Parallel to Series on roof top panels

[billharr]

Added a Victron MTTP SmartSolar 100/20 solar controller. Rewired from parallel to series today to take advantage of the higher voltage.

Before and after pictures.

 

[rando]

Looks like this mod dropped your solar output by 33% ! (kidding of course)

 

[billharr]

Looks like this mod dropped your solar output by 33% ! (kidding of course)

Yep on float, there is not much going on. Sure do like the Victron app.

 

[billharr]

Rewired the loads to go through the Victron Smartsolar MTTP 100/20. Screenshots below show the LED lights, the heater, and the DC Fridge. A lot of information on the APP. I did have a 0.1 amp draw when I thought I had everything off. Took a minute to realize the draw was the Propane detector. Killing the main switch drops the load to zero. Cloudy day and batteries on float so disregard the solar.

 

[Timothy McGowen]

Damn another toy to buy! I love my gadgets.

 

[camelracer]

Bill,

I'm in the process of adding 2 more 100w flexible panels to my existing 100w panel for a total of 300w. I'm now trying to figure out whether to connect them in parallel or series. I'm using the same Victron solar controller that you have so series connection is possible. I know that the series connection will be more efficient but from what I've read the parallel connection is less susceptible to shading degradation.

Since I do a lot of camping in forest areas I am more concerned with the shading problem than maximizing efficiency so I will probably go with the parallel connection. Your thoughts.

 

[pvstoy]

I think you need to look at what voltage you panels put out. Most MPPT controllers need to see at least 18 volts to start doing any thing productive. I wreserled with that question too for a while. I went with Overland Solar 160 watt flex panels the same that FWC is now providing. I settled on wiring three of them in parallel because the operational voltage is 27 volts. I wanted to cumulative add the amps together

Yesterday was the first day I was able to bring it out of the shop to see some sun. The battery was at 86% SLC and i saw 27 volts and 20 something amps . In bulk mode it quickly got it to absorption mode.

On days with partial shading the parellel hookup will protect you and get something out of it. But also on passing clouds mixed lighting if your panels are not seeing much then the output panel voltage is also dropping so you will not get much to the batteries as the voltage is too low to make anything. Series will cumitive add the voltage together and now your panels put out more voltage together and your controller has more to work with.

So take a look at your panel voltage and then you can better make a desicion.

 

[Zirdu]

With three 100 watt panels, you would have to put all 3 in series, or put them all in parallel. You couldn't put two in series and parallel those two with the odd one. With all three in series, you have to be careful the max voltage does not exceed the capacity of your controller. A 12 volt nominal panel might have a max voltage of up to 20 volts? You would have to check the panel specs, then add a bit for safety. My 120 watt panels have several times exceeded the PVmax listed on the panel. So if you figure, for example, each panel puts out 20 volt max, in series of 3 you would have a max voltage of 60. Make sure your controller could handle that.

 

[Lineman]

camelracer, I have three 100w flexible panels in series with a victron controller and two batteries, it has worked great for me. I am not sure which is better for you. I went series for the voltage drop advantage from the panels to the controller. We camp where ever we want and the panels nearly always fill the batteries daily.

 

[billharr]

Bill,

I'm in the process of adding 2 more 100w flexible panels to my existing 100w panel for a total of 300w. I'm now trying to figure out whether to connect them in parallel or series. I'm using the same Victron solar controller that you have so series connection is possible. I know that the series connection will be more efficient but from what I've read the parallel connection is less susceptible to shading degradation.

Since I do a lot of camping in forest areas I am more concerned with the shading problem than maximizing efficiency so I will probably go with the parallel connection. Your thoughts.

Not sure about the shading issue. I did the series to get max benefit from the MTTP controller, also you do get less loss in the FWC wiring from the roof to the controller. I still have my portable 120w solar in a bag folding panel. I have rewired the plugs on the sides of the camper to go to the battery. I did have them wired to the old PWN controller. Hooked up the PWN controller on the folding panel.


From the Victron site:
PWM
The PWM charge controller is a good low cost solution for small systems only, when solar cell temperature is moderate to high (between 45°C and 75°C).
MPPT
To fully exploit the potential of the MPPT controller, the array voltage should be substantially higher than the battery voltage. The MPPT controller is the solution of choice for higher power systems (because of the lowest overall system cost due to smaller cable cross sectional areas). The MPPT controller will also harvest substantially more power when the solar cell temperature is low (below 45°C), or very high (above 75°C), or when irradiance is very low.

PWM
The PWM charge controller is a good low cost solution for small systems only, when solar cell temperature is moderate to high (between 45°C and 75°C).
MPPT
To fully exploit the potential of the MPPT controller, the array voltage should be substantially higher than the battery voltage. The MPPT controller is the solution of choice for higher power systems (because of the lowest overall system cost due to smaller cable cross sectional areas). The MPPT controller will also harvest substantially more power when the solar cell temperature is low (below 45°C), or very high (above 75°C), or when irradiance is very low.

 

[Stokeme]

Bill .....

I am choosing to run two 120W flex panels on the roof in parallel, starting from scratch, in my Grandby Shell. May run a third one if it is necessary. I chose parallel because it simplifies running a 100W flex fold portable from the back wall plug. It remains plug & play if my roof is parallel. It is my understanding, if your roof is in series, your back wall plug has to be run through a separate controller than your roof. You do not get the voltage upgrade, but positioning a portable for Sun at camp, with less components & wiring, appealed to me. But in the end, bottom line AH input into my battery storage, is what matters to me the most. Does 300W @12V in parallel, equal AH achieved, comparable to 100W (200W of panels) @24V in series? Is voltage trade off measurable in that regard?
I’m dense with this stuff, so apologies ahead .....
Mark

 

[camelracer]

I read about the shading problem on several of the boating sites. My understanding is that the shadow from a mast across a portion of one panel in a series system degrades the output of the entire system. My Victron controller has a 100v capacity so series connection is possible but I think I'll start with parallel. I can always change it later if needed. My test trip will be to Owens Valley Memorial Day weekend so shading won't be an issue. I'm hoping that 300W will be enough to overcome any degradation.

 

[billharr]

My set up now, my third one. 150w and 100w in series on the roof. 120w portable has its own controller and wires to the battery. So far I have not needed to plug in the portable.

As with others who learn as I go my system has evolved.

First 120w solar in a bag. Worked to keep battery charged but extra work to set up and carry.

Second 100w and 30amp PWM controller. Package from Renogy. Rewired solar in a bag to bypass the build in controller and feed the 30amp PWM controller.

If I started from scratch I would have gone two 150w or more flex panels on the roof with an MTTP controller. The price of the MTTP controller has dropped a lot. When I started with solar I could buy two extra 150w panels for less than the cost of an MTTP controller.

 

[fwctaco]

Here is a good empirical test on parallel vs series when it comes to shading:

https://www.gonewiththewynns.com/Sailboat-Solar-Series-Parallel-Shading

 

[So Cal Adventurer]

Love the Victron System!!!

Kudos to member Vic Harder for turning me on to it when i asked about installing my own setup!

Checking the info from the cab of the truck without opening the camper to look is huge for me! Love it

 

[Vic Harder]

Love the Victron System!!!

Kudos to member Vic Harder for turning me on to it when i asked about installing my own setup!

Checking the info from the cab of the truck without opening the camper to look is huge for me! Love it