Need advice wiring 12 100-watt panels in series-parallel to a junction box

[Northernsky]

Hey guys,

I’m new to the forum, brand new to solar and I have a number of questions about my RV solar install. I would appreciate any advice, and thank you all in advance.

I just mounted 12 100-watt Renogy compact solar panels on my 23 foot Grand Design travel trailer. I want to wire them in series-parallel, (2 panels per series) so 6 arrays of 2 panels paralleled to a junction box. So I will have 6 positives and 6 negatives coming into the box (through cable glands). This will be a simple roof mounted waterproof junction box with a positive bus bar and a negative bus bar.

I plan to connect all six positive wires (10AWG) to a positive bus bar, and connect all 6 negative wires (10AWG) to a separate bus bar. Then run 1 positive and 1 negative wire off the bus bars (4 or 6AWG) to the charge controller.

I will have an in-line fuse on all 6 positive wires from the panels to the box, and a breaker on the positive lead going to the charge controller.

—Do you see anything wrong with doing it this way, am I missing anything?
—Am I missing anything.
—Is there any potential for back-feeding between the panels doing it this way? Do Renogy panels have diodes to protect from this?
—With 1200 total watts, I’m looking at a Victron 150/100 charge controller. Will it handle 1200 watts Solar?

Thank again for any advice or tips.

Richard

 

[HRTKD]

1200 watts is well within the range of the 150/100 solar charge controller.

Is your battery12v or 24v?

I would put more of those panels in series to reduce the cost/effort of so many paralleled strings.

 

[linkcat]

Will remain here, interested to saw the answers!

 

[pollenface]

Panels usually come standard with a "bypass" diode between and Positive & Negative outputs which allow power to pass through a shaded panel in a series configuration. The shaded panel would otherwise create resistance.

I believe you would want to include a "blocking" diode on each parallel pv input. Occasionally blocking diodes are included in the MC4 connectors, but you'd have to do your own reading with regards to what you're buying.

I'm 99.97% confident that any 100 amp mppt will handle 1200w in a 12v system.

 

[Hedges]

I don't think there is a need for blocking diode. At Vmp of the illuminated panels, little would backfeed through a completely dark string. Simply shaded, it'll still have Voc as high as the other strings Vmp and nothing backfeeds.

Fuses per string takes care of shorted strings and the hazard of backfeeding them.

Any differences in orientation, or rooftop shading affecting some panels? That could influence which you want put in series.

 

[Rocketman]

Here are my thoughts:

You want a switch/breaker on the positive between your panels and your Victron 150/100, which you indicated you are planning. This way you shut-off the "sunshine" and don't disconnect power to the mppt.

Especially, if the wire is not short you want a breaker/fuse just after the mppt. That wire should also be fused when it hits the buss bar.

You may want to consider going to a 3s4p instead of the 2s6p.

The Victron 150/100 can handle 1450 watts. The 150/85 can handle 1200 watts - so if you can drop down to the 150/85 and probably save a couple of bucks. (These stats are on the Data Sheets at Victron).