Solar Panels

mikewilkes

mikewilkes

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Just done a search for " Kyocera" which I seem to remember were stated by some as the best avail now.
Need to keep a Waeco 50l fridge going on solar and I believe it is about 40 / 50 watts.
Any ideas?
 
50 watts call it 4 amps/hr over 24 = 96 amp/hrs

assume 8 hrs of sun 96/8 = 12 amp/hr = 144 watt panel

Have you taken the duty cycle into account for the fridge as it seems a bit heavy on power.

suspect you would be able to manage easily with the new kyocera 130 watt panel.
 
G'day Mike,

We have 2 Waeco fridge freezers on board and they run 24/7 along with other equipment. charging is via 2 x 80 and one x 100 watt solar panels.

Battery bank for above is 8 x 6 volt 225 amp hr deep cycle batteries, plus 2 x starting batteries, one for each engine (30HP Volvo's). Battery monitoring is via a Xantrex Link 10.

She is also wired for shore and has a 3 stage 25 amp Hi-Tech Battery charger.

My only complaint is that access to the 8 x 6 volt batteries located under cockpit floor is not the best, we are looking into relocating them closer to midships.

Avagoodweeknd......
 
Just a correction there on your maths. 12 amps yes but you don't multiply 12 amps by 12 volts to get 144 watts. or even 12 amps by 14volts to get 168 watts........No Solar panbels are watt calculated max volts usually 20 volts x max amps.
So 12 amps would need 240 watts of solar panel. Or put another way a 100 watt panel will only give about 5 amps not the 8 you might calculate.
In my opinion solar are a lot of trouble to mount and expensive if you have shore power and engine generator available for use when away from shore power that is preferable.
(from someone who has relied on solar only for the last 20 years cos it is a swing mooring and no motor.) olewill
 
Hi Olewill

I agree with all you say.

People forget or are not aware that solar panels are approximately constant current devices up to close to their maximum rated voltage (which generally is dependant on the number of cells in the panel) beyond which output current starts falls precipitously.

So while a 90 watt 15 volt panel (for sake of example) may put out 90/15 = 6A at 15 volts it still only puts out around 6A at 12 volt (say when charging a battery or DC system volts are dropped due to a load), so then only 72 watts.

It is possible to get around this by using DC-DC converter technology but that adds to the cost, and to the best of my knowledge is not commonly incorporated in solar panel voltage regulators.

Of course, the output is again decreased according to the level of illumination, by quite alot unless bright and sunny and the panels fiddled with to keep aligned with the sun. All adds up to requiring a lot more wattage (rated wattage that is) in the panels than the DC load indicates - taking both illumination and the decreased power at boat system volatges - maybe at least twice as much, and that for Olewill and I who live in relatively sunny climes.

John
 
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