Adding a panel - diodes required?

[Orion]

I’m adding an additional 60w panel which, for cabling reasons, will be connected in parallel to the existing 115w unit - both are NDS SolarFlex EVO - and then feeding into one input on the NDS 36W Sun Control 2 Regulator, (the second input will be handling another panel on a separate feed).

Question to the knowledgeable as per the thread title is, should I install diode connectors in the panel +ve feeds before the branch connector?

 

[pappajohn]

No need.
Connected in parallel the two panels become one as far as charge amps are concerned and the voltage remains at 12v

 

[Hoovie]

I’m adding an additional 60w panel which, for cabling reasons, will be connected in parallel to the existing 115w unit - both are NDS SolarFlex EVO - and then feeding into one input on the NDS 36W Sun Control 2 Regulator, (the second input will be handling another panel on a separate feed).

do you know the specs of both panels? be interesting to know to get an idea of the total wattage of the new array.
(clue: it will NOT be 60W+115W unless you are VERY lucky).

Question to the knowledgeable as per the thread title is, should I install diode connectors in the panel +ve feeds before the branch connector?

nah.

 

[Orion]

do you know the specs of both panels? be interesting to know to get an idea of the total wattage of the new array.
(clue: it will NOT be 60W+115W unless you are VERY lucky).

Specs of both panels are here.

 

[Hoovie]

Specs of both panels are here.

not too bad - you are only loosing 3W from the theoretical maximum by adding the two panels together in Parallel

(if you connected in series, that 65W would have given you a whopping extra 7W on top of the original 115 )

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[Orion]

not too bad - you are only loosing 3W from the theoretical maximum by adding the two panels together in Parallel

(if you connected in series, that 65W would have given you a whopping extra 7W on top of the original 115 )

I’ve not fitted them yet. Cables from both panels will be joined just inside the roof and thence to the existing 2.5 wiring from the 115w panel to the controller. Are you saying I would be better off connecting them in series in this instance? Would the controller handle the output (maximum 29.5v open circuit input voltage)?

 

[Hoovie]

I’ve not fitted them yet. Cables from both panels will be joined just inside the roof and thence to the existing 2.5 wiring from the 115w panel to the controller. Are you saying I would be better off connecting them in series in this instance? Would the controller handle the output (maximum 29.5v open circuit input voltage)?

absolutely not.
in series, your 65W Panel and 115W panel would give you a maximum 122W Array.
in parallel, the two together will give a maximum 172W array

Too many people think you can just add panels together any way you like and you get the same power. Only time you can be sure of that is with identical panels.
It is actually possible sometimes to LOWER the power of a panel array by adding a really badly matched 2nd one!

 

[Lenny HB]

Are you saying I would be better off connecting them in series in this instance? Would the controller handle the output (maximum 29.5v open circuit input voltage)?

No the series voltage will be around 40v.
On a Motorhome they are better connected parallel as if in series and if one panel is in shade you will lose all output.

 

[Hoovie]

No the series voltage will be around 40v.
On a Motorhome they are better connected parallel as if in series and if one panel is in shade you will lose all output.

it is not always that simple an automatic choice, as my previous post reveals

 

[Gromett]

Depends if you are talking about bypass or blocking diodes. Some panels already include one.

I am just heading to bed so not typing in a big explanation. Here is one I just googled.

Blocking Diode and Bypass Diode for Solar Panels

A blocking diode and bypass diode are commonly used in solar energy systems and solar panels. Learn how and why blocking diodes and bypass diodes are used....

sinovoltaics.com

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[Gromett]

PS: if you do add diodes please use Schottky diodes as they have a lower voltage drop and reduced losses.

This may be of interest.

https://www.digikey.co.uk/en/articles/active-bypass-diodes-improve-solar-panel-efficiency-and-performance

That's me done for tonight. Night

 

[Raul]

The blocking diode should be in the mppt already, if its a real one. And the bypass schottky should be in the panel buss junction if is a accredited certified panel.