Adding and Removing a Portable Panel to an existing Roof Panel System

[dirtybobby423]

Hi,

I was wondering how difficult it would be to add an additional panel (or two) to an already existing RV solar system when I am parked. For instance, could I have 4 panels mounted the roof and connected at all times, and then when stopped add additional panels to the system? I am using the MPP 24v charge controller/inverter. Can I add some quick-disconnect leads or something similar for the additional panels? Anything else I would need to know? Thanks in advance, love the forum.

Thanks!

 

[gnubie]

There are catches adding panels.

If you add a panel in series it needs to have an amp (Imp) rating at least that have the existing array or it will restrict their power output by lowering them to its amp rating. Likewise if it is shaded it will restrict the entire array to what ever amps it is currently producing.

If you add a panel in parallel you need to keep the voltages of the existing system and the additional panel close otherwise various factors may result in the entire system being reduced in power or depending on the exact numbers the new panel contributing little power at all.

What's your existing configuration? Post the panel specs, a readable picture of the label on the back or a link to a web page for the panel etc, and how are they wired, series, parallel or some series / parallel configuration.

 

[dirtybobby423]

This would be for 4 12v 100w panels on the roof. 2 panels wired in series for 24v and then the 2 sets wired in parallel to the charge controller with 2 24v lithium batteries. I would then like the ability to set out 2 additional panels (same panels wired in series for 24v) when I am parked for whatever period of time.

So that would give me 24v/200w on the roof and then I would be adding in another 24v/100w from the portable panels (I think that is right).

I currently only have the 4 panels on the roof, and would be buying the additional panels. Would I be better off just upgrading to some higher wattage panels on the roof rather than trying to do this? Space is at a premium on the roof, that is why I was considering this.

Thanks

 

[dirtybobby423]

 

[Freep]

I've been thinking about the same thing for my rig. I'm toying with several ideas. One is creating a "power generator". basically just a smaller LiFePo4 battery pack that I would charge with portable panels. When charging is done, I would plug it into a port on the camper to charge the main battery.

This way I also have a portable battery I can use in my clamshell tent which I use as an office.( I'm leaning toward this solution since it solves several problems)

The other idea is to add an MPPT controller to the portable(which I'd have to do with the above scenario too) and have a port near my battery compartment and charge it too.

Or! I could mount the additional MPPT controller in the battery compartment and plug the external panels into a port that connects to the MPPT controller.

 

[Freep]

I currently only have the 4 panels on the roof, and would be buying the additional panels. Would I be better off just upgrading to some higher wattage panels on the roof rather than trying to do this? Space is at a premium on the roof, that is why I was considering this.

Thanks

I have space constraints too. I ended up buying these panels because of the size and max power.

https://smile.amazon.com/Newpowa-Solar-Efficiency-Module-Marine/dp/B07WV6P4BT

 

[snoobler]

This would be for 4 12v 100w panels on the roof. 2 panels wired in series for 24v and then the 2 sets wired in parallel to the charge controller with 2 24v lithium batteries. I would then like the ability to set out 2 additional panels (same panels wired in series for 24v) when I am parked for whatever period of time.

So that would give me 24v/200w on the roof and then I would be adding in another 24v/100w from the portable panels (I think that is right).

I currently only have the 4 panels on the roof, and would be buying the additional panels. Would I be better off just upgrading to some higher wattage panels on the roof rather than trying to do this? Space is at a premium on the roof, that is why I was considering this.

Thanks

This is essentially the best way to do it. Take the array on your roof and create the same series on the ground with more in parallel as you need it.

2S2P on the roof?

Same panels could be 2SXP on the ground up to your charge current limit. You'd just need to parallel the two arrays where they go into the charge controller. Since the panels on the roof might be getting very little, you could go as big as you can on the ground.

Even if you can't use the exact same panels, if they have the same or very similar Voc and Vmp, you can expect near optimal performance.

It's a great way to get solar while enjoying shade.

 

[gnubie]

If you are tacking in another 2 of the same panels in parallel with the existing parallel sets that's fine. All you do is add power the power of the new set, that configuration will not result in any reductions.

 

[dirtybobby423]

Sounds doable then. Thank you for the info!

 

[HRTKD]

I ran out of space on my RV roof. I have two panels that I deploy on the ground that go to their own solar charge controller. On a recent trip, I used just one panel and it worked fine. It was a very shady spot so it wasn't the best test.

If I get the ground panels setup right, they have the potential to produce more power than the panels on the RV roof.

 

[chrisski]

I'd be careful about the higher wattage panels. So much stuff is advertised and can't meet the expectations. These panels basically put out the same amount of power per square foot regardless of the brand. I was getting ready to purchase a set of panels not even labeled with a company, when I realized they were 25% smaller, cheaper, than a panel of about the same power from a reputable company. If by more powerful you mean bigger, than maybe, but other than that no. I have a high efficiency panel that is a half inch narrower than the normal panel. That is not that much space saved, and basically the same wattage per square foot.

I will caveat what I said above that perhaps the top name brand will get you four more percent efficient at a premium price, but I'm not sure how noticeable that 4% will be.

About deploying the ground panel in the same configuration you have your roof, you know where you'll be setting up better than me. For me, I considered the same thing, but because places I will be staying at are likely to receive much more shade than my roof, I will get a second Victron Charge controller which are designed to work together via bluetooth. Between shading on the ground, and orientation to the sun, I expect the ground panels to be much less efficient most of the time, but much more efficient at other times. With my strings not matching in output, that'd kind of like with your 2S2P, deciding on other than 2s for that third parallel string. If you have ideal set up conditions and the panels match it's prefect.

For my second charge controller I have yet to buy, I have purchased three portable panels, 100 watts each that are easy to setup and angle to the sun, and will add a fourth to that, then purchase the charge controller.