Electrical (DC)

Maringret had a wide variety of electrical equipment when we bought her. These ranged from original items from the manufacturer and other items that had been added over the years. Some of the larger systems were nearing the end of their working life.

Our boats tend to be fairly electrically intense compared to other boats we have seen. Our philosophy is to invest in soft technology for capturing ambient energy (i.e. solar and wind) and storing it. We have looked into towed log generators (such as the AquaGen and AmpAir) although we have not fitted one yet. We like to have enough depth in our electrical systems that we have multiple days of reserve power. A pet peeve of ours is sharing anchorages with other boats and each morning they start up their engines to charge their refrigeration batteries – bye bye quiet pastoral setting. As we sit out on our silent boat enjoying the panorama we get to compare notes on different diesel engine idle cycles and portable generators on deck.

We started out aware that some systems needed replacing but not sure how much to replace. We had two DC systems – both 12 VDC and 24 VDC. We had both wet acid batteries and gel cell batteries. We thought that it would be nice to try and remove some of the duplicated systems if possible.

The following topics are inter-related and in effect we were working on multiple of them at any given time. I have had to lay them out sequentially below but of course we did not deal with the topics sequentially but rather as an inter-related collection where one decision might cause a previous decision to be reviewed again.

Operating Voltage

One of the most basic issues in the electrical system was which voltage it would use. The HR 41 was built with a 12 volt system and everything except our bow thruster was 12 volt. The first bow thruster fitted was 12 volt and the owners at the time felt it did not provide enough power, they then had the unit swapped with a 24 volt one. One of the implications of this was that a 24 volt electrical supply was required. As bow thrusters work in short bursts it made sense to fit engine starting batteries to the bow thruster, the cheapest ones were wet acid and so a different type of batteries were installed along with two dedicated charging system – one from shore power and the other from the 12 volt system. The result was there were two different battery technologies and two different voltages. This was the highest profile of issues we hoped to resolve when we set out to “rationalize” the electrical system.

Had all costs and other issues been equal we would have preferred to have converted the boat to 24 volts. By doubling the voltage the amperage is halved along with the required size of cabling (cabling is sized on amperage not wattage). With copper prices going ever higher the saving on heavy cables was worth some extra cost on other items. Unfortunately what we found when we looked into it was that some big item (e.g. anchor windlass, bow thrusters, batteries) were available in both voltages; instrumentation was generally available in 24 volts but only as a special order; and generic items that were marketed towards the automotive or leisure world (e.g. light bulbs, small appliances) were only available in 12 volts.

Even though we were replacing the anchor windlass and were open to swapping out the bow thruster we finally had to realize that although we could switch to 24 volts it would not be straight forward. The industry wisdom for the last decade has been that once cars switch to 24 volts then things will start to change. After 10 years there is not much sign of automobiles switching although all heavy equipment and trucking did long ago. Given that it is taking the car manufacturing countries this long to switch voltages it would be foolhardy to imagine that more distant countries who import their cars will have switched in advance. So we reluctantly decided to stay with 12 volts.

Another aspect that coloured our decision was a memory of a boat in the Med who had converted to 24 volts. They had endless problems in getting products in the correct voltage. When we met them they had been some months waiting for a 24 volt part for their engine, the manufacturer (which was one of the large engine manufacturers) kept sending out the 12 volt version. They had to keep sending them back and requesting the correct one, only to have the 12 volt version sent out again.

Hydraulic Option for Anchor Windlass and Bow Thruster

Although this page is on electrical issues it is worth mentioning our exposure to hydraulics on boats. As we had to replace the anchor windlass and were open to replacing the bow thruster we costed out replacing both of them with hydraulic solution. We would have had to have someone fit a hydraulic compressor to the engine, then run a supply and return line to the forepeak as well as a collection tank. This is done all the time for commercial boats such as fishing boats but we couldn’t find anyone in our area capable or interested in this work. It seemed that the cost for one or two devices was about the same as electrical, where the saving comes in once there are more devices. The anchor windlass and bow thruster are not run at the same time so there would only ever be a single load on the hydraulic system. It seemed feasible as far as we went with it but when we could find no one to do the job we let it go. Given that we had to replace the anchor windlass no matter what solution we went with and that we had to replace the copper cables from the main batteries to the windlass hydraulic would not have been the cheapest option for us – despite its other benefits.


Click here for a complete page on Maringret’s batteries.


When we bought Maringret she had instruments which were at the end of their service life, some we chose to replace and others we had to replace when they failed. (Click here for details).

Anchor Windlass

We had a intermittent anchor windlass and needed to remedy the situation (click here for details on the non-electrical aspects of this project).

The original cable had a few breaks in the shielding and the copper had oxidized to black in those areas. We took out 75 mm2 cable and replaced it with 100mm2 cable. We replaced the ETA 100A breaker which protected the anchor windlass circuit. These units are quite expensive and proved hard to find, in the end we ordered ours direct from the manufacturer.

The 1,200 watt model comes with a “black box” that is the power control solenoid, we mounted ours in the forepeak where the cables rise to the windlass. The 2 heavy 100 mm2 cables run from the batteries in the mid and aft portions of the ship to the Lofrans solenoid. Then 3 cables must run from the solenoid to the anchor  windlass: negative as well as positive for lifting and positive for dropping the anchor. There is a problem with the Lofrans casting in that there is not enough space for the cable to enter the cast housing. The cables must be sized to handle the maximum current expected – this is a safety issue especially in circuits where the currents are enough to weld metal with. We compared the casting of our old 800 W unit and it is the same casting as the 1,200 W model – the only difference is that the cable entry holes drilled are larger on the 1,200 W model. Where the cables must run from the entry holes to the internal terminals the clearance space is less than the diameter of the cables required for that current. We tried various methods to work the cables in but each time the chafing is unacceptable. What we did was take two 50 mm2 cables for each of the 3 supplies and use that pair of cables (which has the same total cross sectional area as the larger single cable) to carry the current. This provides the same capacity for the current except if one of the paired cables is broken or impaired in which case the remaining cables will carry all the current.

Bow Thruster

Maringret came with a large bow thruster – a Schlepner SidePower XXX. Previous owners had fitted it to handle operation in severe weather. We were open to down sizing it as we never felt we needed that much power. We looked at converting it to hydraulic operation. In the end we left it in place and resigned ourselves to carrying a 24 volt battery system for it. Finally all we did was replace the batteries.

We investigated converting the bow thruster to 12 volt operation:

convert to 12 volts, keep batteries in forepeak this would still had an undesirable weight up front so the only gain would have been in reducing voltages aboard
convert to 12 volts, use main batteries this would have have removed the forward weight, we would have needed massive cables if we were to keep the same power output; if we were willing to reduce the power output then the cables could have been reduced also.
leave on 24 volt, use main batteries this would have removed the weight forward but required and enormous 12-24 voltage converter rated at 100 amps or so, not easy to find and certainly not cheap
leave on 24 volt, leave batteries in forepeak the battery weight remains forward, the cables are short and being 24 volt are smaller

In the end we left the system as it was, the path of least resistance. We costed out all the 4 different options in the table above and all involved substantial cost for undetermined benefits. Leaving things as is would cost us to replace the batteries (which were worn out) but there would be no other costs. We can always re-visit this in the future if warranted.

The specific batteries installed are documented in the batteries page (click here).


For the second boat in a row, the electrical system worked (mostly) but was untraceable. The Phillipi breaker panel was not the original installation and it had gone through 2 or 3 re-workings where things were added or things which had stopped working were left in place. There an Webasto temperature control module and 2 battery monitor displays on the display – all defunct. In fact they didn’t even have wires leading away from the reverse side anymore. The main decision was how much of the wiring to replace and which sections could be left in place.

Most of the wires in the conduits running forward and aft were in good enough condition and we decided to leave them in place rather than pull new wire. The wires running between the breaker panel and the cockpit locker where there was another distribution panel were in quite good condition but were unlabeled – we decided to replace them as part of organizing them. Part of the problem was that all cables originated at the breaker panel and then fanned out to the end appliances.

We decided to put in 2 distribution panel where cables would be identified to aid tracing in the future. There were junction blocks in each distribution panel so one physical wire ended and the next segment started. For trouble shooting it meant that wiring could be interrupted and checked at each end of each wire segment. The diagram shows the black cables going through the 4 conduits that run forward and aft.

The distribution panel adjacent to the breaker panel has the following circuits:

1 Tri-colour 11 Wind 21 Aft Head lights 31 Bow Thruster
2 Steaming 12 Depth & Speed 22 Engine Room lights 32 Bilge 1
3 Anchor 13 GPS 23 n/c 33 Bilge 2
4 Strobe 14 Instrument Repeater 24 Fresh Water Pump 34 SSB
5 n/c 15 Engine Room Blower 25 Gas Solenoid 35 VHF
6 Fore Deck lights 16 n/c 26 n/c 36 Radar
7 Aft Deck lights 17 Forepeak lights 27 12 VDC sockets 37 Fridge
8 Compass light 18 Forward Head lights 28 Victron Invertor 38 12->24
9 Cockpit Locker light 19 Saloon lights 29 Entertainment 39 Anchor Windlass
10 n/c 20 Aft Cabin lights 30 n/c 40 n/c

The cockpit locker distribution panel has the following circuits:
(the second number on each circuit is the corresponding number on the breaker panel distribution panel)

1 (11) Wind 11 (2) Steaming
2 (12) Depth & Speed 12 (7) Aft Deck
3 (13) GPS 13 (8) Compass light
4 (15) Engine Room Blower 14 (9) Cockpit Locker light
5 (24) Fresh Water Pump 15 (17) Forepeak lights
6 (25) Gas Solenoid 16 (18) Forward Head lights
7 (27) 12 VDC sockets 17 (19) Saloon Light
8 (28) Victron Invertor 18 (20) Aft Cabin lights
9 n/c 19 (21) Aft Head lights
10 n/c 20 (22) Engine Room lights

Appliances not listed in the tables above are wired directly from the beaker panel. We decided to use tinned wire for the re-wiring. Most of the untinned wire had lasted well, the only points of advanced degradation were where water (fresh or salt) had been able to get on the cable core. We re-wired with XX gauge (XX mm2) tinned cable.

One item that was still wired directly to the breaker panel was the fridge which was wired with heavier tinned cable than the rest as it runs for the most hours and draws 5 or so amps when running. Having any type of voltage drop on something that active was just false economy. We had all our heavy cables made up by a firm who specialized in them. The cables were cut to length, crimped with the required lugs and then sealed with heat shrink tubing so there was an air tight seal between the leg and the insulating jacket of the cable.

Distributed Ground Bars

Part of the amount of cable was due to the ground wires returning to the breaker panel.We decided to provide 4 grounding bars in the vicinity of the engine room, cockpit locker and at the breaker panel. These grounding bars were connected with 25 mm2 cables to avoid voltage drop. Individual appliances had their negative return wire run to the nearest grounding bar which cut down on the volume of cables returning to the breaker panel.A heavy 100 mm2 grounding cable was run forward to the anchor windlass. This cable also handled the 12-24 VDC converter for the bow thruster batteries.The final component was a wire to the rear hull anode tying it to the engine block where all other grounding cables terminated.

Reworked Breaker Panel

To clean up the breaker panel we removed the inoperative Webasto heating control as well as the 2 broken battery monitors. We had a piece of sheet aluminum cut to size so it covered the holes left and then had a hole cut to fit the Sterling Power Manager control. This piece was then powder coated black and fixed to the breaker panel with Sikaflex. All breakers were removed from the breaker panel and their wiring verified. The LED indicator lights on the line drawing of Maringret on the breaker panel were replaced and wired so they correctly indicated which running lights were lit.

Power Manager

We installed a Sterling Power Manager which is described on a separate page (click here for details).

There is a lot of complexity in re-wiring a boat of this size – the number of equipment suppliers we dealt with attested to that. We were lucky in that we had re-wired a boat of lower complexity in the Maxi 95 and so could slowly slide into this more complex undertaking. We knew we wanted to and had to re-wire at least portion of the boat when we bought it, what we did was to keep lists of things that didn’t work or didn’t work as we wanted. Slowly over a couple of years those lists became drawings and the drawings became action plans. At some point the logical diagrams (what is connected to what) must change into physical diagrams (what route is taken in connecting something to something else). Certainly with the heavier (100 mm2) cables these physical diagrams are critical as those cables only do what they want to. When running heavy cable the length must be measured so the cable can be cut to length. Obviously cutting short is a disaster (especially at the ever rising cost of copper) but over cutting is almost as bad as trying to”loose” extra cable length in terminated cables can be very hard to do.

Our experience is that it is best to finish all diagrams before starting to dismantle the old arrangement. It is very easy to get confused when faced with numerous wires running every which way, only the diagram will be able to help you avoid tracing every wire.

After 1 year the wiring is experiencing no problems.

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