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Reducing the power draw of the vessels anchor light

What is the issue?

The international COLREGS state that an anchored boat must display a round ball when anchored during the day and an all-around white light at night. The light must be an all-round white light which is visible for 5 miles for vessels between 12–50 metres (39–164 ft) and at least two nautical miles for vessels smaller than this. It must be placed in the forepart of the vessel or “where it can best be seen”. Maintaining these lights throughout the night draws a lot of power.

Why address this?

Most anchoring lights are positioned at the masthead to deliver a clear bright light that can be seen for some distance in busy waterways. The power consumption of mast based anchor lights will require significant resources to replace.

The average dedicated masthead anchor light bulb is a 25-watt incandescent bulb which will pull 2 amps. So the standard bulb will pull more than 20 amp-hours in the course of a tropical night. That would require the full output of a large solar panel of an efficient wind generator for the following day, to replace or an hour's engine time. Reducing it to a 10W bulb will help but this will not be bright enough to meet the legal requirement and it almost uses an amp regardless.

Efficiently managing the vessels limited power resources is central to those who live on yachts for extended periods. As a result, and although it is well understood that there is the requirement to show an anchor light, many boats don't use one to save on electric energy. But if your boat is hit at anchor by another vessel, under maritime rules, you can be deemed to be at fault so it is not worth risking it.

How to address this?

Mast based anchor lights are geared towards delivering the maximum requirement. Yet most yachts anchor in crowded secluded anchorages where there is a known abundance of yachts at anchor and a very strong beam is not necessary.

We had two solutions for this set-up. A self-built LED light for most recognised anchorages and a bright LED camping lantern where there were a lot of boats coming and going.

A standard salt cellar
Photo: Courtesy of OLYMPIA

The self-build light was made from a LED 12v bulb, a length of cable, a plug suitable for your boat's external power socket, some silicon sealant, and an old salt cellar. A glass jar and lid will suffice but the lid will rust in time, whereas a salt cellar provides both a lens and a stainless steel top. All we did was drill a large hole through the stainless salt cellar's stainless steel lid, to allow the power lead to pass through. and we tied it off with an overhand knot to hold the weight. We then soldered an ultrabright LED bulb directly to the cable end.

You may have to switch the polarity about. We had a 5mm LED that was a diode which only allowed the current to flow in one direction. The positive side of the LED was the Anode and the negative side is the Cathode with the anode (positive) having a slightly longer leg. You cannot get it too wrong as when there is no current flow, there will be no light and if it is wired backwards, it will not burn the whole system up, it just won’t come on.

Once it was soldered on we sealed the pass-through of the cable and lid with silicone to make it watertight. With the lid screwed down and the light and lens connected all we did was connect the plug to the opposite end of the power cable. This drew dramatically less power from the boat's resources to provide the same level of protection. Additionally, a small convenient low wattage light lends itself to many roles upon a vessel.

We used the camping lantern when we were in a busy anchorage where there were lots of boats coming and going. When swung off the boom its very bright light lit up the entire cockpit area of the boat. This enabled anyone passing to see a large section of the yacht so that it was impossible to collide with it. The joy of this was that it would easily run for two nights on a charge and did not touch any of the yacht's power resources. Likewise, as with many of these rechargeable type camping lanterns, it could be charged by a standard car adaptor and we could choose when to charge it.

Standard camping lantern
Photo: Courtesy of Uni-Com

With thanks to:

Michael Harpur, with thanks to Johnny and Emer, Yacht Pala.

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