A solar panel thread

[JimD]

I have a 15 foot vee bottom plywood pocket cruiser, looks like this:



The centerboard is a #120 steel plate and I would consider replacing it with a wooden board to allow more battery weigh as inside ballast in the bilge which will handily hold 4 batteries. I would like to convert to electric for auxiliary power. I already have a 24 volt 65# thrust minnkota electric outboard and two batteries. I'm looking at a solar panel charging system which I know nothing about. This is a fair weather boat and our summers are drenched in almost endless sunshine for two or three months. Primary power would still be sail, at least when the wind gets around to blowing in the right direction, if at all. I can make a big hard canopy for panels over the the cockpit area we are sitting in. Ideas?

[knottyBuoyz]

IMHO solar panels would ruin the looks of that very pretty boat. I'd mount them on a pole on the dock next to the boat and leave them behind when you go sailing. Plug them back in when docked. Just my 2 cents worth.

[Full Tilt]

Maybe flexible solar panels could be utilized at deck level when needed? Lead acid batteries and a Minnkota are pretty inefficient compared to a Torqeedo and Lithium manganese. I can't see replacing your ballasted centreboard with wood as viable, compared to upgrading your motor and batteries.
Mike

[JimD]

IMHO solar panels would ruin the looks of that very pretty boat. I'd mount them on a pole on the dock next to the boat and leave them behind when you go sailing. Plug them back in when docked. Just my 2 cents worth.

Thanks for the compliment but there is no dock, hence no pole, and I want to be able to recharge while underway. I will make the canopy look nice, I promise.

[JimD]

... Lead acid batteries and a Minnkota are pretty inefficient compared to a Torqeedo and Lithium manganese. ...
Mike

I'm sure you're right about that but changing the whole system is not in the budget.

[Soundman67]

Hey Jim,
You are going to get a pretty good boost to your batteries by adding 16 ft^2 of panel. I would just suggest you make sure its Monocrystal and not poly. get a good charge controller. If you use your boat once a week it may just take care of the batteries all on its own. I would love to see you do it and report back to us.

[E.Johnson]

Thanks for this thread. I was just mulling over how "green" power could be applied to a boat with a trolling motor, and the Torqueedo site was a good starting point to explore those musings.

As for anyone who is going to say "isn't wind energy kind of inherent to sailboats" the issue is how to store up energy to propel the boat if the wind isn't blowing, or is blowing the wrong way, etc.

[Dan Lyke]

I ran through the basics of how to figure out how much charge you'd get out of a set of solar cells in the "Open electric displacement boat 16-18" thread, and I totally understand the desire for an electric assist: We live near a tidal slough (called the Petaluma River), we've been putting in at the launch ramp, taking 2:30 or 3 hours to tack up into down-town, and then 20 minutes to sail back. We'd love to go further south and east, down the "river" towards the San Francisco Bay, but aren't keen on tacking back later.

On the centerboard replacement: Can you figure out where the axis of rotation when your boat is floating is, and figure out the center of weight of your current centerboard relative to that, and use that to figure out how much battery weight you'd need to replace it? Figuring that if the center of weight of your extended centerboard is twice as far from the axis of heel than your batteries are going to be, you'll need twice as much battery weight?

[Soundman67]

what if he replaced half of the centerboard weight with batteries?
and make a lead plug at the bottom of the centerboard. so your weight in the centerboard has moved downward but remains almost as effective?
then there is some weight to add back into the boat in the way of batteries.

[Mad Scientist]

Given what's possible/practical at the current state of the art, how about one of those wind turbines as used on cruising sailboats? (assuming that you can get one for a good price)
That would give you a bit extra 'juice' diring the nighttime hours.

Tom

[JimD]

what if he replaced half of the centerboard weight with batteries?
and make a lead plug at the bottom of the centerboard. so your weight in the centerboard has moved downward but remains almost as effective?
then there is some weight to add back into the boat in the way of batteries.

There are problems with replacing the steel board with anything at all since the trunk is only designed to hold a half inch thick board.

[JimD]

Hey Jim,
You are going to get a pretty good boost to your batteries by adding 16 ft^2 of panel. I would just suggest you make sure its Monocrystal and not poly. get a good charge controller. If you use your boat once a week it may just take care of the batteries all on its own. I would love to see you do it and report back to us.

I'll start pricing things out.

[Wayne Jeffers]

If you want to go with 4 batteries, I would suggest you look at getting 4 X 6-volt golf cart batteries. They fit on the same footprint as a group 24 battery, but an inch or two taller. Weight is about 68 pounds each. Trojan T-105's are the best known type, but you can get other (cheaper) GC batteries at Sam's Club. They're true deep-cycle batteries and, with proper care, will last a very long time (10 years is not exceptional) under deep-discharge conditions.

Wayne

[Woxbox]

Isn't that a generally cloudy but breezy part of the universe? I'd expect that you'd get more watts/dollar with a wind turbine, which as noted, works 24 hours a day.

Other than that, what Soundman says if you go solar. The controller is just as important a the panels - don't cut corners there.

I put a panel on my boat last year and it's the most useful mod so far -- but I'm not running a motor from it, just a few lights, recharging phones and radio, and occasional autohelm use. For that, I've found a single 60W panel is adequate.

[Soundman67]

well for bigger boats the best thing we can do is get away from Lead acid batteries and not for the newer more exotic blends. The edison battery is one of the best longest lasting battery out there. the problem is that they are too heavy for most applications
In a boat they could last easily for a hundred years. give you reliable deep storage with very little maintenance. abuse them as much as you want over discharging them and they spring right back. every once in a while you can replace the electrolyte and they just keep chugging along.
So now you have a good storage system. Now get a good way to charge where ever you can. Wind is great. when you are at anchor there are always currents passing your boat. so get an towable generator. and of course get the solar panels. But you can get solar panels that are like shingles soon. or even get a solar panel that can be made into a sail. its not far off now.
Luckily though the most difficult part is really the storage. And if you have a bigger boat the weight of these edison batteries wont matter a bit.

[JimD]

Isn't that a generally cloudy but breezy part of the universe?

Nope, as previously mentioned, our summers are virtually cloud free and the winds are very fickle. The sunshine is far more reliable than the wind.

[Mad Scientist]

Funny, your summer is just like ours.

From my recollection of the winter I spent in Victoria, Vancouver Island doesn't get nearly as much rain as does the Lower Mainland/Puget Sound region - it's when the rain clouds hit the mountains that the rain really gets intense.

Tom

[Soundman67]

Yup Some parts of Vancouver get over 150 inches of rain a year. Temperate rainforest.

[JimD]

Funny, your summer is just like ours.

From my recollection of the winter I spent in Victoria, Vancouver Island doesn't get nearly as much rain as does the Lower Mainland/Puget Sound region - it's when the rain clouds hit the mountains that the rain really gets intense.

Tom

Our island winters are still plenty wet but I don't boat much from October through May.

[ahp]

Here are some numbers you need to know. Sunlight is 75 watts per square foot. Solar cells are maybe 10% efficient when you consider the rest of the system. One hp is 746 watts. So, if the sun shines directly on a one square foot solar cell, for one hour, you will store up enough energy to have 1/100 hp for one hour.

[WX]

Keep in mind you can only use around 30% of your battery capacity without damaging the battery. Assuming you are using deep cycle.

[JimD]

Keep in mind you can only use around 30% of your battery capacity without damaging the battery. Assuming you are using deep cycle.

I had no idea.

[Wayne Jeffers]

Keep in mind you can only use around 30% of your battery capacity without damaging the battery. Assuming you are using deep cycle.

Assuming lead-acid deep cycle batteries, I think this would be a rather conservative approach.

It is true that the life of a deep cycle battery is much affected by how deeply they are discharged, and for how long they remain below full charge. But most references I have seen say that discharge to 50% or 40% before recharging is not unduly detrimental to battery life. Below that, and you're definitely shortening battery life.

http://www.marxrv.com/12volt/12volt.htm

Wayne

[Woxbox]

From the above link, here's a good chart to keep handy. It's not the end of the world if your voltage drops below 11.9 volts, but the battery bank will last a lot longer if you can keep it north of that. I just replaced a gauge that showed percent of charge with a digital voltage readout on my boat so I know exactly how things stand.

Battery care can get complicated and depends on what type you have. But there's tons of information out there on the cybernets.

[Breakaway]

+1 ^
The corollary to this is that the less you allow a battery in deep cycle service to discharge, the less of its capacity you are using.

For instance, if you have a 100-Amp-hour battery and you stick at a 50-percent discharge routine, then you will only have 50-amp-hours ( 50 amps for 1 hour; 25 amps for 2 hours; 12.5 amps for 1 hour etc) available from the battery between recharges. If your needs are for 100-ah between charges, and you stick to a 50-percent d/c max, then you need a 200 AH battery.

So you could discharge at a higher rate to keep your batteries smaller and lighter, but they will die and you'll need to buy replacements sooner. Or you can pay more up-front for a bigger battery ( or bank) that will last longer.

Kevin