Solar Power

[Ed]

I need advice on how large a solar panel I would need to power my O'Day 25. I only need power for the lights and various appliances during weekend and long weekend cruises. I day sail occasionally.I keep an extra back-up battery just in case the main battery goes dead during the weekend, I have no charger at this time. Only one battery would be hooked to the charger at a time. I was thinking of a 40watt, but that seems like overkill for a set up like mine. If you have used solar power and can give some advice, I would appreciate the input.Thanks in advance.Ed

 

[Don Evans]

Sharpen Your Pencil Ed...

Add up all the amps you would need to use each day, i.e. let's say 4 amps needed for 8 hours is 32 ampers (amp hours). To replace that you would need to have a 4 amp panel collecting sunlight for 8 hours. Problem is these panels are about 50% of there rated output, typically. So that would be a 4 (2 actual) amp panel going for about 16 hours in total(not going to fully replace the energy used in one day). Another problem with panels is that there output declines as they age.You didn't mention the size of your house battery? Will your present battery give you this and still not be less then 50% discharged? You should not discharge a deep cycle less than about 50% of it's capacity. Is it a deep cycle, rated in amp/hours or is it a starting battery rated in cold cranking amps? Solar panels are a great way of replaceing this energy, but they are fairly inefficient, in that it depends on time of year, time of day, lattitude, cloud cover, shadows, age of the panel etc.. I have used 2 10 watt/1amp, panels and consider them to be just better than toys. You mentioned a 40 watt panel. I am assuming that to be about 2-4 amp output? That is not a toy. You will need a matching sized regulator, to prevent overcharging and blocking diodes to prevent battery discharge after the sun goes down. Other problem with that size is mounting the panel on our respective 25' boats. I had mine over the bimini. I have seen some mount them off the pulpit rail. Not to many other places that are clear of shadows, and not in the way of your feet. I think your probably not to far off the mark with that 40 W panel.Don

 

[Mike]

battery life

Ed-Several things:-Your battery must be a deep cycle type battery for marine applications.-Getting a battery charger will solve all of your short battery life problems.-Buy a good quality marine type charger.-A fully charged deep cycle battery will easily operate things like a VHF radio, CD/AM/FM stereo, Nav lights (night operation) and even start your engine if it is electric start for weekend visits to your boat.You don't say if you have one, but an electric start engine will charge your battery while operating the engine.I recommend a simple marine charger unless the marina you are at doesn't offer electric service or you are leaving the boat during the week on a trailer where there is no electric service. In that case a solar charger may be the only way to go.As far as solar chargers are concerned I ascribe to the belief that if things like that worked then many, many boaters would have them. I think that in all the visits I have made to marinas I have seen a small percentage of the boaters using one.Good Luck,Mike

 

[Ted Siegel]

Solar works for me.

My boat is an O'day 272LE with a 10hp Universal diesel engine. My dock does not have shore power so I supplement my engine charger with an ICP Pro Watt 15 solar panel. I have the typical loads... lights, stereo, etc. I also have a 1000w inverter that runs a microwave and tv (for the kids). I use the boat about 3 times a week running most of the loads.I have 2, group 31 batteries that I haven't had to charge all summer. I would prefer to have shore power for charging, but in my situation solar has worked very well for me.

 

[Jonathan Sherlock]

Works for me too

I have been using a Siemens 10 watt panel that I got from West Marine for about two years. I have one 105 amp hr battery on board and have a pull start motor. I use the boat at least one full day each weekend all year round. I run a depth finder and a cd player constantly on the boat. I run lights, a washdown pump system, the kitchen sink pump and two fans occasionally. I have never had to think about electricity. The battery is always ready to go. I have no power on my dock and never charge the battery with anything else. The Siemens solar panel works perfectly as far as I am concerned. But other owners may think that am not using very much power, I'm not sure. And it is true that it is very predictably sunny here in San Luis Obispo for at least 10 months of the year.