Fixed Solar Installation

[Dockhead]

I'm about ready to admit defeat in my attempt to use wind power to keep my batteries up on my mooring (my boat is on a mid-river mooring with no shore power). The Rutland factory couldn't find anything wrong with my 914i wind turbine. So I guess I'm just going to sell it and write off the installation costs.

One way to deal with the problem is to install solar panels in a frame over my davits. This would give me power both on the mooring and while out cruising, a nice plus. But it also means yet more windage and ugliness on top of the existing windage and ugliness of my davits. So I'm not quite sure I want to do that.

One idea I had was to install solar panels on my pontoon. That would not give me power while cruising, but I am pretty much ok with my power situation while cruising -- a couple hours a day of running the generator keeps me in high cotton, power wise, without any particular need to economize, and with the inverter running 24/7. I don't have any pressing need to change that situation.

But the mooring is a different story. I'm away from the boat for a month at a time (I live in a different country!), during which the batteries lose power (small drain somewhere I think, which I haven't been able to find). But even worse -- I have no good way of getting the batteries up to 100% before I leave the boat. I usually run the generator nearly all day on my last day aboard, which is terrible for the generator, and wastes a lot of diesel. If I had solar on the pontoon, I wouldn't need to do that -- I could leave the batts half-charged and just take off, knowing that the solar panels would get them gradually up to 100% and keep them there while I'm gone. Much better for the batts, too, to keep them on a float charge, than leaving them for weeks at a time with a partial charge.

So what do you guys think? Any of you done anything like this? Have any tips? Seems like I could put a couple of panels on a pole and just plug in. Further advantage is that with a fixed installation, I could align the panels just so for better efficiency. My pontoon neighbor is enthusiastic and would participate. I have asked the harbormaster whether they have any rule against it.

[ullar]

Hello Dockhead,

It's good to know that Rutland 914i is useless in your situation. My boat is standing in marina with shore power freely available but it I've never felt a need to plug in. On my boats I've been using semi-flexible solar cells glued to whatever place I felt reasonable. They don't have to be big to successfully charge your batteries when the boat is idling. ~50W on rooftop was enough for 140 Ah batteries on my earlier small boats and 2x65W on hard dodger are serving me fine now with 200 Ah house battery. And I get a big part of my energy budget from solar. The pontoon installation will work just fine but its still better to have that additional energy source with you when sailing or at anchor. If you don't count wirh solar energy when sailing just find a place for a semi-flexible walk-on solar panel somewhere on your boat and it will keep your batteries happy.

Regards,
Üllar

[Dockhead]

Originally Posted by ullar

Hello Dockhead,

It's good to know that Rutland 914i is useless in your situation. My boat is standing in marina with shore power freely available but it I've never felt a need to plug in. On my boats I've been using semi-flexible solar cells glued to whatever place I felt reasonable. They don't have to be big to successfully charge your batteries when the boat is idling. ~50W on rooftop was enough for 140 Ah batteries on my earlier small boats and 2x65W on hard dodger are serving me fine now with 200 Ah house battery. And I get a big part of my energy budget from solar. The pontoon installation will work just fine but its still better to have that additional energy source with you when sailing or at anchor. If you don't count wirh solar energy when sailing just find a place for a semi-flexible walk-on solar panel somewhere on your boat and it will keep your batteries happy.

Regards,
Üllar

Thanks for that.

I have 420 amp/hours x 24 volts of batteries, equivalent to 840 amp/hours at 12v. I am concerned that a too small charging source won't overcome the internal resistance of the batteries to do any charging. I don't know for sure whether such a mechanism actually exists, but I do know that the Rutland 914i just didn't do any charging at all unless 20 knots of wind were blowing, and then, only very little.

So I wonder how much solar I need to get any usable power into my batts. If you have 130 watts for 200 amp/hours, then I would need over 500 watts to have the same proportion. But maybe that's what I need; certainly no problem finding space for that much on my pontoon.

[Dockhead]

Here's one:

http://www.shop.solar-wind.co.uk/aca...0_Brochure.PDF

235 watts nominal for 380 pounds (about $500).

It's actually not all that gigantic; might not be all that noticeable above my davits. Hmmm.

Query whether that would be enough power -- I guess 4x nominal maximum power for a typical day? So about 1 kW/hour? That's more than 1.5 amp/hours per hour at 24 volts -- that seems like a usable amount of power to me.

[StuM]

130 watts is a bit over 5 amps at 24 volts. So for 420 amp hours ( no "/") you need about 84 hours of charging. At 8 hours a day, that's 10 - 11 days.

[Pete7]

Since it's going on the pontoon asesthetics are perhaps not as important. So in the UK there is 25mm galvanised pipe, corners and junctions used to create garden frames for netting over fruit plants. I did think about it for a stern arch but it just wouldn't look right. However, easy enough to assemble a frame bolted to the pontoon, particularly at the down stream end of your pontoon and share with your neighbour. 2 x 100w panels would give what? 30AH a day @ 24v in the summer and perhaps 10AH in the depths of winter. You have the advantage of long summer days at 50 North and cooler temperatures which help too. So 4 panels for the two yachts ought to work.

The alternative is a couple of 2x80w "suitcase panels" which fold in half for stowage and just placed on the bow area using the built in frame, lots on ebay at the moment. Paralleled up for 24v would give a fair output and a bicycle cable lock to stop them going walkabout in the night adds security.

Pete

[Pete7]

Originally Posted by StuM

130 watts is a bit over 5 amps at 24 volts

Are you sure? we see a maximum of 7.5 amps per hour from 125w panels at 12v during the summer mid day sun. At 24v it would be 3-4 AH.

Originally Posted by StuM

So for 420 amp hours ( no "/") you need about 84 hours of charging. At 8 hours a day, that's 10 - 11 days.

Uk summers can see 17 hours of daylight, makes a big difference but the opposite during the winter with just 9 hours and the sun barely reaching 20-30 deg from the horizon.

Pete

[poiu]

It can work well and really you need to do this to look after the batteries. A battery manual will tell you they need to be kept at 100% charge to ensure a long life.

I did this on 2 portable installations with different small panels, a flexible and a plastic rigid one. Ran leads to the battery with croc clips. No controller needed so long as the fully charged vote drop takes you below the max charge volts for your battery, which should be the case on a small installation, just a diode to stop discharge through the panel at night. Bundle up and sling under a berth when you get back. Simple.

In summer a location under the deckhouse windows is ok. Ensure there can be no partial shadow cast on it as that will kill output dead. In winter, angled to the sun outside is necessary as there is not much sun and winter is the worst case situation you need to size for. Could be 2 hrs full sun per day in an average week as with a small installation you get no power under an overcast sky. If you have flooded cells they will loose 15% per month and you will run to keep still. 3% for AGM or less with LiFePo. You might then manage with nothing by isolating the main battery and connecting the bilge pump directly. That's my current set up.

[StuM]

> Are you sure? we see a maximum of 7.5 amps per hour from 125w panels at 12v

I was giving theoretical figures. There are a lot of variables which affect the actual usable amps you can get for a panel in the real world.

[Dockhead]

Originally Posted by poiu

It can work well and really you need to do this to look after the batteries. A battery manual will tell you they need to be kept at 100% charge to ensure a long life.

I did this on 2 portable installations with different small panels, a flexible and a plastic rigid one. Ran leads to the battery with croc clips. No controller needed so long as the fully charged vote drop takes you below the max charge volts for your battery, which should be the case on a small installation, just a diode to stop discharge through the panel at night. Bundle up and sling under a berth when you get back. Simple.

In summer a location under the deckhouse windows is ok. Ensure there can be no partial shadow cast on it as that will kill output dead. In winter, angled to the sun outside is necessary as there is not much sun and winter is the worst case situation you need to size for. Could be 2 hrs full sun per day in an average week as with a small installation you get no power under an overcast sky. If you have flooded cells they will loose 15% per month and you will run to keep still. 3% for AGM or less with LiFePo. You might then manage with nothing by isolating the main battery and connecting the bilge pump directly. That's my current set up.

My batts are also isolated, but some small drain somehow gets around. I have spent a lot of time chasing it, but without success.

So I am guessing that I leave my batts at 90%, probably, and after a month I come back and they are at 65% to 70%. I guess that's not the end of the world, but I'm sure the batts would be much happier being stored at 100%, rather than 65% -- 90%.

[poiu]

420A x15% = 63A/month. /31 days= 2.03A/day. / 2 hrs = 1.02A. So a 25w panel Is the min. I'd go for 75 to 100w. Small enough to pack away and does the job plus will top you up to full charge in a short time.

[Dockhead]

Originally Posted by Pete7

Since it's going on the pontoon asesthetics are perhaps not as important. So in the UK there is 25mm galvanised pipe, corners and junctions used to create garden frames for netting over fruit plants. I did think about it for a stern arch but it just wouldn't look right. However, easy enough to assemble a frame bolted to the pontoon, particularly at the down stream end of your pontoon and share with your neighbour. 2 x 100w panels would give what? 30AH a day @ 24v in the summer and perhaps 10AH in the depths of winter. You have the advantage of long summer days at 50 North and cooler temperatures which help too. So 4 panels for the two yachts ought to work.

The alternative is a couple of 2x80w "suitcase panels" which fold in half for stowage and just placed on the bow area using the built in frame, lots on ebay at the moment. Paralleled up for 24v would give a fair output and a bicycle cable lock to stop them going walkabout in the night adds security.

Pete

I think 30AH/day in summer and 10AH/day in winter would be quite good for me. I think even in winter, that kind of output would gradually recharge my batteries over a week or two, after leaving them at say 70%, and that's really the task -- to allow me to not run my generator all day when I leave, and to allow me to come to the boat to find the batts at 100%.

I am aware that although the UK has less sun than more southerly climes, the lower temperature boosts the output enough to mean that you get almost as much practical power out of solar panels in the UK as you do in the tropics. That sounds good.

So if even 200 watts would do that, then I should be fine with a single 235 watt panel and MPPT controller, it seems to me

[poiu]

Originally Posted by Dockhead

My batts are also isolated, but some small drain somehow gets around. I have spent a lot of time chasing it, but without success.

So I am guessing that I leave my batts at 90%, probably, and after a month I come back and they are at 65% to 70%. I guess that's not the end of the world, but I'm sure the batts would be much happier being stored at 100%, rather than 65% -- 90%.

If you have disconnected the + then the batteries or one of them may be in bad shape as they shouldn't loose that much. The bilge pump also may have failing insulation and a current leak. Important to test as it might promote electrolytic corrosion.

[Dockhead]

Originally Posted by poiu

If you have disconnected the + then the batteries or one of them may be in bad shape as they shouldn't loose that much. The bilge pump also may have failing insulation and a current leak. Important to test as it might promote electrolytic corrosion.

I've been through all that -- the bilge pump is new and wiring has been tested.

The batteries are relatively new (less than two years) and are in great shape -- tested regularly for weak cells with an Argus tester plus specific gravity tests.

The electrical system on my boat is extremely complex and there are a number of places where it could be happening. I now have a sensitive DC clamp meter so will be going through it again over the winter.

[witchcraft]

We have a 130 solar panel on our davits. The specs assume 5 hours of sunlight, however there are many variables that can affect output. Our house bank is 420 amps. Our mppt controller assists the whole installation. We do achieve full output however, shade, clouds etc will change the output.
We are satisfied with our panel. If we were installing today we would have a more powerful panel for the same footprint. On our mooring we are not always pointed in the optimum position to take the most advantage of the sun. I suspect you will find the same thing, still power will be sent to the batteries.
The secret with all installations is to also reduce the power one uses.