Fitting extra panel

Ian G · Senior Member

Fitting extra panel

Peter_n_Margaret · Guru

First questions are what are the specifications of each panel, how many cells does each have and what is their physical size?
Cheers,
Peter

Whenarewethere · Guru

You are missing the point of MPPT to get the best out of a quality system. You really should have 2 panels (the same) in series to get the early & late sun.

My setup & a lot of testing & a bit of discussion on diodes at the end.

https://thegreynomads.activeboard.com/t65231112/custom-6x20-watts-solar-setup-with-mppt/

Jaahn · Guru

Whenarewethere wrote:
You are missing the point of MPPT to get the best out of a quality system. You really should have 2 panels (the same) in series to get the early & late sun.
etc etc

----------------------------------------------------------------------------------------------

Hi smile

Really YOU are missing the point of Ian's questions. He did not ask how to get the best out of a quality system. He did ask about adding a 200 w panel in parallel and changing controller to Victron MPPT 30 amp and also Do I assume it has blocking diodes fitted or put 1 in to be sure.

Possibly people should try to answer the questions asked directly rather than show how to redesign it in their perceived ideas. Might save some off the point discussion.

My answer is this Ian. If the two panels are of similar voltage output at full power MPV, then they will will work OK in parallel into that controller. If they are both 36 cell panels that is probably good enough. Count the cells by looking at them. It may not be an optimum setup but !! hmm

The diode is a bit tricky. You could possibly measure that but I would have to think about that. You certainly can fit one in the connections or the terminal box or similar. Just put one in the positive lead so it blocks on reverse voltage,(either lead is OK) I suggest a 50V 15 Amp schottky diode and buy a couple, at Jaycar or ebay or ? cheap as chips. It will cause a small voltage drop if it was not necessary but could save the panel in a bad solar situation if it was needed. wink I guess the other new panel has one.

Jaahn

-- Edited by Jaahn on Thursday 3rd of December 2020 03:34:32 PM

Whenarewethere · Guru

Whenarewethere wrote:
My setup & a lot of testing & a bit of discussion on diodes at the end.

'a bit of discussion on diodes'

Ian G · Senior Member

Thanks for the replies
Peter the physical size of my panels are 1500 x 680 for the 200 w, 19.8 v x 10.4 amp, and 1200 x 800 for the 140 w panel, both 36 cell panels, I don't have any voltage or amp details of the 140 w panel as I said it is fixed to my roof and I don't want remove it and remount it as it is working fine but I assume it will be a similar voltage with less amps.

Thanks Whenarewethere, but I already have the panel and controller so I am past the design stage, I decided to go parallel from discussions I have read on this forum, plus as I want to use the existing 140 w panel and don't know all the details of it, so adding another larger panel seems like a no brainer.
Thanks Jaahn I will buy some schottky diodes and put 1 in my positive feed from the 140 w panel, you say this is not the optimum setup , how could I have done it better ?

Thanks Ian

Peter_n_Margaret · Guru

Just some rough checks before we get to the detail.
1200 x 800 = 0.96M2 x 150W/M2 = 144W. That is about right for a 140W panel.
1500 x 680 = 1.02M2 x 150W/M2 = 153W. mmmmm Maybe it is a REALY good expensive high efficiency panel? X 180W/M2 = 183W.
So the first conclusion is that the new panel is VERY unlikely to be 200W.

The fact that they are both 36 cells is a good sign, but they may still be different and that difference will mean a less than optimum outcome.
It would be worthwhile going to some effort to get the details of the old panel.

That difference in the panels could be overcome by having them both on different small controllers.
You could retain the old panel exactly as it is and buy a small controller for the new panel.
What is the old controller?
Cheers,
Peter

Whenarewethere · Guru

The actual solar cell area on my solar panels cover 72.7% of the overall panel (it is a small panel so it will be more wasteful of dead space).

The efficiency of the actual cells is 155W/m².

The efficiency of the panel's overall area is 113W/m².

Ian G · Senior Member

Hi Peter
The controller with the 140 w panel doesn't have a brand on it but it is PWM. the new 200 w panel is Alvolta [not as cheap as most ], I ordered Victron 160 w but they were out of stock and this was offered as an alternative. I am not fussed if it is over rated as I will have plenty of solar, I also have a 200 w portable which has it's own controller. I didn't realize it would be this complicated, I thought it was not an issue to install dissimilar panels in parallel, opposed to series. I already have the 30 amp Victron controller and don't really have room to keep the original, I went for 30 amp so I could add another panel in the future if I wanted to fit a compressor fridge. I am not prepared to to remove the 140 w panel as I would have to re mount it and it is working fine

Thanks Ian

Peter_n_Margaret · Guru

Then just go for it Ian.
The Victron is a good controller.
The 2 panels being different may mean you don't get the max possible charging, but I expect it will work OK.
Good luck and let us know how it goes.
Cheers,
Peter

Ian G · Senior Member

Thanks Peter So should I put a diode on the input from the 140 as a precaution ?

Peter_n_Margaret · Guru

Won't hurt.
Cheers,
Peter

Jaahn · Guru

Peter_n_Margaret wrote:
Then just go for it Ian.
The Victron is a good controller.
The 2 panels being different may mean you don't get the max possible charging, but I expect it will work OK.
Good luck and let us know how it goes.
Cheers,
Peter

Hi Ian smile

I agree with this too, and fit the diode. It will work OK and be good.

Make sure you use generous sized wiring to reduce the voltage drops. That is just wasting power. Actually the Victron will track the Power point for two panels if they are a bit different and work the two points ?? They are the best IMHO. wink

You asked "you say this is not the optimum setup , how could I have done it better ?" Well of course starting from a different point and selecting the best item that are matched would be best as was pointed out. smile But life is not always as easy as that. I have used mismatched panels for years when they were expensive, while camping and they all worked OK. Now-a-days I try to get a more planned matched system.

Good luck jaahn

Get a multi meter and use it to check the system is performing well.

"

Ian G · Senior Member

I will be running 8mm cable, it is approx a 9 metre run. Thanks to all for your help

Ian

Whenarewethere · Guru

8mm² is ok. I have used 6awg on my 120w setup but was keen to get every last drop. Actually use a 4awg cable to the panels as it doubles up at my compressor lead.

If you want to change the length or amps just multiply the Loss or Voltage by that factor.

Aus-Kiwi · Guru

I have various sized panels . 3 batches . All in parallel !! Through this reg . By 10AM most days its on trickle charge . Green light flashing .

-- Edited by Aus-Kiwi on Sunday 6th of December 2020 02:21:43 PM

Yes Dear · Newbie

Hi,
I'm in a similar situation.
Just picked up a 2020 jayco journey outback pop top.
It has a 160 w panel on the roof for a single 100 AH battery.
This is great if the place we are at is in ful sun but we are often in places that are shady throughout the day nd I would like to add a movable panel for these locations.
I have a spare 140 w panel with 10 meter cable and built in MPPT reg from the old camper trailer.
I was just going to add a new Anderson plug and lead to the battery and mount on A frame.
But from reading above I have concerens that it is not the correct way to go.
Jayco have the JHUB thingy and i don't want to screw that up.
any advise would be greatly appreciated.

Ian G · Senior Member

Hi Jamie Most people would assume this post has ended, so you would be better to start another post, then Peter, Jaahn and others will set you on the right track. Though what you are doing is fine, if your portable panel has it's own controller then just hook it up via an anderson plug to your batteries, I do this. My post was regarding joining 2 different panels permanently to the one controller. Ian

Jaahn · Guru

Yes Dear wrote:
Hi,
I'm in a similar situation.
Just picked up a 2020 jayco journey outback pop top.
It has a 160 w panel on the roof for a single 100 AH battery.
This is great if the place we are at is in ful sun but we are often in places that are shady throughout the day nd I would like to add a movable panel for these locations.
I have a spare 140 w panel with 10 meter cable and built in MPPT reg from the old camper trailer.
I was just going to add a new Anderson plug and lead to the battery and mount on A frame.
But from reading above I have concerens that it is not the correct way to go.
Jayco have the JHUB thingy and i don't want to screw that up.
any advise would be greatly appreciated.

Hi Yes Dear ? smile

I would just do what you planned. If you put the new power directly to the battery from its controller that will avoid any conflicts. The two controller will handle the problems and it may not be optimum but works OK most times.

A movable panel is a handy thing to have in shady places, or if the sun is soo hot you decide to park in the shade anyway. wink

Jaahn