New solar panel

[Fred Cook]

I am in the process of replacing my my original 100 Watt solar panel with a 100 Watts Monocrystalline 100W 12V Solar Panel High Efficiency Mono Module RV Marine Boat Off Grid (100W Classic) panel. My question is... can I just plug the two original wires coming through the roof to the new panel and expect it to work properly?

[Bill Lampkin]

yes

[Fred Cook]

yes

Thanks Bill. I wasn’t sure if these panels had unique controllers attached to them.

[Bill Lampkin]

Your solar controller (heliotrope) , if original) should work fine with a new panel. A 100w panel puts our about 5 amps in full sun, so its at best a trickle charger that only works when the sun shines. Don't expect to go boondocking now without your generator!

[Bob Disney]

How many solar panels would be required to boondock without using the generator?
Not including microwave and AC
400 watts?

[Joel Ashley]

I understand that there are 200W panels now that are nearly the same size as our factory 100W ones, Bob, and some can be adjusted to face more toward the sun as needed, manually, electrically, perhaps even automatically.  I’d think the number of panels needed then depends on that, but 400 watts would be a minimum total for the way we carefully use power dry camped, assuming full solar exposure.  800W (four 200W panels) would be great. 

So obviously habit of use, individual panel wattage, and solar availability all play into how many you’ll want, not to mention cost including that of an appropriate controller.

Others here have recent updates to their solar and may provide more experienced opinions.

Joel

[Bill Lampkin]

The question to ask (or answer) is not how many solar panels you need, but how much power to you consume each day. Do you have a residential refrig?  How much power you have available to use is dependent on your battery capacity. We have 4 GC2 6v +flooded (not AGM) batteries rated at 210 amp hrs each, but because they are 6v and connected in series-parallel, you have only 420 amp hrs total. And if you use the 50% rule, then you have only 210 amp hrs available. The 50% rule says don't discharge your batteries below 50% state of charge voltage (12.2 v). So back to our 210 amp hrs available. You will only have 5 hrs or so of sun to recharge your batteries, so you would need 800 watts of solar or so to keep from using your generator. That's a lot of solar on a motorhome.

[Robert Lawrence]

I have been pricing this out for a while. Additional solar vs Lithium

My plan is to replace the original 2005 residential fridge with a new 2022 energy efficient model.  Dropping my electrical demand significantly. 
 
Then upgrade solar panels.

[Bill Lampkin]

Solar panels should be thought of as a 'trickle charger' as a 100w panel only produces about 5 amps in full sun, no shade, in the summer, daytime. so to get a 40w charge, you would need about 800w of solar. that's nearly a roof full. Our residential fridge has helped with the DC usage. I would upgrade your batteries first.

[Fred Brooks]

    Here is another consideration, A typical controller is a PWM style. (Pulse width modulation) The newer and more efficient controller is a MPPT. (Maximum power point tracking). It combines voltage and wattage in the charging sequence. The better units out there have 3 stage charging, Bulk, absorb, and float and also have the equalize option for lead acid batteries. I have a Victron 50amp mppt with 700 watts of solar power. It keeps up with all my dry camping adventures and Samsung refer. Fred

[Bill Lampkin]

Fred, How many batteries does your Marquis have (house). Our '05 PT has 4x GC2 lead acid batteries. I think they are about 6-8 years old!

[Fred Brooks]

   Bill, I have 6 GC-2 interstate extreme service.