Solar panel fitting

[Manxcat54]

I want to begin to work out where and how I am going to be fitting 3 solar panels onto the roof, I am unsure of how to run the cables, obviously the cables will all have to return to my engine bay/ electrical panel. So I take it each panel has 2 cables, do I have them enter the roof right near to the panel they come from, then run the cables in some fashion to the stern of the boat, then if there are 6 cables how do they go to the controller? I suppose I could look for a youtube video, but I thought the big brains on here must know the best way of doing it.

Edited June 9 by Manxcat54

[robtheplod]

Lots of variables.... it depends if you connect these panels in parallel or series...  parallel you connect all the + together and then all the - together and run 2 wires to your controller, or series you daisychain them all (+ from one goes to - on the next etc) so you end up with two ends and these connect to the controller. The main thing is there is a BIG difference between the two over voltage and amps and you need to know and be aware of the difference and have the correctly rated controller etc...  this has been discussed lots of times on here - a search will bring it all up.

 

Physically connecting, I'd personally use the nearest mushroom to bring the wires in can run above the roof lining. I have mine connected outside with just the two wires coming in via the back mushroom (roof lining not an option..  ).

 

Your idea about YouTube is a good one as loads of vids to explain all the above....

 

What info do you have on your panels as this will help people get specific for you....

Edited June 9 by robtheplod

[Tony Brooks]

If you have flat panels on feet, then you can run the cable under them, especially if they but against each other. The cable is normally two cables in one outer sheath, a bit like domestic flex.

[Manxcat54]

I have purchased (not arrived yet) 3 x 215W panels with all the tilt hardware, also a Victron 100/50 MPPT controller and all the cables, shrouds where cables enter the roof etc, I hope I have bought the right thing as I know bugger all about solar.

[robtheplod]

13 minutes ago, Manxcat54 said:

I have purchased (not arrived yet) 3 x 215W panels with all the tilt hardware, also a Victron 100/50 MPPT controller and all the cables, shrouds where cables enter the roof etc, I hope I have bought the right thing as I know bugger all about solar.

 

do you have a link to the the panels so we can look at the other specs?   Good choice re controller by the way, should be fine!

[Rincewind]

21 minutes ago, Manxcat54 said:

I have purchased (not arrived yet) 3 x 215W panels with all the tilt hardware, also a Victron 100/50 MPPT controller and all the cables, shrouds where cables enter the roof etc, I hope I have bought the right thing as I know bugger all about solar.

 

Regarding roof entry shrouds:-

If you intend to pass the cables through a hole drilled into your roof then the weather protective covers usually supplied, (like the one in the picture below), are intended mostly for plastic / GRP caravan roofs where they are glued into position.  They may not stand the test of time on a steel narrowboat roof.

I would suggest a more rugged solution with an IP65 rated junction box like the one below.

https://www.toolstation.com/ip65-moulded-pvc-box/p96199

 

  

 

To protect the cables from chaffing where they pass through the roof attach a conduit fitting to the underside of the box.  This will allow the box to sit flush to the roof secured by two screws inside the box and you can seal the outside edge of the box where it meets the roof with suitable mastic / sealant.

https://www.toolstation.com/pvc-conduit-female-adaptor/p91534

[robtheplod]

1 hour ago, Rincewind said:

 

Regarding roof entry shrouds:-

If you intend to pass the cables through a hole drilled into your roof then the weather protective covers usually supplied, (like the one in the picture below), are intended mostly for plastic / GRP caravan roofs where they are glued into position.  They may not stand the test of time on a steel narrowboat roof.

I would suggest a more rugged solution with an IP65 rated junction box like the one below.

https://www.toolstation.com/ip65-moulded-pvc-box/p96199

 

  

 

To protect the cables from chaffing where they pass through the roof attach a conduit fitting to the underside of the box.  This will allow the box to sit flush to the roof secured by two screws inside the box and you can seal the outside edge of the box where it meets the roof with suitable mastic / sealant.

https://www.toolstation.com/pvc-conduit-female-adaptor/p91534

or go in through the mushroom..... no drilling required....

[Manxcat54]

Thanks for the info, wouldn't going through a mushroom invite water to creep in ? in my experience it goes uphill when it shouldn't 

[robtheplod]

16 minutes ago, Manxcat54 said:

Thanks for the info, wouldn't going through a mushroom invite water to creep in ? in my experience it goes uphill when it shouldn't 

Cable bends up and over and down again on mine, so no issue....  

 

Edited June 9 by robtheplod

[robtheplod]

1 hour ago, Manxcat54 said:

Thanks for the info, wouldn't going through a mushroom invite water to creep in ? in my experience it goes uphill when it shouldn't 

let me know the specs of your panels - volts/amps etc and we can double check best way to connect them - a link to them would be ideal.

[blackrose]

6 hours ago, robtheplod said:

Good choice re controller by the way, should be fine!

 

That very much depends on the panel specification and how they're are being connected. If the they're being connected in series (which will give a better overall solar harvest than connecting in parallel) and the open voltage of each panel is say 40v x3 then the 100v limit of the OP's controller won't be sufficient.

 

You can exceed the amp rating of a MPPT controller and the current will just be clipped. But if you exceed the voltage rating of the controller the electronics will be fried and it will only be of use as a paperweight.

Edited June 9 by blackrose

[Alan de Enfield]

15 minutes ago, blackrose said:

 

That very much depends on the panel specification and how they're are being connected. If the they're being connected in series (which will give a better overall solar harvest than connecting in parallel) and the open voltage of each panel is say 40v x3 then the 100v limit of the OP's controller won't be sufficient.

 

You can exceed the amp rating of a MPPT controller and the current will just be clipped. But if you exceed the voltage rating of the controller the electronics will be fried and it will only be of use as a paperweight.

 

 

My solar panels are 120 volt - put 3 of them in series with a 100v controller and you'd be seeing 'stars'.

[Manxcat54]

Robtheplod

 

I can't find the video link you sent regarding fitting the panels with magnets, could you please post it again

[Tony Brooks]

17 minutes ago, Manxcat54 said:

Robtheplod

 

I can't find the video link you sent regarding fitting the panels with magnets, could you please post it again

 

As you seem to have ordered tilting brackets the panels will be more upright and act as sails, so I would be reluctant to secure the brackets with magnets. Horizontal ones, yes, tilting ones no. The actual advantage of tilting panels on a canal boat is open to some question.

[IanD]

58 minutes ago, blackrose said:

 

That very much depends on the panel specification and how they're are being connected. If the they're being connected in series (which will give a better overall solar harvest than connecting in parallel) and the open voltage of each panel is say 40v x3 then the 100v limit of the OP's controller won't be sufficient.

 

You can exceed the amp rating of a MPPT controller and the current will just be clipped. But if you exceed the voltage rating of the controller the electronics will be fried and it will only be of use as a paperweight.

 

It's usually better to put identical panels in parallel to combat partial shading; a solar panel is essentially a current source, if you put them in parallel the currents add even with different outputs, if you put them in series the current is that from the lowest output panel.

 

For sure, the *maximum* open-circuit voltage (including variation with temperature) must not exceed the rating of the MPPT controller.

[ditchcrawler]

46 minutes ago, IanD said:

 

It's usually better to put identical panels in parallel to combat partial shading; a solar panel is essentially a current source, if you put them in parallel the currents add even with different outputs, if you put them in series the current is that from the lowest output panel.

I wasn't even going to go there with that statement although I fully agree with you 

[Tony Brooks]

54 minutes ago, IanD said:

 

It's usually better to put identical panels in parallel to combat partial shading; a solar panel is essentially a current source, if you put them in parallel the currents add even with different outputs, if you put them in series the current is that from the lowest output panel.

 

For sure, the *maximum* open-circuit voltage (including variation with temperature) must not exceed the rating of the MPPT controller.

 

But with an MPPT controller should you not consider power (A x V), so although the current will be limited by the shaded panel the voltage will be much higher giving a higher power output. I can't work it out mathematically, but series connection seems to work for some/many.

[IanD]

3 hours ago, Tony Brooks said:

 

But with an MPPT controller should you not consider power (A x V), so although the current will be limited by the shaded panel the voltage will be much higher giving a higher power output. I can't work it out mathematically, but series connection seems to work for some/many.

That's not how solar panels work, they act as a current source which maintains a constant current as you raise the voltage across them so power goes up, until you get close to the open-circuit voltage when current starts to drop. There's a voltage where the output power is maximum, amd this is what the MPPT controller tries to find and track.

 

Say you have two 30V panels, one in full sun putting out 15A and one in partial shade putting out 10A. Connect them in parallel and you'll get 25A current, the MPPT controller will hold them at 30V, output power is 750W.

 

Put them in series and the shaded panel will still put out 10A, but the other one can't push any more current through it, so you get 10A into 60V (MPPT voltage) which is 600W.

 

Series connection works and can mean a cheaper MPPT controller and easier wiring, which is why many do it. If you have the choice, parallel connection is better to maximise power under partially shaded conditions.

Edited June 9 by IanD

[Tony Brooks]

Thanks Ian, still not sure if I fully understand, probably old age.

[robtheplod]

16 hours ago, Manxcat54 said:

Robtheplod

 

I can't find the video link you sent regarding fitting the panels with magnets, could you please post it again

Hi, its in your messages if you look at your profile. As Tony said though, use magnets to mount your panels or tilting brackets, but not both. Still waiting on your panel spec so we can check you're going to be in limits on the controller....?

[blackrose]

21 hours ago, Tony Brooks said:

The actual advantage of tilting panels on a canal boat is open to some question.

 

 

Is it? I'd say the only people who would question the actual advantage of tilting panels are those who don't have the option of doing it. There may be some disadvantages of course such as how to fit the brackets, the potential for the panels to get caught by the wind and whether one thinks tilted panels look aesthetically pleasing or not. However, purely in terms of a solar harvest comparison between panels which are laid flat and those tilted towards a low sun there is no question.

 

I live on a farm mooring and part of the farm has been turned over to a couple of fields of solar panels. Hundreds of solar panels all fitted with motors so that they are automatically angled to track the sun. Commercial solar farmers wouldn't invest in the infrastructure required to do that were it not advantageous.

16 hours ago, IanD said:

Series connection works and can mean a cheaper MPPT controller and easier wiring, which is why many do it. If you have the choice, parallel connection is better to maximise power under partially shaded conditions.

 

Yes, that's true, but in unshaded conditions panels connected in series will result in a more solar gain in the mornings and evenings compared to parallel connection, resulting in an overall greater solar harvest. The only advantage of parallel connection is if one or more of series panels is in partial shade. Then parallel output will be greater than panels in series. 

Edited June 10 by blackrose

[David Floyd]

We fitted tilting mounts for our panels after looking at almost any system I could find.

 

I also did a little research into how much to tilt for the optimum power during the day, but this is very dependent on being at the right angle to the sun. 

At present we only use about 10% of our power overnight and are recharged after the first couple of hours, but we designed the system for winter use, so we will what happens then.

 

Here is my round up of mounting systems.

 

https://floydtilla.co.uk/2023/03/25/planning-for-solar-panels-part-2-panel-mounting-options/

 

Hope this helps

 

D

Edited June 10 by David Floyd

[blackrose]

Here's mine. I made my own brackets and tilting system and they can be tilted either way -to port or starboard.

 

Whether it's worth having tilting panels is open to discussion. I only tilt them on clear days in winter when there's not too much wind. But on those days they produce about a third more amps than having them flat. 

 

[IanD]

5 hours ago, blackrose said:

 

Is it? I'd say the only people who would question the actual advantage of tilting panels are those who don't have the option of doing it. There may be some disadvantages of course such as how to fit the brackets, the potential for the panels to get caught by the wind and whether one thinks tilted panels look aesthetically pleasing or not. However, purely in terms of a solar harvest comparison between panels which are laid flat and those tilted towards a low sun there is no question.

 

I live on a farm mooring and part of the farm has been turned over to a couple of fields of solar panels. Hundreds of solar panels all fitted with motors so that they are automatically angled to track the sun. Commercial solar farmers wouldn't invest in the infrastructure required to do that were it not advantageous.

 

Yes, that's true, but in unshaded conditions panels connected in series will result in a more solar gain in the mornings and evenings compared to parallel connection, resulting in an overall greater solar harvest. The only advantage of parallel connection is if one or more of series panels is in partial shade. Then parallel output will be greater than panels in series. 

Sorry but that's not correct -- if you have identical panels with no shading it makes no difference to power output whether they're in series or parallel -- series gives higher voltage and lower current, parallel gives lower voltage and higher current, but power is identical.

[Manxcat54]

After reading and watching  videos I have decided I'm not tilting them and I have a friend who runs a magnet company who will supply strong magnets rubber mounted with M8 studs, and I think in series because I don't want the fuss of those 3 way connectors, for once I have gained something from the forum. Thanks