Splitting Solar Panels

[noelex 77]

Originally Posted by s/v Jedi

It is very clear. With partial shading the parallel setup always looses the whole panel, while series setup has a very good chance to still deliver part of it's power.

There are certainly scenarios where this is true, but it is not universal, or absolute, as your quote suggests.

A large diffuse shade for example will severely restrict the current, but the Vmp will remain similar.
In this sort of example the panel will be shut down with series connection, but will still contribute significantly in parallel connection.

[s/v Jedi]

Originally Posted by noelex 77

There are certainly scenarios where this is true, but it is not universal, or absolute, as your quote suggests.

A large diffuse shade for example will severely restrict the current, but the Vmp will remain similar.
In this sort of example the panel will be shut down with series connection, but will still contribute significantly in parallel connection.

No, you said partly shaded, not large diffusely shaded. I don't play when rules change during the game

[sailinglegend]

Originally Posted by s/v Jedi

It is very clear. With partial shading the parallel setup always looses the whole panel, while series setup has a very good chance to still deliver part of it's power.

It is not very clear, and that is always the problem with this very complicated subject which involves a combination of bypass diodes and blocking diodes.

Many panels may be wired with their cells in a combination of parallel and series to help minimise shading problems. Many arrays may then be wired with their panels in a combination of parallel and series to help minimise shading problems. The cells within the panels and then the panels within the arrays should not be confused.

Bypass diodes may already be built into the solar panel in the junction box to limit the shading losses from the series cells within the panels. Blocking diodes are used to stop current flow from the battery feeding into the solar panel at night. With a regulator blocking diodes are not needed.

When more than one panel is wired in series, as Jedi says, extra bypass diodes should be used across each panel. I do not believe panel manufacturers supply their panels fitted with an extra panel bypass diode as well as their internal cell bypass diodes. The panel may never be connected into an array in series so this is as added cost to them. This information is not always easy to find from the manufacturer’s literature and many land-based solar installers may not be aware of these problems because they don’t usually encounter shade.

I did tests on my Solara panels and the output in series was far worse with shade than in parallel. My UK dealer confirmed that parallel would be better unless extra bypass diodes were fitted - which they don't supply!!!!!

[sailinglegend]

Originally Posted by s/v Jedi

No, you said partly shaded, not large diffusely shaded. I don't play when rules change during the game

This such an unhelpful post - again!

I agree with all Noelex 77's posts.

[4fish]

Let's be positive . From this discussion It seems to me that there is not really a wrong setting each one has it' s drawbacks.
Maybe getting several large but not enormous modern panels, because its "serial" cell construction and connecting them in parallel will have more good things than bad....

[sailorchic34]

Well being a cheap lady, I buy my panels when there is a deal. So I have one 130 watt and one 100 watt panel. With unmatched panels, parallel is the only way to go.

I'm also of the school that rather then get a MPPT controller, that the money is better spend buying another panel and distributing the panels about the boat.

On a sailboat shading is always going to be a problem at anchor.

Too reduce shading, I use the preventer to move the boom over the starboard side which reduces shading to the panels.

So solar is just like anchors. There are many ways to do it and all work most of the time...

[s/v Jedi]

Originally Posted by sailorchic34

Well being a cheap lady[...]

I'm also of the school that rather then get a MPPT controller, that the money is better spend buying another panel and distributing the panels about the boat.

So solar is just like anchors. There are many ways to do it and all work most of the time...

An MPPT controller can increase the power output by 25% compared to a non-MPPT controller and even more than using no controller at all. I still have my 6 panels in parallel but recently connected an Outback MPPT controller and I have 20% more output already. This will get better when I configure the array in series.

It is "cheap" to get more power out of the same panels. It is also better for the environment

[s/v Jedi]

Originally Posted by 4fish

Let's be positive . From this discussion It seems to me that there is not really a wrong setting each one has it' s drawbacks.
Maybe getting several large but not enormous modern panels, because its "serial" cell construction and connecting them in parallel will have more good things than bad....

I only see suppressed messages because that user is on my ignore list... from your reaction it seems I must keep him there

[Dustymc]

Originally Posted by sailorchic34

With unmatched panels, parallel is the only way to go.

I have 2 100W panels and 1 125W panel in series feeding a Morningstar controller - is there something I should know??

[Paul Elliott]

Originally Posted by Dustymc

I have 2 100W panels and 1 125W panel in series feeding a Morningstar controller - is there something I should know??

Yes. Your 125W panel is probably not delivering all the power it could. If each of the panels have the same number of cells, then the lower-current 100W panels are restricting the current that the 125W panel could be delivering.

[Dustymc]

Originally Posted by Paul Elliott

Yes. Your 125W panel is probably not delivering all the power it could. If each of the panels have the same number of cells, then the lower-current 100W panels are restricting the current that the 125W panel could be delivering.

Awesome....

So, given my three panels (they're what fits on my boat!) and an MPPT controller - wut do?

[nimblemotors]

I have been researching solar panels, and found that shading is a serious problem.
Look at this website: Sailboat Solar - Installing Solar Power & a Solar Panel Arch on a Boat
I summerize for you:
Panels in full sun:22.5 amps
One panel partly shaded:15.5 amps
Two panels slightly shaded:9.5 amps
So going fro 22.5 to 9.5 with only this much shading:


As I plan on building a heavily electric powered boat and use solar panel extensively,
I am thinking another approach is needed, use active electronics dc-dc converter to combine all CELLS in parallel.

[Paul Elliott]

Originally Posted by Dustymc

Awesome....

So, given my three panels (they're what fits on my boat!) and an MPPT controller - wut do?

I hope you get some other opinions (because I could be wrong!), but as I see it you either

• wire them all in parallel (this only works if each panel has the same number of cells),

• or keep them configured as is. The way you have it, you are getting perhaps 100W from the 125W panel. That's still a very useful amount of power.

On a sailboat he "correct" answer depends so much on geometry and shading. You also need to accept the fact that no matter how you optimize your system, it's never going to be perfect because the conditions are always changing. Strive for "good enough, considering the situation."

[sailorchic34]

Originally Posted by s/v Jedi

It is "cheap" to get more power out of the same panels. It is also better for the environment

Well for the big boater with lots O panels and money, sure MPPT works. For the little boater, spending $170 for an extra 120 watt panel will give more power per buck then installing a $225 to $400+ mppt unit.

For the small boat cruiser (me for example) with two 12V panels putting out say 11 amps actual, Using your 20% gain will give about 2 extra amps per hour. Adding a 120 watt panel gives about 6 amps (in real life) per hour for less then the cost of a MPPT controller. So until you get to about 30 amps per hour, adding a panel will give more power then a MPPT controller.

So for smaller systems, using 12V panels, Mppt is not always the best way to go. Like anchors and guns it all depends and one way is not right for all people.

BTW My two 12v panels provides all the power I need at anchor.

[Paul Elliott]

There are a couple of good reasons to get an MPPT controller:
1) You have no room for more panels.
2) You will eventually have no room for more panels.

Until you have all the panels you want to carry, you probably get better bang for your buck by buying more panels. If you aren't at max yet, but plan to get there, then you may as well get the MPPT controller sooner rather than later.