3s with 2s panels into one charge controller?

[Stewfish]

Can I Parallel 3s panels with 2s panels into my charge controller?

3s = 3 Panels 38v x 3 =114 x 1.2 for cold coefecient = 136.8v

2s= 2 panels at 38v x 2 =76v x 1.2 cold = 91.2v

Will they average out going into then CC?

Are my calculations correct for MPPT, doesn't its raise above the panel amps? I have 250w 38v 8.3a panels. If I have two of those panels 2s. Is that going to be 16amps with a mppt to calculate the wire gauge for 100ft? The Southwire wire calculator is saying 8 gauge for 16 amps?

 

[Dzl]

Can I Parallel 3s panels with 2s panels into my charge controller?

Not without losses. In parallel its important to keep the string voltages close together, in series voltage isn't an issue, but matching current is very important.

Will they average out going into then CC?

I'm not sure. I used to think both strings would operate at the lower voltage (91.2V) (60V? VMP x 2), but I've since heard its a bit more complicated. Long story short, I'm not confident on the details.

Are my calculations correct for MPPT, doesn't its raise above the panel amps?

I don't understand this question, can you rephrase?

I have 250w 38v 8.3a panels. If I have two of those panels 2s. Is that going to be 16amps with a mppt to calculate the wire gauge for 100ft?

2 x 8.3A panels in series = 8.3A

But if you put two panels (or strings of panels in parallel) you will get 16.6A.

For the voltage drop / wire size calculation, use VMP, it should be ~30V or so per panel, its on the sticker/datasheet.

100ft is your actual round trip distance? or one way?

I like this calculator:

Interactive Wire Size Calculator

Battery Chargers, Inverters, Solar Components, and Wiring Supplies for Boats, RVs, and Off-Grid Applications.

baymarinesupply.com

 

[Hedges]

Not average out, the 2s with 76 V (open circuit?) will simply get dragged up a small amount in voltage - maybe 1 volt - and will sink enough current from the 3s to accomplish that. You don't get anything out of the 3rd panel.

Simply wire 2s2p. Use the 5th panel for something else (spare, or with a different charge controller, or to run a DC fan, etc.)

 

[Stewfish]

Not average out, the 2s with 76 V (open circuit?) will simply get dragged up a small amount in voltage - maybe 1 volt - and will sink enough current from the 3s to accomplish that. You don't get anything out of the 3rd panel.

Simply wire 2s2p. Use the 5th panel for something else (spare, or with a different charge controller, or to run a DC fan, etc.)

Yeah it was just too hard to get a decent price on 120a worth of charge controllers to charge 4 golfcart batteries for lights, heater fan, and fridge LCD, and charge 5v stuff like phones and micro wifi travel router. It was 500+ for two 60a or 700+ for a 120a. I ended up with a 100a 1250w max epever. I can use it at our new property later w our 48v system. So I didn't mount the 6th panel since thats 1500w total. I guess I could wire 24v and get converters to go down to 12v but those always seem to be a failure point and a pain to swap often.

4 panels will work but the wire guage will go up for 100ft at 60v 2s2p = 16a so the calculator says 10g = 2.77% loss for smallest wire possible.

If I did 90v 3s1p at 8a thats only 14g, maybe I should just use 3 panels and get some decently priced 12g. Its def enough to charge those batteries.

I was going to put the controller in my 5th wheel basement w the batteries. Then run my panels to the RV at the highest voltage possible to decrease wire size, then 12v short thick wires to the batteries.

I got a combiner box to play with, it has breakers and such to be mounted near the panels ( will use later at property). Then research DC fuses between the controller and batteries along with other safeties

 

[Hedges]

Most MPPT charge controllers tolerate over-paneling. So long as you're within max Voc on a cold day and any max Isc they spec.
6 x 250W = 1500W STC of panels would rarely exceed 1250W.
If you put one string of panels on the side or the rear of the RV (different angle from those on the roof), that would ensure lower peak power and could help when the sun is low.