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.
Alternator-Regulator Engine Charging
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
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
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.
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:
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
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
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
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
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
I used this electrical layout on our CSY, and have just (2018)
installed it on our new catamaran. Here are the components required:
And links to online sources:
20amp Thermal Circuit Breaker
35v Schottky Diode (MBR6035)
And a picture of ours, installed. I just mounted it on
a piece of scrap aluminum, near the battery box:
Solar Charging System
evolution of our solar system on Soggy Paws the CSY, see this page.
CSY Solar Charging Evolution
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.
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
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.
Parts and Tools Needed for
Parts and Tools Needed for
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