFICIENCY - 96-98% electrical.  Charge current comes on instantly with sun light.  (Fast MPPT tracking speed at 15 samples/sec while maintaining charge current).  

EFFICIENCY - 94-99% electrical.  Charge current comes on instantly with sun light.  (Fast MPPT tracking speed while maintaining charge current). 

OPERATING RANGE -  -40C to +85C.

OPERATING RANGE -  -40C to +60C.

ELECTRICAL CONNECTION - #10 wire; 2 from solar array, 2 to common negative battery.

ELECTRICAL CONNECTION - #6 wire; 2 from solar array, 2 to common negative battery, 2 to load, 1 for earth ground.

* CONNECTION WARNING * - A solar charge controller must always be connected to a battery (load).  Switch the solar input off first to safely service the system without damaging the controller.  To facilitate this, install a circuit breaker, fuse, or switch between the solar panel and the charge controller input. 

  • INSTALLATION - Connect the output (battery) first, then connect the input (solar panel). 

  • SERVICING - Disconnect the input (solar panel) first, then the output (battery). 

  • MULT PANELS - Click here if your solar panels are connected in parallel

  • TESTING - If the solar panels are connected to a terminal strip, it creates a convenient test point to measure and isolate a problem.

  • START UP CURRENT - Connect an inductive load (inverter, motor, compressor or generator) directly to the battery posts.  The start up surge current of these devices is too high for a charge controller e/w terminals to connect a load or is equipped with a low voltage disconnect (LVD) feature.  The start up current is also too high for a load shunt meter.

BATTERY SELECTION - A single jumper to select deep cycle battery charge rate for flooded or sealed/AGM.  System charge voltage is fixed at 12V nominal.

BATTERY SELECTION - Dip switches to select battery type for Gel, Sealed, AGM or Flooded.  System charge voltage is automatic, 12/24V.

EQUALIZE CHARGE - Auto-equalize 1 per 28 days for a flooded battery.  Disabled for other battery types but check with manufacturer.

EQUALIZE CHARGE - Auto-equalize 1 per 28 days for a flooded battery.  Disabled for other battery types but check with manufacturer.

BATTERY TEMPERATURE - Internal sensor.  For battery protection and optimal charging install the controller close to the battery to reduce the charge current to a warm battery.

BATTERY TEMPERATURE - External sensor.  For battery protection and optimal charging connect the temperature probe to the top of the battery to automatically reduce the charge current when warm.

INTERNAL PROTECTION - Over-charging, over-discharging, reverse polarity, over-load, over-temperature and an internal 20A fuse.  No LVD to prevent battery discharge.

INTERNAL PROTECTION - Over-charging, over-discharging, reverse polarity, over-load, over-temperature.  LVD to prevent battery discharge if load connected to LVD terminals.

STATUS LED - Shows charging mode (2 colour LED, very accurate).  Best to post a laminated chart next to the controller to understand the following flash patterns.

 - Battery Charge Status.
 2 sec green flashes = Ready to charge when solar available.
 solid green = absorption or maintenance mode.
 fast short green flashes = charging <3.7A (bulk mode).
 slower, longer green flashes = charging >3.7A (bulk mode).
 long, then short green flashes = charging limit >10.5A (bulk mode).

NOTE - When the AGM battery is fully charged the Status LEDs alternate between fast short green flashes and solid green at about a 2 sec flash rate.  Very convenient.

 - Battery Alarm Status.
 2 red flashes = high temp.
 3 red flashes = current overload.
 4 red flashes = battery V too low.
 5 red flashes = battery V too high.
 6 red flashes = solar panel V too high.
 2 long flashes followed by short flashes = internal error.

STATUS LEDs - Shows charging mode (dual LEDs, very accurate).  Best to post a laminated chart next to the controller to understand the following flash patterns.

 - Charging Status.
 solid green = bulk mode.
 1 sec flash = absorption mode.
 2 sec flash = maintenance mode.
 red - error.

 - Battery Status (SOC)
 Full, Partial, Low. (Lit under matching battery image).

- Temp Sensor = high temp from remote sensor.  

Install the optional external Remote Meter for precise measurements or use a PC to view 30 days of internal logging. 

Radio Frequency Interference (RFI) - The majority of MPPT charge controllers transmit radio frequency interference (RFI) to some degree due to the internal DC switching.  The sharp power switching generates voltage transients that are transmitted as voltage spikes on the boat wiring and radiated through the air (RFI), interfering with the boat's VHF and audio electronics through the antenna.  I've tested the Genasun, SunSaver MPPT and the Victron to know they are amongst the few controllers that don't transmit RFI.  Unfortunately my previous Renogy Rover Elite does, so for this reason it will be used elsewhere.  More on RFI below.

PANACHE INSTALLATION - This charge controller was installed on the starboard bulkhead with the other electronics as my bench testing confirmed there is no RFI.  If the status LED shines green the controller is wired in the correct polarity.  The flash pattern of the LED shows the charge rate, <3.7A or >3.7A, which is operational confirmation at a glance.  For a precise power measurement I read the meters on the power distribution panel.  This Genasun GV-10 is working extremely well on Panache as is the Morningstar SunSaver on my friend's boat. 




IMPORTANT for LONG TERM STORAGE - If the battery is left onboard for long term storage and the solar panels cannot receive sun to maintain the battery charge, then disconnect the charge leads to the battery so the self consumption current of the MPPT charge controller does not discharge the battery.



RECOVERY FROM NIGHT TIME POWER DRAW - Most MPPT charge controllers draw some power from the battery when the sun doesn't shine.  I was curious to know how long it takes to recover the overnight deficit.  For this test I used a 2A variable power supply to simulate a solar panel with the controller output power charging a 12V AGM battery.  Assuming 6 hours of darkness (no charge) below are my results. 


STARTS CHARGING - At ~2V above battery voltage with a smooth rise in charge current that reaches maximum near instantly. (very fast tracking).
RECOVER NIGHT LOSS - Takes ~2 sec at 10A charge current.


STARTS CHARGING - ~2V above battery voltage with a smooth rise in charge current that reaches max near instantly. (fast tracking).
RECOVER NIGHT LOSS - Takes ~50 sec at 10A charge current.

CONCLUSION - To recover the night time power loss first thing in the morning with either of these controllers takes less time than drinking a cup of coffee, which makes either unit an excellent choice!  Be aware that the first morning light is weak and cannot produce full charge current till the input voltage is ~2V above battery voltage.  Having said this, my Genasun charge controller is usually charging at about 5AM in the summer.  The lower quality charge controller manufacturers don't mention this parameter in their specifications.  Hmmm.

TRACKING SPEED - There are two aspects to this:
  • Q - How quickly can an MPPT controller start charging after the resumption of solar panel output?
    A - While tracking speed is seldom an issue for a permanent land based installation, movement and shading are a constant issue on a sail boat.  For this reason you want an MPPT charge controller that can switch the charge power on immediately after the solar panel is illuminated and maintain charge while tracking.
  • Q - How often does the controller sample the incoming power (samples / second) to determine the optimal power transfer?
    A - The faster the better and the controller should continue to charge while sampling.  Some can't.

The fast tracking feature is very important on a sailboat.  The following are all fast tracking charge controllers suitable for a sailboat; Genasun, MorningStar, Victron, Midnite & Outback.  Outback is designed for a solar array starting at 100W, so too big for an SJ23.  The most inexpensive controllers (not listed here) have slow tracking and should not be considered for the dynamic conditions on a sailboat.

IMPORTANT for LONG TERM STORAGE - If the battery is left onboard for winter and the solar panels cannot receive sun to maintain the battery charge, then disconnect the charge leads to the battery so the self consumption current of the MPPT charge controller does not discharge the battery. 


PANACHE WIRING with MPPT CHARGE CONTROLLER (2020) - In the diagram below (looking at the top of the battery into settee) the DC power originating from the MPPT controller is fed directly to the battery via dedicated #10 stranded wires.  This is the desired wiring configuration for a single battery.  While not required with a Genasun or Morningstar MPPT charge controller, I decided to retain the ferrite beads to attenuate any RFI signal sent to the power panel wiring.  If another high load circuit is added to these buss bars, I will slip some ferrite beads over those wires as well.  It is the VHF radio and the media receiver that are affected by RFI on the power wires. 

CONCLUSION - The major advantage of an MPPT charge controller is the power tracking feature that utilizes excess panel voltage to convert it to useable charge current during bulk chargingBulk charging occurs when the battery terminal voltage has not yet risen to the limiting voltage of the controller.  This is why an MPPT controller is about 15% more efficient than a PWM controller.  With this feature it can typically ram in 35% more power per day resulting in an average 90-95% state of charge compared to 55-60% for a linear regulator.  Just don't expect the charge controller to maintain the battery from moon light, OK!   TOP

RADIO FREQUENCY INTERFERENCE (RFI) - All MPPT charge controllers emit RFI to some degree due to the internal DC switching used to regulate the output.  The majority of RFI is transmitted while the solar charge controller is charging the battery in bulk mode.  Once the controller goes to maintenance mode (battery charged) the RFI is usually much reduced, but still annoying.  RFI on power cable can originate from the alternator, a cooling fan, a DC/DC inverter, certain LEDs, etc.  RFI can radiate through the air or along power cables acting as an "antenna".  You can hear the radiated interference when it breaks the squelch on your VHF radio, intermittent or continuous.  To understand the full scope of the interference listen to a quiet channel on the VHF, other than 16 or 9, with the squelch open.  At times the quality of the NOISE can give you a hint as to the source of the unwanted signal.  Tightening the squelch is NOT a solution as this shortens the receiving range.  My tests show the majority of the signal is radiated from the charge controller input wires and to a lesser degree the output wires.  The RFI is broad spectrum 0-300 mHz, peaking around 150 mHz, as shown on a spectrum analyzer.  We also saw signal spikes on the wiring that coincide with the switching frequency of the microprocessor in the controller.  These are the noise bursts (squelch breaks) you hear on a VHF radio.

To ISOLATE RFI to a particular device, make use of the power switches:

  1. Confirm that VHF squelch operates correctly and set the volume to a comfortable level.
  2. Confirm if the radio is affected with the NOISE.  It may be intermittent.  Another clue.
  3. If the NOISE is heard, open the squelch.
  4. Remove the antenna connector.  If the NOISE is gone the signal is radiated through the air.  If the noise stays on it is radiated on the power cables.  Now you have to chase down the culprit so reconnect the antenna.
  5. Switch off the electrical power to all the devices on the boat, except the VHF.  Shut off the MPPT charge controller by covering the solar panels or open the wiring.  Hopefully the NOISE is gone with one of these actions.
  6. Switch on each electrical circuit, one at a time, to determine which culprit is transmitting the NOISE.
  7. NOISE could come from the alternator, a cooling fan, a DC/DC inverter, a solar charge controller, etc.  Electrical motors in general can be noisy.  But then so can a loose power/ground connection or one with high resistance.
  8. As a temporary solution you may have to operate the VHF with the culprit temporarily switched off.
  9. Follow the steps listed below to reduce or eliminate the RFI.


  1. Twist a pair of power wires around each other, about 8 turns or more per foot, to correct the characteristic impedance to pure resistance. 
  2. Install the power wires away from boat signal wiring.  If the power wires have to cross boat wiring, do so at 900 for the least cross talk.  This is always a good practice. 
  3. Install the VHF co-axial cable away from the power wires.  This is always a good practice. 
  4. The installation of a ferrite bead over each power wire can attenuate the RFI, provided you choose a bead that attenuates in the VHF range.  It is best to slip a bead over each conductor.  The composition of a ferrite bead determines the frequency band it attenuates; 30kHz-100mHz or 100-500mHz are two examples.  I'm not sure what composition determines the impedance of a bead but highest attenuation (dB) is best.  You will have to search through an electronic wholesaler for these.  If one bead isn't effective try installing a second bead adjacent to the first.  Alternatively loop the wire several times through a large diameter bead.  Clamp on beads are easiest to install over existing wires. 
  5. Install clamp on ferrite on the VHF coax cable.
  6. Block RF In & Out - The optimum place to protect a device is to install a ferrite where the power enters the device.  The optimum place to stop the signals from leaving a device (MPPT controller) is to install a ferrite where the power leaves the controller.  In the schematic above, the MPPT controller input and output leads are both protected. 
  7. While bench testing a charge controller I discovered the addition of a power line RFI filter on the input and output leads attenuated the RFI by 30dB.  The interference (RFI) was reduced to only 2 feet as confirmed with a hand held VHF.  Determining this distance is tricky as my body was acting as an antenna.  With my hand close to the radio it broke squelch.  However, these filters typically limit the system current as well so this is a questionable solution. 
  8. Short Out RF - Install a .1 uFd ceramic capacitor across the input and output terminals of the MPPT controller.  The leads must be as short as possible to be effective.  The idea is to short out the RF signal back to its source.  This isn't the best technique but it reduced the signal propagation on Panache from 10M to only 2M distance, resulting in fewer squelch breaks on the VHF.
  9. Short Out RF - Alternatively, install a .1 uFd ceramic capacitor from each wire terminal of the MPPT controller to a thin copper plate installed behind the controller using the MPPT mounting screws.  This shorts out the RF signal to a low impedance ground. 
    To be successful the capacitor leads must be very short, which I couldn't do, so I can't confirm if this technique works.  It might be more effective if the copper plate is connected to earth ground.
  10. So far I tested the Genasun, MorningStar & Victron MPPT charge controllers and confirmed them to be free of RFI.  I'll add others when I can.
  11. IGNITION NOISE - When an outboard engine equipped with an electric starter/generator is operated, the generator and the ignition may create electrical "noise", imposing it on the boat wiring harness.  The noise of either one can make it near impossible to understand speech on the VHF or listen to an AM/FM radio.  The operation of any other sensitive electronics may also be affected. You can eliminate most of this with good electrical connections and ferrites.

Never commit your installation design till all devices work in every mode.  After that it is OK to bundle up the wiring.



  1. STARTER - If your battery voltage is low and you release the starter switch of the outboard, the starter could induce a damaging voltage spike onto the electrical wiring due to the sudden change in current.  Although I have not measured this.
  2. INDUCTIVE LOAD - Switching off an electric fan or other inductive load appliance can induce a damaging voltage spike.  The spikes are opposite polarity to the normal power and can therefore damage an LED, VHF radio, Tiller Pilot, or other electronic device that is switched on and not protected from this.  Unfortunately most marine electronics is NOT protected against a voltage spike.

The fix for this problem is to install a Schottky diode across the power leads of the transmitting electrical device.  A Schottky diode can conduct the induced voltage spike quicker than a silicon power diode, resulting in excellent protection.  But if you can't find a Schottky diode then a 1A silicon diode is next best.  Connect the striped end of the diode to motor positive and the other end to motor negative.  Connect it electrically as close to the motor as possible.  Also connect a diode ahead of every LED circuit in the boat.  The normal power flow to or from the motor is not affected.

NOTE - A Schottky diode is a special type of diode with a very low forward-voltage drop and very fast switching speed, (faster than a silicon power diode).  The voltage drop of a Schottky diode is between 0.15-0.45 VDC while the voltage drop of a silicon diode is usually 0.7 VDC.  The lower voltage drop is why it dissipate less power and the faster switching speed is why it can short out the high frequency "noise" spikes.  This translates to better protection and a quieter electrical system.  See Tech Tip E11.  TOP


BATTERY  - The boat battery chemically stores electricity to supply DC power.  It regulates the system voltage, discharges current beyond what a solar panel or alternator can provide and absorbs electrical noise on the wiring.  To do any of these effectively the battery capacity must be capable of supplying sufficient power to operate the devices and the charging system should be sized to power the devices plus charge the battery as quickly as possible.  The following are some golden rules concerning batteries.

  • A battery must be secured in place so it CANNOT be dislodged when the boat lays on her side.  It will happen!

  • For safety a flooded battery must be vented to the open to dissipate the hydrogen gas.  Not so a sealed AGM battery.

  • For safety reasons a flooded battery must have an absorption blanket under it capable of soaking up all the electrolyte. 
    While a blanket is not required for a gel or AGM battery, it wouldn't hurt.  It spreads the weight evenly across the bottom.

  • A battery should be equipped with a cover or have insulated posts to prevent an accidental short circuit across the terminals.

  • As a rule of thumb battery capacity should be double the daily consumption. 

  • Charge and maintain each battery type correctly as per the manufacturer's recommendations. 

  • A filled or AGM battery should be discharged to only 50%.  The exception is the Optima spiral wound AGM battery that can be fully discharged without damage.  I have discharged Panache's Optima AGM to low without damage, but never fully discharged it.

  • A battery is an excellent absorber of transient voltages and a major component of an RF ground for the VHF radio. 

  • If you remove the boat battery during the off season, remember that a solar charge controller cannot generate 12V on its own.  It must be connected to a battery.

PHYSICAL SIZE - The battery must fit the SJ23 compartment and be accessible for inspection.
- A Group 27 battery can fit under an SJ23 settee (L- 12.5", W-6.75", H-9.4") (L-32cm, W-19.5cm, H-23.6cm) and is likely popular for an SJ23.
- A Group 31 battery can fit under an SJ23 settee (L- 13", W-6.75", H-9.5") (L-33cm, W-17cm, H-24cm) but is better placed under the cockpit due to its extra weight.

BATTERY TERMINALS - The charge and discharge wires must be connected using ring lugs to the stud terminals.  They are the most secure, ensuring optimal current.  Battery terminals come with many styles and are generally coated for protection against corrosion.  Terminals can be top or front mounted, with some batteries having both sets.  A Group 27 battery generally has T6-7 6MM threaded or T-11 8MM threaded terminals.  Observe correct torque specs to protect the battery plates.

STORAGE CAPACITY - I can't imagine an SJ23 requiring more than 100AH of storage but then it all depends on how many "toys" you have on board and how long you want to operate them at anchor or for night sailing without charging.

BATTERY TYPE - The following battery types require the same lead-acid solar charge controller.

  • FLOODED BATTERY - While there are many types of batteries, a popular one used on a pocket cruiser is a flooded deep cycle RV battery.  It can generate sufficient current to crank start an electric start outboard, operate cabin lights and other "toys" on board.  It can withstand long term charge/discharge cycles without damage but never full discharge.  The fluid level must be maintained up to the split rings in each cell.  Look under the filler cap.  A standard flooded battery is excellent for starting a diesel engine.  If there are filler caps, the battery is NOT maintenance free, despite what is written on the label.

  • GEL BATTERY (VRLA) - A gel battery has the advantage of having vibration resistance and extended life due to the thick putty like gel formed by adding silica dust to the electrolyte.  It is sealed so no spillage but is usually installed right side up for venting and a precaution to leakage.

  • AGM BATTERY (VRLA) - An Optima Spiral D34/78 55AH battery has the advantage of having excellent vibration resistance and extended life due to the fibreglass mesh between the plates that contains the electrolyte and separates the plates.  The Absorbed Glass Mat holds the electrolyte like a sponge to eliminate spilling, has 99.99% pure lead plates, and does not require adding water which minimizes maintenance.  It is sealed so no spillage but is usually installed right side up as a precaution to leakage.  It can be operated from -40C to +65C (-40F to 149F) so safe to leave on boat during winter, albeit at reduced capacity.  This is Panache's current battery and is by far the least expensive battery due to its long life, $/days.  It finally died after 23 years of service.  See Note 2.

  • LEAD CARBON BATTERY -  A CANBAT Lead Carbon battery is designed to recharge must faster than an AGM battery, which is very useful on a moving sailboat with shadows dancing across its solar panels.  With a designed float life of over 20 years at 200C, it offers more than 2,000 cycles down to 50% depth of discharge (DoD).  It is constructed with premium sealed lead-acid chemistry with added carbon ingredients to the negative electrodes.  The carbon ingredients increase power and minimize sulfation.  This battery has pure lead plates and does not require adding water which minimizes maintenance.  It is sealed so no spillage but is usually installed right side up as a precaution to leakage.  It can be operated from -40C to +65C (-40F to 149F) so safe to leave on boat during winter, albeit at reduced capacity.  The model CLC100-12 battery with 8MM terminals will fit nicely under the SJ23 settee.

NOTE 2 - I have installed numerous CANBAT CLC100-12 Lead Carbon batteries in various Alberta cell sites and none of them have failed during the last 15 years, performing exactly as stated on their web site.  For this reason it is tempting to install one on Panache.  However, in late 2023 I replaced Panache's battery with another Optima Spiral D34/78 55AH AGM battery for the following reasons: It is 30 lbs lighter than a Lead Carbon battery, the Optima stands up extremely well to vibration and rough handling, the battery tie down doesn't have to be changed, the Optima side posts result in no strain on the power cables, the Optima is a working configuration that doesn't require further research to function with the existing MPPT solar charge controller.

PROLONG LIFE OF AGM BATTERY - An AGM battery has a higher storage rating than a flooded battery.  It is sealed so no gassing or filling cells with water.  Equalize charging is not required but it is sensitive to overcharging.  The voltage holds up better under a heavy load than does a flooded battery.  Has low internal resistance so can be charged & discharged faster than a flooded battery.  The spiral wound cell structure is extremely robust so less likely to deteriorate under vibration.  The following tips help to prolong the life of your AGM house battery.  Many of them apply to a flooded battery.

  1. An AGM battery is best suited for house use.  A flooded battery is best suited for engine starting.  Although you can now buy an AGM designed for engine starting.

  2. Avoid discharging your AGM battery below 50% state of charge

  3. Charge an AGM to at least 80-85 % state of charge on the first cycle and get to 100% state of charge as soon as you can
    While an AGM can be left discharged to 50% for several weeks without damage, it is better to charge to 100% as quick as possible. 

  4. Size your most powerful charging source for a minimum of 20% of bank capacity.  This is usually an alternator or AC powered inverter/charger.  For example, an Odyssey TPPL AGM battery prefers 40% of amp-hour capacity as minimum charge current.

  5. Use temperature compensated charging for all charging sources.  While an AGM battery can take a lot of current from an alternator, the heat created can shorten its life or cause premature failure.  Therefore use a temperature controlled alternator with an external regulator and temperature sensor that touches the battery to reduce charging accordingly.

  6. Use a smart solar charge controller.  Not all solar chargers that claim to be smart are in fact smart.  Some charge controllers start each day at a new absorption voltage charging cycle.  This is not healthy for an AGM house battery that has low self-discharge and minimal parasitic loads.  A smarter solar charge controller has a voltage trigger to drop it out of float charge mode.  If it doesn't drop to the trigger voltage it remains in float mode.

  7. Using the correct charge float voltage is a critical for an AGM battery.  A charge controller that uses dip switches for programming often lacks the correct charge voltage for both absorption and float settings.

  8. Minimize the voltage drop in the system wiring for the best charging performance.  With small gauge wire even a 3% voltage drop from 14.4V means just 13.96V at the battery terminals, thereby under charging the battery.  Low voltage robs the battery of the fastest charging potential, especially during a short duration, high current charge cycle.  In addition, the battery can never reach full charge.

  9. Know your correct state of charge at all times.  This may mean investing in a battery monitoring device to help in overall cycle life.  If you use voltage to determine state of charge be sure to measure it as accurate as possible.

  10. Although a flooded battery benefits from monthly equalize charging (higher-than-normal voltage to recover lost storage capacity), equalize charging is NOT recommended for an AGM battery
    Having said that, Lifeline Batteries states that careful equalization is possible with their batteries.  But equalize charging must be configured correctly (and monitored closely) as the optimal process can vary by battery situation.  Lifeline can help develop a custom equalization program for your boat batteries.

  11. Avoid installing the battery in an engine room or other hot area of the boat.  Heat shortens battery life.

  12. At the completion of your installation, confirm operation by measuring and recording the voltage across exposed terminals.  This is extremely important to understand the system for future maintenance and trouble resolution.


  • An AGM battery accepts charge current more readily than a flooded battery. 

  • An AGM battery converts as little as 4% of the electrical charge into heat, making them prefect for a solar panel.  Whereas a flooded cell convert 15-20% of the electrical charge into heat.

  • An AGM battery can dispense power at a higher rate than a flooded battery.  A deep cycle flooded battery cannot deliver more than 25% of its rated capacity in amps without rapidly exhausting its charge.  It is recommended to have a ratio of 4 to 1 between battery bank size and the largest load.  Whereas an AGM is recommended to have a ratio of 3 to 1.  This makes a significant difference when considering engine starting, etc.

  • AGM self discharge is lower than a flooded battery.  An AGM looses only 1-3%/month due to self discharge.  Whereas a flooded battery can lose up to 1%/day. 

  • An AGM battery is not harmed by high current charging (or discharging) provided the charge voltage is correctly regulated (14.4V max) and the battery temperature is measured to prevent over warming.  Any voltage higher than 14.4V will kill an AGM battery.

  • An AGM battery operates safely in any orientation.  They are sealed, so can't leak.


BATTERY AT REST ~12.7 V ~12.7 V ~13.0 V
BULK CHARGE ~14.2 V ~14.0 V ~14.4 V
ABSORPTION CHARGE ~14.2 V ~14.0 V ~14.2 V
MAINTENANCE CHARGE ~13.7 V ~13.7 V ~13.7 V
EQUALIZE CHARGE ~14.2 V Do NOT equalize 14.5 V.  See battery manual
if OK to equalize
BATTERY AT REST ~12.7 V ~12.7 V ~13.0 V

Can't remember voltage numbers for a battery at rest?

12.7 we're in heaven, 90% charged.
12.5 we're still alive, 70% charged.
12.2 there's a lot to do, 40% charged.
11.8 is just too late, dead.

DUAL BATTERIES CHARGED BY A SINGLE SOLAR CHARGE CONTROLLER - An AGM battery should be discharged to only 50% of its capacity to keep it healthy.  So if you want more capacity you should add a second battery.  If wired in parallel they can be charged from the same controller.  If wired separate the most efficient way to charge two batteries from a single charge controller is to install a Blue Sea "ADD A BATTERY" switch.  This electronic "A/B" switch is basically a voltage sensitive switch that automates charging of two batteries from a single source without manual switching.  If the ACR senses a charge is present on either battery it will offer the charge to both batteries.  If the battery voltage drops to a preset threshold the ACR will isolate the batteries thereby maintaining the charge in the starting battery.  Switching is achieved with "make before break" logic to maintain battery voltage to the output of the charge controller, thereby preventing controller failure.  Its peace of mind to guarantee all your batteries are charged.  The switch can be manually operated to deal with a power dilemma. 

I finally found the rules programmed into the ACR (Automatic Charge Relay).  Its a very interesting device.

       Battery = 13.6V for 30 seconds or 13.0V for 90 seconds. (Sensed at either the house or start battery).
       Battery = 12.75V for 30 seconds or 12.35V for 10 seconds (Sensed at either the house or start battery).
  3. Engine start isolation feature, momentarily opens the connection between battery banks while the starter motor is engaged.
  4. Over-Voltage Lockout at 16.0V If the sensed voltage at either the house or start battery terminal is 16.0V or higher the ACR will lock out and open itself till the battery voltage drops to the correct value.
  5. Under-Voltage Lockout at 9.5V If the sensed voltage at either the  house or start battery terminal is 9.50V or lower the ACR will lock out and open itself to prevent further discharge.

BATTERY DISCHARGE PROTECTION (LVD) - Many larger sailboats have dual batteries.  One to crank the engine and the other to supply house needs.  I think most SJ23s are equipped with only one battery.  If you want sufficient power to start the outboard, operate the electronics or make that emergency call on the VHF then you must monitor the battery voltage.  Digital VOMs are quite inexpensive these days and I have seen them permanently mounted adjacent to the power distribution panel.  However this demands that you monitor it on a regular basis.  If you can't monitor it and want to preserve the battery charge then you require a charge controller equipped with low voltage disconnect (LVD) or a separate LVD to remove the load automatically.  These devices are equipped with circuitry that monitors the battery voltage to automatically switch off the electrical load at a preset low voltage.  For specific products click on this Google search result   
HINT - Many MPPT charge controllers are equipped with a low voltage disconnect (LVD) feature.

HINT - I go to great lengths to maintain Panache's battery charge by minimizing the load and maximizing the charge capacity.  Most systems are designed with this in mind and many diligent skippers likely do this, thinking it is the optimal procedure.  This practice is OK with a flooded, gell, or AGM or battery when each cell is in excellent condition.  However the problem with this practice is that if a flooded battery is never discharged then with time the weakest cell will have the lowest voltage and the strongest cell will have the highest voltage, the overall battery voltage remaining the same.  Then when the battery power is needed, it can't produce the rated current and voltage for as long as it is rated.  This situation is created by never equalize charging a flooded battery to ensure all cells are charged equally.  If your charging system is not equipped with automatic equalize charging you can achieve a similar effect by cycling the battery occasionally (discharge to 50% then charge it).  The charger senses the low battery voltage and automatically charges it with a voltage higher than float thereby equalizing the cells.  If you discharge by only 20% it should also achieve the desired results. 

WINTER BATTERY MAINTENANCE - Remove the battery from the boat and use an AC powered "smart charger" to maintain the battery charge during the winter.  Most of these smart chargers use 3 step bulk/absorption/float to maintain a battery in a healthy state.  The optimal temperature to store the battery is just above freezing.  OK to sit on dry concrete.  A flooded battery should be charge equalized once a month.  I charged Panache's AGM battery once a month with a smart charger and use a Honda desulphate charger once a winter to clean the plates.   TOP


2023 Update - After three years of using the Go Power! Flex-35 solar panels with the Genasun GV-10-Pb-12V MPPT solar charge controller I have experienced no problems.  The two panels supply all the power I need through sunny or cloudy weather and the charge controller does not generate annoying RFI that affects or limits the use of the VHF or AM/FM radios.  It's a working combination that I wouldn't change because I can now operate any device without fear of discharging the battery.

To use the stored electricity on your boat you need to distribute it safely.  So go to Tech Tip E02.  TOP

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