solar need some advice

[buddhadawg]

I currently have two brand new agm batteries powering the ac side of the panel on our island trader. currently set up to charge via generator only. I have flexible panels that I would like to add as a passive charging system for these batteries while we are on the hook. please advise the proper hook up and set up for me.. thanks bill

[Pete7]

Bill,

How big are the panels?

You will need an appropriate solar controller, the Victron range are used by many on the forum with good results. MPPT will have an advantage over PWM controllers for only a little increase in initial cost. The Victron Blue Solar will need a widget to connect to a PC or iPhone. The Smart Solar models have built in wifi, at a slight increase in cost. This is handy to connect to an iPhone so you can adjust the setting to match your battery type, essential for best performance. You can also monitor what is happening with the panels using the Victron App, which is simple to use.

https://www.victronenergy.com/solar-charge-controllers

You should include fuses or circuit breakers in the wiring and the wiring will need to be sized to match the the output of the panels and the MPPT to avoid excessive voltage drops. Connect to bus bars rather than directly to the battery terminals.

If the panels are close together then they can be wired either in series or parallel. Alternatively if they are in different locations which would make wiring together difficult then two solar controllers can be used and in practice they do play nicely together.

If you don't already have some form of battery monitoring widget Victron also do a variety so you can see at a glance what is happening to all the loads on board. Other makes include NASA BM1 (cheap) or Sterling rather more expensive.

I think you meant DC rather than AC in your first paragraph.

Pete

[buddhadawg]

hey pete7, ive got two panels flexible mount in the bimini they had been purchased before I bought the boat but never installed I believe the 100 watt each, I can install them either in parallel or series. I have two other panels and wind for charging the dc bank, also charges off the engine. so this would be a passive charging for the batteries to power the ac bus. only have refrig and whatever we plug in, plus potential water maker. for the ac power draw. sounds like diret to bus may make good sense.. bill

[Pete7]

The separate, parallel or in series really comes down to if you think one panel will be shaded more than occasionally. If parallel and one is shaded then the other will continue to work. However, in series and one shaded then greater losses.

Since they are closely mounted together suggest parallel them and use something like the Victron Smart Controller 75/15. However, just be aware that the Victron needs 5v over the battery voltage from the panels to start working so worth checking that.

https://www.victronenergy.com/upload...-100-15-EN.pdf

When you say ac bus, do you mean air conditioning bus or accessory bus or something else?

[StuM]

Originally Posted by Pete7

When you say ac bus, do you mean air conditioning bus or accessory bus or something else?

He's not very clear, but I got the impression he meant a bus supplying alternating current through an inverter.

"batteries to power the ac bus. only have refrig and whatever we plug in, plus potential water maker. for the ac power draw"

[KP44]

I used 3 flex panels last year as an experiment in solar power. I learned a few things.

If one flex panel is not working to capacity, it degrades all the others to its capacity. That is, all the panels to your controller are limited by the least panel.

The solution is to use one controller for each panel. This is especially relevant for flex panels because they often have problems. This works the same of one panels is shaded. So rather than one controller that is capable of 100 amps, I now have one controller for each solar panel.

And I shut off the system at dark. My panels were diode-protected from discharging the batteries at night. But the little volt meter / ammeter seemed to take a little power. So I shut off the system every night.

[mvweebles]

Originally Posted by KP44

I used 3 flex panels last year as an experiment in solar power. I learned a few things.

If one flex panel is not working to capacity, it degrades all the others to its capacity. That is, all the panels to your controller are limited by the least panel.

The solution is to use one controller for each panel. This is especially relevant for flex panels because they often have problems. This works the same of one panels is shaded. So rather than one controller that is capable of 100 amps, I now have one controller for each solar panel.

And I shut off the system at dark. My panels were diode-protected from discharging the batteries at night. But the little volt meter / ammeter seemed to take a little power. So I shut off the system every night.

If there is asymmetry in solar due to shading or different orientation, you can split the panels and combine in a combiner box, essentially switch the panels separately prior to running to the MPPT controller. It takes some engineering, but within the means of a decent shade tree mechanic with reasonable electrical skills and understanding of Ohms Law. Attached diagram is my system - 4x200W panels on an arched hard top so wanted to separate port pair from starboard pair. I used breakers to form the combiner box for a clean install into my DC panel, but there are off the shelf boxes with breakers available too.

[Uncle Bob]

Originally Posted by mvweebles

If there is asymmetry in solar due to shading or different orientation, you can split the panels and combine in a combiner box, essentially switch the panels separately prior to running to the MPPT controller. It takes some engineering, but within the means of a decent shade tree mechanic with reasonable electrical skills and understanding of Ohms Law. Attached diagram is my system - 4x200W panels on an arched hard top so wanted to separate port pair from starboard pair. I used breakers to form the combiner box for a clean install into my DC panel, but there are off the shelf boxes with breakers available too. Attachment 204877

I am unable to understand the reasoning behind the use of breakers on the panel wiring. I believe that panels have bypass diodes built into them to prevent one shaded panel in an array from drawing down another non shaded panel and controllers have a blocking diode to prevent back feeding at times of no panel output, so may I ask, why the breakers?

[mvweebles]

Originally Posted by Uncle Bob

I am unable to understand the reasoning behind the use of breakers on the panel wiring. I believe that panels have bypass diodes built into them to prevent one shaded panel in an array from drawing down another non shaded panel and controllers have a blocking diode to prevent back feeding at times of no panel output, so may I ask, why the breakers?

Diodes prevent reverse of current for safety reasons. But if you have panels that will be shaded, best to separate into separate strings for larger arrays or run parallel vs series for smaller arrays. String combiner box does just that and fuses the inputs. Just depends on how big and diverse your array is. My array is four 200w panels - voltage and current starts to get pretty serious - final output is 56A at 14V. Not sure what point to recommend controls such as breakers, but they can't be a bad thing.

[noelex 77]

Originally Posted by Uncle Bob

I am unable to understand the reasoning behind the use of breakers on the panel wiring.

In some solar installations fuses or breakers are needed on the solar side. The wires inside the solar panel are the concern. The internal wires are kept as small as possible to reduce the shading on the solar cells. Consequently these wires are only rated for just above the output of the panels.

Also some solar controllers require the power to be disconnected in a set sequence, often the solar side first so switches/breakers are required. This applies to the Victron controllers and I suspect is the primary reason in the diagram.

The general rule is that if you have three or more strings, then fuses/breakers on the solar side will be needed and these are obviously in addition to a fuse on the battery side. The reason behind this general rule is that a fault in a single string could force the current of the two other strings through the faulted string. The internal wires within the solar panel are not rated for this level of current. They would melt and become a fire hazard.

This is especially a concern when flexible solar panels are mounted on flammable materials such as dodger.

We need to dispel the myth that fuses/breakers on the solar side are never required. This advice is often repeated in forums. It is incorrect. Fortunately many marine installations are only one or two strings.

Fuses/breakers on the solar side are not always required, but solar systems on boats are becoming larger and more complex and the lack of correct fusing is becoming a concern.

Originally Posted by Uncle Bob

I believe that panels have bypass diodes built into them to prevent one shaded panel in an array from drawing down another non shaded panel and controllers have a blocking diode to prevent back feeding at times of no panel output, so may I ask, why the breakers?

As the name implies bypass diodes allow a panel, or series of cells to be bypassed. They do not prevent the output of one panel from feeding into another. This is the job of blocking diodes. These are not fitted to most solar panels. As you point out most controller have an electronic control that acts a blocking diode, but this is only for the total input. It does not prevent one solar panel discharging into another.

[SV Bacchus]

Originally Posted by Pete7

If the panels are close together then they can be wired either in series or parallel. Alternatively if they are in different locations which would make wiring together difficult then two solar controllers can be used and in practice they do play nicely together.

Pete

i have 2 LG 350 panels and I had 2 Victron controllers. Fought with them for a year, never could get them to play nice. One would constantly shut the other down by, I assume, telling the other the batts were charged. Wasn’t always the same unit, it seemed to depend on which got the most sun first.

Victron forums indicate this is a known problem and they may have a fix by 2020.

Pete, if you have a fix for it I wish we had spoken before I went back to a single controller. Although I gotta say the system is now pumping Amps into the batts like never before!

[Pete7]

Originally Posted by SV Bacchus

i have 2 LG 350 panels and I had 2 Victron controllers. Fought with them for a year, never could get them to play nice. One would constantly shut the other down by, I assume, telling the other the batts were charged. Wasn’t always the same unit, it seemed to depend on which got the most sun first.

Victron forums indicate this is a known problem and they may have a fix by 2020.

Pete, if you have a fix for it I wish we had spoken before I went back to a single controller. Although I gotta say the system is now pumping Amps into the batts like never before!

Ok, that's a bit odd. I have been running a Victron 75/15 and 75/10 with different panels but smaller than yours, for a while and they always seem to play together. Random checks during the day would show both working and producing what I expected. I did make sure both Victrons were running the same software version and it was up to date also identical charging settings.

The reason for two Victrons is one panel mounted on a stern arch and the other is either a small panel in front of the sprayhood or a portable 110w panel we move around the deck to point at the sun. Therefore two Victrons meant shorter simple wiring runs.

I have now decided to up the charging from a 150w panel to 300w or so. Victron 100/20 installed, just pondering which panel to buy. What do you think of the LG panels? they are towards the more expensive end of the market in the UK. How long have you had them and corrosion problems being mounted on a yacht?

Pete

[SV Bacchus]

Hey Pete,

Both my panels are mounted on the hardtop (catamaran) and I went with two controllers thinking i would be ahead of the game with boom shading. I was thinking one might be shaded and the other in full sun so two controllers would be better. Others have pointed out to me that is the purpose behind the MPPT and suggested one controller.

Panels, cable lengths etc. were all identical so that wasn't the problem. I'm not sure why I had problems but seemingly others have had some issues as it is talked about on their public forums.

I now have one controller and have noticed considerable difference in the output. I am quite happy now. The only difference in my setup, beside going from 2 to 1, is that the one controller is mounted much closer to the batteries than the two were before. That was probably a mistake on the initial install of the two controllers, they were too far away. The two were about 10 feet away and the single is now 3 feet.

The LG panels have been good, they are 14 months old and so far I see no signs of corrosion. I have been happy with them. At the time I bought them there was a special, not sure how or why, but I got them for about the same price as other offerings. The dealer had a stack of them and maybe he was running the special himself just to delete inventory.