Upgrading RV solar - need feedback

[eatSleepWoof]

I've got a 2022 2108FBS Winnebago travel trailer.

Trailer currently has a 190W panel on the roof, which is wired through 10/2 wire to a 30a PWM controller. There is also an external port for portable solar panels. The diagrams Winnebago shared with me (below) suggest this port is also connected to the charge controller.

The controller then outputs to the batteries (LifePo4) through another length of 10/2 wire; 10 gauge wiring is good for 15a of transmission, which is maxed out by the 190W panel on the roof. Looking at the back of my solar controller, I see four wires connected. Two coming from solar inputs, two going to the battery. This means that the inputs from the roof and the "solar on the side" port are joined into one set of wires. This lines up with the 30a controller rating (two 12v inputs, each up to 200w, 30a total), however that doesn't really fit with the 10/2 wire coming into the controller. Perhaps the 30a of current is okay for a short run of 10 gauge? Then there's the 10/2 wiring running from the controller to the batteries, which also seems potentially undersized. (Two panels at ~200W each would mean 400W at 12v, or 33.3a.)

So...

My goal is to add more solar capacity to the roof, and at the same time, upgrade to a MPPT controller.

Additional panels must be wired in series, so doubling the solar capacity, in series, would result in ~400W at 24v, and the same 15a (that the wiring is rated for) running to the controller. But what happens if I now plug in a single 200W, 12v panel into the side port? I'll have 400W, 24v coming from the roof, and 12v coming from the side... into the same set of input wires. What the heck would this result in, as far as input wattage and voltage goes?

Or is this simply a no-go, and I have to ensure that external solar panels are also 24v?

For what it's worth, if it's possible to setup more than 400W, 24v on my roof setup without running new wiring from the roof to the controller, I'd love to hear how. Can I simply keep stacking panels in series, reaching, say, 800W at 48v?

I need to figure this out before I can go solar controller shopping...

 

[eatSleepWoof]

Here are the OEM diagrams:

 

[rruff]

Or is this simply a no-go, and I have to ensure that external solar panels are also 24v?

If you have two controllers you can mix voltages, but if they are all inputs to the same MPPT they should be 24V. Even then, variable shading, sun angle, and panel specs will make it less than optimal to put everything in one controller... but it should work fine.

I use 24V (actually ~32V) portables. They are 12V folding glass/aluminum panels that I rewired for 24V. Each half is 12V so I just wired them in series instead of parallel. 24V is very good for long runs, which is nice for a portable.

One aspect of series wiring is that shading any of the panels in a string will drop output a lot.

For what it's worth, if it's possible to setup more than 400W, 24v on my roof setup without running new wiring from the roof to the controller, I'd love to hear how. Can I simply keep stacking panels in series, reaching, say, 800W at 48v?

If the controller can handle the voltage (and most can) then it should be fine.

 

[eatSleepWoof]

If you have two controllers you can mix voltages, but if they are all inputs to the same MPPT they should be 24V. Even then, variable shading, sun angle, and panel specs will make it less than optimal to put everything in one controller... but it should work fine.

Thanks, @rruff .

I've read a few posts on Winniebago forums/groups that state that the inputs for the side port solar panel actually join with the OUTPUT of the solar controller, and then run directly to the batteries. I think I should be able to test this by reading voltage of the prongs on the external side port, once I de-winterize and put my batteries back into the trailer.

This means the portable solar panel would need its own controller, but at the end of the day we'd have 12v OUTPUT from both controllers being joined together, vs. potentially risking mixing voltages at the input, which makes a heck of a lot more sense.

The geniuses at Winnebago must have messed up their own diagram.