St Francis

  Home Page
  Workshop Home
  Old CSY Workshop Pages
  Electrical Systems
  Plumbing Systems
  Rig & Sails
  Workshop Links
  About Us
  Contact Us
  About St. Francis Cats



Battery Charging System Tips Trickle Charging Start Battery
Solar Energy System Lightning Issues
Alternator Repair

Last Updated: 22 Feb 2019

The electrical systems and issues on our previous boat, a 1980's CSY monohull, were quite different than those on our 2004 St. Francis Catamaran.  For all great stuff I did on the CSY electrical system, go to this link:  CSY Electrical Systems.

Future Additions:
Alternator-Regulator Engine Charging

Lightning Issues

Here is a bit of interesting info on lightning, its cause, prevention and cure from a discussion on an SSCA forum:

"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".

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".

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 on the CSY was thru bolted to the hull on the port side running from about the forward main cabin bulkhead aft into the engine room. 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.

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".

We took both the spike and the bottle brush from the top of the mast on the CSY when we sold it, and mounted it on our catamaran mast.  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.  Some pics of the CSY setup here:

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.

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.

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

It has taken me several years to get my new catamaran set up the way I wanted it... with all charging systems wired to the House bank and a trickle charge arrangement for the Start battery.  On the catamaran it is a little more complicated because we now have 2 engines and 2 alternators to worry about.

My system keeps the House and Start batteries 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 15 years on two boats, 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.  See Trickle Charging the Start Battery, below.

So, if you leave the battery 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 Thermal Circuit Breaker (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.

Battery Charging System Wiring 

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.

I used this electrical layout on our CSY, and have just (2018) installed it on our new catamaran.  Here are the components required:

Thermal Circuit Breaker and Schotke Diode

And links to online sources:

20amp Thermal Circuit Breaker

60amp 35v Schottky Diode (MBR6035)

And a picture of ours, installed.  I just mounted it on a piece of scrap aluminum, near the battery box:

TCB and Diode Installed

Solar Charging System

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

When 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 watts 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 watts, 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.