Portable Panel with Roof Top Panels on Truck Camper

[johnpitts01]

I want to add a portable ground mounted solar panel to our existing roof mounted system.
Lithium batteries in the camper.
MPPT controller on the camper for the roof mounted panels.
The portable ground mounted panel will have its own MPPT controller.
Can we simply connect the portable panel to the battery terminals?

 

[snoobler]

Yes.

You might be able to parallel the ground panels with your roof panels if they have similar Voc and Vmp, AND your SCC can handle the extra current.

 

[MisterSandals]

Can we simply connect the portable panel to the battery terminals?

No!
You need a charge controller. But your MPPT charge controller with the portable panels attached can be attached to the battery terminals.

 

[snoobler]

I'm clearly sleepy... I mis-read that.

MisterSandals is spot on.

 

[johnpitts01]

Hey guys. Sorry if I misrepresented my plan.
The portable panel will ABSOLUTELY have its own MPPT controller. My original post had conflicting information.

To be clear
Portable Panel -> MPPT controller -> battery terminals
Rooftop panels -> MPPT controller -> battery terminals

This is ok?
The portable panel / mppt controller will "compliment" the rooftop panel / mppt controller. the net result will be the combined output of the portable and rooftop systems to the battery?

The rooftop system will not see the power from the portable system as a "charged" battery and thus not send output to the battery?

Thanks in advance for answering my newbie questions.

 

[MisterSandals]

This is ok?

Yep, not uncommon to have multiple chargers hooked to the same battery.

the net result will be the combined output of the portable and rooftop systems to the battery?

Yep.

The rooftop system will not see the power from the portable system as a "charged" battery and thus not send output to the battery?

Each of the MPPT chargers only sees the voltage of the "battery". If its own charge parameters indicate
that the battery needs charging, it will charge. Thats the easy way to look at it and is essentially what the MPPT's sense and act upon.

 

[HRTKD]

Hey guys. Sorry if I misrepresented my plan.
The portable panel will ABSOLUTELY have its own MPPT controller. My original post had conflicting information.

To be clear
Portable Panel -> MPPT controller -> battery terminals
Rooftop panels -> MPPT controller -> battery terminals

This is ok?
The portable panel / mppt controller will "compliment" the rooftop panel / mppt controller. the net result will be the combined output of the portable and rooftop systems to the battery?

The rooftop system will not see the power from the portable system as a "charged" battery and thus not send output to the battery?

Thanks in advance for answering my newbie questions.

This is how my system is setup. Works fine. I use two Victron SmartSolar 100/50 controllers.

 

[Sean Steele]

I just ordered my rooftop solar setup and would also like to use my cheap folding panel as "expansion". Does the panel have to have its own charge controller or can I feed its output into the same charge controller as the rooftop panels? The rooftop setup will be two 12v/100W Renogy panels wired in series for 24 volts. The portable panel is 18v. The charge controller is a 12/24v 40Amp Renogy MPPT.

If it needs it's own controller, can I cheap out and get a PWM controller for that panel?

 

[HRTKD]

Most likely, you're going to want to use a different solar charge controller to get the most of our each deployment.

See this video for a better explanation than I can give.

 

[Sean Steele]

Thanks for the video. I watched that one and the one about mismatched single panels. The video you linked showed that the best option is two controllers. The second video showed that a 24v panel in series with a 12v panel was the better setup and only used one controller. I can add my folding panel in series by having the port I plug it into wired in series with the roof panels and just have a jumper installed if not using the folding panel. This would be as in the second video I watched. If I wanted to do the two controller method, would it be a problem using a PWM for the folding panel and an MPPT for the roof system?

 

[HRTKD]

I don't see a problem with using two different types of controllers. It's all volts and amps to the battery.

I installed an SAE port on the side of my trailer for connecting the ground panels. The wires from the SAE port go to a 2 pole circuit breaker, which then goes to the solar charge controller.

I chose the two pole circuit breaker because it allowed me to completely shut off access from outside the trailer to my system. Just in case someone tried to damage my electric system by connecting a high voltage or high amperage source to the port, it wouldn't do anything. I leave the circuit breaker in the off position until my panels are deployed and connected to the port.

When buying DC circuit breakers, be very careful that they are actual DC breakers. My first purchase was a mistake, they were AC breakers. I now using these breakers.

2P 250V Low-voltage DC Miniature Circuit Breaker For Solar Panels Grid System Din Rail Mount 16A - - Amazon.com

2P 250V Low-voltage DC Miniature Circuit Breaker For Solar Panels Grid System Din Rail Mount 16A - - Amazon.com

www.amazon.com

 

[snoobler]

Thanks for the video. I watched that one and the one about mismatched single panels. The video you linked showed that the best option is two controllers. The second video showed that a 24v panel in series with a 12v panel was the better setup and only used one controller. I can add my folding panel in series by having the port I plug it into wired in series with the roof panels and just have a jumper installed if not using the folding panel. This would be as in the second video I watched. If I wanted to do the two controller method, would it be a problem using a PWM for the folding panel and an MPPT for the roof system?

To reiterate the video, if your folding panel has the same Isc/Imp, then you can put it in series. If it doesn't, all panels in series will operate at the lowest current value.

PWM+MPPT+generator+grid+solar+wind all at once is fine as long as each charger is appropriate for the battery being charged.

 

[Sean Steele]

I don't see a problem with using two different types of controllers. It's all volts and amps to the battery.

I installed an SAE port on the side of my trailer for connecting the ground panels. The wires from the SAE port go to a 2 pole circuit breaker, which then goes to the solar charge controller.

I chose the two pole circuit breaker because it allowed me to completely shut off access from outside the trailer to my system. Just in case someone tried to damage my electric system by connecting a high voltage or high amperage source to the port, it wouldn't do anything. I leave the circuit breaker in the off position until my panels are deployed and connected to the port.

When buying DC circuit breakers, be very careful that they are actual DC breakers. My first purchase was a mistake, they were AC breakers. I now using these breakers.

2P 250V Low-voltage DC Miniature Circuit Breaker For Solar Panels Grid System Din Rail Mount 16A - - Amazon.com

2P 250V Low-voltage DC Miniature Circuit Breaker For Solar Panels Grid System Din Rail Mount 16A - - Amazon.com

www.amazon.com

My plan was to use an SAE port as well, already have the adapter coming and the ports sourced locally. I plan to have a in line fuse, 10A, but that was it. I'll probably go with a cheap PWM controller for this panel since it will be supplemental power anyway. Maybe I'll upgrade it to MPPT down the line.

 

[Sean Steele]

To reiterate the video, if your folding panel has the same Isc/Imp, then you can put it in series. If it doesn't, all panels in series will operate at the lowest current value.

PWM+MPPT+generator+grid+solar+wind all at once is fine as long as each charger is appropriate for the battery being charged.

Thank you for the confirmation. I think I will go with the PWM for now. I just wanted to make sure it wouldn't "interfere" with the MPPT functionally. I'm probably giving up a few watts but would probably lose more running them all thru the same MPPT. I may just hook up a meter on a sunny day and do the "scientific method" and try it out both ways.

 

[snoobler]

If an MPPT has unutilized capacity, even a small loss due to slight current disparities may be advantageous over a separate PWM controller. If the lower current panels are 5.5A and the higher are 6A, running the higher current panels at 5.5A will only be an 8% penalty to the 6A panels. You will probably be ahead in series on the MPPT controller due to its higher efficiency and improved efficiency from higher PV voltage.

It helps to think of charging as batteries PULLING current from sources, not the sources pushing. The chargers modulate their behavior based on the battery voltage response to current, so when all chargers are configured properly, they all get along just fine.

What will usually happen with multiple sources is that once absorption voltage is hit, the strongest charger will quickly be the only charger as all the others have dropped to float because the battery won't pull more current.

 

[pollenface]

Totally fine to have multiple charge controllers with their own sub-arrays charging the same battery bank.

 

[Sean Steele]

The more I think and talk about using these two "systems" together, the more I think I should try to find actual specs for the panels. Of course, the Renogy panels have all the proper specs listed on their website. The cheap Paxcess panel doesn't list everything but has some specs.

Is it just me or do these panels look very similar in volts and amps? Like the Paxcess panel is only listing "peak" numbers.

 

[Sean Steele]

Crap. Just remembered that I plan to run the two Renogy panels in series. So that would be 24v in series with the 18v, making 42v going to the Renogy controller. I better look up the specs on that too.

Ok, 100v max input.

Should still be good, correct?

 

[snoobler]

I don't like the Paxcess panel specs at all. They are odd and not consistent with every other legit panel out there. I would hesitate to use them for ANY reason in any config.

 

[Sean Steele]

Yeah, I kinda wish I had been a little more knowledgeable about this stuff when I bought that thing. I've had it for a few months and so far have only used the USB ports. It's supposed to be "compatible" with all of the "solar generators" on the market but it just has a 4 way adapter on the end of a 16AWG wire. The USB ports are in a small black box on the back of the panel and haven't burned up my phone yet. No charge controller that I can see but I assume that the ports are regulated since they spec those out clearly in the adverts.

I'll have the Bluetooth monitor connected to the Rover and would be able to see the change in panel input when connecting it in series. Since I already own it, do you think it is safe to use? If it will hurt the system, I won't use it but if it would just be less efficient than specified but still add useable watts to my system, I'm fine with that.

I have a good multimeter. Is there some tests that I can run on it "stand alone" that would put minds at ease, yours and mine?