Solar Panel Expansion

As long as the specs are similar, any panel will work. I doubt that the existing wiring would work well for 400 watts so you will probably have to upgrade to heavier wire. One option that you might want to consider is to go portable. Here's a portable 200 watt setup that I saw a fellow camper using which is available on Amazon:
Dokio 200 watt portable $249.99

With the addition of a 100 watt panel on the roof and the portable would give you a total of 400 watts.

I have 3-100w Renogy panels through PMW (bogart engineering 2030 with Solar) controller.
I have one 3' section of 12 gauge wire between panels and controller (factory installed wire through wall I can't replace). The other couple feet is 10 gauge.
I plan on adding a 4th panel this summer.

My thought are my camper never meets "lab conditions". I never get full output because panels are flat on roof (2 are tilted only by drop of roof on front of camper), plus by the time the sun is high (still not correct angle) my batters are past the bunk charge state and are doing more Higher voltage finish charge. my controller is also limited to 30a (Charger will safely reduce output if panel current exceeds 31 amp) so I have no fear using 400w worth of panels.

I had the Bogart Engineering Trimeter first, so to me it made sense to just add the solar controller that is controlled by the trimeter. I liked it so much, I bought the same system again when I bought my ArcticFox

I would contact Eagler Cap and ask them the size of the wire. You can calculate from there your options. The wire might be bigger than you think. In their online brochure Eagle Cap lists the ability to upgrade to a total of 300 watts as factory option. If your voltage drop calculates to be too high for the factory roof-controller cable you could run the panels in pairs in series than to parallel to controller. The wiring should be fine voltage wise in this configuration. I would check with the specs on the MPPT controller and see what their max solar input is. Inexpensive MPPT controllers shouldn't be exceeded in many cases as they can't shunt off excess amperages the way some expensive units will do. Our last renogy 40 amp MPPT shut off a couple times when our 500 watts of solar and a high load appliance was being used. The MPPT specs should give a max input in watts.

As towpro notes maximum performance is rarely achieved although that will vary with time of year an location. We are seeing 95%+ with flat non tilting panels in the southwest right now (we actually hit 1045 watts with a total roof away of 1080 )when the sun is overhead and sky is very clear.

As far as the renogy panels I have used them in the past and they worked very well.

Eagle Cap runs a 10ga wire from the roof. If you plan on running 4 panels, you have 3 options:

If you get an MPPT Controller:
* Run them either all in series for a 80v circuit, the amperage down the wire will be no different than a single panel.
* Run them in two 2 pairs of 40v. The amperage down the wire will then be double, but still well within the limits of a 10ga wire.
* With an MPPT in either configuration, you could get a max of 33 amps charge @12v w/400 watts of panel.

PWM:
* All 4 in parallel. 4x the amperage, and the highest amount of loss due to cabling. The 10ga wire will handle it due to the average Impp is 5.5a, so ~22a.
* Major downside - the most charge you will get is 22a with the PWM. There is no voltage-to-amperage conversion with PWM, just the amps the panels put out directly.

I don't recommend a PWM for that many watts. You'll get a substantial amount of additional charge amps going with an MPPT.

Worth noting, I bought eight of these for my TC, and they're still on sale---
Grape Solar 100w Panel for $97 w-free shpg


On edit--
One other thought - sell that panel and controller you currently have and get 4 matching panels from Home Repot.

Tom_M wrote:
As long as the specs are similar, any panel will work. I doubt that the existing wiring would work well for 400 watts so you will probably have to upgrade to heavier wire. One option that you might want to consider is to go portable. Here's a portable 200 watt setup that I saw a fellow camper using which is available on Amazon:
Dokio 200 watt portable $249.99

With the addition of a 100 watt panel on the roof and the portable would give you a total of 400 watts.

With each such purchase I read the reviews and question.
There is review for above panel by dober-man and he says is is getting 6 amp in full AZ sun with one time record of 8 amp.
Another buyer reported 2.8 amp
Bit disappointing for 200W.
Wonder if dober-man is a member here?

this picture is 2x 100w Renogy panels on my last camper, with Bogart 2030 set to show Solar charge current.
this is with batteries that were around 75% charged and in bright sun with nice angles (well as best as Southern PA would have in spring @ 13.8V on controller output

I have 3 Renogy panels and they've been working great for the last two years. We're modest power users so this is lots for us. I am using a Morningstar MPPT-45 controller, overkill but it's been solid.

My Adventurer oem wiring was 10gauge, although I believe the SAE connector embedded in the fridge vent is actually 12gauge wire. May be the same since Adventurer and EC are same parent company.

I ran 4awg wire down from the roof but if I was doing again I think I'd wire in series.

Hightec Solar has some 165W Monos for about a $1 / watt. Vmpp on mine is 18.1V. 2 would give you a total of 430W.

I picked up a 30A EPsolar/EPever MPPT with external display and temp sense for around $150. Less if you don't get the external display.

Both are on ebay.