Solar and 12V Power

Solar Lightning Solar Panels
12V Halogen Lights 12V Fluorescent Lightning
Lead Acid Batteries 12V-240V Inverters

 

General
Solar power provides a good stand-alone method of providing power for your houseboat or cruiser, however, unless you do some calculations of your power consumption, battery capacity and charging capacity, it is easy to become disappointed with solar power. To get the most out of your solar power system, requires an investment in deep cycle batteries as they are designed to handle deep discharges, unlike car and truck batteries that are designed to supply large currents for very short periods of time.

Normally on a boat, any solar installation is supplimented by charging current from the outboard motors and possibly a DC outlet from the generator. In most installations, it is really these two sources that keep your batteries charged during a voyage, especially in winter and most especially if you are using an inverter. If you are only travelling a couple of hours a day and do not have full summer sun, it is likely that the batteries will not be able fully recharge during the day.

For most recreational boats, the demands on the system are not rigorous, as there is usually relatively long periods between use which allows the solar panels to fully recharge the batteries, even in winter. If you intend to live on your vessel or take long voyages where the motors will not be run frequently, then it is more important to understand the limitations of your system.

For example, My Lady has a battery with a capacity of 450AH (ampere hour). The solar panels are capable of supplying about 8A of charging current under optimum conditions (noon on a summer day with a cooling breeze). In winter, this may come down to about 1~2A over the effective daylight period which is probably about 6~7 hours a day at best. This would provide about 14AH of energy to the battery each day.

The domestic lights are 20W fluorescent or halogen lamps which draw about 2A each. With three lights on in the houseboat from 6pm to 10pm, the daily energy drain on the battery would be 24AH - a net loss of 10AH per day compared to the solar energy being supplied. Normally, the stereo, two-way radio, water pumps and miscellaneous items such as small battery chargers for cameras and torches, lap top computers and depth sounders, will add to the net drain. If an inverter is used, the net drain can sky-rocket.

Thus, the engines must provide the additional energy to recharge the batteries.

 

Solar Lightning

One of the prime considerations for houseboat lighting is low power consumption. Where very basic lighting is required without the hassle of running wiring or extra battery drain, the standard solar power path lights can be very useful. These lights use high efficiency LED (Light Emitting Diodes) to provide efficient, but relatively low level lighting. When on special, these units can sell for about $5 each (late-2004). When fully charged, the lights can provide up to eight (8) hours of light. The My Lady houseboat uses twelve (12) of these units to ring the upper deck. The light level is enough to allow people to move around the deck safely, but not enough to read by.

The units are usually supplied with a socket and spike to plant the units in the ground, It is a simple matter to cut off the spike with a hacksaw and then screw the socket to the railing or other suitable location. The lights can then be attached to the sockets and the job is complete.

Because these units only have a press fit into the socket, it is not prudent to leave the units installed if they could be knocked by branches when you are mooring. Most units have an off-on switch which allows you to store the units without them discharging in the dark. This can be handy if you remove the units when the boat is unattended.

 

12V Fluorescent Lighting
The most common way to have fluorescent lighting is to use the small fitting that can be purchased from boating or camping shops. These normally have one or two small tubes. These units provide good light are not normally as effective at providing light as the common domestic fluorescent lights (18W or 36W). Larger vessels such as houseboats sometimes have both lighting systems. The use of an inverter allows the use of normal domestic fluorescent tubes. These inverters replace the ballast and capacitor in a normal domestic fitting, allowing the use of the normal domestic tubes.

Light fittings with these inverters already fitted are available, or you can take an existing light fitting and install an inverter. Inverters for 18W tubes and 36W tubes can be purchased from the Rainbow Power Company or other similar companies. Each inverter comes with an instruction sheet for installing the inverter.

My Lady uses a weather resistant (IP65 rated) fluorescent light fitting with an 18W inverter attached to the bimini cover's frame on the top deck. This light is controlled by an IP65 rated switch mounted on the railing. This light is used when the light from the solar powered lights around the deck is inadequate.

 

12V Halogen Lightning
Low voltage Halogen lighting provides an efficient source of light and is available in a number of fittings than are normally connected to a low voltage 12V transformer. These units can be connected to the vessel's domestic 12V battery with the same effect. However, some Halogen lighting has an inbuilt transformer. If you have some knowledge of electrical wiring, or have a friend who does, these units can be quickly converted to run directly from 12V. Most of these lamps have a small fuse in the base. You should ensure that the fuse and the switch are connected in series with the 12V line, not the earth line.

My Lady's cabins have bedside halogen reading lamps that have been converted from 240V to 12V operation. If you convert these lamps, you should leave the disconnected transformer in the base to counter-balance the lamp housing when it is fully extended.

Caution: In the Halogen lights pictured, the 12V supply to the globe is via the metal telescopic stand. This means if you place anything metallic across these posts, you will be shorting your domestic battery. Also if the frame of your houseboat is connected to the battery, knocking over the lamp so that it hits the metal frame may also result in the shorting of your battery. This why it is important that the unit's fuse should be retained in circuit.

There are an increasing number of high intensity LED (Light Emitting Diode) replacements for halogen lamps which feature a much lower power consumption for an equivalent light output. These are being investigated to replace the globes in the lamps above.

 

12V - 240V Inverters
Inverters are used to convert 12V DC to 240V AC. This allows mains powered devices to run from the vessel's battery supply. This allows you to run things like your television without running the generator. This can reduce the noise at night and save a bit of fuel. However, with all things you don't get something for nothing. The drain on the vessel's DC supply can be enormous.

For example, if the AC load is 240W, the draw on a 12V supply would be over 20A. If your vessel has a solar panel capable of charging your battery at a rate of 2A, it would take over 10 hours of full charge to recharge your battery after just one hour of viewing. In these cases, it is the power from your generator and/or the alternator in your motors that will be needed to recharge your batteries within a reasonable time.

Once you have decided that you want to use an inverter and that your use and DC system are compatible, there are two basic types of inverter: Modified sine wave and sine wave.

The modified sine wave models are generally cheaper than the sine wave models, but they can cause problems with some electronic equipment. They are generally alright if you want to run equipment such as electric drills, but you should check to see if they will drive your equipment properly.

The sine wave inverters more closely emulate the mains power from the mains or your generator. This means that they are less likely to cause problems, but the drawback is that they are more expensive.

Another thing to be aware of is that the ratings shown on appliances is the average power consumption. For appliances such as washing machines or air conditioners, the power requirements when the motor starts can be much, much higher than the average power consumption for a short period. While an inverter may be capable of handling the average power consumption, it still may be unable to operate the appliance correctly.

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