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Electrical System Wiring High Amp Fuses Anti-Theft Starting Circuit
Battery Charging System Tips Charging System Wiring Deep Cycle Batteries
Solar Energy System Precision Electronic Battery Tester Honda 2000 Generator
Lightning Issues Progressive Dynamics
Battery Charger
Alternator Repair

Last Updated: 14 Nov 2017

Future Additions:
Freedom 2000 Charger Inverter
Alternator-Regulator Engine Charging

Lightning Issues

(31 July 09 CSYO Post)  Here is a bit of interesting info on lightning, its cause, prevention and cure from a discussion on an SSCA forum at this link:

"Actually, lightning is very well understood in the scientific community. How it forms and how it reacts is also understood. The University of Illinois and others have many detailed scientific papers available on the subject. Exactly where and when lightning will strike is a variable as it is part of Mother Nature and there is a reason she is called "Mother Nature" and not "Father Nature."
As to lightning and boats, the issue comes in two parts - 1. Prior to the strike; and 2. During the strike.

Part 1. concerns how to reduce the probabilities of a lightning strike. Lightning is a two part event. The ionized "leader" sweeps an area below the generating cloud and an opposite "leader" sweeps back and forth up from the surface of the earth. When they connect a pathway is opened and the energy is discharged. To a boat the ground/earth "leader" is of most interest. As this "leader" oscillates around it reaches up "x" distance into the atmosphere. Whenever this leader encounters a vertical object like a tree, house, telephone/power pole, or the mast of a boat it can reach further up into the atmosphere and has a better chance of making a "connection." [same thing as tall men in a bar full of good looking women].

So reducing the "electrical" apparent height of your boat is good. This can be done with static dissipators such as the Forespar Lightning Master. (Which is a copy of the static wick principle used on airplanes and airliners). The sharp small "spikes" of the device "bleeds" off ions as they build up and electrically reduces your mast height to equal that of the ocean. However, to do this it must have a "significant" and good ground to the ocean. That translates to 4 square feet of flat plate copper in contact with the ocean and 2/0 welding cable between the mast and the plates submerged in the ocean. A static dissipator will not dissipate if it is not connected with the ocean.

So the result of part 1. is to electrically make your boat height equal to the ocean. If you are anchored close to shore or in the close vicinity of other "unprotected" masts/boats your probability of being hit is significantly lower than theirs. If you are out in the middle of no-where/ocean by yourself you are now "even-steven" with the ocean as to getting a hit.

Part 2. is what can you do to prevent/minimize damage to the boat and its contents during a strike. Again, the 4 sq ft. of copper joined with significant sized welding cable to the mast(s) will provide a highly desirable pathway for the lightning's energy to get directly to its only objective - earth ground. If the mast(s) are not sufficiently well-grounded then the lightning energy will try to find an alternate path to the ocean. If the mast is not available to the lightning, then it will travel down the shrouds/stays to the bonding system and set up a "field" inside the boat that will "fry" most electronics and has been known to heat metal thru-hulls sufficiently enough to melt them out of the hull and you are left with 1.5" holes for the ocean to enter. Lack of any grounding to the ocean and you can end up with holes blown through the hull.

Side note: while your boat is floating in the water it is grounded. When you boat is "on the hard" (out of the water) it is not grounded and any lightning strike to your boat or to a neighbors boat will fry your electronics or other fine metal objects or more serious damage. It is advisable if you are going to leave your boat on the hard, in an area with probable lightning, to drive a copper or steel grounding stake into the ground beneath your boat and hook up a significant sized wire from it to your masts or boat grounding system.

There are many other esoteric factors available to folks wanting to get the "whole story" such as positive versus negative forms of lightning, high frequency vs low frequency lightning, etc. but for the boater I think the primary interest is minimizing damage to the boat, contents, and not curling the crew's hair. This is done by dealing with the before and during aspects of protecting/guarding your boat from the energy in lightning.

Exactly where and when a strike will occurs is not determinable - the same as the actual path of a hurricane or tropical storm is not totally predicable as there are too many variables in nature for even the powerful human built computer to input and resolve. So you can only do what you think is cost-effective to "lower the odds" that you will be the target".

On Soggy Paws, for grounding, we use a 18"x 5/8" mast top aluminum spike connected through the mast and heavy copper wire to a 10'x2"x1/4" copper grounding bar mounted underwater on the hull. The three radios and the tuner all have quick disconnects, but I still have coax grounds to install. We use the oven and microwave as faraday cages for computers/electronics that are out but not permanently installed, and metalized shielding bags for all stored electrical/electronic equipment. So far no problems; I hope it stays that way.

(2 Aug 09 CSYO Post)  The idea for the copper bar lightning ground came from the ABYC rules for boat lightning protection. Here is a link with a good discussion of lightning protection systems and the ABYC rules from a custom yacht designer dated 2007-09:

Here's what he says (comparing a 12' strip to a 1 sf plate):

"The ABYC suggests the use of a grounding strip, rather than a plate. The ABYC rule states: 'A grounding strip shall have a minimum thickness of 3/ 16 inch (5 mm), and a minimum width of 3/4 inch (19 mm).' A strip approximately one inch (25 mm) wide and 12 feet long (3.7 m) has nearly six times the amount of edge area exposed to the water, which will improve the dissipation of charges. 'The grounding strip, if used, shall extend from a point directly below the lightning protection mast, toward the aft end of the boat, where a direct connection can be made to the boat's engine'.
A grounding plate, if used instead, should be solid, rather than the sintered bronze type often used as radio grounds. The sponge-like structure of the sintered bronze plates may, in the event of a strike, allow the instant formation of steam, which could blow the plate apart, resulting in possible severe damage to the surrounding hull".

Your 4x6" grounding plate is probably a sintered Dynaplate, or similar, meant for use with an insulated backstay and an automatic antenna tuner to provide a connection to seawater as a ground plane (not ground) for an HF radio. As indicated above it should not be used as a lightning ground.

An excellent discussion on Marine Grounding issues (lightning grounds vs radio grounds vs electrical grounds) can be found in Stan Honey's article on Marine Grounding Systems.

My copper bar is thru bolted to the hull on the port side running from about the forward main cabin bulkhead aft into the engine room. It took me some time to get the bolt spacing right so I could access them from inside the boat and not run them into a floor stringer. Two of the 3/8" bolts are nearly even with the mast so that I could get short runs of 2/0 wire to each from the mast without much bend. The connections need to be really solid, so I did the mast thru bolted connections while the mast was out of the boat 12 years ago.

I think the info you often see in lightning literature referring to a plate is old, and the bar recommendation is more recent. Several universities, including Florida and Illinois, and others, including NOAA and ABYC, have done a great deal of recent research on this subject. It is worthwhile knowing the source and date of info you read, as the recommendations are changing as new info becomes available. If you Google boat lightning grounds/protection you will find much more info on this, including this useful tidbit on Kasten's site:

"The top-most end, or air terminal, should be a sharply pointed spike. Alternately, a wire 'brush' type terminal can be placed at the masthead, with the bristles pointed upward. There are several claims that a single spike is more effective than a brush for dissipating the charge built up by the boat".

My spike is 5/8" aluminum, about 18" long. I threaded the bottom so I could bolt it through a web in the mast cap. I also have a short 6" spike I used when in the Fla Keys running under the 65' bridges. We have the 18" one on now that we have no bridges to go under.

I'll add a couple of pics to this link on our website when I get time:

Of all the scary things about cruising and boat ownership, lightning scares me the most. Not only because of the potential for huge repair expenses, but also because of the very real threat of loss of life. It is a serious subject worth careful consideration by anyone using a boat.

(5 Aug 09 CSYO Post)  Re a Dynaplate, it provides a very effective connection to sea water for your HF radio ground plane. We also have one for that purpose. No need for lots of copper in the bilge if you have a modern automatic coupler. Just make sure the Dynaplate is connected up properly and cleanly with flat copper strips to your coupler.

(6 Oct 09 CSYO Post)  The underwater copper bar is 1/4" thick, through bolted to the hull, with a 1/2" starboard spacers. I use a oring of black window sealant for the outside seal and 3M Marine Silicone for the inside under the washer. 3M 5200 would also work, just make sure to chamfer the holes on the outside so the seal forms an oring around the bolts.

(28 Nov 09 CSYO Post)  I don’t have any notes on how far apart the bolts are for the bar.  Start by drilling the furthest forward bolt hole first and then measure back using a total of 6 bolts. Make sure your holes go into an accessible space beneath your floor. You need the first two to go through the hull to take wires from the mast. Then you should have at least one or two all the way aft to ensure the bar stays securely fastened to the hull. The others can be short screws into the hull. All fasteners should be bronze. I used ½” Starboard spacers to hold the bar ½” off the hull so I could clean underneath.

For a really good article on the differences between the lightning ground, the radio ground, and the electrical ground, see Stan Honey's great article on Marine Grounding Systems (pdf file).

AC System Wiring

(Topica Post 6/1999) Below find some info regarding an electrical casualty we suffered in Trinidad. Hope this will help someone else avoid a rather large repair bill.

While in the Power Boats yard in Trinidad we suffered a voltage spike from shore power that ruined the FETs in the motherboard of our 1993 Heart Interface 2500 watt inverter/charger. Evidently surges like that, and from lightning strikes, are quite common in Trinidad, and in other developing countries also. I had wrongly assumed that the internal circuitry of the unit and my main circuit breaker would have protected it from such an occurrence.

A Heart representative giving a seminar in Trinidad verified that it would not. Evidently some surges are too fast for the internal protection to be effective. At the time I had it wired according to one of the diagrams in their installation manual, so that had the shore power went through the unit in order to make use of the power sharing feature before it fed my 110 v sub breakers.

I was lucky in that there was a local electrical repair shop that is one of the few authorized repair facilities worldwide. After paying up, I was determined not to let this happen again. So after discussing wiring options with the shop manager and the Heart rep mentioned above I used the following arrangement, which might be of help to those of you setting up your own electrical system with an inverter/charger.

The goals were to minimize time of exposure of the inverter/charger to shore power, ensure no possibility of back feeding the inverter from shore power and separate out the loads that should be fed from shore power only. My current  110 v loads consist of a hot water heater, the battery charger and two 110 v wall outlets, totaling four sub circuit breakers. The first two are not suitable for being fed by the inverter and therefore are fed by shore power only. The other two can be fed by either shore power or the inverter.  Additional components in the circuit include a 35 amp rotary 2 pole 3 position (‘shore/off/gen’) switch (available through Defender and others), the 30 amp main breaker, a Link 2000 monitor that also turns on/off the inverter/charger and the Heart 2500 watt inverter/130 amp battery charger. The new circuit goes like this:

  • 110 v shore power (positive/black and neutral/white wires) comes in to the main circuit breaker via the boat’s 30 amp electrical connector.
  • One set of black/white wires from the main breaker feeds the hot water heater and battery charger sub breakers (white goes to a common neutral buss) which are isolated from the other two. These are the shore power only loads.
  • Another set of black/white wires from the main breaker feeds the shore side of the rotary switch.
  • The 110 v output black/white wires from the inverter feed the gen side of the rotary switch.
  • The output black/white wires from the rotary switch feed the two 110 v wall outlets (white goes to the common neutral buss).
  • All green ground wires go to a common post/bar and are not switched. I have installed a galvanic isolator in the green wire between the shore power connection and the common green wire post/bar to reduce galvanic corrosion underwater.

When all wired up if you have the rotary switch in the ‘shore’ position you will feed all four 110 v sub breakers with shore power through the main breaker. The battery charger is on one of these sub breakers which must be turned on to start the charger with the Link 2000. In order to minimize its exposure to shore power the charger is switched on only when we need it. The inverter is isolated from the 110 v system by the rotary switch. With the rotary switch in the ‘gen’ position shore power is disconnected from the two wall outlets but still feeds the water heater and battery charger sub breakers. The inverter when energized with the Link 2000 feeds the two wall outlets. With the rotary switch in the ‘off’ position nothing feeds the two wall outlets, but shore power still feeds the water heater and battery charger sub breakers through the main breaker.

Analog meters for AC volts and amps next to the rotary switch allow us to monitor the shore power quality. By only using the battery charger when needed and keeping the rest of the Heart unit out of the shore power circuit we minimize the chance of another problem with questionable shore power sources.

One other component I’d like to have is a 30 amp-capable surge protector to protect the battery charger, microwave and other 110 v equipment when they’re on. I haven’t found one yet.

From experience, my advice, if you have an inverter/battery charger, is to be sure you understand how it’s wired and do all you can to protect it from shore power surges. If you don’t it could be a costly lesson.

High Amp Fuses

(Topica Post 6/29/1999)  Here’s another electrical issue that I came across recently that may be of some use to those of you outfitting your boats for cruising.

We left Florida with an electrical system that I had thoroughly gone through in order to ensure we did not have a problem. I had traced every wire, removing all dead ends, replaced much of the smaller wiring and connections, rewired the battery circuits to provide a house bank and separate dedicated starting battery, replaced and upgraded all the larger cables and end fittings, replaced the batteries and refurbished the box and its shelf, added tie downs for the batteries, added a Link 2000 monitoring system, added a 110 v system, and added a new bank of circuit breakers for our expanded circuits.

I carefully terminated wires and cables with heat shrink and routed the cables so there was minimal chance of a short. The one thing I did not get to was installing high amperage fuses or circuit breakers in the battery cables. Until I had time to install them I figured that I could be careful enough not to cause a short when working around the batteries. Also we normally turn off all loads when we leave the boat.

When we reached Trinidad I was talking with a fellow cruiser who indicated that two boats he personally knew had had fires aboard due to the intense heat buildup from shorted battery cells. A single Trojan T105 for instance can provide over 1000 amps for a short time to a dead short. This is enough to cause a fire even in the large battery cables between the batteries with no other loads turned on-ie your main battery switch turned off.

It was scary enough to cause me to immediately review all my electrical manuals and figure out where I should put in fuses. So far we have added two 300 amp Blue Seas ANL fuses, one each on the positive battery cables about 6 inches from our house and start battery. To protect us from a shorted cell fire we should also have fuses or on/off switches located in the cables between the batteries, but that’s a lot of fuses/switches. This looks like another one of those how much is enough protection issues.

In any case we now comply with the ABYC standards for battery cable fusing and I feel much safer. Many cruisers leave home without the basic high amp fuses. As we build more and more into our electrical systems I believe that this is asking for serious trouble. These fuses are cheap insurance against electrical disaster. I would encourage all of you to take a close look at this issue as you prepare your boats for sea. By the way if you’re going to do this work yourself purchasing a quality cable terminal crimper is a good investment and makes all this work easy.

Anti-Theft Starting Circuit

(Topica Post 6/30/1999)  Have you been looking for a good way to set up your starting circuit to prevent theft and still provide the capability to instantly start your engine from the cockpit in an emergency? Here’s one good way to do it.

First, set up your battery banks so that you have a separate dedicated starting battery, separate, but able to be cross connected to the house bank through a 4 position main battery switch. Route the positive starter cable only to the starter battery such that the engine can only be started through the starter battery. Install a suitable hidden, but easily accessible, on/off switch with a removable key in this starter cable. The $15 Hella on/off switch with red key works fine and is available almost everywhere.

When you leave the boat for a long time take the key with you or hide it aboard. When you’re aboard and the engine is not in use at a dock or at anchor, leave the switch off but key in to prevent draining the start battery if you have a short in the starter. When you are sailing with the engine off, leave the key on so the engine can be started quickly in an emergency.

Besides the keyed starter cable switch you should have a suitable ignition circuit breaker below on the panel and a keyed ignition/starter switch in the cockpit, both wired in series. When you are underway sailing, leave the ignition circuit breaker on below and the keyed ignition switch above off. If your below decks switches are both on and you need to do an emergency start, just use the cockpit ignition switch.

When leaving the boat take the two keys with you or hide them aboard.  Anyone trying to steal your boat in your absence will have to have two keys, good electrical knowledge and access to your interior. Of course you have your hatch bars in place, so it won’t be easy for them to get in. Also, they will have to find your starter cable switch or use jumpers to your starter and figure out the rest of this purposely complicated wiring plan. Given all the trouble you’ll put them through they’ll hopefully go to your neighbor’s boat to do their dirty work.    (top)

Deep Cycle Batteries

Right - L16 Batteries: Trojan L 16 HC (maroon) and Rolls CH 375 (red). 

The Rolls have almost twice the plate thickness and expected cycle life.

(August 07) Originally the boat came with 4 12 volt deep cycle batteries.  In 1997 I switched to Trojan T105 golf cart batteries.  They are rated at about 220 amp hours at 6 volts each when new and provide more than 400 full deep discharge cycles if properly cared for over their service life.  According to Trojan this should give a 3-4 year life span in deep cycling service.   I purchased 6 from a dealer in Miami.  He mentioned that T105s sell so well because they are well made, provide the most amp hours for the dollar and are one of the few deep cycle batteries that are available worldwide--even in small developing countries.   Here is what I wrote in a Topica post then "Trojan T 105 golf cart batteries are an industry standard and very well made for an inexpensive battery,  provide the most amp hours for the dollar of any battery and are available worldwide.  They can be expected to last 5 years in constant use if they  are well maintained and equalized periodically."

Two and a half years later, while still in the Caribbean, my T105's had lost about a third of their capacity and were unable to support the large refrigeration draw; that is their voltage dropped below 12 volts with the refrigerator running, unless I ran the engine.  They had been well maintained and equalized every 2-3 months.  I purchased another set of 6 locally produced golf cart batteries in Panama which lasted about two years .   Upon returning to Florida in late 2002 I researched other options including L16s.

L16 batteries are 6 volt "sweeper" batteries that are 4 inches taller but with the same footprint as "golf cart" batteries.  Trojan L16s are about 3 times the cost of T105s ($55 for the T105s vs $170 for the L16 HCs).  Their amp hour rating is about 400 amp hours and cycle life is about 1000 cycles.  Generally they are more robust than T 105s and have a 5-7 year lifespan according to Trojan.   I purchased 6 Trojan L16 HC batteries in late 2002.  By 2006 they had lost more than 25 percent of their capacity and were having difficulty supporting the refrigeration load.  As we were getting close to leaving on our circumnavigation it was time for more research to try to determine what was causing my batteries to fail prematurely.   

I first talked to a friend who had Trojan L16s.  He had had problems with his first set also.  He had called Trojan and according to a Trojan engineer, he had killed his by not cycling them enough while using a shore power charger while living aboard at a dock.  This was not my problem.  He also mentioned that the current thinking on the importance of equalizing of lead acid batteries is to do it when the batteries show a loss of charging acceptance or when the specific gravity readings in individual cells vary by more than .03 and not on a periodic (2-3 month) basis.  He stated that if you don't equalize your lead acid batteries you will see a significant cycle life loss.   A call to the Trojan engineer, Jim Lee, confirmed this and he also recommended monthly specific gravity readings to track any irregularities. 

Soon after I read an article with a real eye opener.  It indicated that charging batteries installed in the engine room with the engine running was a killer because of the heat generated by the engine.  Based on the data in the article and other information I obtained it looked like I could expect over 50 percent cycle life/capacity loss if I left the batteries in the engine room while charging with the engine on.  There also was repeated mention of the benefit of using a temperature sensor on the batteries to help the charger regulate the voltage during charging.  Bingo, my battery box was in the engine room and I was experiencing repeated premature failures.

It was time for drastic measures to protect the batteries from heat while charging.  There are only a few options for locating the house bank of four L 16 batteries out of the engine room, balanced port and starboard, and within a reasonable distance from the load circuit breaker panel.  I had settled on L 16s as being the most efficient from a footprint and cycle life standpoint.  I removed the house batteries from the engine room and placed two in a new box under the forward end of the navigation table and two on a pull out shelf in place of the trash bin in the galley.  By carefully building the boxes I  was able to get them well secured and still provide reasonable access for maintenance.  Routing the cables under the galley floor was a trick but solved by persevering and discussion with Steve Silverman.   I also made sure both sets of batteries have a big fuse and shut off switch near the batteries and that the cable runs were nearly even from each set to the charging sources. 

After moving the boxes I spent a great deal of time researching the three battery types: Gel, AGM and Lead Acid.  I found the the Gels and AGMs to be very costly, have relatively short cycle life, and are not made in the L16 case size.  For these reasons and, after thorough research on the internet and by phone I purchased 4 new Rolls CH 375 L16 batteries in April 2007 at a very good price with Steve Silverman's help.  They have much thicker plates than the Trojans, have a much better cycle life than any of the others and with proper care should last 7-10 years.  I talked at some length with Jeremy Surrette  at the Canadian factory.  The company and their batteries have an outstanding reputation and do have worldwide service.  I was looking for batteries that had a reasonable chance of surviving our planned 10 year circumnavigation and the Rolls/Surrette batteries seemed like the  only  ones that might.  See

12/01/2012 Update:  Our Rolls Batteries are still going strong, having been used now for 5+ years, as full-time liveaboards.  We have a 'nanopulser' onboard, Watermiser Caps, and I religiously equalize my batteries about every 3 months.  I have bought a precision battery tester, which helps me determine how often and for how long I need to equalize.

Topica Post  11/25/08  There is much info on batteries on the web. You should look carefully at some of that before you buy. Especially the issues of lead acid vs AGM vs Gell and cycle life. Believe what independent experts have to say rather than what the manufacturers write.

You can't do better than Rolls for quality lead acid deep cycle batteries. Their deep cycle line has the best cycle life of any battery. Another Rolls option would be to use their equivalent of 6 volt L 16 sweeper batteries, Rolls CH-375s. I now have four of these aboard giving me about 700 ah capacity. I bought them because I wanted an exceptionally long life battery.

An alternative to keeping your batteries in the cockpit lockers is to build in a new box under the companionway steps as several 44 WO owners have done. This puts the battery weight low, in the center of the boat, and in a relatively cool place. Heat is a killer for batteries so you certainly don't want them where they will feel the engine room heat.

For anyone interested in an excellent article on batteries, here's one of many on the web. The 12 Volt Side of Life, here's the link:

Down in the section titled Selecting Batteries is this little tidbit of info:

Battery life is reduced at higher temperatures - for every 15 degrees F over 77F, battery life is cut in half. Although he states that RVers don't need to worry much about this, anyone with batteries in the engine room, where temps are around 115F, certainly does. I've seen this info before and also written a bit differently in Nigel Calder books. It explains why the original 44 WT battery location in the engine room was a battery killer for me. 

Four Trojan L16s in original
engine room location under
the workbench

New port battery compartment for
 two L16s under navigation table

Two Trojan L16s in new stbd
Galley trash bin cabinet

Galley location showing
roll-out tray

2016 Final Rolls Battery Update:  We sold Soggy Paws the CSY in April 2016, and the Rolls Batteries were just starting to fail.  We got an astounding 9 years out of those batteries, using them 9 months of the year in full cruising mode (and stored with trickle charge for 3 months).

The batteries on our new boat are Sonnenschien Gel Batteries, that are also 10 years old.  They are still performing well, so we will stick with them until they need replacement.  Next batteries will probably be LifePO4 batteries.

Battery Charging System and Tips

This is a big subject and it is always interesting to see how others are set up also. Much of how you set up the boat depends on how you plan to use it. If you are dockside most of the time you will want a different system than if you are cruising and away from docks. We are currently cruising, often away from docks and also away from good (expensive) repair facilities.

This section needs to be updated for our new catamaran...

For what we used with our CSY, see this page:

Here's a safe way to charge both your house bank and starting battery, at the same time with one alternator/regulator (and/or wind or solar system). This system keeps them physically isolated from each other in the normal use/charging situation. It allows multi step charging for the house bank and trickle charging for the start battery. It uses a simple, effective and inexpensive system designed by Bill Owra, formerly of Everfair Enterprises in Punta Gorda, FL. I have used this system now for 10 years and it does the job well.

Postive connections using appropriate size wire:

First, connect all your charging sources (alternator, 120v charger, solar, etc) directly to the house bank. Run your charging sense and temperature wires to the house bank. Connect your starting battery direct to the starter. Then connect the house bank to terminal 1 of the battery selector switch and the start battery to terminal 2. Next connect all your loads to the common terminal of your battery selector switch. Add cutout switches and/or fuses as desired in the battery cables within 18" of the batteries if you want to comply with ABYC specs.

Finally, connect the positive posts of the house and starting batteries together with 12 ga wire and a thermal circuit breaker and diode. The diode keeps current going toward the start battery and starts trickle charging the starting battery when the house bank voltage gets .5 volts above the start battery. The thermal circuit breaker breaks the circuit if there is a problem (high amperage in the 12 ga wire produces heat). This keeps the start battery isolated and always fully charged, no cycling. The house bank does the cycling.

So, if you leave the batt selector switch on 1, the normal situation, the starting battery starts the engine and the house bank runs all the loads. And the two batteries/banks are isolated. If the start battery fails, place the switch on Both to combine them for starting. This system takes the place of expensive isolators and combiners and costs less than $50. And you never have to remember to switch your battery charging system from the House bank to the Start battery.

A shorted/dead battery in either bank is the main reason you do this type of system to isolate the batteries.

I have watched my system closely when starting my engine and charging the house bank. A good starting battery (rated about 600 cold cranking amps or better) will not drop below about 10.5 volts according to Nigel Calder. That is one of his tests to determine if the start battery is good. My observations confirm that. As long as your engine starts as it should, within a few seconds, it will draw only a couple of amps out of the starting battery. I have never seen more than 2 amps trickle charging back into my start battery using this system. Normally it is more like .5 amps trickle charging when charging the house bank.

If you get a shorted cell in the start battery or it dies for some other reason the TCB will break the circuit and isolate the start battery from the house bank. That is the reason for the TCB.

The system works well and is every bit as good and safe as a combiner/isolator. Look carefully though at Bill's diagram and compare it to my description. I think my layout is better as it eliminates the separate house banks and streamlines the system a bit.

Also, keep you house batteries away from heat while charging, as it is a killer. If in the engine room, for example, with temps over 115 degrees F you will lose 75% of your cycle life! And don't forget to equalize.

Start Battery Trickle Charging

At the 1998 SSCA Gam the Four Winds/Everfair owner, Bill Owra, gave what I thought was a very well thought out and much better wiring diagram for a house bank and a starting battery setup.  It featured, among other things, hands off trickle charging of the start battery off the house bank, an anti theft switch in the starter/starter battery cable,  using the battery selector switch to normally control only battery loads, rather than charging and loading, emergency cross connect for starting and house loads, and routing all charging source cables directly to the house bank so there’s no possibility of an alternator or other disconnect problem while charging.  It was the best layout I've seen and I've looked at many in the past 20 years of boat ownership.

I thought that the best feature was the automatic trickle charging of the starting battery from the house bank through a short 12 gauge wire with a diode (one way current flow) and thermal circuit breaker.  The idea is that when the house bank is being charged from any charging source the diode will keep the voltage to the starting battery about 1/2 volt below the house bank voltage, and the thermal circuit breaker will break the charging circuit off if the charging amperage get too high.  The starting battery can take up to about 15 amps if it needs it but with this system it normally just takes small float current.  I've never seen more than about 2 amps going into my starting battery from the house bank. 

This circuit provides a reasonable float charge to keep the starting battery always at 100 percent, just like in your car.  A true starting battery with thin, large surface area plates and a high CCA/MCA rating is great for starting your engine and will last as long as your house bank if kept this way.  And it's all automatic with no risk of inadvertently disconnecting the house bank from its alternator charging source.  I also keep a couple of spare diodes and thermal circuit breakers aboard just in case.   Now in 2007 I'm still using the same system and it has worked flawlessly since installation.

In any case I've been using this electrical layout on our CSY, and have just (2018) installed it on our new catamaran.  A small diagram (source unknown) is here:

Trickle Charging Start Battery Diagam

20amp Thermal Circuit Breaker

60amp 35v Schottky Diode (MBR6035)

Solar Charging System

For the evolution of our solar system on Soggy Paws the CSY, see this page.  CSY Solar Charging Evolution

IWhen we bought the catamaran, I sold off the old system that came with the boat and installed 4 new 200 watt 36v panels, and a new Morningstar MPPT solar regulator.  Though we really liked the Outback, the Morningstar offered a way to monitor the system via computer connection.

Though the catamaran mounting doesn't allow rotation of the panels fore and aft, as we had on the CSY, we made up for it by adding another 200 amps of solar capacity.

As with the CSY system, on a good solar day, we are cranking out the amps, and our batteries are fully charged at mid-day on a sunny day, even if we're wantonly charging computers and stuff.  With the excess amps, we can handle several days worth of overcast days before we have to think about charging with other means.  Also, in the wintertime, when the solar days are much shorter and the sun angle is not directly overhead even at midday, we have enough power to run the boat at anchor without running any other charging system.



Alternator Repair

Parts and Tools Needed for
Alternator Disassembly

Parts and Tools Needed for
Alternator Repair

I have taken apart and rebuilt my own alternators ever since I paid about $100 for a rebuild down in the islands that did not work. The problem was that the shop installed 30a diodes in my 150a alternator that needed 50a diodes. Back then I was still trusting third world mechanics with some of the work on my boat. They are real simple to take apart, test and replace parts. See Nigel Calder's Mechanical and Electrical Manual. You certainly don't need to send them anywhere for repair if you have basic tools, electrical skills and first time instructions. If you have one of the older Delco, Balmar or Powerlines, it is fairly simple.

The older Balmars and Powerlines look the same, are both based on Delco alternators and most of the parts are the same including the cases. Parts are available many places in the US including some Alternator/Starter parts stores like Royal Battery in Florida and elsewhere. Used parts are available at auto junk yards and alternator shops everywhere. The small case alternators are built with capacities up to 150 amps, over that they use large cases. If you have a Perkins 4154 with the original alternator, which is what I started with, the larger alternators with small cases will fit fine.