Ordering solar panels

[Snotter]

Though there are tons of information associated with solar panels in the archives, I am still having trouble determining which panel to use and the number of panels I can fit on my boat.

My boat is a Morgan 41’ Out Island. The beam of the boat is almost 14 ft. My plan is to have Wigfield Marine in Mobil to fabricate custom davits and to weld tangs to them up so that I can mount PV panels to them. I am not on the boat right now (and won’t be able to visit the boat until December). I’ve called Wigfield and they will meet with me on the boat to discuss the design and building process. However, before the design can be finished, they want me to obtain the PV panels. The trouble is I am not sure of what size panels I should order.

What I would like is a long-reached davit system to accommodate a rounded stern; hence the davits will need to have a reach of about ~52” or so. Also, since the boarding ladder will be at the stern too, the PV panels will have to be mounted high enough so that I can get under them to use the boarding ladder.

Looking at some of the Kyocera literature, a typical panel is ~60” long and ~40” wide. I would love to be able to put 2 panels on the davits but this seems it would be very difficult to get under the panels to use the boarding ladder.

I have 6 group 31 batteries on board. The plan would be to use the genset to bulk charge and to use solar to try to get the batteries near to 100% charge as possible.

Running down the Ten-Tom the last two or three weeks and using the built in ice-box/refrigerator and a dorm styled stand-up refrigerator plugged into a modified sine wave inverter would cause my batteries to go from 85% charge to 60% charge when anchored out overnight. We would like to tour the Bahamas and anchor out as much as possible. Everything seems to indicate that the move panels I can get on my davits the better off we will be.

Please help me to order the correct PV panels.

 

[Justin_NSA]

Can you get enough juice from the sun for all that equipment? The cruisers I saw in the BVI seemed to prefer wind power. Doesn't take as much space either. Look at Solar Stik too. Just throwing that out there.

 

[Snotter]

No I can't and that is the point. I would like to get as many panels on the Davies as possible.

 

[dlochner]

There are 2 directions to go, increase available power or decrease power consumption. The dorm style refrigerator is not a very efficient unit to start with and then powering off a an inverter just adds to the inefficiency.

If there is not enough refrigerator space, consider getting a portable Dometic or Engle freezer/cooler. Some of the units will run off 120 v when available and 12v otherwise. These units are well insulated and have efficient compressors and avoid the energy loss from the inverter.

Have you replaced all the incandescent and fluorescent bulbs with LED lights, especially the anchor light?

 

[GGordonWoody]

Right. You are trying to determine how much power you need to replenish 6 group 31 batteries from 60% to to 85% (25%). Based on a purely theoretical sketch, these batteries appear to have a 105AH capacity, and if all 6 are involved, that's a total of 630AH. 25% of that is 158AH, or around 2000WH of power to replace. If you purchased 100W panels, and got the equivalent of 4 hours of 100W output (400WH*), you would need 5 panels (2000/400=5).
* based on this cheesy 100W panel claim: http://www.windynation.com/Polycrys...roller-Battery-Charger-RV-Boat-Off-Grid/-/366

 

[Stu Jackson]

Also, since the boarding ladder will be at the stern too, the PV panels will have to be mounted high enough so that I can get under them to use the boarding ladder.

I know this doesn't answer your question, at all! , but in reading your post, this immediately jumped out at me.

I think you should seriously reconsider this. Unless you intend to raft up every night with a boat on either side of you, you will always have access to the sides of your boat. Get a ladder that mounts on the side of your boat. It is a more stable location to get into and out of your dinghy. It avoids this really "Challenging" design issue between the davits, the panels and, well uhm, the top of your head!

As for the panels, the size is based not only on the amount of batteries you have (the size of the house bank) but what your energy budget is. Without that info, anyone who suggests sizing for you is making BIG assumptions that may not be appropriate for you. Gordon gave it a good shot, but notice his clarity about the BIG assumption he made.

I've documented our daily ah use at 100 ah. With yours it could well be twice that.

The other consideration is how long you want to be able to go without using your engine.

Sizing solar systems is pretty much all over the internet. Solar vendors have worksheets on their websites. I think you should be able to find out how to do it without much hassle on your part searching for it.

Good luck.

 

[heritage]

This Morgan 41in the pic has a typical davit setup. It's much like what we did on our Oday 37. In order to comfortable use the stern ladder the panel or panels can't extend very far forward, but they can extend more aft. In the pic three small panels are used to fill the space. You might be able to mount two of the 40" x 60" Kyoceras lengthwise with a little overlap on each side of the davits and about 2' of overhang on the stern. Lots of nice shade for the dingy in the tropics and I don't think the looks of your Out Island would suffer much.

 

[thinwater]

Slightly off-topic, but...

IMHO, a cruising boat without a boarding ladder that can be pulled down by a swimmer in the water is a safety hazard. Not just a rope ladder either; something with 3 steps below the water that a tired, injured, or unfit person can climb. I'm sure there are many ways to resolve this, but I've read a lot of stories about folks that nearly drown because they couldn't get out of the water, and a few that did. The fatalities weren't in storms, but rather in calm conditions with cold water.

Seems obvious to me. Wouldn't you be embarrassed to explain why you didn't have something so basic? I would.

 

[Bad Obsession]

Thinwater has a very valid point. You never know WHEN, because it is not if, you will go into the drink. When I anchor I always put my ladder down. It would be best to be able to deploy the ladder if you are in the water.

 

[Snotter]

Right. You are trying to determine how much power you need to replenish 6 group 31 batteries from 60% to to 85% (25%). Based on a purely theoretical sketch, these batteries appear to have a 105AH capacity, and if all 6 are involved, that's a total of 630AH. 25% of that is 158AH, or around 2000WH of power to replace. If you purchased 100W panels, and got the equivalent of 4 hours of 100W output (400WH*), you would need 5 panels (2000/400=5).
* based on this cheesy 100W panel claim: http://www.windynation.com/Polycrys...roller-Battery-Charger-RV-Boat-Off-Grid/-/366

The OP wasn't about how to go sailing such that I never have to use a genset. I'm not a full-time cruiser. 100% solar sustainability is a nice goal down the road and may happen eventually; however, I will still be limited by space on my boat for panels. I need to efficiently use the space on my davits since I have a center cockpit boat. PV panels would be shaded by the boom so that is not an option at this point. I have a genset and it makes sense to use it for bulk charging and to use solar for absorption charging to get the LA batteries to as near as 100% charge as possible.

 

[Snotter]

This Morgan 41in the pic has a typical davit setup. It's much like what we did on our Oday 37. In order to comfortable use the stern ladder the panel or panels can't extend very far forward, but they can extend more aft. In the pic three small panels are used to fill the space. You might be able to mount two of the 40" x 60" Kyoceras lengthwise with a little overlap on each side of the davits and about 2' of overhang on the stern. Lots of nice shade for the dingy in the tropics and I don't think the looks of your Out Island would suffer much.

Heritage, your post is spot on. Thanks for taking the time to include the picture. I was wondering if 80+" was too much for the davits.

 

[Snotter]

I know this doesn't answer your question, at all! , but in reading your post, this immediately jumped out at me.

I think you should seriously reconsider this. Unless you intend to raft up every night with a boat on either side of you, you will always have access to the sides of your boat. Get a ladder that mounts on the side of your boat. It is a more stable location to get into and out of your dinghy. It avoids this really "Challenging" design issue between the davits, the panels and, well uhm, the top of your head!

As for the panels, the size is based not only on the amount of batteries you have (the size of the house bank) but what your energy budget is. Without that info, anyone who suggests sizing for you is making BIG assumptions that may not be appropriate for you. Gordon gave it a good shot, but notice his clarity about the BIG assumption he made.

I've documented our daily ah use at 100 ah. With yours it could well be twice that.

The other consideration is how long you want to be able to go without using your engine.

Sizing solar systems is pretty much all over the internet. Solar vendors have worksheets on their websites. I think you should be able to find out how to do it without much hassle on your part searching for it.

Good luck.

Stu, You bring up a very good point. The trouble with side-mount ladders is that they probably won't be there if you fall off your boat while under way when single-handing which is something I do quite a bit. Maybe a good compromise would be to keep the stern ladder which can be unfolded from the water. Also, a proper removable boarding ladder that can be removed from the side could be used for boarding the dink. Having both ladders would allow me to keep the PV panels and davits to a reasonable height.

 

[GGordonWoody]

http://www.bing.com/images/search?q...045E7E9BF2A726A3E58EA1C31B3CCADD4&FORM=IQFRBA

I have a genset and it makes sense to use it for bulk charging and to use solar for absorption charging to get the LA batteries to as near as 100% charge as possible.

Got it. You just need to rig two fixed size solar panels to help the bank. Can't help there - but just be careful with that genset!

 

[Bill Roosa]

Think you need to assess the magnitude of what you are considering. sounds like the physical limits are 2-100 watt panels. GordonWoody's rough order of magnitude calculation is leaning toward 5 panels. That is less than half of what you need. Is that going to get you what you want?

 

[Snotter]

SunPower has a 345 watt panel that is ~ 40" x 60" that should work. I was hoping to get more but there seems to be no place to put more panels unless I put two on the Bimini. Has anyone had good performance from panels mounted on a Bimini on a center cockpit boat?

 

[Justin_NSA]

You probably will never get full panel efficiency with the boom and mainsail partial shade. Just another random thought.

 

[dlochner]

If shade is a concern, several smaller panels are better than on large panel. Wire the panels in parallel so that the shaded panel does not affect the unshaded panel. Check this video:

Wiring Shaded Solar Panels | altE Solar Blog

 

[Snotter]

If I did put panels on the Bimini, I would use a separate mppt controller for the panels on each side of the boom. However what semi flexible panels will last? Renogy panels seem to have reports of failing after a year or so. I am not convinced that panels on the Bimini are worth the effort and money. Can somebody convince me?

 

[Snotter]

This ebay add it found (http://www.ebay.com/itm/320-Watt-Se...olt-Made-in-USA-MonoCrystalline-/272329685331) seems too good to be true. Another source for flexible panels is https://www.emarineinc.com/Gioco-170W-Flexible-Monocrystalline-Solar-Panel-GSC-170.

 

[seadaddler]

I have 2-190 watt panels and run 1 front load ref and 1 engel portable and a star portable ref and run the Gen late at night before going to bed and the batteries are usually at 12.5 and the panels charge the batteries all the day,all led bulbs and like running fans when warm.
I would try the bigger the better panels would be better.
Nick