Yet again...series or parallel?

[Rbertalotto]

I have three 140w/12v panels on roof of travel trailer. Epever 40a Trader 4210AN solar charge controller. Currently the panels are in parallel. They charge my batteries from usual 85% to 100% in just a few hours in the morning. Would I have even better performance in series? My concern is there are lots of other things on the roof to cast shadows on the panels during the morning with low sun angle.

Any advise appreciated.​

 

[John Frum]

With 3 panels your only options are 3s or 3p.
Since you don't post any details of your panels we can't determine if 3s is even an option with your current solar charge controller.
Seems that shading is a concern so 3s may not be advisable even if its a possibility.

 

[Al D]

It appears your setup is optimal in the current parallel configuration. Given the probability of shadows, a series configuration would not be advised.

You could, of course, try seeing if it does make a difference tomorrow morning ?. It's suggested to perform rewiring when panels are not active (ie. at night or covered).

 

[Rbertalotto]

Thanks folk!

 

[rburkat]

Well you can have 2 in parallel and the those in series with the other one. It would be as if you had a higher wattage panel in series with a lower wattage panel, which should be fine in series.
I have this type of setup where the 2 panels in parallel are positioned on each side of the Aircon unit, which might cast a shadow on one of the panels but them being in parallel will still give me current flow. That parallel circuit is then in series with a third panel that that is more in an open area. This way I figure I get best of both worlds. The series benefit of getting voltage in low light conditions but not impacting my whole circuit if one of the panels on the side of the aircon is in the shadow.

 

[mikefitz]

Where you have a series string the current is limited to the lowest output panel. Thus two in parallel with a single in series would in effect limit the power to that of two panels.
The '12 volt' panels have a OC volts of around 22 volts , so 3 in series is well within the working region of the Epever controller.
In my experience panels with bypass diodes ( that most will have) when connected in series or parallel produce more or less similar power outputs under most conditions. The series connected panels will generate enough volts early and late in the day to keep the controller active, however the low current under these conditions makes very little Increased power yield.
The power reduction of the panel will depend just what part of the panel is conpromised. Panels are divided into 2 or more series strings of cells, so if the shadow falls on any cell or cells in all the strings at the same time, the current will be very low.

On balance if the OP is pleased with the existing setup there seems little need to make changes other than an experimental exercise to compare the two options.
Note that with 3 panels in parallel, a fuse is needed in series with each panel before the parallel junction. This prevents two panels allowing excess current to flow into the faulty third panel.

Mike

 

[Rbertalotto]

Thank you Mike. Extremely informative!

 

[Vigo]

As far as i'm aware the only real advantage to series is minimizing the physical size and amount of wiring and connections you need to use. For example if i had 3 panels and had the option to wire all in parallel, or 2 in parallel in series with the other one as rburkat mentioned, I would only do that if it simplified something about the physical installation process greatly. Although putting panels in series will reduce the 'loss' in the wiring because of voltage drop, my gut feeling is that with only 3 panels that benefit would be immeasurable, while IF it did force you to add an extra length of wire or extra set of connections, that would be enough of a downside to dissuade me from it. Obviously the value placed on each factor changes as the total size of the installation grows. When you get to the point of 'needing' combiner boxes you are well into the point where wiring in series would reduce your cost and complexity of wiring significantly.

rbertalotto, i recognize you from youtube and tractor forums. Tip o' the hat to ya.

 

[Rbertalotto]

As far as i'm aware the only real advantage to series is minimizing the physical size and amount of wiring and connections you need to use. For example if i had 3 panels and had the option to wire all in parallel, or 2 in parallel in series with the other one as rburkat mentioned, I would only do that if it simplified something about the physical installation process greatly. Although putting panels in series will reduce the 'loss' in the wiring because of voltage drop, my gut feeling is that with only 3 panels that benefit would be immeasurable, while IF it did force you to add an extra length of wire or extra set of connections, that would be enough of a downside to dissuade me from it. Obviously the value placed on each factor changes as the total size of the installation grows. When you get to the point of 'needing' combiner boxes you are well into the point where wiring in series would reduce your cost and complexity of wiring significantly.

rbertalotto, i recognize you from youtube and tractor forums. Tip o' the hat to ya.

Yup, That's me....Converting gas tractors to electric! Among many other endeavours! www.rvbprecision.com

 

[rburkat]

Where you have a series string the current is limited to the lowest output panel. Thus two in parallel with a single in series would in effect limit the power to that of two panels.
The '12 volt' panels have a OC volts of around 22 volts , so 3 in series is well within the working region of the Epever controller.
In my experience panels with bypass diodes ( that most will have) when connected in series or parallel produce more or less similar power outputs under most conditions. The series connected panels will generate enough volts early and late in the day to keep the controller active, however the low current under these conditions makes very little Increased power yield.
The power reduction of the panel will depend just what part of the panel is conpromised. Panels are divided into 2 or more series strings of cells, so if the shadow falls on any cell or cells in all the strings at the same time, the current will be very low.

On balance if the OP is pleased with the existing setup there seems little need to make changes other than an experimental exercise to compare the two options.
Note that with 3 panels in parallel, a fuse is needed in series with each panel before the parallel junction. This prevents two panels allowing excess current to flow into the faulty third panel.

Mike

I just picked up a 3 to 1 mc4 connector so ill do a test tomorrow 3 in parallel, 3 in series and 2 parrallal/1 series and report back.