Essential systems: Compartments Painting
Interior finishing
Contact me Email:
Say "thank you"
Do you like the content and my ad-free web pages?

Electrical system

December 2008. New Bedford, USA. Old electrical system - must be re-done!

electrical panel - back

As you may see from the picture, it's the project of its own. The boat should be rewired.

April 2009. New Bedford, USA. New electrical system - to the book!

The first impression of rewiring to the standard - it is expensive! Very expensive!

I began with relocating batteries from a cockpit portside locker to underneath a quarter berth. Originally there had been just two batteries: one for starting an engine and another for serving as a house battery. I decided to double the house side capacity and add one more deep cycle battery.

battery boxes framing

Moving is usually a hassle. Moving batteries had not been an exception. First, I noticed that the glazing fiberglass tape of the berth frame detached in some places and had to be fixed, of course. Second, the battery boxes didn't fit with their covers on. Third, the supporting frame structure must have been built to hold heavy batteries in place during a severe weather and even a potential overkeel. I had to make a trip to the so familiar Home Depot and bought couple of red oak planks and metal brackets. The battery boxes came with straps, so I decided to use them without the covers and drill six more "a la ventilation" holes in the berth plywood for the battery studs allowance.

The new Yanmar engine is fattier than the old Volvo; therefore, I had no room to access the engine components on the port side where a starter and an alternator are located. Hence, to get to the starter, the alternator must be removed. Ah, what a job! I spent half a day for connecting just two wires to the starter. The service manual for a Yanmar engine specifies that only two wires should be attached to an engine from a battery. One should be wired to an alternator's positive stud, another - to negative. The engine has already a cable that goes from an alternator to a starter as part of a standard engine wiring.

I had to play the game of matching terminals to wire and stud sizes. The starter, for example, has 3/8" studs, the original two SeaVolt group 27 batteries have 5/16" negative studs and 3/8" positive ones but the new SeaVolt 90Ah deep cycle battery has both studs 5/16". See the tables for all stud and wire sizes below.


To crimp large gauges I had to purchase a special tool. See the picture to the left with a resulted crimped 1/0 wire finished with a heat-shrinking adhesive tubing.

Batteries info
Battery MakeNominal Capacity, ADischarge Cycles at 0°CReserved Capacity at 25A, minCranking AmpsGroupWeight, kg
SeaVolt dual purpose802001507452722
SeaVolt deep cycle903001757152724
SeaVolt deep cycle903001757152724
battery banks

The simplest way of course, would have been to wire the batteries via a three way switch to an engine but I went the "proper" way. I installed an electronic isolation switch in addition to the regular one. Its purpose was to isolate the house circuit during engine cranking to protect sensitive electronics and to combine a starting battery with a house bank of two during charging. I mounted the manual three way switch in a difficult to see and access place, to avoid messing with it during a running engine as it would result in an alternator's diodes damage.

I added high amperage fuses between each bank and the starter to avoid a fire upon accidental short circuiting. I put 300A fuses because the starter takes 250A. I installed two more 80A fuses between each bank and the isolation switch because my alternator is rated at 60A and I used AWG 4 short pieces of wire in between the batteries and the switch. I also fused an electrical panel positive feed (80A between the COM stud of the three way switch and the panel's 50A 50mV ammeter shunt connected with AWG 4 wire).

electrical panel front
Stud sizes
DeviceStud size, inches
Batteries, old3/8 positive, 5/16 negative
Three way switch3/8
300A fuse block5/16
80A fuse block#10
Battery Combination/Isolation switch3/8
Panel's ammeter shunt1/4
Common ground 4-stud bar1/4
electrical panel back

A complement to the stud game was a wire gauge play. Three parameters determine the correct gauge: a ampacity of a wire, a 3% voltage drop and an insulation temperature rating. The better the rating, the higher the current can pass through a wire without burning it. It is especially important for engine spaces where an ambient air can get relatively warm or even hot. The good insulation helps to go with a smaller gauge for a given amperage.

The standards call for a high quality marine wire such as BC5W2, which stands for Boat Cable with 105°C dry and 75°C wet heat and moisture resistance. The Boat Cable means that it is flexible, i.e. multistranded and usually tinned.

I managed to install a 3/4" electrical PVC conduit on a starboard side. The original one was too small for the number of wires that I had to pull through it. I used it for data wires though such as a wind vane, a flux gate compass and an antenna for a short wave receiver. I ran a VHF cable separately.

The good thing was that Niemiec Marine had parts department and West Marine was next to the boatyard. Plus two other West Marine stores in 5 and 15 minutes away. The fact that they sometimes didn't charge me for bolts and nuts and replace wrong or defective parts without asking for receipts may give you a hint about the amount of money I spent there. Unfortunately, their 10 percent discount for a new boat owner program expired in a month when I hadn't yet finished my project. Sometimes guys at the store were nice and gave me a discount anyway.

Electrical panel
mast wiring

I got a high quality 13 circuit electrical panel with LED indicators for each circuit that came with 10 15A breakers, an ammeter, a voltmeter to monitor up to three sources and backlights. I adopted one of the unused panel's LEDs as a remote indicator for my battery banks' isolation/combining switch. I added one 10A breaker for an autopilot. The 15A breakers are really useless on my boat and they are expensive to replace, so I just complemented the breakers with a 10-circuit fuse panel. The breakers will be used as simple on-off switches and the over-current protection will be provided by the fuses. Above the panel I mounted the Rule's bilge pump auto-manual-off switch with an indicator and a 10A fuse.

I installed the panel into a black marine plywood called starboard, which is a plastic half-inch thick board. The plastic is similar to ABS, it can be drilled or cut with wood-working tools. The only problem with it is a saw dust that gets electrified and sticks everywhere - a pain to clean.

Because the panel is where a navigation desk is I mounted a white-red LED light there.

Leading mast wires under the deck was another challenge, especially with flat cables. Most through-deck fittings are designed for round wires such as rubber ring compression style ones. I used them for a VHF antenna and a wind vane cables. Three light cables are flat and I had to go with plugs. I was not happy about them. I think they might leak.

through-deck fittings

July 2009. Replacing though-deck fittings

Indeed, the plugs did not hold well and I somehow managed to use non-stainless screw for mounting one of the plugs which caused the plug to be eatten by the corrosion in no time (could be a stray current, the plugs did not seem to have been waterproof).

As you see to the left, I replaced the plugs with the standard compression fittings, those that come with a rubber disk and require drilling a hole in it. I tried to make a hole in a shape to accommodate a flat wire rather than drilling a round hole. I just crimped the wires under the deck. I doubt that I demast often.

Amperage, Wires, Breakers/Fuses
CircuitRequired Amperage, AFuse/Breaker, AAWG wire size
Starter positive to three way switch--1/0
Starter negative to common bus bar--1/0
Battery positive to three way switch250300, fuse2
Battery negative to common bus bar--2
Battery to isolation/combining switch6080, fuse4
Isolation/combining switch to common bus bar-10, fuse14
Isolation/combining switch to engine start switch-5, fuse16
Isolation/combining switch to a remote LED on the panel-1, fuse16
Panel positive to three way switch-80, fuse4
Panel negative to common bus bar--4
Bilge pump/float switch positive to auto/manual switch on the panel510, fuse14
Bilge pump negative to common bus bar--14
Raymarine autopilot510, breaker
Raymarine electronics10, autopilot breaker
Mast-top tri-color LEDunder 12, fuse16
Anchor LEDunder 12, fuse16
Steaming LED lightunder 12, fuse16
Deck light15, fuse16
Running LED lights3, fuse16
Cabin LED lights5, fuse16
Car adapter for 100W inverter815, breaker16
Multifunctional display C90W with GPS7, fuse16
Short wave receiver and VHF15, breaker16
Backlights and compass lights-1, fuse16
October 2010. New 130 Watt Solar Panel

Kyocera KC130TM. Connected to the SES Flexcharge USA high efficiency charge controller (NC25A-12) as the solar panel.

October 2010. Fridge

WAECO CU-55 35-watt compressor and VD-07 evaporator.

June 2011. Windgenerator

LVM Products Aero4gen. 6 blades. 6 to 8 amps at 20-25 knots. Connected to the same charge controller as the solar panel. Added 70 Amp blocking diode on the heat sink to protect the solar panel from possibly high voltage of the wind generator. Installed the 24-volt 240-watt halogen bulb as a divert load.

In November 2012 I replaced the burned out bulb with 1-ohm 300-watt resistor.

In May 2014 before my third Atlantic crossing two ball bearings that allow the windgenerator turn around its vertical axis fell apart. Literally. The balls converted to the rust dust. Therefore, it seemed impossible to pull the inside ring from the axis to install the new bearings. I ended up inserting a plastic ring there instead.

Because the plastic rings were not made precisely, the wind generator wobbled and its brass rings that connect to brushes touched the body connected to the ungrounded railing. In wind gusts one could get an electric shock, especially if hold the railing with wet hands.

In January 2016 in my preparations for the Pacific, I managed to break those inside steel rings with a hummer and install two new bearings. I also grounded the railing. I guess it might help with lightening strike too.

May 2014. Curacao. Third battery in the house bank

I replaced one battery in the house bank and added one more. The other old battery seemed to be ok after I treated it with higher voltage (16 volts, the maximum that my voltage regulator allowed) for a few days to kill the sulfation.

January 2016. Curacao. Replaced the old battery in the house bank

June 2019. Auckand. NZ. New alternator

My original 60A Hitachi alternator that came with the new Yanmar engine, finally died from corrosion after 10 years of service. I replaced it with 80A Chinese replica.