Solar panel/ MPPT controller system design

[socaldmax]

There are 3 major factors that should drive solar system design on a boat.

1. Lack of space.
2. Weight considerations.
3. Potential for partial shading.

#1 and #2 encourage one to use the most efficient panels one can find. #3 encourages one to carefully position the panels to minimize shading and wire in parallel or one panel per controller to minimize power losses.

There is a solution that nicely covers all of the bases. Sunpower panels are over 20% efficient and come in 327w panels, yet are the same size as most panels. 61"x40" and only 41 lbs. If one were to buy 5x 100w panels, not only are they doing considerably more work wiring it all and screwing in 3 more panels, the total weight could be considerably higher.

Since each panel could put out up to the following under optimal conditions:

327w / 15v = 21.8A
327w / 14v = 23.36A
327w / 13v = 25.15A
327w / 12v = 27.25A

I would recommend a 30A MPPT controller for each, or a 60A controller for both.

The Sunpower panels are more robust and capable of longer life under temp. extremes, not to mention much less loss from shading than other panels. There are youtube videos explaining all of this. The hard part might be finding the panels for sale somewhere, but they are available.

If you have room for 5x100w panels, you probably have room for 3 or 4 Sunpower panels. You can never have too much solar power, imagine having 3 panels and almost 1,000 watts, or 4 panels and over 1300 watts!

[sailormed]

Hello pcmm,

There is one aspect that has not been mentioned so far, the reduction in output of the nominal panel wattage. Unless you are cruising extensively in the tropics you only get about 70% of the nominal value out of your panels. This is the loss incurred because of the flat installation of your panels on your boat. If you can angle the panels the loss will be less or can disappear completely.

[socaldmax]

Originally Posted by sailormed

Hello pcmm,

There is one aspect that has not been mentioned so far, the reduction in output of the nominal panel wattage. Unless you are cruising extensively in the tropics you only get about 70% of the nominal value out of your panels. This is the loss incurred because of the flat installation of your panels on your boat. If you can angle the panels the loss will be less or can disappear completely.

That's true, but who knows which way the boat is going to swing when at anchor?

Who is really going to readjust the panels every couple of hours for optimum harvest?

The typical solution is to go with bigger panels or one more and just mount them flat.

[moseriw]

Well I solved it.
Here is my solution:

2,8 m² Solar panels giving 2000 Wp and 10A constant even on a cloudy day.

Bought one VICTRON - BlueSolar MPPT 15035 but my elecgtrician said this is scrap I shall buy two Victron BlueSolar-DUO-Charger one port and one starboard.

Works perfect I have 3x225 Ah House AGM's and everything is powered by solar, day and night. Everything is fridge/FREEZER, Autopilot, Navigation including Radar, Lights, Navigation Lights. Had no problem with the inverter and microwave too...

If you want I can send you the wiring diagram and a picture... the panels are on the pilothouse.



SUNPOWER Solarmodul SPR-130
135 Wp620 Wh/dSUNPOWER Solarmodul SPR-85
85 Wp390 Wh/

[BobH260]

My approach was one large Kyocera panel, 325 W, 40V. to minimize the current and wire size. It is mounted aft of our arch on a home built s/s frame using 1" s/s tubing, off the shelf connectors pop-riveted (s/s) together. A Rogue MPPT controller works well, logs the performance.

We have LED lights, large fridge and freezer. We are usually back to 100% by noon hour in Florida/Bahamas, winter cruising.

Total cost was just over $1K.

Pictures here, Cruisers & Sailing Forums - BobH260's Album: Solar panel

Bob

[ramblinrod]

Originally Posted by Nicholson58

Your pannels will inevitabley be part shaded. If you wire in series you will loose a lot. Panels shoud be purchased if possible with multiple diodes internal to bypass partially shades parts of a panel. Panels in parallel will need diodes if they are not already so equipped. Only if you can guarantee no partial shading should you wire in series.

I found that I cold buy 2-pole breakers on Amazon that would double as switches. This eliminates fuses and switches. Each panel has its own 2-pole breaker with wires run from each panel to the interior of the boat there the breakers are located. The panels are then combined on a large junction block into two high amp lines to the charge controller. The charge controller output has its own 2-pole breaker. The 2-pole breakers let us isolate all of the solar stuff in an electric storm or for work.

Why do you feel you need to "fuse and switch" a solar panel. I certainly would not recommend this. I can't think of a reason to switch off a solar panel nor any reason to include a current limiting device as they do this naturally.

[colemj]

I find numerous reasons to have a switch between our panels and our controller.

Mark

[pcmm]

thanks everyone for their input. For now I'm going to go with a 315 watt Mono eclipsail panel. with a 30amp epsolar 3210A mppt controller. that should get me going for under $600 including the mount (ladder frame type mount on top of my cast aluminum davits) I'll add another 250 watts worth ontop of the hard dodger I'm planning to build and connect those up to another 30amp controller. I'm going with the epsolar controllers partially because of cost, but also because of the feature set. they can be connected to software for monitoring and configuring. I'll do that from my laptop and reduce the number of displays I need to have. my victron BMV will give me the amps in/ out info that I need.

[travellerw]

Originally Posted by pcmm

thanks everyone for their input. For now I'm going to go with a 315 watt Mono eclipsail panel. with a 30amp epsolar 3210A mppt controller. that should get me going for under $600 including the mount (ladder frame type mount on top of my cast aluminum davits) I'll add another 250 watts worth ontop of the hard dodger I'm planning to build and connect those up to another 30amp controller. I'm going with the epsolar controllers partially because of cost, but also because of the feature set. they can be connected to software for monitoring and configuring. I'll do that from my laptop and reduce the number of displays I need to have. my victron BMV will give me the amps in/ out info that I need.

I did some quick poking around the specs, and it looks like the A series cannot have custom charging algorithms. Looks like you have 3 presets Gel, Sealed, Flooded. The BN series is completely adjustable for all charging actions (Boost, float, low, ect).

Might be a concern if you want to move to Li batteries in the future. Then again, you could just buy another controller since they are pretty cheap.

[socaldmax]

The other interesting thing I noticed is the max. PV wattage. Depending on which brand, the owner's manual stipulates a max. input wattage of either 520 or 540 watts. The math doesn't make sense.


540w/40A = 13.5v max charging voltage

if it does charge at the max. claimed voltage of 14.6V (which in some cases, is not high enough to fully charge some batteries) it's only putting out 37A max., assuming no cable or controller losses.

This series of controllers looks pretty interesting, low cost, high input voltage, "A" series has PC interface. If I bought one, I'd install it with around 600w of solar panels to try and get an actual 40A of output, considering we very rarely get the full rated output out of PV panels.

[pcmm]

Scaldmax, you make a number of good points. I probably won't ever go lithium for batteries just on cost. I'm planning on a bank of 6 or 8 golf cat batteries to arrive at 400ah of usable charge ( before 50% ). The A series is hard to beat, a 40amp controller for around $100. I'll probably go with a 40 pump model as there is no price difference between the 30 and 40, I figure with the 40. We should not have to worry about over driving the controller at all. I'll probably try a second 40amp when I do the dodger panels.