Solar Panel Setup Question.

[delmarrey]

Originally Posted by noelex 77

The best policy is to try and fit as many watts as you can in the space available and at the lowest cost. The number and voltage of panels only has a small impact on the final output.

Keep in mind that sometimes the delivery costs for large panels can be high. Couriers don't like large glass fronted objects.
With the cheap costs of solar these days the installation costs can become dominant.
So look at the total installed cost per watt rather than the raw panel price.

That's what I'm thinking too. But I've been reading solar info for the past two days and there seems to be multiple problems with solar setups on sailboats. So, now I'm thinking about the 24v panels again.

e.g. Shading, space, price, parallel vs series, 24V vs 12V, wiring and so on.
This is not a cheap venture and I'd like to get it right the first time. I have enough spare parts laying around that I can't seem to sell.

Retrofitting boats is a hit and miss affair at times. Especially when the boat is not very large. I thought a 40' racer would be enough for a complete self sufficient vessel but I'm finding I'm running out of space real quick.
Who needs food or clothes as long as you can live off the grid.
But I'm getting there.

[noelex 77]

Originally Posted by delmarrey

That's what I'm thinking too. But I've been reading solar info for the past two days and there seems to be multiple problems with solar setups on sailboats. So, now I'm thinking about the 24v panels again.

e.g. Shading, space, price, parallel vs series, 24V vs 12V, wiring and so on.
This is not a cheap venture and I'd like to get it right the first time. I have enough spare parts laying around that I can't seem to sell.

Solar is a great for any cruising boat. A lot of the threads on CF are debating the last 5-10% in output so don't get too concerned.

Make the measurements of what will fit , the controller choices and post the options, together with the prices, and you will get some opinions which is the best way to go.
Some of the opinions might even recommend the same thing.

[sailorboy1]

If it helps I went though it all just recently and decided that 1 large 290W 24V panel with a MPPT controller was better than many small panels. It was just easier to mount and wire etc and the problems are the same no matter what so I diecide why not.

[s/v Jedi]

Originally Posted by Don L

If it helps I went though it all just recently and decided that 1 large 290W 24V panel with a MPPT controller was better than many small panels. It was just easier to mount and wire etc and the problems are the same no matter what so I diecide why not.

I agree. Mounting panels is my least favorite project. I even accept a little less wattage when that means much less panels for much less work and a much cleaner look.

[willardj]

Originally Posted by delmarrey

I thought I knew electrical and Ohms Law but I'm getting some contradictions in some of the solar threads on the forum here. I've just started getting into solar systems.
If I were to take 24V/240W panels and reduce them down to 12V output thru a MPPT controller, does that half the wattage at 12V to 120W? Or am I getting mixed up here?

Are they like batteries, or not?



Due to space restrictions I'm thinking of going with 2 X 12V/100W panels. It seems if one goes over 100watts the price shoots up with every 5 watts from about $1.25 per watt to $2.90 per watt. But these maybe too long, so I'm considering 3 X 12V/75W panels. All this would be in parallel.

As well I'm considering the Moringstar ST-MPPT-45 controller. But I've read that it has to be hooked to a computer to program it. Or is there something off with that too? Does the TRistar meter TS-RM-2 allow for programing.

There is so much info out there that seems to contradict itself that it's hard to know what's what. My brain is getting numb with the confusion.

You can find good deals on larger panels, but the cost of shipping is thru the roof. Time you add that in the deal turns out to be not be as good. If you get a small mppt say (Sunsaver mppt about $225)to go with those 2-100w would work very well. I have one it really allows us to take advantage early morn and late afternoon light. Every lil bit helps.

[delmarrey]

Thanks All!

I'll take another measurement again today and see what I can squeeze in on the top of the arch. It'll just add more beauty to the "Ugly Duckling".

Last night I read the manual for the MorningStar but couldn't find any mention of battery banks.
So, one other thing I need to ask, which I think I ran across in my research is about battery banks. Can one hook a system up to multiple banks thru combiners, or does it have to be set on one bank of it's own. I did read that all the batteries need to be the same size and age. There are a pair of "Sense Wires" on the MorningStar.

At this time I have a pair of 12V cranking batteries in one bank, a pair of 6V deep cell house batteries in another with one gp 27 up forward for the winch, all with combiners off the alternator going to the cranking batteries.

Also, what about when the motor is running? should I disconnect the panels first? None of this was mentioned in the manual.

[Dustymc]

The Morningstar is "one sided."

Mine came with a temperature sensor. (And about 900 feet of wire which you're not supposed to cut.....)

I have mine (and everything else) hooked to an A/B/ALL switch, where A is my house bank (4x6V), B is a WalMart "marine" battery (and ALL is never used), with a Blue Sea ACR in the middle. I've been told that the ACR isn't the appropriate device, especially now that I have equalize capabilities (from the solar), but after 2 years the starting battery - which had been bouncing around in my fishing boat for a couple years before I promoted it to "backup" battery - is still starting the Westerbeke and not squirting acid at my tools and all that other stuff a battery is supposed to do.

I assume my alternator is smart enough to deal with whatever the solar's doing and vice-versa. In any case, my batteries just seem to get charged faster when the engine is running and the sun's out.

[Bash]

Originally Posted by delmarrey

So with that, would ya'll think 3 x 12V/75W panels would be better. I sure would be able to fit them in a lot easier then two 100+W panels?

Forget about voltage for a minute, and focus solely on watts. 3x75=225. 2x100=200. So you'll get more of a charge out of the three 75W panels.

[Nicholson58]

Originally Posted by Pelagic

My limited understanding as explained by Nolex and others is that the higher output (VOC) you can buy for a given area, the better that will translate into useable charging power thru a good MPPT, when solar energy lessens because of clouds or time of day.

BINGO! the MPPT continues to deliver amps even as the sun sets and/or the clouds drop the output. As long as the panel VOLTAGE is above your charge voltage, the MPPT will make the conversion to deliver some amps at the correct voltage. The MPPT cannot boost the volts but it can convert volts too high to exactly the right volts and the amps will be roughly in accordance with Ohm's law. For this reason, you select a panel to give you as high an open circuit voltage as possible and size the MPPT accordingly. Please please read Handy Bob Solar blog. Its a PHD dissertation in solar off-grid living.