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hobbyhorse
hobbyhorse

Posted: Sat Jan 02, 2010 4:29pm

Post Subject: Solar Panel

I have one 110a/h starter battery and 3 110a/h domestic batteries charged via a Power Master 1800w inverter and charger. a) Is it possible to charge both starter and domestic batteries from a solar panel? b) What capacity solar panel would I need?

Tony-B
Tony-B

Posted: Sat Jan 02, 2010 5:19pm

Post Subject: Solar Panel

Dear Len please explain exactly what you mean by "charge". If you mean that the panels will be the sole source of charging and you live aboard with a less than frugal electrical load then the answer to b) will probably be far larger than you can afford or even fit on the roof. However without seeing your power audit calculations any recommendation will be meaningless. If you mean that you want to keep both batteries fully charged between visits to a leisure boat them my 60 watt panel seems to do all I require. Some controllers will charge two batteries but as the engine battery will be very well charged perhaps half an hour after starting I would question the need to charge both banks from a panel. As long a both banks are in reasonable condition and there are no loads on the system when you are away from the boat then a jump lead joining both bank's positives will allow the panel to charge both banks. Do not do this if there is any doubt about the condition of the domestic bank because it could discharge the engine battery over night. If you decide to try this it might be a good idea to fit a couple of (say) 20 amp inline fuses, one close to each clip, to guard against accidental short circuits on the jump lead. If you want a more complete answer I need a lot more information from you about your electrical use, methods of charging and the time period for charging and what you are seeking to achieve. Tony Brooks

hobbyhorse
hobbyhorse

Posted: Sun Jan 03, 2010 2:42pm

Post Subject: Solar Panel

Hi Tony, Thanks for the response. By charge I mean using the solar panel to reduce the need to charge the batteries using the engine. the current usage of the boat is as a live aboard 3 - 4 days per week. When occupied it is no problem to run the engine. What I am trying to do is find a way not to have to run the engine on the days that no one is there. The only things drawing current then are the inverter and a 12v fridge. Past experience shows that the battery charge is reduced to between a half and a quarter full in 24 hours with this load. I hope this is enough information for you, not being very technically minded. Regards Len

Tony-B
Tony-B

Posted: Sun Jan 03, 2010 6:04pm

Post Subject: Solar Panel

Dear Len, I am afraid that I still can not answer that until I see a power audit but trying to run a compressor fridge during the winter on solar is going to require a larger panel. To be honest I would suggest that it would be far more satisfactory to organise the catering etc so the boat can be left with all the electrical equipment turned off. A compressor fridge requires about 4 amps and will be on for about 12 hours per day giving a demand of 48 amp hours. Mt 60 watt panel is only producing an average of about 1 Ah per day at present so this implies about 240 watts of panels. In the summer this will probably totally cover the load, but not in the winter. Depending upon location a wind turbine may be a better idea for the winter seeing it generates 24/7 when there is wind rather than perhaps 6 hours a day from solar. My data is for a horizontally mounted panel;. If you can keep it at 90 degrees to the sun you wouldn't need as much, but still probably 160 to 200 watts. Tony Brooks

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