Do I include Solar Panel Junction box cable and Adaptor cable lengths in my calculation?

[Johnny Nova]

Hi
I'd appreciate help on this query relating to cable sizing.

When calculating the cable sizing from the MPPT regulator to the Roof mounted single 200W solar panel do I also include the length of the Solar panel junction box cable plus and a short Adaptor cable I plan to use??
The adaptor cable (10AWG) plus Panel cable (11AWG) total approx. 4 feet

Adding this extra 4 feet in my calculation pushes the size to 8AWG on some calculators and 10AWG wire if I omit the 4 feet

Cheers

 

[chrisski]

Yes, but what is the loss you get by going to 10AWG?

Honestly, most of the time it comes to 30 minutes extra charging time and may not be worth the extra cable if there’s quite a few sun hours left.

 

[Johnny Nova]

Yes, but what is the loss you get by going to 10AWG?

Honestly, most of the time it comes to 30 minutes extra charging time and may not be worth the extra cable if there’s quite a few sun hours left.

Hi Chrisski
Thank you for your response
I have been using 3% voltage drop on various calculators but sometimes the recommendation can vary up or down in wire size depending on the calculator. Not sure why this is......maybe being more conservative in calcs.

I have been using the following calculators by Faroutride, Explorist, Bluesea Circuit Wizard, Jcalc.net just to compare

Any that you would recommend for a beginner?

 

[BryceFreeman]

Yes I think you should choose 8AWG.

 

[chrisski]

Any that you would recommend for a beginner?

If you do go with 8 AWG, there may be some other issues.

I would not recommend a chart but a calculator. I use this:

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

Please note it is a one way length.

I notice 11AWG panel cable. That is an odd size. Usually sold in even AWG and because panels don’t get above 10 amps, I’d expect 12 or 14 AWG.

I correct what I said earlier and I do not include the pigtails on the solar panel itself in the voltage drop calculation.

I’d also be surprised if such a short length, 4 or 8 feet requires 8 AWG.

8 AWG has problems of connector size. 8 AWG does not fit in MC4 connectors. What I did in this case is use connect the panel to a MC4 connector with 6 AWG wire. Since 10 AWG folds in half to approx 6 AWG, I but crimped the two wires together.

Now my calculator met the magic less than 3% connection I was looking for. What I don’t know is if those two extra connections I put in have any loss.

There are pre wired connectors in various lengths with 8 AWG wires in them. Although they fit in an MC4 connector, they are not Stabuli MC4 connectors. I suspect these are Amphenol H4. Now you get into matching MC4 connectors to prevent corrosion down the road.

I also don’t think cutting and replacing your MC4 connector with a 10 AWG to 8 AWG but crimp is a good idea. I trust a properly installed MC4 connector which has been used in millions of installations with a low failure rate for weather resistance much more than the but crimp method I mentioned that a piece of glue heat shrink covered by a second piece of glue heat shrink or any electrical tape.

 

[Johnny Nova]

If you do go with 8 AWG, there may be some other issues.

I would not recommend a chart but a calculator. I use this:

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

Please note it is a one way length.

I notice 11AWG panel cable. That is an odd size. Usually sold in even AWG and because panels don’t get above 10 amps, I’d expect 12 or 14 AWG.

I correct what I said earlier and I do not include the pigtails on the solar panel itself in the voltage drop calculation.

I’d also be surprised if such a short length, 4 or 8 feet requires 8 AWG.

8 AWG has problems of connector size. 8 AWG does not fit in MC4 connectors. What I did in this case is use connect the panel to a MC4 connector with 6 AWG wire. Since 10 AWG folds in half to approx 6 AWG, I but crimped the two wires together.

Now my calculator met the magic less than 3% connection I was looking for. What I don’t know is if those two extra connections I put in have any loss.

There are pre wired connectors in various lengths with 8 AWG wires in them. Although they fit in an MC4 connector, they are not Stabuli MC4 connectors. I suspect these are Amphenol H4. Now you get into matching MC4 connectors to prevent corrosion down the road.

I also don’t think cutting and replacing your MC4 connector with a 10 AWG to 8 AWG but crimp is a good idea. I trust a properly installed MC4 connector which has been used in millions of installations with a low failure rate for weather resistance much more than the but crimp method I mentioned that a piece of glue heat shrink covered by a second piece of glue heat shrink or any electrical tape.

Thanks for the calculator recommendation.
Couple of questions relating to the calculator
What is the No of conductors mean ?
And also Power factor ?
Just to explain my setup on small Campervan with a 200w solar panel-
I’ve been playing around with different cable runs and get one way lengths of 17.3 feet and 23 feet depending on which way I run the cables. (These lengths include both the panel pigtails and a short adapter)

My panel setup on top of my van rooftop is going to be removable so I am looking at an Anderson plug with weather proof rubber boot or maybe even a SAE type plug for outdoors.

 

[chrisski]

If you run the current through one wire, then one conductor. If it’s split between 2, then two conductors.

I leave power factor as is and don’t change. There’s another version of the calculator without the power factor, but I can’t find it.

 

[Johnny Nova]

If you run the current through one wire, then one conductor. If it’s split between 2, then two conductors.

I leave power factor as is and don’t change. There’s another version of the calculator without the power factor, but I can’t find it.

I'm planning to run a twin core wire with both RED +ve and BLACK -ve wires ie: both insulated separately but bonded together.......is this what you mean would be 2 conductors??.........apologies for asking basic questions.

Also reading off the solar panel specs do I use the Max Power Current Imp=9.76 A for this calculator?...............or the Short circuit current Isc=10.24 A

 

[chrisski]

I'm planning to run a twin core wire with both RED +ve and BLACK -ve wires ie: both insulated separately but bonded together.

Sounds like red one strand there and one black strand back, that’s a single conductor.

Also reading off the solar panel specs do I use the Max Power Current Imp=9.76 A for this calculator?...............or the Short circuit current Isc=10.24 A

I use the higher amount which will drive thicker wire.