Solar - series vs parallel ?

[Kedwinh]

Hello everyone
I have 2 400w Renergy solar suit setups. What would be the advantage/disadvantage of running them in series with a 40a controller? I currently have them in parallel with 2 40a controllers but like the idea of 1 set of cables and 1 controller.
Thanks
Keith

[SafariBen]

Assuming 12V output, a cold clear day could be over the capacity of the 40A output. Possibly even the input voltage of the controller, which I'm told is a very bad thing to do. Exceeding the 40A output will just waste power at max production, when you probably don't need the power anyway.

[PS89]

There is math and research to be done before any such recommendation can be made.

You need to first get the specs for the panels and then the specs for the SCC, primarily the max input voltage the SCC can withstand. if it's too low, a series connection may not be doable.

[Sunnyfalls]

In series keeps the current lower but increases the voltage. This is best for long runs of cablebetwen the solar panels and the SCC since it is high current that causes high voltage drop and associated power loss which is proportional to the square of the current.

In parallel keeps the voltage lower but increases the current.

So your SCC needs to be able to handle both the maximum current and the maximum voltage that it will receive from the solar panels...and the SCC also needs to be located very close to the battery too.

https://www.renogy.com/blog/solar-pa...s-vs-parallel/

And the entire system first needs to be properly designed before buying/selecting any of the RV appliances or your solar panel system elements. The first step is determining your daily AH depletion, which should be made as small as you can reasonably make it by careful/thoughtful selection of your RV appliances. This than determines the battery AH, solar panel power wattage and SCC requirements which should be designed to enable fully replenishing the daily AH depletion in 4 hours or less and preferably using a low cost and robust PWM SCC or if necessary, a more complicated, expensive, and failure prone but about 25% more efficient MPPT SCC. And of course, few people actually do this and you can read about their moronic approaches on RV forums such as this... So yeah, some math, research and soul searching is required...

Gayle & Bob
"Los Gatos Casita"

[Kedwinh]

Thanks for the replies everyone
Well I guess I'll just leave it like it is and call it good. I was just thinking it would be nice to only have a single set of cables and controller.

[B-Man]

Post the specs of the panels and the controller. Assuming you are at 12 VDC, that would mean the controller would deliver roughly 29 amps charging current if the panels were indeed producing 400 watts. (400 watts / 13.8 volts = 28.9 amps)

That is well within the 40 amp output rating - but what is really important is the wattage rating of the controller at 12 VDC.

With a small array like that, there is no real difference in how you connect the panels - as long as neither panel is ever affected by shadows. If either panel is ever affected by shadows, run them in parallel. If not, series is usually better.

My gut tells me you can easily remove one of the controllers and keep it as a spare.

[corn18]

If these are the Renogy 400W solar suitcase for RV's, each has a Voc of 47.2V @ 72 deg F. The Renogy 40A MPPT has an input limit of 100V. If you put both sets of panels in series, the voltage would be 94.4V. When it gets colder than 72 deg F, the panels will output more voltage and exceed the 100V input limit on a single MPPT.


You could parallel the two sets of panels into a single MPPT, but a single MPPT can only handle 550W, so that may leave some energy at the panels.