Charger System

There are two sources of electricity on my boat: the 2 cycle Tohatsu provides about 4 A at full power, and there is a solar panel installed on the main hatch which can provide about 2 A when well lit by the sun.

I have the GPS plotter which consumes about 0.3 A, then the VHF radio, also about 0.3 A, autopilot, about 1.0 – 2.0 A, depending on conditions. So the solar panel alone usually does not have enough energy to maintain the battery charged when all this equipment is running. Not to mention navigation at night, where I need about 0.5 A extra for the LED navigation lights.

I am forced to run the engine most of the time to keep the batteries charged, and if running just on wind, I have only about 12 – 15 hours of navigation time before the battery would be completely depleted.

The solar panel is mounted on top of the hatch by means of three bolts and wing nuts and can be easily taken down. It is one of the cheapest models and measures about 60 x 50 cm. and has nominal output of 30 Watt (2.5 A), I paid for it less than 60 USD and it works perfectly. It has a glass cover, so it is quite fragile. There are special flexible marine solar panels, but they are about 5 times as expensive per watt delivered, and they are not smaller, just lighter. So I do not see any major advantages in using them. And for very bad weather I can take down my solar panel in three minutes. The solar panel connects to the battery by means of a connector.

One obvious problem with solar panel is that it does not operate well when partially obscured. 50 % of shadow over the panel does not mean 50 % of power, but maybe just 20%. The location where I have the panel is prone to shadowing. Even without sails, the boom hangs just above the panel and can reduce significantly its efficiency. With sails, it dependens on the tack, but quite often it is in the shadows as well. So the total practical power of the pannel with good sunshine is about 2 A x 10 hours x 50 % = 10 Ah per day, 10 % of the nominal capacity of my battery.

The solar panel is excellent as secondary source of electricity and also as a replacement in case of breakdown of the engine charger (or the engine itself).

There are no good alternative locations on my boat for installing more solar panels permanently. One could maybe consider installing another panel over the board under the tiller, but it would be prone to physical damage.

The engine charger connects to the boat also by means of a connector, and the cable runs all the way from the transom inside the boat to the battery. There is another connector close to the switchboard. I found that I have sometimes to disconnect the charger to prevent overcharging. It can not be done with the outside connector, because it wrapped with insulating tape to prevent oxidation damage from sea water. Ideally, I think that I should add a switch which would allow me to disconnect the charger.