Series vs parallel

[Rustynails]

Hi folks,
I know this has been asked before but I still don’t have a clear understanding of what I should do. I want use 4-6 solar panels, probably 4-200ah lithium batteries.
Would I be better off In series or parallel, I’ll have 12v and 110 lights. A frig, microwave, dishwasher, washer/dryer, fans…. etc. what would better suit my needs and pocketbook?
Thank you very much everyone!
Safe travels!!!
Frank

[dzl_]

Hi Frank,
You dont really give enough info to answer your question, lets begin by narrowing down what you are really asking, and gathering some info on what you have so far and want to accomplish.


Assuming you are wondering about series vs parallel wiring for your solar panels, we can safely ignore the second bit of your post, it is not relevant (this part):

I’ll have 12v and 110 lights. A frig, microwave, dishwasher, washer/dryer, fans…. etc. what would better suit my needs and pocketbook?

The info that would be helpful:
1. Do you have a solar charge controller yet? What is the max input voltage and max input current?
2. Will your battery bank be 12v, 24v or 48v?
3. How likely/common will it be for one or more panels to be partially shaded, will there be shade sources on the roof?
4. What are the panel specs (specifically the "Voc" and the "Isc" found on the sticker on the back, or the datasheet on the sales page).


Putting together your system is a bit like a crossword puzzle or sudoku, fitting it all together in the abstract is overwhelming in the beginning, but once you've got a few components picked out, the rest of the decisions become much more clear and less overwhelming.


How the math works, combine things in series, voltage increases and current stays the same, combine things in parallel and current increases but voltage stays the same, either way, you get the same power out (since volts x amps = watts)

[rossvtaylor]

What dzl said! ^^

And...after we find out what you have and plan, it's very likely that you'll have both parallel and series connections...because we wouldn't want either option to feel left out. Seriously, though, there are pros and cons to both...and limitations of the charge controller's specs to deal with...so don't be surprised if you end up with two parallel connections of 3-panel series strings. Let's see the answers to dzl's questions, please.

[HamSkoolie]

You also want to get into the habit of stating things in WATTS and WATT HOURS as those are the only way to keep things apples to apples.


4, 200ah batteries could be a lot of different capabilities. Though it's a safe assumption that you mean 12 vdc batteries



If they're 12 volt batteries they'd be 9.6kWh and should be sufficient.


As for the panels, if all panels are in series and ONE is damaged or shaded, you lose ALL PV input. Two series in parallel is probably a much safer bet.

[Rustynails]

It seems to me now that my question is alittle premature. The only thing I have right now are plans/ideas of what I’m going to put in the skoolie. So planning on a frig/freezer microwave, washer/dryer, lights, tv or 2, on demand water heater, water pump. I’m going to try to have all the comforts while being able to boondock for a month.
What would be recommend for battery count and wiring and panel count and wiring. And I’d really like lots of redundancies!!! Thank you very much everyone!!

[Iceni John]

Panels are so cheap that there's really little reason to not just carpet the whole roof with them, then you'll never be wishing you'd installed more for the simple reason there's no room for any more! This is essentially what I did: I first built a walkway between my two roof hatches, then put four tiltable 255W panels on each side of the walkway. Each array's four panels are wired in parallel, producing about 34A at 30V to its own charge controller that then charges its own bank of four series/parallel golfcart batteries. In effect I have two entirely separate PV systems running in parallel, giving me maximum redundency and reliability. As has been noted, if you connect the panels in series, one under-performing or dead panel will kill the entire array's output; it only takes a few leaves or bird poop to noticeably reduce a panel's output.

It ain't rocket surgery to install a PV system; just a modicum of common sense is needed! It was one of the easier jobs I've done for my conversion, and if a dummy like me can make it work well than anyone can do it. The solar and PV experts on the Northern Arizona Wind & Sun forum are an indispensable source of real-world wisdom and experience, so ignore their advice at your peril!

John

[rossvtaylor]

Originally Posted by Iceni John

The solar and PV experts on the Northern Arizona Wind & Sun forum are an indispensable source of real-world wisdom and experience, so ignore their advice at your peril!

John

This is very true. I'm fortunate to live in Northern Arizona, where they are based. I used to work with several of their staff, at another renewable business which folded, and have lots of respect for them. Good folks, indeed.