Where to start with solar. (1 Viewer)

[Em and Tim]

Hi all,
We are full timing off grid round Europe, and have a ?100?W? Panel in the roof (its second hand, so I'm guessing, based on the fact that it is 1.2m by 0.53m), feeding into the batteries by a pwm solar charge controller (a CMTP03 with 2 x 2.5mm cables from panel to controller, 2 x 4mm cables to the battery terminals). It has been great all summer, but now that the days are short, and the weather turned, and the heating is being used, we are needing more juice, and have decided to use the roof space (which already has a mount the same size as the panel) for additional solar. Are we best to just start again with a new system alongside the old one, or could we use the same controller and route additional panels to it, be they in line or parallel?

How much should we put up there?
Generally any other recommendations, because I keep getting bogged down in the detail, and confused.

Thanks in advance.

 

[HandyAndy]

the correct answers will depend on which model exactly
There is a 5a a 15a and a 20 amp model

It should be something like CMTP03-12XX where 12 is the voltage and XX is the amperage
I assume it's 12v as there are also 24v and 48v versions available...
but in truthfulness on how much should you put up there.. the answer is invariably......
As much as you can fit / afford to..

 

[two]

How much you need will depend on how you use the vehicle. It's a difficult balancing act and will depend on your battery capacity, also. I get by without any, to keep the weight down, but have used panels on previous vehicles with a bigger payload. When the sun is low, you start to fight a losing battle - and it's also the time of year when you need more power.
We move frequently or stop where we can get EHU. You may find that the cost of more solar would buy many nights on hook-up. Consider a better battery bank, perhaps? If I was adding a second panel, I'd go for a completely separate installation (new controller) alongside the old one.

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[Richard n Ann]

If you tilt your existing panel up on hinges facing the sun you will get about the same output from it as you did in the summer, albeit for less time. So 2 x 100w tilting will be enough, probably ?

 

[Abacist]

You should consider a battery to battery charger like a Sterling. This fools your alternator into thinking that your cab battery needs charging but it is routed through to charge your cab batteries whilst you are driving around. Ideal for all year round use but especially good when the days are short and the sun is low making solar ineffective. Certainly worth checking them out. I have a 25amp hour Sterling but 50amp hour B2B chargers are now available.

 

[Lenny HB]

Depends where you are spending the winter months. If Spain can just about get away with 300 watts places with less sun probably going to need at least 600 watts.
Fit a decent MPPT regulator like a Votronic, marked difference in output on dull days. And as Abacist says fit a BtoB.

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[stevec]

I'd look at cable sizes too. I used 6mm all round. But had longish cable runs. Also how old is the second hand panel. They drop in efficiency as the years go by (25% less after 10years?). Would second the MPPT controller.

 

[Em and Tim]

the correct answers will depend on which model exactly
There is a 5a a 15a and a 20 amp model

It should be something like CMTP03-12XX where 12 is the voltage and XX is the amperage
I assume it's 12v as there are also 24v and 48v versions available...
but in truthfulness on how much should you put up there.. the answer is invariably......
As much as you can fit / afford to..

I have finally emptied the cupboard to check, it's a 2410 model, which confuses me somewhat...

As we are in Spain at the moment, I wonder if it will be cheaper to buy panels down here, or wait till we are back in the UK, does anyone know of good Spanish solar suppliers?

 

[HandyAndy]

24 = 24volts (but it can still do 12v)
10 = 10 amp
Nothing confusing about that.
So you can have a maximum of 10 amps output with that controller
The upper voltage limit (from the panels) is unknown it seems..
but pretty immaterial as if you are thinking of connecting more than two 100w panels together you are going to be over 10 amps anyway and this will be in the bin

Yes toosolar.it

Woops that's italy not spain hahahaha oh well, only a short drive LOL

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[Em and Tim]

Ok, that's great, thanks Andy.

So, I am looking at some big panels at a good price in Spain, is there any advantage to say 1x300w panel as opposed to 3x100w panels. Does a maximum voltage of say 39v mean a more expensive controller, or are we better to stick to panels with a 12 or 24 voltage?

 

[autorouter]

So, I am looking at some big panels at a good price in Spain, is there any advantage to say 1x300w panel as opposed to 3x100w panels. Does a maximum voltage of say 39v mean a more expensive controller, or are we better to stick to panels with a 12 or 24 voltage?

For a motorhome, the problem is often what will fit on the roof, and not be shaded by the satellite dish etc. A single 300 watt panel is better if it will fit, but if three separate panels are required it's no great disadvantage.

Once you have over 100 watts of panel, you have to think about wire thickness. For 300 watts, the current could be 8 amps at 36 volts, but 24 amps at 12 volts.

My opinion is a good MPPT controller with proper smart charging, and charging profiles for different battery types, is worthwhile. These controllers will handle 12V, 36V and usually much higher voltages if required.

 

[HandyAndy]

?☝? what he said!

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[Em and Tim]

Something else, is there a difference between a solar panel, a solar board or a solar plate? I think ut may be translation, but wanted to check!

 

[Em and Tim]

WILL THIS WORK?

I may start a new thread with this question, but thought I would ask here, so as to not jam up the forum with more threads.

I have now measured space, and found suitable dealers and looked at the panels they have that will fit, and asked the boss for a budget, and have come to this array as the conclusion. I was expecting to wire it all in parallel, but the two sizes of panels I have proposed are different voltages, so was unsure how the Regulator would deal with that. The technician at the Spanish solar dealer (the sales person took the query, and emailed me back after checking with a technician) came back with the following proposal:

In relation to your question, here it is our technician recommendation:

1 Solar panel 400wp JINKO SOLAR
2 Solar panels 150wp SCL
1 Victron Blue Solar MPPT regulator 100/50


The regulator features confirm that it can support up to 700wp in 12v, so, the combination you’ve proposed is ok (see attached the regulator datasheet file).

The connection of the whole system to run properly, please see the scheme below

<Broken link removed>

Meaning, 400wp solar panel wired in parallel and 150wp solar panels wired in series

The price of these 3 products is 718,80€ (VAT included)

BACK TO ME
So, this leaves me confused, with what I believe to be a 48v 400w panel running into two 12v 150w Panels. Then on into the controller. If panels are wired as parallel, I thought that meant wires from each panel going to the regulator. I am now guessing that I am mistaken in that belief.

So, how do different voltage panels get wired up to work together of the same regulator? Does that set up look like a good one (we are full timing, and want it to work when it is cold and grey, so we want to maximise our yield up there) or would I be better sticking with 4 of the 150w panels (which are poly, the 400w is mono)?

I feel like they must know what they are talking about, but really didn't expect the answer to be half parallel and half in series!

 

[DBK]

I can't see the wiring diagram but I guess the two 150W panels are wired in series and then this combination is wired in parallel with the 400W panel. Assuming the voltages match this will work fine. By matching voltages I mean the open circuit voltage of the 400 is twice that of each150.

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[Em and Tim]

PS, this involves taking an Oyster Satellite dish that we never use off the roof. Would it be worth posting on here as for sale? We have never even tried to use it, but I believe it works.

 

[Em and Tim]

I can't see the wiring diagram but I guess the two 150W panels are wired in series and then this combination is wired in parallel with the 400W panel. Assuming the voltages match this will work fine. By matching voltages I mean the open circuit voltage of the 400 is twice that of each150.

Just realised and added it as an attachment.

Open circuit voltages are 22.6v for the 150w panels, 49.8v for the 400W panel, so close to it.

 

[Silver-Fox]

Try the dish to make sure it works then put it up for sale.

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[Em and Tim]

Try the dish to make sure it works then put it up for sale.

Any idea what it is worth? The dish is about 0.85m by 0.9m, and has a control unit that tracks it to the correct orientation.

 

[autorouter]

Who did that diagram? The 400 watt panel is shorted by the link between the two 150 watt panels. The 400W panel's wires should be to the other terminals of the 150W panels.

 

[Em and Tim]

Who did that diagram? The 400 watt panel is shorted by the link between the two 150 watt panels. The 400W panel's wires should be to the other terminals of the 150W panels.

That was one of the bits which doesn't make sense to me, it came from the technician at a firm called Tecnosol, who I was planning to buy from. My thoughts were to run each different spec panel to the regulator, but I'm not sure if a regulator can cope with more than one input. Once again, the more I understand the more confused I seem to be able to get!

So, How should you wire up 2 x 12v 150w panels, and 1 x 48v 400w panel? Can it all go to the same regulator? would I need two separate regulators for this?

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[autorouter]

Regulator positive to 400W positive and the positive of first 150W.
Regulator negative to 400W negative and the negative of second 150W.
Link the negative of first 150W to positive of second 150W.

 

[Silver-Fox]

Any idea what it is worth? The dish is about 0.85m by 0.9m, and has a control unit that tracks it to the correct orientation.

Not a clue I’m afraid but anything is good if it’s coming off ?

 

[HandyAndy]

The victron regulator can handle up to 100 volts on the input so as long as however you wire the panels, you don't exceed 100v, that's all you need to worry about..

So all they are doing in the schematic (despite it not being drawn correctly) is joining the two 26v panels together in series to get them up to 50v and then adding in the one large panel in parallel as that is already 50v..
DONE, simple, shame they couldn't draw for shit though

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[DBK]

Just realised and added it as an attachment.

Open circuit voltages are 22.6v for the 150w panels, 49.8v for the 400W panel, so close to it.

That wiring diagram is bonkers, the 400W panel is short-circuited if I'm reading it correctly.

If you can wait I suggest getting it done in the UK.

 

[HandyAndy]

Not exactly hard to fix the drawing...

 

[Em and Tim]

Thanks all for your input, I was thinking it would work but not how they had advised, but am at the point where I would trust they know best. I'll now check with them that the mistake and revision are correct and proceed (that way there will be no warranty issues.). Cheers, it is really appreciated.

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[eddie]

I wouldn't advise panels in series on a motorhome roof. If the larger panel is in the shade it will seriously impact on the efficiency of other two.

Great on a house roof or a solar farm where the orientation and the calculated and there is no chance of shading.

 

[Em and Tim]

I wouldn't advise panels in series on a motorhome roof. If the larger panel is in the shade it will seriously impact on the efficiency of other two.

Great on a house roof or a solar farm where the orientation and the calculated and there is no chance of shading.

This was my understanding.

How would it work if each panel is wired directly to an mppt controller (I assume they'd all need the same voltage). Is it better to have a controller for each panel, or type or sequence of parallel panels?

 

[eddie]

We install a lot of solar and there is no hard and fast rule and lots depends on the individual job and what the customer wants. When we (Van Bitz) installed three 150w panels on my own motorhome they are connected to three Victron MPPT regulators, and the three regulators are connected to a Positive and Negative BUS bar and a 100 amp connection run directly to the batteries via the Victron battery computer.

The way I have built in back up in case of failure and I have minimised my chance of all three panels being in the shade, or, being able for one panel to influence the other two in any way.

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