solar set-up

[SailFastTri]

One problem with the wealth of information on the Internet is that it's difficult to separate fact from legend. If enough people repeat something, it becomes accepted fact.

[arjand]

Thank you all very much for your comments, I will follow up with the final set-up inc pics. The reason for 3 times 40W semiflex is space/vanity. I hate the look of large panels along the lifelines but maybe 8 months down the line practicality wins from good looks. It will definitely be parrelel. It will be one MPPT to the housebanks and I will try it first without diodes. If it works for cfarrar, it should work or me! Thank you and happy holidays!

[cfarrar]

I just realized that our diode discussion is apples and oranges. Noelex's point is that you don't need (or want) blocking diodes to prevent current back flow at night. My point (actually Noelex's, too) is that with parallel wiring you don't need bypass diodes to prevent a single shaded panel from shutting down the other panels. But SaiFastTri makes a good point that our experience may be biased by using panels that already have bypass diodes installed between rows of cells. I think most panels come this way, but you should check yours.

[sww914]

My new Blue Sky Energy MPPT charge controller has a second output that only gives 2 amps, perfect for the starting battery. I bought the 3024il which is a lot more than you need, I have 380 watts, but they have smaller offerings as well.

[arjand]

Thank you cfarrar. I just called the US distributor for Ganz and there are indeed NO bypass diodes installed in the Gan modules.I will have to read some more...

[SailFastTri]

Originally Posted by cfarrar

I just realized that our diode discussion is apples and oranges. Noelex's point is that you don't need (or want) blocking diodes to prevent current back flow at night. My point (actually Noelex's, too) is that with parallel wiring you don't need bypass diodes to prevent a single shaded panel from shutting down the other panels. But SaiFastTri makes a good point that our experience may be biased by using panels that already have bypass diodes installed between rows of cells. I think most panels come this way, but you should check yours.

The Ganz panels do not. It sounds from the data sheet that they come with the diodes attached to the end of the cable. Assuming the cable will need to be extended or run through narrow spots, they will need to be re-attached at a junction (I recommend a terminal strip) inside the boat.

[arjand]

@ SailFastTri, does the lack of internal bypass diodes inside the panel impact the overall performance of the panel in any other way?

[SailFastTri]

Originally Posted by sww914

My new Blue Sky Energy MPPT charge controller has a second output that only gives 2 amps, perfect for the starting battery. I bought the 3024il which is a lot more than you need, I have 380 watts, but they have smaller offerings as well.

You'd be better off using a voltage sensing relay (aka "battery combiner") to join the start and house banks, and just charge the hous ebank with the solar array. JMHO.

[SailFastTri]

Originally Posted by arjand

@ SailFastTri, does the lack of internal bypass diodes inside the panel impact the overall performance of the panel in any other way?

It's a little more efficient without the diode. A diode will drop the output voltage 0.2 to 0.5 volts, depending on the diode. There is a trade-off any time you insert a diode, but the payback happens when a panel is shaded (or partially shaded) when others in the same array aren't.

There is a lot written about this. Search for white-papers that describe when to use a blocking diode and when to use a by-pass diode. I posted a link to one very simple article in one of my posts above.

[Celestialsailor]

Personally, I do not use a battery combiner or blocking diodes. The discharge is minimal. Another myth to bust here is blocking one cell does not kill the output of panels that are of the newer variety. That might have been true for older ones made in the 80s-90's, but not now. That said, it is wise to tie the boom off to allow as much sun as possible. I wire my panels to a Flexcharge 25 then to the common post of the battery switch. I know this seems low tech but I like to control where the charge goes with out a lot of hoopla circuitry to go wrong.

[cal40john]

Originally Posted by SailFastTri

It's a little more efficient without the diode. A diode will drop the output voltage 0.2 to 0.5 volts, depending on the diode. There is a trade-off any time you insert a diode, but the payback happens when a panel is shaded (or partially shaded) when others in the same array aren't.

There is a lot written about this. Search for white-papers that describe when to use a blocking diode and when to use a by-pass diode. I posted a link to one very simple article in one of my posts above.

I believe you're wrong about the bypass diode. They are in parallel with either the whole panel or with newer panels there are two, one for each half of the panel. When the panel is in sun the bypass diodes are reverse biased and since in parallel can be thought of as disconnected from the circuit.

nolex posts above that no bypass diodes are needed for panels in parallel, and I agree with that.

[arjand]

Will put pics on when it is all done!

[Nicholson58]

Many of the better panels use multiple diodes on the panels so that various partial shading does not necessasarily shut down the panel.

I also hav been studying this a lot. It seems like black arts but it is really worth the learning. Presently, we are planning on the new thin film SANYO panels at about 18% efficiency. Kyorcia and most others are about 11 to 12 %. This will let us install about 700 watts name plate capacity above the bimini. I think the panels have three internal diode separated circuits.

The only other player in the high efficiency panel world is SOLAR POWER. They gained promenance by powering a boat on a circumnavigation but WILL NOT SELL to boaters. WOW! They only operate through their licensed installing contractors. Call the to arrange a team to evaluate your site. Ha HA $$$$$$$$$$$$

I found very good assistance and brain trust at Blue Sky on the charge controllers. They were totally familliar with the various panels and quickly matched my panels and batteries with an MPPT. We will run panels in parallel. Open circuit voltage is about 50 volts. We charge 24 VDC.

Stuff will be ordered in January for spring installation 2012. I read the Federal tax BS on renewables and found reason to be able to claim them on next year's taxes.