Adding a 2nd solar panel in parallel

[VXman]

The plan is/was to link a 2nd panel to the first on the roof to keep it simple. Was going to use some MC4 Y connectors like below. However. Looking at my roof I don't seem to have a lot of cable to play with. Is this going to work?

 

[Robb]

I used those connectors on my last van which worked well and were hidden under the panels, with the new van I've done a series connection to both the Sargent system and the Ecoflow, both are working great!

 

[Lenny HB]

Will these give you enough to play with.
Otherwise it's easy enough to replace the cables on the panels.

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[Andacami]

I'm about to add a second panel in parallel too.

I assume for you, as with mine, there is more cable with MC4 connections under the panel unless it has been cut to length. If so, Y connectors/cables will be what I'll use.

As Lenny HB says, if not, I'll get some more cable and MC4 connectors and make/crimp up the appropriate lengths.

Parallel is the way to go I understand unless you need the extra voltage and can guarantee complete coverage of both panels?

 

[Lenny HB]

As Lenny HB says, if not, I'll get some more cable and MC4 connectors and make/crimp up the appropriate lengths.

Better to buy ready made cables without the right tools they are not the easiest cables to strip & crimp. For a pair of male & female cables buy a male to female extention lead twice the length you need and cut in half.

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[VXman]

I've no idea how the cables are attached underneath. I don't really want to be removing the panel to access them. So the question is can I manage it with the small amount of cable that is visible?

I assume it would be a case of cutting the cables somewhere between the gland and where the cable disappears underneath the panel, putting a Y connector in line in each cable. Then connect the new panel cables to the other connection point on the Y connector. Is that correct?

I'm just thinking there is no where to mount the y connectors securely and neatly.

 

[Lenny HB]

I've no idea how the cables are attached underneath. I don't really want to be removing the panel to access them. So the question is can I manage it with the small amount of cable that is visible?

I assume it would be a case of cutting the cables somewhere between the gland and where the cable disappears underneath the panel, putting a Y connector in line in each cable. Then connect the new panel cables to the other connection point on the Y connector. Is that correct?

There should be MC4 connectors on the cables from the panel are you sure you can't fiddle then out.

 

[VXman]

Will these give you enough to play with.
Otherwise it's easy enough to replace the cables on the panels.

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Ah - yes. Missed this reply. It doesn't state the length of cables on those buy yes it looks likely that would create some additional length to work with.

 

[Dorwyn]

I used y connectors very similar to that on one installation, but in series for the higher voltage as I understood that the mppt controller I was using worked better. It certainly was good. One of the quickest upgrades I did.

 

[cyberyacht]

I've got my panels in series. Not least as the charging voltage kicks in earlier and off later.

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[Hoovie]

Ah - yes. Missed this reply. It doesn't state the length of cables on those buy yes it looks likely that would create some additional length to work with.

I have my 3 panels in parallel and found the moulded ones were around 2" too short for the cables Bought the ones with the little flying leads and jobs a good 'un

 

[VXman]

So, I have these. Can I ask what may be a stupid question but here goes.....

The obvious way to wire these would be A1 to the positive and B1 Negative of the controller. Then A2/3 to the positive of each solar panel. B 2/3 to the negatives.

For ease of routing it would work better to put A3/B3 to the controller and A1/B1 to panel 1 and A3/B3 to panel 2.

Shouldn't make any difference should it?

 

[VXman]

I've got my panels in series. Not least as the charging voltage kicks in earlier and off later.

My controller only takes a max of 30V so that wouldn't work. What do you mean by ....

Not least as the charging voltage kicks in earlier and off later.

 

[cyberyacht]

My controller only takes a max of 30V so that wouldn't work. What do you mean by ....

"Not least as the charging voltage kicks in earlier and off later."
e.g. 3 panels producing 11 volts = 33V, sufficient to begin charging. If in parallel, 11V would be below the battery voltage.

 

[VXman]

"Not least as the charging voltage kicks in earlier and off later."
e.g. 3 panels producing 11 volts = 33V, sufficient to begin charging. If in parallel, 11V would be below the battery voltage.

Ah...so in lower light levels more possibility of charging taking place.

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[Hoovie]

"Not least as the charging voltage kicks in earlier and off later."
e.g. 3 panels producing 11 volts = 33V, sufficient to begin charging. If in parallel, 11V would be below the battery voltage.

Have to say, I have no idea what your post means. your numbers don't tie up with any panels anyone would fit.

a "12V" Panel runs at more or less 20V. Connect 2 panels in series and you have a input voltage around 40V - way above the 30V limit the OPs controller has. Connect in parallel and you have a 20V input. Works fine.

Now Series vs Parallel ... assuming your controller will work at any voltage, Series theroretically will 'wake up' the controller slightly earlier, but in reality the amount of harvesting at the point will be so little it can be ignored and is not actually a benefit to care about.

Parallel is good for helping against shading impact, but has a greater current and lower voltage so has more potential losses compared to series - but again is not much difference in truth and the benefit of "shade protection" for parallel does, IMO, make it the one to go for.

 

[cyberyacht]

Park in the sun.

 

[Hoovie]

So, I have these. Can I ask what may be a stupid question but here goes.....

The obvious way to wire these would be A1 to the positive and B1 Negative of the controller. Then A2/3 to the positive of each solar panel. B 2/3 to the negatives.

For ease of routing it would work better to put A3/B3 to the controller and A1/B1 to panel 1 and A3/B3 to panel 2.

Shouldn't make any difference should it?

View attachment 712982

the end with two connectors go to the panels. The end with the one connection goes to the controller. Which is +ve and -ve you don't need to worry about as that takes care of itself as the connectors are keyed

PS. The Connectors are marked with a "+" and a "-" but just ignore those, they are very misleading as either connector type can be +ve OR -ve.

 

[Hoovie]

Ah...so in lower light levels more possibility of charging taking place.

Possibility - yes. Actuality - no.

To show a real life example of Series vs Parallel, have a look at these graphs.
These are very similar arrays, one is 3 x 90W; the other is 3 x 100W. One is configured in Parallel and the other in Series and both arrays are flat and around 20 foot apart (to tell which is which, look at the Voltage values on the left Y axis). Each array is connected to its own MPPT 20W Controller and those controllers are connected to the same battery.

Interestingly, the Parallel array actually started harvesting before the Series in the graphing below, but you can see from the current, there is sod all current at that stage even if harvesting has started (what difference is 0.1A going to make for an extra 10 minutes?)

 

[Peregrinator]

The plan is/was to link a 2nd panel to the first on the roof to keep it simple. Was going to use some MC4 Y connectors like below. However. Looking at my roof I don't seem to have a lot of cable to play with. Is this going to work?

View attachment 712429View attachment 712430

Yes it will work, just make sure your all your power is switched off before connecting, and always switch off before working on it, when I done it the system received a large spike and messed up my power controller.

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[VXman]

OK - I have all my bits but I'll need an extra metre or so of cable. Can someone tell me what size is needed. (What size is normal for solar panels) Preferably a link to Amazon would be helpful.

 

[Lenny HB]

OK - I have all my bits but I'll need an extra metre or so of cable. Can someone tell me what size is needed. Preferably a link to Amazon would be helpful.

Do you need MC4 connectors on the leads?

 

[Doobray]

I used the Y connectors on mine and put them under the panel. I then bought 4mm extension cable from Sunshine Solar.

 

[VXman]

Do you need MC4 connectors on the leads?

No - got all the connectors.

Is this ok? Amazon product ASIN B0BJ9BHQS7

 

[VXman]

I used the Y connectors on mine and put them under the panel. I then bought 4mm extension cable from Sunshine Solar.

Out of interest. Did you secure the Y connectors down at all? Wondering about wind on the roof when driving.

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[Peregrinator]

Out of interest. Did you secure the Y connectors down at all? Wondering about wind on the roof when driving.

I drilled holes in the frame and used plastic ties to hold them under the frame

 

[Lenny HB]

I drilled holes in the frame and used plastic ties to hold them under the frame

Thats what I do.

 

[VXman]

Thanks for all the responses so far. All very helpful. One more question....

I need to drill and screw the aluminium brackets to the Aluminium solar panel. Self tappers or nut and bolt?

 

[Lenny HB]

Thanks for all the responses so far. All very helpful. One more question....

I need to drill and screw the aluminium brackets to the Aluminium solar panel. Self tappers or nut and bolt?

Pop rivets are easiest, very secure and easy to drill out if you ever need to remove the panel. I wouldn't use self tappers as any corrosion around the hole and they will work loose. If you nut and bolt I've done it but wouldn't bother again, I used stainless steel socket cap screws & nylock nuts. If you use stainless steel make sure you put a layer of silicone grease between contact surfaces to prevent galvanic corrosion.

 

[Peregrinator]

Thanks for all the responses so far. All very helpful. One more question....

I need to drill and screw the aluminium brackets to the Aluminium solar panel. Self tappers or nut and bolt?

I used stainless steel nuts & bolts with thread lock, I have the plastic brackets (six of them) Only thing I would change, would be the brackets, I would use the ones that go the full length of the panel on the front facing only, as it would be more aerodynamic and protect underneath

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