Solar q’s

[fred1diver]

Hello again everyone.
I am looking at solar panels and I have a few questions, first what size of solar controller do I need? Second. How do I hook it up to charge both batteries ?

 

[dlochner]

what size of solar controller do I need?

Size the controller to the panel.

How do I hook it up to charge both batteries ?

Oh, now you have opened a can of worms! It all depends on how the system is wired and used.

 

[SycloneDriver]

Typically, on a 12 volt system, every 100 watts of panel gets roughly 10 amps of controller.

You could use an echo charger or a voltage sensing relay to charger a second battery.

We really need more information about your boat and your power requirements.

 

[fred1diver]

Ok, I keep looking at different panel brands, any brands you all recommend? I’m looking on Amazon at the moment some really good price for a 2 panel 400w system but are they worth it?

 

[dlochner]

If they are Renogy panels, it is a crap shoot. Apparently Renogy's quality control is poor and there is a high rate of failure for their products. MaineSail definitely does not recommend them.

There is a lot of variety in the way panels can be constructed and the quality of the individual cells. Those factors are reflected in the price. High quality panels use the best cells wired in the most efficient manner which produce the most power, they are expensive. Higher quality panels will also be less affected by shading and will produce power even in low light, i.e. early morning and late evening than lower grade panels. To a large extent, you get what you pay for.

The Alte store has a lot of good information on planning and buying panels. Some time spent there will be well spent. As for controllers, the Victron Controllers are good and reasonably affordable, do get the one that has bluetooth. It will be easier to program and provides good information on how the panel is performing. Genusun also makes good controllers, but I haven't used one.

DIY Solar Power & Energy Storage Systems | altE

AltE Store

www.altestore.com

 

[fred1diver]

A big thank you Dave

 

[Project_Mayhem]

MorningStar is also another reputable brand that was recomended to me by MaineSail. I have a 100w Renogy panel and two very basic MorningStar 6A controllers. One per battery. The system will charge a dead battery in less than 24 hours on a sunny day. So far no issues with the Renogy panel over the past two seasons

 

[fred1diver]

Now I’m really confused, 12v 24v … does the mppt controller bring it all back to 12v ? Or do I need to look only at 12v panels?
Are flexible panels any good? Or are they a waste of money?

 

[Johann]

Now I’m really confused, 12v 24v … does the mppt controller bring it all back to 12v ? Or do I need to look only at 12v panels?
Are flexible panels any good? Or are they a waste of money?

Panels will have an open circuit voltage (Voc) and a maximum power voltage (Vmp). Look for this in the data sheet. Unless you use a boost controller (not typical) the panel will need to produce about 5V more than the battery voltage to allow the MPPT to begin charging. When you see a panel advertised as ”12V” that means its Vmp is generally around 18V-28V… Not high enough for charging a 24V battery. A “24V” panel will have a Vmp > 30V or so. You can use a 24V panel to charge a 12V bank, the MPPT will convert the voltage. Flexible panels have shorter lifespans than rigid panels (Like maybe 5 years vs 20). Cheap flexible panels can fail pretty rapidly.

 

[leo310]

I've used ECO- Worthy solar panels from Amazon for 3 years with no problems, just got one more this year to make 400 watts found they have made them 3" shorter for the same output.

 

[kappykaplan]

Ok, I keep looking at different panel brands, any brands you all recommend?

I have a pair of Kyocera 130w panels on my boat. They've been on the boat for about 13 seasons and are still going strong.

 

[dlochner]

Now I’m really confused, 12v 24v … does the mppt controller bring it all back to 12v ? Or do I need to look only at 12v panels?
Are flexible panels any good? Or are they a waste of money?

Back to basics, Watts are a measure of power and are calculated by multiplying voltage by current (amps). So a 120 watt panel produces 10 amps at 12 volts. Each individual cell in the panel produces a small amount of power, so they are wired in a combination of series and parralell to produce a usable amount of power. One indicator of the panel's quality is the surface area and power produced from that surface area. If two panels have the same power rating, say 100 watts, the one with the smaller footprint (shade print?) will be more efficient and will have used higher quality cells. Another way of looking at this, if 2 panels have the same power rating, the one with the high open circuit voltage will have used more efficient cells and wired them in a more efficient manner.

The question you haven't asked is "how much solar do I need?" The answer to that question takes some thinking and planning. Start with amp hour consumption on the boat. Next, determine how many days can I go before the batteries need charging? This will tell you how big a battery bank you will need and how much charging capacity you will need. Remember, charging is inefficient, i.e., you will need to put more amps back into the battery than you take out. Figure a 20% loss, take out 50 amps, you'll need to put back 60 amps. 20% is at the high end of inefficiency estimates, however, better to over estimate this than underestimate this.

On average a solar panel will provide 3 times the nominal capacity each day, thus a 100 watt panel will produce about 300 watt hours of power or 25 amp hours at 12v. Better quality panels will do a little better, lesser quality panels will do a little worse. There are other factors involved too, like weather, latitude, shading, etc. etc. My panels are high quality panels (Solar), I typically got more than 3 times the nominal rating and on really really good days I would push four times.

This article is one of the best I have read on solar panels. Fair warning, it does get kind of technical.

Advances in Onboard Solar - Professional BoatBuilder: An IBEX Technical Journal

Advances in onboard marine solar technology improved efficiency and lowered the cost. But they also introduced more complexity.

www.proboat.com

 

[JBP-PA]

Now I’m really confused, 12v 24v … does the mppt controller bring it all back to 12v ? Or do I need to look only at 12v panels?
Are flexible panels any good? Or are they a waste of money?

A MPPT controller will bring 24V or more down to the range needed for 12V batteries. You can also wire multiple panels in series, for example a Victron 75/10 can handle up to 75V input and produce up to 10A at voltages appropriate for a 12V system. The less expensive PWM controllers will not do this, they will only work with panels designed for 12V batteries.

Flexible panels are lightweight and slightly flexible. If you need light weight and slight flexibility such a on a canvas bimini or on a curving deck, these are what you want.

If you can handle the weight and rigidity, such as on a hard top Bimini, dodger, dedicated arch, or unused deck area, then rigid panels are more durable and more efficient.

Note that there are "semi-flexible" panels with a fiberglass substrate that are more durable than the standard plastic backing on most flexible panels. Nature Power ($$$$) and Lensun are two brands I know of. These are not officially walk-on panels, but I do it all the time with no apparent detrimental effect after 5 years as long as the panel is flat on deck. There are official walk-on flexible panels, but they are mega expensive.

There are also fold up and roll up panels that are easier to store. You can then put them out when you want extra power. Many people also attach them to their lifelines and keep them down while sailing but tilt them out for extra power.

 

[Captain Larry-DH]

A MPPT controller will bring 24V or more down to the range needed for 12V batteries. You can also wire multiple panels in series, for example a Victron 75/10 can handle up to 75V input and produce up to 10A at voltages appropriate for a 12V system. The less expensive PWM controllers will not do this, they will only work with panels designed for 12V batteries.

Flexible panels are lightweight and slightly flexible. If you need light weight and slight flexibility such a on a canvas bimini or on a curving deck, these are what you want.

If you can handle the weight and rigidity, such as on a hard top Bimini, dodger, dedicated arch, or unused deck area, then rigid panels are more durable and more efficient.

Note that there are "semi-flexible" panels with a fiberglass substrate that are more durable than the standard plastic backing on most flexible panels. Nature Power ($$$$) and Lensun are two brands I know of. These are not officially walk-on panels, but I do it all the time with no apparent detrimental effect after 5 years as long as the panel is flat on deck. There are official walk-on flexible panels, but they are mega expensive.

There are also fold up and roll up panels that are easier to store. You can then put them out when you want extra power. Many people also attach them to their lifelines and keep them down while sailing but tilt them out for extra power.

This is a good overview. However, you should consider that the more flexing a "flexible" panel endures, the more likely it is to fail. The internal electrical connections can only take so much, and the physical limits of efforts to seal from water ingress are also tested by flexing. The best use for flexible panels IMHO is to mount them on a slightly curved deck with 2-sided tape such as 3M VHB tape. Once mounted they are effectively held rigid by the deck.
(Edit -- I'm not a fan of mounting on flexible biminis or dodgers. Also, some of the implementations I've seen on canvas have patrially overlapped edges, and even a small amount of shading on a panel will have a major disproportional effect on cutting down its production.)

 

[Project_Mayhem]

This is a good overview. However, you should consider that the more flexing a "flexible" panel endures, the more likely it is to fail. The internal electrical connections can only take so much, and the physical limits of efforts to seal from water ingress are also tested by flexing. The best use for flexible panels IMHO is to mount them on a slightly curved deck with 2-sided tape such as 3M VHB tape. Once mounted they are effectively held rigid by the deck.
(Edit -- I'm not a fan of mounting on flexible biminis or dodgers. Also, some of the implementations I've seen on canvas have patrially overlapped edges, and even a small amount of shading on a panel will have a major disproportional effect on cutting down its production.)

How well, if at all, do these handle someone accidentally stepping on them? I've also seen some exotic boats where it's embedded into the fiberglass

 

[dlochner]

How well, if at all, do these handle someone accidentally stepping on them? I've also seen some exotic boats where it's embedded into the fiberglass

Depends on the panel. High quality panels designed to be stepped on will survive. You get what you pay for.

If you go for a deck mounted panel, it will be necessary to increase the capacity to compensate for the inevitable shading that will occur. One of the differences between expensive high quality panels and cheap panels is the effect of shading on the output. Better panels can tolerate shading more effectively than cheap panels. Calder discusses this in the article I linked to earlier.

Above the Bimini is a popular location because it is the most shade free area on the boat. Shade from the back stay is minimal and has little effect on the panels output.

 

[Captain Larry-DH]

How well, if at all, do these handle someone accidentally stepping on them? I've also seen some exotic boats where it's embedded into the fiberglass

As @dlochner wrote, it depends. No hard-soled shoes, rolling luggage or dropped tools! If your tools miss the water they're sure to hit a panel.

 

[Davidasailor26]

If your tools miss the water they're sure to hit a panel.

I think they could manage to catch both.

 

[fred1diver]

Ok, looking at solar equipment, what type of solar charge controller would you recommend? I know MPPT seems to be the best but why? What brand do you all recommend?

 

[SycloneDriver]

I'm fond of Victron.

MPPT because it's more efficient and should put more power into the batteries. It also allows you to put your panels in series or use high voltage panels.