New Bimini Solar Project

[PhilDuhs]

Hi All,

After discovering the semi-flexible, very light and fairly efficient solar panels from Solbian I've ditched the idea of a dedicated stainless arch across the stern of my boat (Beneteau Oceanis 54) and will instead mount 5 of the Solbian solar panels on my bimini to give me 550W of solar power to keep my 840Ah bank of service batteries charged. Or at least that's the plan.

I have attached a PDF schematic of my proposed layout of solar panels, charge controllers, wiring, fuses and switches which it'd be great to get some feedback on! A few notes:

• The aft panels will get very little shade (thus the choice of wiring in series)
• The forward panels are more likely to get shade (thus wired in parallel)
• I like the idea of being able to route all panels to a single controller in the case of failure (thus the 3-way switches to disconnect or reroute the panels)
• I plan to use Morningstar TS-MPPT-45 controllers (as they're quite high capacity and also have a data connection so I can monitor better)

The main questions I have (although there may be more I should be asking!) are:

• What size wiring should I use for each section of the design:
  • solar panels 1, 2 & 3 to controller B (assuming 10m run)
  • solar panels 4 & 5 to controller A (assuming 10m run)
  • charge controllers to battery (assuming 3m run or alternatively an 8m run)
• Are the fuses adequate (bearing in mind all panels may be routed to either controller A or B)
• Do the positions and functions of the switches make sense
• Do I need to be concerned about the voltage differences between the output of panels 1-2-3 and panels 4-5 if (in case of a controller failure) if I route all panels to the remaining controller
• Have I left anything important out!!

Any other comments, suggestions, etc very much appreciated. The only other configuration I've considered is wiring the port and the starboard side panels together in parallel (ie. one circuit for port panels, another for starboard panels) each connected to their own controller and then buying a 3rd controller for the centre panel - which could then be augmented by a 6th panel mounted between the forward side panels if I got really carried away!

Rgds,
Phil

[GrowleyMonster]

I dont like to overthink things and start a growing cascade of design cimplexity. Simple is better, to me. You are making your system fairly complex in order to squeeze a bit more efficiency out of it and that could be a good or a bad thing.

For low voltage DC you want heavy wire, especially for longer runs. Voltage drop is related to current andof course current is proportionally high at 12v or so. Even 48v.

[Paul L]

A couple of comments. As Growley mentioned, you have made this pretty complicated to deal with a possible controller failure. But the complication also increases the likelihood of failure and corrosion/connection losses. I'd dump all the switches and just put together a clean wiring block where all the inputs end up. That way in case of failure you can move wires on a terminal block. A failure in a controller is not a failure that needs to be fixed immediately.
Secondly, what are you trying to protect with the two 20amp fuses? I don't see anyway that they could ever blow. The fuse that is useful is protecting current FROM the battery, not from the solar panels.
I really like the idea of using these thin semi-flexible panels. I plan to add one to my bimini next summer. Not sure if I'll bother to use a separate controller or just tie in parallel with the other panels. Even without a controller, you could use the panels manually tied to the batteries when they are low in an emergency.

[Paul L]

One more comment, on the series panels in the stern. You'll need to be real sure that they are shadow free. Not too many sailboats really have an unshadowed area back there. I get a shadow from the 3/4in PVC and standoffs that go up the back stay for my SSB feed. There always seems to be something that throws a shadow sometime on one side or the other. Not sure where you plan to cruise, but the sun angle is pretty different from 10* to 25* to 45* lat. So the directions that the shadows come from change.

[PhilDuhs]

Thanks Paul - yes, I think you and GrowleyMonster are right and rather than add unnecessary complexity an accessible wiring block that can be reconfigured in the event of a failure (which again as you say isn't an urgent thing) is much smarter.

The two 20A fuses are there to safeguard each solar panel circuit from the other one should things be bridged together (as per above). I'm not actually sure of the size fuses that might be needed but if for example all panels were wired to a single controller, and that controller failed, then it would be possible for the current from one set of solar panels to flow to the other set?? Or am I wrong here and as you say don't need to be concerned with this scenario?

I suppose there is no real downside to putting the 3 aft panels in parallel with each other instead of in series assuming I use thick enough wire to carry the increased amperage. Are there any other reasons to configure in series rather than in parallel - I've read as much as I can on this topic and seems hard to get a clear answer!

Phil

[noelex 77]

I agree with the comments to KISS.
There is a lot of debate between series and parallel connection. One difficulty is linking panels with different outputs.
I am having trouble finding the panel you are planning to use I the Solbian products.
The Vmp of the panels you list are different which makes linking them up in parrallel, which i would normally recommend, unwise.
Can you provide a link to the panels?

[Paul L]

Even if the panels somehow shorted, you still will not get enough current to blow the fuses, as they need to be large enough for the max current the panels can create. You do need the protection from the battery bank going outbound. The advantage of series is the higher voltage leading to lower losses. It is a pain to run big multiple thick cables from the panels aft. I run normal sized cables from the panels to a wiring block just below deck, then from that block run large cable to the controller near the battery.
Have you found a place to get a decent deal on these thin panels?

[PhilDuhs]

The web site (Solbian Energie Alternative - Pannelli Fotovoltaici Flessibili) is a bit behind the product releases. I've attached the latest pricelist that I've been sent.

I will be getting the panels from Solbian directly as they've got a stand at the Dubai boat show which starts in 2 days time and happens to be where I live. They do offer discounts if purchasing multiple units at the same time but I won't put the actual offer I got on this forum in case they do these things on a case-by-case basis - sorry to be a bit vague.

Nolex77 - your comment reminded me of why I put those aft 3 panels in series rather than in parallel - because of the different voltage outputs of the panels. Unfortunately I can't get 5 panels with the same voltage outputs due to space restrictions on the bimini/with the back stay.

So perhaps a better configuration would be to wire all the 112W panels in parallel to one TS-MPPT-45 controller, and just the 100W panel to the other TS-MPPT-45 controller - this seems to make more sense??

[Nicholson58]

Originally Posted by PhilDuhs

Hi All,

The aft panels will get very little shade (thus the choice of wiring in series)

The forward panels are more likely to get shade (thus wired in parallel)

I like the idea of being able to route all panels to a single controller in the case of failure (thus the 3-way switches to disconnect or reroute the panels)

I plan to use Morningstar TS-MPPT-45 controllers (as they're quite high capacity and also have a data connection so I can monitor better)
The main questions I have (although there may be more I should be asking!) are:

• What size wiring should I use for each section of the design:
  • solar panels 1, 2 & 3 to controller B (assuming 10m run)
  • solar panels 4 & 5 to controller A (assuming 10m run)
  • charge controllers to battery (assuming 3m run or alternatively an 8m run)
• Are the fuses adequate (bearing in mind all panels may be routed to either controller A or B)
• Do the positions and functions of the switches make sense
• Do I need to be concerned about the voltage differences between the output of panels 1-2-3 and panels 4-5 if (in case of a controller failure) if I route all panels to the remaining controller
• Have I left anything important out!!

Rgds,
Phil

Let me intorduce you to HANDY BOB SOLAR. He lives off-grid and his blog is a wealth of good information. Anyone doing what you are planning should take the time to read every last tidbit on his site. You may change your plans and you will make fewer mistakes. You may also learn how better to manage your batteries.

HandyBob's Blog « Making off grid RV electrical systems work

[noelex 77]

I could not find detailed specifications for the 112 L/Q, but from the information I could find, I think you will have to stay with series installation for this panel in conjunction with the SP 100L the Vmp is too different to support parallel connection.

[PhilDuhs]

Yeah, I've been told the spec sheets for the SP112L/Q panels will only be available from this week - but according to the price list they run at 20V whereas the SP100 panel runs at 18V. What did you think of following suggestion:

So perhaps a better configuration would be to wire all the 112W panels in parallel to one TS-MPPT-45 controller, and just the 100W panel to the other TS-MPPT-45 controller.

No real downside apart from the heavier cable needed running from a wiring block where all SP112 panel connections come into (eg. in the lazarette) to the controller and the heavier cable running from the controller to the battery.

What size cable would you use for an 8m run carrying 22A at 20V? From the online calculators it seems to suggest 25mm2 / 4 AWG - sound right to you?

[ChuckSK]

Another option would be to use a separate Morningstar MPPT SunSaver for each panel. Not much more than 2 TriStar 45 amp controllers. Simple connection, problem isolation, no added bypass diodes, small wire size.

[noelex 77]

Originally Posted by PhilDuhs

What did you think of following suggestion:

So perhaps a better configuration would be to wire all the 112W panels in parallel to one TS-MPPT-45 controller, and just the 100W panel to the other TS-MPPT-45 controller.

I really don't know what would be more efficient the differences would be small, but Its a pity that we cannot answer these basic questions definitively.

For a total distance of 16m (+and -) 25mm is good for 22A.

[LeaseOnLife]

Originally Posted by ChuckSK

Another option would be to use a separate Morningstar MPPT SunSaver for each panel. Not much more than 2 TriStar 45 amp controllers. Simple connection, problem isolation, no added bypass diodes, small wire size.

We did this for our boat, four ~18V solar panels, four MPPT controllers, worked well, plus adds redundancy.

[levm]

I am putting the final touches on installation of solar panels over my cockpit (no Bimini). I use two 3x6 panels (300w each) and one Morningstar MPPT 45 controller. So far it works excellent, delivers more power than I ever need while at the same time provide weather protection for the cockpit.