Splitting Solar Panels

[noelex 77]

Originally Posted by sailorchic34

adding a panel will give more power then a MPPT controller.

That's good advice.
Adding more watts will nearly always be much cheaper than adding a MPPT contoler.
The real world gains from MPPT are small. 5-15% is a reasonable estimate.
Even these gains only apply to the best MPPT controllers.

Don't buy a cheap MPPT controller.

However batteries are expensive and accurate adjustable voltage regulation is needed to keep them happy. This is available in non MPPT regulators, but is getting more difficult to find, and more expensive.

The real benefits of MPPT regulators are when the maximium amount of solar has been installed.

[s/v Jedi]

Originally Posted by 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.

Exactly, and small boats run out ofroom quicker. It is big boats who could keep adding panels longer but then, when you get many panels, a 20-25% increase in output from all panels becomes even more interresting!

[sailorboy1]

Originally Posted by 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.
.

3) the larger higher voltage panels are so much less money/watt that it makes up for the cost of the controller

#3 is how I went. My 290W 24V panel was $0.97/W compared to 140W 12V panels of $2.14/W

Also the nicer MPPT panels provide so much better programing and info that in the long run it just seems the way to go.

[nimblemotors]

Adding a panel won't help at all, if it is in the shade!
For the lowest cost, getting them out of the shade is the most important thing.

For a sailboat, as far I can tell, there really is only one good place to put them, which
is as far back behind the stern as possible. So like the link in my previous post, having some super solid arch mount to cantilever them off the stern is needed.
Doesn't having that stuff up there make a lot of really loud noise in high winds?
I would think it best to make them easily removable.

[Maine Sail]

I don't think the answer to series or parallel is an easy or cut & dry one on a boat, especially one that swings at anchor or on a mooring.

I have actually done some fairly extensive testing on customers boats and directly compared parallel to series on sailboats and power. Parallel, thus far, has won each time on sail boats.. On power boats (trawlers etc.) that suffer from no shading issues series wins most of the time but not all. I suspect that with enough "crown" in a bimini late day and early day low sun angles cut into the gains of series and this is why I have not see it win all the time on boats that have zero shade issues. There are instances when series still works best but it is very boat and installation specific so plan to do some of your own testing to confirm what works best for your own boat....

My friend Bruce, along with Nigel Calder, also did some testing last year and found similar results to what I have.

[sailinglegend]

Originally Posted by Maine Sail

.....I have actually done some fairly extensive testing on customers boats and directly compared parallel to series on sailboats and power. Parallel, thus far, has won each time on sail boats.

This seems to be the result that everyone is getting - but in your series testing did you ever add extra bypass diodes across the whole panel, or did you assume that the panels came with bypass diodes across their output?

[Maine Sail]

Originally Posted by sailinglegend

This seems to be the result that everyone is getting - but in your series testing did you ever add extra bypass diodes across the whole panel, or did you assume that the panels came with bypass diodes across their output?

No extra diodes. Most of the panels I did the testing on were Kyocera.

[sailinglegend]

Originally Posted by Maine Sail

No extra diodes. Most of the panels I did the testing on were Kyocera.

The Kyocera KC installation manual says bypass diodes are included, but suggests that if panels are wired in series then extra parallel diodes should be wired between two of the terminals in the junction box:

They say:
Diodes that are used as bypass diodes must:
・ Have a Rated Average Forward Current [IF(AV)] Above maximum system current at highest module operating temperature.
・ Have a Rated Repetitive Peak Reverse Voltage [VRRM] Above maximum system voltage at lowest module operating temperature.

Has anybody ever, with any make of panels, added extra bypass diodes across each panel when panels are wired in series - to make the best use of MPPT controllers high i/p voltages?