Solar Panels- Wired in Series vs. Parallel question

[teeznu]

So the debate between wiring panels in Series or Parallel. Please tell me the benefits of wiring either way and if there are negatives, please educate me on that as well.
Thanks to those that respond.

[Sam_Spade]

beemerphile1 wrote:
The statement was made that a system with panels in series could be dragged down by a poorly functioning panel. A system with panels in parallel would not be affected by a poorly functioning panel.

Not exactly correct.

In a series arrangement, ALL the current flowing goes through ALL of the panels. If one goes partially open (gets a high resistance and low output), it might severely limit the total output well below the capacity of the remaining good panels.

In a parallel arrangement, one panel going totally dead only removes the capacity of that panel and leaves the others unaffected.

[Almot]

teeznu wrote:
So the debate between wiring panels in Series or Parallel. Please tell me the benefits of wiring either way

It's like asking about benefits of fresh air vs fresh water.
WHAT IS YOUR WATTAGE?

[JiminDenver]

beemerphile1 wrote:
Saw a tv show about solar on houses and other buildings. The statement was made that a system with panels in series could be dragged down by a poorly functioning panel. A system with panels in parallel would not be affected by a poorly functioning panel.

Others may be able to explain the hows and whys of the statement.

It basically works like the results of my mixed panel test. The array is controlled by the weakest panel so when I added a smaller panel to the array, it lower the voltage of all of the rest. It also caused my MPPT controller to constantly search for a peak voltage. This possible could happen with a off sized panel, a shaded panel, a damaged panel or even one that acts differently under different conditions. A 24v mono panel will play better with a similar poly panel in bright sunlight but act different in lower light conditions crippling the poly.

[JiminDenver]

There a ton of decisions to be made when making a system. Start with the decisions that have limitations, Roof space, needs, room for batteries, budget and what's available to you. These are the things you work around with decisions like MPPT vs PWM, series vs parallel, 12v vs 24v, what controller, what batteries, etc. etc.

Each decision you make will affect or limit another so don't make any until you have a handle on the basics so that you can make choices that work well together.

We all look at things differently because our individual set of circumstances require different approaches. Controller efficiency and heat are important to me because our system does little battery charging and a lot of acting like a generator. It's expected to run at full power running things like a small air conditioner with out depleting the bank. So more amps and a cooler controller is a big thing for me. It's just one of the decisions I've made and am still making balancing the whole system out.

[beemerphile1]

Saw a tv show about solar on houses and other buildings. The statement was made that a system with panels in series could be dragged down by a poorly functioning panel. A system with panels in parallel would not be affected by a poorly functioning panel.

Others may be able to explain the hows and whys of the statement.

[pianotuna]

So start with an energy audit. From that project the battery bank size. From that decide on the wattage needed to sustain your camping style.

I'm an energy hog, personally.

[time2roll]

Efficiency only matters during the often short bulk phase of charging.
Once the absorption voltage is reached the efficiency does not matter because you have excess power.

Loss of efficiency during bulk will usually be made up by the MPPT function over PWM. Yes if you have 90v in series vs 3x 30v in parallel both through MPPT your efficiency will drop a bit with higher voltage. But again it only matters during Bulk.

That is probably the hard part is comparing the higher vs lower MPPT and separately comparing parallel PWM to MPPT. Several variables in play at the same time.

All a moot point until you actually choose a wattage and start building a system.

[Ed_Gee]

Not sure some of you understand the way the more expensive MPPT charge controllers work. With series panels sending a higher voltage to the MPPT controllers, the controller converts the excess voltage to current. Example: With Four 5.5Amp panels wired in series, a proper MPPT charge controller can output (charge) your battery bank at near 22 Amps current. Well engineered MPPT controllers can operate up to 98% efficiency.
Another advantage of using series panels instead of parallel panels is that when the sun gets so low that any individual panel operating in parallel cannot generate enough voltage for the charge controller to work, series wired panels are still outputting enough voltage for the controller to provide charge to the batteries.... thus extending the daily charge time.

[RoyB]

Series wiring will be just like the 6V battery wiring... Series will add the voltages coming from each panel however the current which is also very important will only be as high as the lowest panel DC current output...

for instance with my two batteries in my battery bank I would want the solar controller to provide 14.4VDC @ 40 Amps DC capacity if I wanted them to recharge in a three hour periods. Battery science tells me each battery needs 14.4VDC with 17-20AMPS DC current for each battery in the bank to recharge from a 50% charge state to a 90% charge in a three hour period... That would be alot of of solar panels since a typical 120WATT panel only produces around 5-6AMPS DC current.

So in this case I can probably come up with enough panels (two each 120WATT panels and one 240Watt Panel) to give me 17-20AMPS DC current wired in parallel and then would have to plan on a longer time frame of being in the high sun to get them charged up since it is feeding multiple batteries.

This is the way I understand at any rate...

Roy ken

[red31]

$$$$ higher cost controller, lower cost wire and/or panels

[Sam_Spade]

hypoxia wrote:
Series provides a higher voltage which allows the use of smaller wiring to the controller. If wire size is not a factor then parallel is best.

You can't just pick and choose at random.

It is best if the panels are designed for the voltage of the system and are wired in parallel.

Or are designed for half system voltage and wired in series.
There is NO good reason, for example, to wiring two 12V panels in series (for 24 V) and then having to drop the voltage back down again with extra electronics.

[2oldman]

Series v Parallel Sept 2015

Series v Parallel - shading 2012

[MrWizard]

Moved from technology

[time2roll]

How many watts? Series tends to be for larger systems with 400+ watts.

[RLS7201]

:W