handymariner - Australian boat repair&maintenance information

Electrics & Electronics

WARNING Incorrectly wired installations can kill, or cause serious damage. This section deals with electrical and electronic components on your vessel. Please remember it is essentialy for repair and maintenance issues and although the articles are written by industry professionals and others with substantial experience, they are not substitutes for the services of a qualified professional when it comes to installation, diagnosis or repair of complex equipment.

Article - Estimating power consumption

To determine the total power consumption per 24-hour day in order to decide the size of battery and what charging method will be appropriate, it is essential to assess the comsumption of each item and the time is is used. For space-saving reasons, the table below is an extract of the full table that may be downloaded by clicking the link in the left hand panel of this page.

Please note the hours listed are “typical” and should be replaced by your own data. Engine requirements are NOT listed here – always use a separate starting battery totally isolated from the “house” battery

Item (extract from full iist)	Amps	Hours per day	Amp-hours (amps X hours
Anchor windlass	150	0.1
Autopilot	0.7	4	The download version of this table allows you to calculate your own amp-hours and battery/charging needs
Cabin fan (each)	0.3	3
Computer -laptop	2.5	2
Deck light 20 w)	1.8	0.1
Depth sounder	0.2	4
DVD player	0.3	1
Fridge (50% cycling)	5.5	12
Inverter—on standby	0.2	2
Light 8w fluorescent	0.7	2
Microwave (800 w)	120	0.2
Navigation lights - tricolour	0.8	2
Pump—bilge	15	0.1
Pump—freshwater	3	0.1
Radio – VHF (receive)	0.5	0.5
Radio – VHF (transmit)	5	0.2
Toilet - electric	40	0.2

Battery capacity should be at LEAST twice the number of amp-hours – more if possible. Your generator or solar panels must AVERAGE this figure. An 80 watt solar panel in a 12V system delivers about 6 AMPS per hour in direct sunlight, but it smart to allow a margin of error or for extended overcast conditions. For security, consider providing a back-up charging system with a power (or engine-driven) generator, wind vane or towed generator

Solar panels

Energy Content of Sunlight Sunlight has an energy content of 1 kW (1,000 watts) per square metre. The typical Solar Panel today achieves between 10% and 15% conversion. The theoretical maximum efficiency of a silicon cell is about 21%. Using a more costly technology 31% conversion has been achieved.

This and far more information on just about everything you need to know about energy systems for your boat can be found at the website of the Rainbow Power Corporation or at North Arizona Wind & Sun

Article - installing an electronic bird scarer

Transonic IX-L is a patented, completely solid-state electronic device that emits high intensity sound waves at frequencies on which the pests communicate. This special sound is produced by three rapidly shifting ultrasonic carrier frequencies (FM), then three square-wave amplitude modulating frequencies (AM) at three different rates, thereby jamming the nerve signals in the pest's body which causes confusion and irritation sufficient to repel him.

When the unit is on, the front panel light will flash. In the "Quiet Mode" there will be a faint sound coming from the unit. This setting is recommended for rodents. In the "Medium Mode" setting, the sound coming out is more audible and should be used to repel insects from interior or exterior spaces. The waveform of the medium mode is essentially the same as the quiet mode, but with lower sidebands present. To help get rid of birds use the "Loud Mode" setting. This mode combines the quiet and medium wavebands - like two separate systems operating at once plus the addition of loud sonic frequencies.

The unit can be wired directly into the boat's 12V power circuit OR may use a mains converter (supplied) that MUST not be exposed to weather