Solar Panels and Controllers

[eMarineSystems]

These are all great recommendations from other members. Buying a high quality charge controller is an important consideration as lower quality ones tend to not last long and could be detrimental to batteries. Solar panels of the same rating will harvest in different amounts of energy (A-H) per day. Look at the cell technology in understand what you are purchasing. Unfortunately there is no standard rating for daily energy production on solar panels so you have to spend time doing the investigation. Also look at the frame size and construction of the fixed frame solar panel. Less expensive ones have flimsy frames and given they are to be mounted an arch, they will be exposed to flexing due to wind and sea conditions which could lead to early failure. I would also recommend wiring the panels in series to get the solar panel circuit voltage higher as this allows for more headroom for the MPPT to harvest the maximum amount of energy given environmental conditions. Install a disconnect DC rated switch between the solar panels and charge controller is also a good safety device.

[noelex 77]

Installing the most watts in the available space is the first and most important step. Solar panels are available in a multitude of sizes so some reasearch is needed to find the best option. High efficiency solar panels are smaller for the same wattage so these usually yield the best result. They also usually have slightly better performance watt for watt, but are also the most expensive.

Rigid panels are significantly more durable, reliable and longer lasting, but do not suit all mounting locations.

For solar controllers, generally a separate controller per panel will produce the most output on a boat. Tracking each panel individually allows the controller to adjust the input voltage to the optimum value for each panel. The shadows created by rigging, mast aerials, etc mean that often boat panels, even in a similar position and with the same orientation will experience different conditions with different power points. A single controller can only select a single power point. This is unlikely to be the best option for all panels.

You do need to be careful about the self consumption of multiple controllers, but there are some good low self consumption controllers available so this is rarely an issue with reasonable sized panels. Also be careful about selecting multiple poor quality controllers. Some of the cheaper models have very poor tracking, which will reduce the output. MPPT tracking can be designed and constructed in many ways, so don’t assume all MPPT controllers will have identical performance.

If multiple controllers are not practical, parallel connection is generally the next best option. Series connection generally produces the lowest yield on a boat (although this is often the easiest to install).

[Marathon1150]

Originally Posted by CassidyNZ

I’ve connected a separate controller to each panel. I based this on the belief that if one controller controls more than one panel and one of the panels gets shaded, performance of the whole array will be compromised. This is true for elements in one panel (3 elements in 20 get shaded, whole panel output reduces?) so why would it not be true for a multi-panel array?

Is that incorrect?

I'm quite hopeless at electrics but what you have done sounds logical. I was recently told by a local boat electrics specialist (Pacific Yacht Systems) that I could not attach flexible and rigid solar panels to the same controller. So in the future if I decide to add a flexible panel or two (if and when price declines and longevity/efficiency increase), I will add a second controller.

This video shows some interesting results regarding parallel vs series wiring. The producers are boat people wondering which would be best for their boat.

https://www.youtube.com/watch?v=1qD3mN8VotQ

[4kMike]

I have understood that shading does not effect much the output voltage of panels. So, if panels are working at abt similar voltages, you can connect them parallel to one controller. Different panel currents are added together and any additional controller can not create somewhere more power than that. (P=U*I where U is constant output voltage)

[Uncle Bob]

Originally Posted by 4kMike

I have understood that shading does not effect much the output voltage of panels. So, if panels are working at abt similar voltages, you can connect them parallel to one controller. Different panel currents are added together and any additional controller can not create somewhere more power than that. (P=U*I where U is constant output voltage)

https://youtu.be/QzzB1i1w_kM
Voltage may not change that much but amps are severely reduced.

[noelex 77]

Originally Posted by Marathon1150

I'm quite hopeless at electrics but what you have done sounds logical. I was recently told by a local boat electrics specialist (Pacific Yacht Systems) that I could not attach flexible and rigid solar panels to the same controller. So in the future if I decide to add a flexible panel or two (if and when price declines and longevity/efficiency increase), I will add a second controller.

I think you probably misunderstood their advice (or it was wrong). Multiple solar panels should only be connected to one controller in parallel if the Vmp is the same (within 0.5v or better). Ideally the voltage temperature coefficient should also be identical and the panels should receive similar cooling. Finally, the closer the solar conditions are, the better.

So rather than a problem using a single controller for flexible and rigid panels, it is more a problem related to different panel specifications. I suspect your rigid and flexible panels had different voltage characteristics, hence the advice. While these different characteristics are not uncommon, it not a universal rule that flexible and rigid panels cannot be mixed.

[noelex 77]

Originally Posted by 4kMike

I have understood that shading does not effect much the output voltage of panels. So, if panels are working at abt similar voltages, you can connect them parallel to one controller. Different panel currents are added together and any additional controller can not create somewhere more power than that. (P=U*I where U is constant output voltage)

This depends on if you are considering diffuse general shadows or small patches of hard shadows, but what you say is reasonable. Solar panels maintain a similar voltage (but not current) in different conditions. This is why parallel connection to a single controller works satisfactorily.

However, with multiple solar panels at different voltages connected to one solar controller, the controller is forced to select the lowest voltage of all the panels (or very close to the lowest voltage) unless the output of the lower voltage panel or panels can be disregarded completely. This is because if the input voltage the solar controller selects is even slightly above the panel Vmp, the current output is very small.

Thus the whole solar array connected to a single controller is forced to operate at the voltage of the lowest panel.

Therefore, even a small difference in voltage from one panel will result in drop in output from all the connected panels in many circumstances. Multiple solar controllers prevent this happening, but the gains while useful are not dramatic because as you point out, the voltage differences are not dramatic.

With the availability of good quality inexpensive small solar controllers with low parasitic consumption, using multiple solar controllers is worth considering. The total output will be (slightly) greater and the system has valuable redundancy. The extra cost of this option depends upon the specifics of the system, but often this difference is quite small. The wiring is more complex, but as thinner more flexible cable can be used, often the extra difficulty and wiring cost is also only slight.

[CaptainRivet]

Originally Posted by lifeofreilly57

We're adding solar to our boat this year which will be mounted to an arch.
I've decided on rigid panels so 8 can get the max watts for our application.
If you had your druthers whose panels would you buy? Why? What's your experience with them?
Same goes for controllers.
We're currently in the Caribbean but are looking to get to the Pacific in the future.

First it’s a question what you can buy or get shipped...wanted below, the only panel I could get to canaries was the LG 355W neon 2. Doing very good but the bifacials would be 100W more on the same Surface...

Panel:
Best ridget panel for reasonable money are LG and then BenQ...it’s starts with the rigidity of the frame and continuous...till 12 bars to connect the cells. It’s the partly shaded performance, the low light performance and the degregation over the years which separates a cheap from a good Panel.....
My recommendation would be lg neon 2 bifacial panels in the size you can fit.

MPPT Controller:

Victron Smart MPPT, nothing else...and if possible one big one for all panels. Created 1/3 more output then the 3 MPPT what I had before. If you have more then one controller they interfere with each other and be able to cook your bank...each was limited to 14.6V overvoltage but due to interfering they reached 20V on my battery monitor without going into overvoltage...

victron, as far as I know, the only one you can join your controller into a Bluetooth network and talking to each to eliminate this interference. I run 2 Victron 50A/100V connected via Bluetooth. this because the solar array 1 with LG ridget panels runs on 38-40V and Array 2 with semiflexible panels on around 18V. This on one controller would interfere too much and lower the performance significantly.

[CaptainRivet]

Originally Posted by noelex 77

This depends on if you are considering diffuse general shadows or small patches of hard shadows, but what you say is reasonable. Solar panels maintain a similar voltage (but not current) in different conditions. This is why parallel connection to a single controller works satisfactorily.

However, with multiple solar panels at different voltages connected to one solar controller, the controller is forced to select the lowest voltage of all the panels (or very close to the lowest voltage) unless the output of the lower voltage panel or panels can be disregarded completely. This is because if the input voltage the solar controller selects is even slightly above the panel Vmp, the current output is very small.

Thus the whole solar array connected to a single controller is forced to operate at the voltage of the lowest panel.

Therefore, even a small difference in voltage from one panel will result in drop in output from all the connected panels in many circumstances. Multiple solar controllers prevent this happening, but the gains while useful are not dramatic because as you point out, the voltage differences are not dramatic.

With the availability of good quality inexpensive small solar controllers with low parasitic consumption, using multiple solar controllers is worth considering. The total output will be (slightly) greater and the system has valuable redundancy. The extra cost of this option depends upon the specifics of the system, but often this difference is quite small. The wiring is more complex, but as thinner more flexible cable can be used, often the extra difficulty and wiring cost is also only slight.

But several controllers interfere with each other...I had this problem and nearly destroyed my bank, see post above. It only cured when I got 2 Victron Smart MPPT connected via Bluetooth.

2nd MPPT means multi point power tracking so not 1 point with the lowest voltage panel is tracked. Victron definitely has a very good multipoint tracking...have different flexible panels from 14V till 20V on one Victron which shows 18V input in average and it raised the output significantly compared to 2 MPPT connected before (one the solar part of the SilentWind controller, the worst MPPT...)

[noelex 77]

Originally Posted by CaptainRivet

If you have more then one controller they interfere with each other and be able to cook your bank...each was limited to 14.6V overvoltage but due to interfering they reached 20V on my battery monitor without going into overvoltage...

There are some minor conflicts caused by using multiple solar controllers, but the effect is minimal. The popular Victon Smartsolar controllers (and some other brands) can be synchronised to eliminate these issues.

It is not likely your 20v battery voltage was caused by any conflict. If both controllers are programmed to stop the charging at 14.6v, this is what they will do (if functioning correctly) whether you have one controller or many. This is not dependent on syncronisationation.

[CaptainRivet]

Originally Posted by barnakiel

I would buy again Victron panels and controllers.


One catch: do not wire 12V panels into 12V bats. Wire panels up to get well above the voltage of the batteries. This is due to Victron mppt controlers kicking up only when there is a sound V difference at start up (mornings). Not mentioned in bold print on the facts sheets.



Other than this 24V / 12V trick, fabulous kit - and works as advertised (at least 15% gain over our PWN kit).


BTW buying 24V panels makes big sense if your batts are 12V. You can get more W per $ this way too.



b.

Victron panels are so la la, controllers are fantastic...
Just replaced 6x 110W victron 3 years old with 3 LG 245W neon 2 panels on a friends boat, output is nearly doubled amps out on the same surface of the victron MPPT 50/100...
The Victron panels run on 19V while lg on 32V....less loss in the 10m cables too...

[Elcid]

What about SunPower SPR-MAX3-400 when compared to the LG Neon 2 Bifacial LG400?
It looks like it’s quite a bit smaller at 1690 mm vs 2064 width (and same height).

[Dsanduril]

Originally Posted by Elcid

What about SunPower SPR-MAX3-400 when compared to the LG Neon 2 Bifacial LG400?
It looks like it’s quite a bit smaller at 1690 mm vs 2064 width (and same height).

Sunpower is still the king in the power per square meter area. MAX3-400 has a module efficiency about 22.6% while the NEON2 is 19.3%. Doesn't sound like a lot, but that's a 17% difference in the amount of power you get from the same area.

To get close/competitive with the Sunpower panels you need to move up to the LG NEON-R series. Their 370W is just slightly smaller than the SPR MAX3-400 and with a module efficiency of 21.4% you're only losing about 5%. The all backside contacts, like Sunpower's, help with lower light production.

The NEONs are 60-cell/40V vs. 104-cell/65V, which means cables are smaller with the Sunpower. Sunpower guarantees 92% at 25 years, NEON-R 90.8%, NEON-2 Bifacial 95.9% (all of which mostly do not apply to boat installations, but it gives you an idea what the manufacturer expects in the way of light induced degradation).

All-in I'd compare the R with the SPR more than the bifacial. They're all decent and above the average crop so it might come down to cost, availability, and specific fit on your boat.

[CaptainRivet]

The LG neon 2 bifacial has 390W Front and 120W back, so in total 510W while sunpower only 400W front. On davits the bifacial work well.
LG also has a better low light perfomance and due to the 12 bus bars partial shade on the panel only takes the row down which is shaded, the other rows deliver full power. Additional they deliver on lower sun angles to the panel. I have 2 LGs on my davits and they perform really well.
So i would prefer LG over sun power, max performance per sqm is not all.

[CaptainRivet]

Originally Posted by noelex 77

There are some minor conflicts caused by using multiple solar controllers, but the effect is minimal. The popular Victon Smartsolar controllers (and some other brands) can be synchronised to eliminate these issues.

It is not likely your 20v battery voltage was caused by any conflict. If both controllers are programmed to stop the charging at 14.6v, this is what they will do (if functioning correctly) whether you have one controller or many. This is not dependent on syncronisationation.

But they did interfere, i could reproduce it.
It were the integrated solar charger from the silentwind wind gen controller and one victron MPPT 50/100.
Swaping to 2 victron MPPT 50/100 connected via VE-bus and synchronization solved it.