Installing serial solar panels

[Vladis]

Originally Posted by ramblinrod

This is the issue with putting panels in series.

What size of panels?

It is not recommended that MC4s be disconnected with current flowing, but it is no big deal for a couple hundred watts.

Even with a huge array, if one starts at the panel level, disconnecting MC4s as they work toward the controller, no issue.

What is the concern with shading a panel to reduce current?

In a series string, one just needs to shade one half of one cell of one panel to bring the current down to near zero.

Which is a major drawback to series connection.

Any shading on any cell of any panel in the string, and output drops to near zero.

Going above 50 Vdc increases risk of shock/electrocution hazard.

So why connect in series?

Saving money on lighter gauge cable only to spend it on other devices, with the shading issue, and shock hazard doesn't seem wise.

Hello,

I disagree that connecting the panels in series has the problems that you mention regarding shading. My understanding is explained here:

Vela-Navega - Solar Panels

Regards, Vladis

[Paul Elliott]

Originally Posted by Vladis

Hello,

I disagree that connecting the panels in series has the problems that you mention regarding shading. My understanding is explained here:

Vela-Navega - Solar Panels

Regards, Vladis

NOTE: Vladis' link discusses the shading effect when using panels having four internal bypass diodes.

Yes, the bypass diodes you show will mitigate the issue of panel shading in a series configuration. Unfortunately, not all panels have this number of bypass diodes. My older panels have one or two diodes, and so the voltage drop will be excessive.

With my admittedly poor top-of-the-dodger panel location, it's not unusual to have two of the three panels somewhat shaded. There's no way a series connection would work for me. With less severe shading and more distributed bypass diodes, a series connection may be appropriate.

[noelex 77]

Congratulations on what looks like an interesting blog, but I don't think your solar panel modelling is representative.

You have only considered a shadow that covers one string in one panel. Unfortunately mathematically modelling shading on solar panels is very complex. There are many shadow permutations. Some of these individual scenarios will favour series, and some will favour parallel connection. The one you have chosen is the option that most favours series connection. There are a few other errors such as including blocking diodes which are unnecessary.

To model this correctly you need to consider all the other shadow options and then have some idea of the chance of each of these options occurring. I don't think anyone has attempted this.

So we are left with experimental evidence and user reports. These strongly suggest parallel connection will produce more power than series connection on a shadow prone boat. It would be great to get some more data, but most installers are convinced (correctly in my view) that parallel connection is preferred for most boat installations if you want the most power.

[john61ct]

Yes, pretty much a consensus out there that series is not for shadowing situations.

[DotDun]

Modern solar panels equipped with diodes will produce like results whether connected in series or parallel.

[s/v Jedi]

Originally Posted by DotDun

Modern solar panels equipped with diodes will produce like results whether connected in series or parallel.

Exactly, how disappointing that so many still don't know this. Solar panels have bypass diodes for at least two decades. When a parallel panel gets half a cell shading, you loose the whole panel. Do the same with a series panel and you only lose 1/3rd of it's power, or 1/2 when you have a cheap one.

When you lose all power with half a cell shaded in series then your diodes have been blown and need to be replaced.

The best solution is a small MPPT regulator for each panel. Right after that is series connection

[ramblinrod]

Originally Posted by Vladis

Hello,

I disagree that connecting the panels in series has the problems that you mention regarding shading. My understanding is explained here:

Vela-Navega - Solar Panels

Regards, Vladis

I sell and install solar charging systems. This theoretical explanation does not match my experience in a real application. Series panels in shade don't work.
each de

[noelex 77]

Originally Posted by DotDun

Modern solar panels equipped with diodes will produce like results whether connected in series or parallel.

The number of bypass diodes fitted to modern panels has been tending to drop rather than increase. The primary role of the bypass diodes is to prevent local overheating of the cells and it seems modern cells are less prone to this problem. Hence the manufacturers can get away with fitting less. In addition, the wattage of the individual panels in a typical installation is now larger.

The result of this change is that the number of bypass diodes seen in a modern installation is now typically less, especially in terms of the number of bypass diodes per watt. Bypass diodes are particularly important when solar panels are wired in series, so this change makes modern installations more suited to parallel connection.

The solar installation on my last couple of yachts is an example. It is perhaps not typical as some of the Kyocera panels had a lot of bypass diodes, but it does show the trend. Both installations were the best I could fit at the time.

On my old boat we had 330w of Kyocera panels. There were 4 panels and each panel had 8 bypass diodes. So there was a total of 32 bypass diodes for 330w. The new yacht will have 1005w of Sunpower panels. There are three panels and each has 3 bypass diodes. So there is 9 bypass diodes for 1005w.

Both series and parallel connection of solar panels works. The difference between the two options is not enormous, but it is silly to connect the panels in a less efficient manner and have a reduced output, unless there very good reason (such as no room for the larger of diameter cables needed for parallel installation).

It would be nice to have more data on the difference between the options of series and parallel connection. While most favour parallel connection, there is not an absolute consensus (as this thread demonstrates).

It would also be helpful to quantify the difference between the two methods. Does wiring the panels the wrong way reduce the output on average by 5%, 10% or more? These are very basic questions and it is unfortunate that there are not more definitive answers.

[newhaul]

Originally Posted by noelex 77

).

It would be nice to have more data on the difference between the options of series and parallel connection. While most favour parallel connection, there is not an absolute consensus (as this thread demonstrates).

It would also be helpful to quantify the difference between the two methods. Does wiring the panels the wrong way reduce the output on average by 5%, 10% or more? These are very basic questions and it is unfortunate that there are not more definitive answers.

Yes it would be nice to have a definitive answer however that is not possible.
There are to many varia les with each installation. I can do identical installs on two boats and have different charging characteristics.

[john61ct]

I dunno from "series panels" vs "parallel panels", I thought we were talking about different ways of configuring wiring for multiple identical panels connecting to a single controller.

​Most modern panels come only with bypass diodes so if you want blocking diodes you will need to add them. Soldering them into the supply wire is not difficult.

​On this topic, I am looking for US retail suppliers of (or willing to ship in) gear using the new embedded "MPPT on each cell string" ICs from Maxim.

Jinko "Eagle MX" is one line, others mentioned on Maxim's site are Trinapeak, and "ET COM"?

Also Zerun SunLoam "turnkey junction-box solution" incorporates the Maxim chips, not sure how that would work away from the panel itself.

[pcmm]

I have to ask why are you running your panels in series? shading on one panel will knock out the output of ALL THREE panels! put a towel on one panel and check the resulting output, you'll be shocked!

[ramblinrod]

Originally Posted by pcmm

I have to ask why are you running your panels in series? shading on one panel will knock out the output of ALL THREE panels! put a towel on one panel and check the resulting output, you'll be shocked!

Actually, er, no he won't be. ;-)

[TeddyDiver]

Originally Posted by pcmm

I have to ask why are you running your panels in series? shading on one panel will knock out the output of ALL THREE panels! put a towel on one panel and check the resulting output, you'll be shocked!

This has been addressed in earlier posts but here we go again just becouse some people can't read.
Some panels will some panels don't. It depends if the panels have bypass diodes or not..

BR Teddy

[ramblinrod]

Originally Posted by s/v Jedi

Exactly, how disappointing that so many still don't know this. Solar panels have bypass diodes for at least two decades. When a parallel panel gets half a cell shading, you loose the whole panel. Do the same with a series panel and you only lose 1/3rd of it's power, or 1/2 when you have a cheap one.

When you lose all power with half a cell shaded in series then your diodes have been blown and need to be replaced.

The best solution is a small MPPT regulator for each panel. Right after that is series connection

Your statements are too definitive.

Not all solar panels have built in bypass diodes.

If not, one can install bypass diodes, but this may add components and complexity (waterproof junction boxes, connectors, diodes), that simply aren't needed when panels are connected in parallel.

Additionally, the higher the combined panel voltage, the more dangerous the array is, from a shock and electrocution standpoint.

A small MPPT controller per panel is not necessarily the "best" solution. While it may harness slightly more power than a single controller, again it adds complexity, connections, and likely more wire to keep them out of the elements.

You really need to tone down your definitive statements. Rarely is it possible to determine what is "best" for an application, without reviewing the boat design, desired layout, and user needs. I have yet to find a solution for anything that is best in all circumstances. If it every existed, there would be no alternative (at least for long).

[pcmm]

Originally Posted by s/v Jedi

Exactly, how disappointing that so many still don't know this. Solar panels have bypass diodes for at least two decades. When a parallel panel gets half a cell shading, you loose the whole panel. Do the same with a series panel and you only lose 1/3rd of it's power, or 1/2 when you have a cheap one.

When you lose all power with half a cell shaded in series then your diodes have been blown and need to be replaced.

The best solution is a small MPPT regulator for each panel. Right after that is series connection

Check out this video ( using brand name panels)

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

Series knocks out the whole output when shaded. Modern panels STILL don't often have bypass diodes that work as well as expected!