Mixing Solar panels

[xsilvergs]

I have two Renogy 50W monocrystalline solar panels in series on a Victron MPPT solar controller. On the trailer I have two Photonic Universe 150W xxxcrystalline solar panels in series which I put into the same solar controller when I take the trailer, for more solar power. The trailer panels tilt where the 50W ones don't.

I know these panels have different characteristics but I've never tried to work out whether any power is lost into one pair of panels should there be any shading or just because they are different.

So I bought a pair of these https://ebay.us/4TwlwQ in 40 Amp flavour and will try them. There is a pair of diodes in each device which I'll parallel just to give some redundancy. I will fit one device in the positive lead from each panel set. Schottky diodes have a low Vf drop (about 0.3v) and as the series panels give about 36v the loss should be negligible.

I will try and look for any gains in output.

Has anyone else looked into using Blocking diodes (NOT by-pass diodes)?

 

[wildebus]

how do you connect? all in parallel? series? or a mix?

 

[xsilvergs]

how do you connect? all in parallel? series? or a mix?

Something like this:

 

[PeteS]

I fitted some to my two panels that I have in paralell, the main reason being to stop one panel from dragging the other down if short circuit. The bypass diodes only really benefit series connected panels as in your case.
I've always had my blocking diodes in place and can happily get 90-95% of rated output. Theyve been there since 2012 so I dont think youll notice any diffeence.
In your case above would the 2 50W panels actually contribute anything as I'm guessing the voltage output would be lower so would possibly sink current so I think the diodes are essential but I guess the bypass diodes would help with that

 

[wildebus]

I think how important or necessary it is to add blocking diodes depends on what is fitted within the panel as standard?

As far as mixing panels goes, the basic rule of thumb is in parallel the voltage reverts to the lowest in the set and the current adds together; and in series, the current reverts to the lowest in the string and the voltage adds together.

It was on this principle I added 2 30W panels to an existing 4 x 100W setup. connected 2 x 100W and 1 x 30W as a parallel set (the voltages were near identical between the 100W and the 30W), repeated for the other 2 x 100W and 1 x 30W to make an indentical 2nd parallel set. Then connected the two sets up in series to connect to the controller.
There wasn't a massive benefit in adding the 2 x 30W panels - I just happened to 1) - have them kicking around; 2) had some in-fill space on the roof; and 3) fancied trying a mix-up to play with

If I had connected the 2 x 100W panels and the 1 x 30W panel in series, I think I would have ended up with effectively a 90W panel, which would not have been much of an upgrade


With two identical panels, I almost always favour paralleling them as the potential downside of shading is a lot bigger than the potential upside of a great voltage (IMO). If you only ever park in open areas where you will never have shadow cast, then maybe then series could be the better option.

 

[Sprinter 1 cup]

What is the output in anps on the 50w pannles? I've just seen youtuber says if fitted wrong they are cancelled out.
Or the lower / smaller pannles are the dominant amps used. So not worth fitting

At that size the 50w can't have much voltage.amps so sell and buy 3rd 8amp if your solar controller can handle all wattage

But fit them if your full timeing .

16 amps will charge usage up by midday on my van!

 

[xsilvergs]

I've just seen youtuber says if fitted wrong they are cancelled out.

I guess anything fitted 'wrong' could have a negative effect.

Fitting something correctly could have a positive effect.

You only have to look at Gadget John's YouTube channel, who many follow, to realise how much misinformation is on YouTube.

 

[Sprinter 1 cup]

You only have to look at Gadget John's YouTube channel, who many follow, to realise how much misinformation is on YouTube.
[/QUOTE]

Yes yes, but, No!.

What's Your 50w pv output ?? In summer. In amps please!
As they are not fitted maybe a pic of the back description plate maybe.

Tia

 

[xsilvergs]

You only have to look at Gadget John's YouTube channel, who many follow, to realise how much misinformation is on YouTube.

Yes yes, but, No!.

What's Your 50w pv output ?? In summer. In amps please!
As they are not fitted maybe a pic of the back description plate maybe.

Tia
[/QUOTE]

50 Watt 12 Volt Monocrystalline Small Solar Panels

Renogy 50 watt home solar panel is perfect for all adventures including dry camping and marine activities. This panel can withstand extreme weather elements.

uk.renogy.com

I have two in series so voltage will be double, current the same.

 

[HarryW]

I’m assuming your 50w panels are 18.3v and 2.9A and you PU 150w panels are 20.2v and 7.43A.

The 50w pair in series would be 36.6v @2.9A.
The 150 pair would be 40.4v @7.43A.

in parallel together it would be 36.6v x 10.33A = 378w

Therefore by my reckoning with that series parallel configuration your maximum output will theoretically be 378w so only a 5.5% drop on the 400w available.
If they were more wildly dissimilar then it would be a matter of feeding each leg via separate solar controllers.

 

[xsilvergs]

I’m assuming your 50w panels are 18.3v and 2.9A and you PU 150w panels are 20.2v and 7.43A.

The 50w pair in series would be 36.6v @2.9A.
The 150 pair would be 40.4v @7.43A.

in parallel together it would be 36.6v x 10.33A = 378w

Therefore by my reckoning with that series parallel configuration your maximum output will theoretically be 378w so only a 5.5% drop on the 400w available.
If they were more wildly dissimilar then it would be a matter of feeding each leg via separate solar controllers.

The figures you quote sound good.

Look on the black side and things can only get better, is my moto. Add a bit of shading to one panel and the terminal voltage of that pair will drop.

Bypass diodes within the panels allow the now limited current to flow but we now have one pair of panels at ~20v in parallel with a source of a lot less.

How much load does this low voltage source put on the high voltage source?

 

[SquirrellCook]

The figures you quote sound good.

Look on the black side and things can only get better, is my moto. Add a bit of shading to one panel and the terminal voltage of that pair will drop.

Bypass diodes within the panels allow the now limited current to flow but we now have one pair of panels at ~20v in parallel with a source of a lot less.

How much load does this low voltage source put on the high voltage source?

Because of any potential worries, I put a Mppt on each strings of panels. I even have a spare Mppt for future portable panels.


Violating a Princess! | Page 10 | Motorhome Builder

 

[xsilvergs]

Because of any potential worries, I put a Mppt on each strings of panels. I even have a spare Mppt for future portable panels.


Violating a Princess! | Page 10 | Motorhome Builder

I have two Victron 100/30 SmartSolars in the van, one only has the two 50 watt panels so loads of capacity left.

Interesting to hear what others do and why.

 

[wildebus]

I have two Victron 100/30 SmartSolars in the van, one only has the two 50 watt panels so loads of capacity left.

Interesting to hear what others do and why.

The Victron Controllers talk to each other via the VE Smart Networking so the performance from the pair is optimized. I'd be inclined to use one controller for the van array and the other for the trailer array - maximise performance and also provide redundancy.

 

[xsilvergs]

The Victron Controllers talk to each other via the VE Smart Networking so the performance from the pair is optimized. I'd be inclined to use one controller for the van array and the other for the trailer array - maximise performance and also provide redundancy.

It would be far to easy to buy a third Victron MPPT (ouch) but I for one wouldn't have hard data on what load a shaded/different panel has on the system.

In an all parallel array, if one panel becomes shaded what effect does it have on the rest. Does shading on the most positive cell group of a panel differ from any of the others in that panel without a blocking diode?

I admit to being no expert in this field.

 

[HarryW]

To be honest I don’t understand the role of the blocking diode? A solar panel is like one big diode in itself, any back feed through it is going to be in the 10’s of mA at best (worse!).

A shaded panel, whilst not producing much in the way of power will during daylight hours still have a voltage near its operating level but with very low or non extant current flow (hence low power). This in turn, using your proposed array, would just mean the leg that is in the shade isn’t contributing much and the leg that is in the sun will produce power albeit reduced a bit by the voltage drop off being felt by the shaded side...

Well that’s how I see it....

 

[xsilvergs]

Today I did a quick test using a 120W Vechline solar panel and a DC power supply. The DC power supply was used to simulate a second solar panel.

This panel should have a Max Power voltage of 18.6V. I connected the DC Power Supply (PSU) to the solar panel as if they were in parallel, +ve to +ve, -ve to -ve with a DC Amp meter in the positive line. With this panel sat in the garage with no direct sunlight it did produce a small voltage.

With the PSU set at 18.6V the solar panel could sink ~26mA. This was to simulate two panels of the same type in parallel but shows a shaded panel can load the remaining panels.

Next the PSU was set to 19.5V, the solar panel could sink ~30mA. This test was trying to simulate a panel from a different manufacturer with different characteristics. The Victron Mono's I intend to fit are this higher voltage and so could be less efficient if they were mixed.

So fitting Blocking diodes in series with each panel in a parallel setup could reduce this loading through panel shading. This series diode would have a volt drop across it and contribute some loss of power.

 

[HarryW]

So that fits with what I put, it would drop a few tens of mA if one panel was shaded. How much is the drop across the diode again?

 

[xsilvergs]

So that fits with what I put, it would drop a few tens of mA if one panel was shaded. How much is the drop across the diode again?

Yes your values were very close. I do always like hard facts, @wildebus always gives graphs etc which I love as I've had to prove fact from instrumentation.

I will try more things when it warms up and when the sun shines for more than 2 minutes.

Regular silicone diode drops about 0.6 Vf, a Schottky drops about 0.3 Vf. Large (30A) silicone diodes are relatively cheap.

 

[HarryW]

Rough reckoning; the diodes will lose you about 4w all the time purely by the standing voltage drop and if you didn’t fit them you would save about 4w when one panel is shaded...