Best solar panels for the buck

Bill Roosa · Jan 11, 2012

prroots
IF the controler is truly MPP then it would work on a 5 volt panel and you would get a 4ish volt output under 1 sun. The problem is 4 volts will not work to charge at 14.4. the real reason panels very is because they are designed for different applications or designed before MPP became popular. General wisdom was you need to be able to provide 14.4 to charge your batts and once you get the panel under full sun it will get hot and loose some volts or when it is a cloudy day it will not be producing full voltage so they generally went with 36 cell panels = 18ish volts
The bleeding edge controlers have mpp and a buck-boost converter (DC to DC voltage transformer) so you can hook up just about any panel to it and it will charge your batts, even a 5 volt panel.

joker460 · Jan 11, 2012

There was a company in Quebec that was getting started and they had an opening sale where I picked up 2 x 100 watt monocrystaline panels for $220. I also added the Blue Sky MPPT controller with remote display.

http://www.emarineinc.com/products/Blue-Sky-3024iL-12V%2d40A{47}24V%2d30A.html.

With the boat on the hard and covered with a white translucent tarp I'm still getting 4 amps from the panels to keep the batteries topped up over the winter. No need to keep going down and plugging in the charger to 110v.

Had them now for 2 years with no problems.

Sumner · Jan 11, 2012

prroots said:
SolarBlvd has been recommended. They have a Solar Cynergy 185 for $240 which is 12 Volt nominal. Seems like a great price, but not sure about that brand. Shawn said it was their private label? Anyone have experience with this brand?
Pete

I can't find the 185, but the Solar Cynergy is their 'in-house' brand. The sizes can change and the ones in stock can change. That is the reason we bought a spare to have with us. All of the panels we have bought are their Solar Cynergy and at this point I have no complaints.

The first one we bought was a 40 watt and it has now been on the boat for over 2 years, outside all of the time and on the water in Florida for 3 months and elsewhere for an other couple. Still looks pretty much like the day it went on.

We have had a 60 and 80 watt on the boat for a year and the same.

All of the panels we have gotten from them are called 12 volt panels, but the Optimum Operating Voltage (Vmp) is listed as 17.2 for all of them. As has been mentioned they need to be over 14 volts and the controller will then do the job of regulating them. With the MPPT to get maximum benefit you need them to be of similar voltage and cell type. You don't want to mix a 12 volt panel with a 24 volt panel. It sounds like you are going to get two exactly the same and that is even better than what we have on the Mac. All of the panels going on the Endeavour are exactly the same panels.

Good luck,

Sum

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Maine Sail · Jan 11, 2012

prroots said:
Thanks; that helps. I do worry about having to replace one in the event of breakage. They admitted it would be tough to replace down the road with another having the same dimensional and electrical specs. On another subject, they said it comes with a positive and negative cable about 4 feet long terminated with MC4 connectors. He recommended I get a male and a female MC4 y-connector to join the two positives and two negatives together. Is this what you've done or is there a better way to hook them up? Without having seen them I would prefer to terminate my cables inside the junction boxes and go directly to the controller without any intermediate connections. He said it would be tough to seal my cables where they entered the junction box.
Pete

I am NOT a big fan of the MC4 connectors for marine applications.. I much prefer a typical J-Box under the panel. It is getting hard to find non-MC4 panels these days but they are out there if you look.

Sumner · Jan 11, 2012

prroots said:
.. On another subject, they said it comes with a positive and negative cable about 4 feet long terminated with MC4 connectors. He recommended I get a male and a female MC4 y-connector to join the two positives and two negatives together. Is this what you've done or is there a better way to hook them up? ....Pete

My older panels were all connected at the box under the panel and then down...

...into the Laz. individually and connected to a terminal strip there with one pos./neg. from there forward to the ....

...controller in the cabin.

The new 100 watt I got for the Mac and all of the 80 watt panels have the connectors and I ordered the ones they suggested. I guess I'll try them and see what happens. I will go from the connectors to a box under the panel array where the individual panels will be fused and from there down into the cabin area with one #4 pos./neg. lead.

We will probably only make one trip to Florida a year to go out on the Endeavour. At that time we could be in the water for 2-5 months. The rest of the year it will be hauled out and on stands. I'd like to be able to pretty easily remove all of the panels except one when we are gone so the connectors will be nice for that. If problems arise I guess I'll deal with them then.

On the Mac I'm actually going to put those connectors on the 40 and 60 watt panels so that they are easier to remove when the boat is home on the trailer. I'll leave the 40 on since it ...

..tilts for better winter sun angles to keep the batteries up. The others I'd like to remove due to the snow loads we can get here, but this winter has been really dry.

I guess you will just have to decide what is best for you,

Sum

Maine Sail · Jan 12, 2012

prroots said:
I'm still trying to figure out how best to do the wiring, but I'm favoring cutting off the MC4 connectors and running all wires into a single watertight junction box on the center line of boat. I would need to locate some watertight stress relief devices to get the wires into and out of the junction box. I would mount the junction box to the underside of custom frame. A big advantage of this approach is that I can shop for good price on cable since it's not solar specific and run, for example, 6 AWG 2 conductor cable on the longer run from panels to controller. I've calculated that 6 AWG is required to keep voltage drop to less than the recommended 3% for 22 Amps and distance of 30 feet one way.
Pete

Pete,

Just try to buy panels that don't ship with MC4 connectors. They are out there..

thinwater · Jan 12, 2012

Or you can simply replace the factory cables

Maine Sail said:
Pete,

Just try to buy panels that don't ship with MC4 connectors. They are out there..

With a good junction box, simply pull the old cables and replace. You may need to replace the gromet in the compression fitting with the proper size--I did--but since I also used one of the boxes to combine the pannels, I had to add fittings anyway.

No, I wouldn't use the MC4 conector in the salt. I replaced them all with continuous #10 (I think) wire.

Maine Sail · Jan 12, 2012

prroots said:
Thanks. I will certainly search, but the panels I'm looking at sell for $1.24/watt and it might be tough to compete with that especially since I'm also wanting to stick with nominal 12 Volt panels to save on the MPPT controller.
Pete

Pete,

A good PWM controller won't cost a heck of a lot less than an MPPT over the long haul. The least I would choose, for an array like yours, would be a Morningstar ProStar 30 and they run about $120.00 - $180.00.. Panels are one thing to do on the cheap but controllers are not in my experience...

Your talking $178.00 or so for a Blue Sky 2512i vs. about $120.00 for the bare bones ProStar 30 PWM... For the $60.00 difference I would choose the MPPT on your array. On arrays below 200W, unless using a Genasun MPPT, the MPPT will not add a whole lot. But, on a system like yours, it can mean a real 10% or more boost. That's an additional 2+ amps for less that what you'd pay in additional sq in.......

Maine Sail · Jan 12, 2012

prroots said:
Thanks. You may have misunderstood me. The savings I referenced was based on a comparison between two different MPPT controllers. I will definitely go with MPPT. It turns out that one can save about $140 on the MPPT controller by going with a nominal 12 Volt panel vs one with a higher voltage (at least with the Blue Sky series).
Pete

Yes that is true the dedicated 12V MPPT controllers are less money than the larger ones that will handle more voltage.. I find 12V panels are most often the least expensive way to go unless mounting one big panel results in less over all cost... Mounting these can get expensive on a boat to do it well...

Evergreen made some large 12V nominal rated panels but I don't know if any are left out there. Look for the ES-A-205 or ES-A-210 are around 17+ volts..... Even their ES panels are not a true 24V and are in the 25 -27 volt range..

Bill Roosa · Jan 12, 2012

If you buy 12 volt nominal panels your batteries will not charge!!!!!!!
You need AT THE VERY LEAST 14.4 volts output with hot panels. Either 36 cells or 18 volts is considered the MINIMUM needed to effectively charge a "12 volt wet cell" battery.
Remember a "12 volt battery" does not operate at 12 volts and is almost dead when it gets to 12 volts. 13.6 is the standard resting voltage for a fully charged battery so plugging in a 12 volt nominal panel will not accomplish much of anything except to empty your wallet.

Bill Roosa · Jan 12, 2012

That is probably why those panels are less expensive. They are not designed to charge batteries.

Count the individual cells. I'll bet there are only 32.

Now if you use a boost converter your 12 panels can have just about any output voltage you want. In fact you can make the case that wiring ALL the cells in parallel @0.6 volts and boost converting to 14.4 is actually more efficient than a series string with lots of bypass diodes. The parallel connection does not have the partial shading issues that the series connection method does.