In series or parallel

[pteck]

Originally Posted by blacklab

For my own education when I get to the point where we want to install 4 x 100w Solar Panels on a Globetrotter 27 and am faced with the smaller AWG of the AS solar prewire and the 3-port combiner box (unless they upgrade both before then---hint, hint, anyone listening?), does anyone know what Lewster says about it?

Or AMSolar?

When doing a 4 x 100w (or more) configuration, do Lewster and/or AMSolar run larger AWG to replace the AS factory pre-wire and replace the combiner box, or take a hybrid approach?

BTW, I'm not saying that how Lewster and/or AMSolar do it means it will be determinative in my decision, as I know others are certainly happy with their hybrid approach. But, interested to know.

Thanks.

Cheers,

Bryan

Systems installed by Lewster and AMSolar, utilizing high quality Victron components, are always full parallel.

[daleyocum]

Originally Posted by blacklab

For my own education when I get to the point where we want to install 4 x 100w Solar Panels on a Globetrotter 27 and am faced with the smaller AWG of the AS solar prewire and the 3-port combiner box (unless they upgrade both before then---hint, hint, anyone listening?), does anyone know what Lewster says about it?

Or AMSolar?

When doing a 4 x 100w (or more) configuration, do Lewster and/or AMSolar run larger AWG to replace the AS factory pre-wire and replace the combiner box, or take a hybrid approach?

BTW, I'm not saying that how Lewster and/or AMSolar do it means it will be determinative in my decision, as I know others are certainly happy with their hybrid approach. But, interested to know.

Thanks.

Cheers,

Bryan

Lewster and AMsolar both recommend running in parallel with a new wire run of 6ga or larger. Airmiles has shown series/parallel can be a good option for those who don't want to run a new wire.

I think I heard new Airstreams are coming with 8ga wire rather than 10ga. At 400w I'd be tempted to use it rather than running a new wire but that's just me.

I installed 500w in parallel on my FC25 because that's what fit given all the other junk on the roof. I ran a new 6ga wire rather use the 10ga pre-wire. Series-parallel wasn't an option in my case given the odd number of panels.

[blacklab]

ptech:

Thank you for your reply.

Daleyocum:

Did you also replace the rooftop combiner box, or did yours have more than 3 input jacks?

Cheers,

Bryan

[daleyocum]

Originally Posted by blacklab

ptech:

Thank you for your reply.

Daleyocum:

Did you also replace the rooftop combiner box, or did yours have more than 3 input jacks?

Cheers,

Bryan

I added my own box (from AMSolar) since I had five panels and a new wire drop. You can get MC4 Y adapters and SAE to MC4 adapters on Amazon if you wanted to use the pre-wire distribution box. My distribution box is partially under the panel on the lower right. It drops down inside the raceway inside the bathroom on the FC25FB.

[AirMiles]

Originally Posted by blacklab

ptech:

Thank you for your reply.

Daleyocum:

Did you also replace the rooftop combiner box, or did yours have more than 3 input jacks?

Cheers,

Bryan

You can use the factory prewire and three-port rooftop box with 400W Parallel configurations. I would use two of the three ports, wiring two panels together positive-to-positive and negative-to-negative and then into a single port. Repeat for the second two panels. The result would be 400W of parallel connected panels on the factory prewire. Follow the link in post 6 above to the Solar Show and Tell thread to see the excellent performance results from 400W of parallel on the factory prewire from Bigventure.

[GMFL]

Originally Posted by FC7039

Why? I am thinking (watch out) that if the panels are not getting much sun then in series may provide enough voltage. Won’t the mppt controller handle the high voltage of in series full sun?

Again. Feel free to PM me

[CarterKraft]

Originally Posted by pteck

Yes, it's certainly a variable and the assumption is the trailer under use. AirMiles uses his trailer a lot and posts a lot of data where you can clearly see when it's consumption limited or production limited. His best and high production watermark is lower than expected. You can peruse that data yourself. Never peaking over 1.3kWH with his 400W series-parallel system. Now he has 600W in series-parallel. With limited use, showing a high watermark of 1.54kWH.



You know fully well I've posted definitive results on multiple occasions from my own system in your thread, so you can sop pretending here. Like I said, you have a nicer system with more sophisticated electronics that paints pretty pictures.

The numbers speak for themselves. Easily 1.78kWH out of my fully parallel 400W system. On a compromised intermittently shaded day no less. I have had production in excess of this but I have to manually take pictures.

http://www.airforums.com/forums/f448...ml#post2263612

I have posted 1.69kwh from 4x100w HQST panels over 8ga series/parallel wire. I just don't see any of these TOP numbers being useful for determining a configuration. These numbers are very useful for determining what is possible for a given solar array size but that is about the end of it as far as I can tell.

[The Maverick]

Hello All:
Thanks for all the posts good pragmatic information and I especially like the monitoring capabilities of the Victron charge controllers, I will have to get one of those and prototype it for upcoming solar installs. I like series connections, higher voltage to a good quality MPPT charge controller i.e., Morningstar. Also, there are solar modules available in a 60 cell frame size, where they have taken (60) of the 6" x6" cells cut them in half, and take (60) 3" x3" cells and another 60 3" x 3" cell and " parallel them together. So you have 120 3" x3" cells 2 sets of 60 paralleled. This helps greatly to mitigate the effects of shading. However, the solar modules are large, we install them on Coaches and RV's have not installed on trailers. Frame size 66" x 40" by 1.5 " 40 pounds. We have used REC Solar 290 watt Twin Peaks with great success. Huntsville Solar Works, LLC.

[AirMiles]

Pteck, no I didn’t remember your post on the Solar Show and Tell thread. Thanks for the link. But again you keep trying to cut down my system rather than showing why yours is better. I understand now that your controller can’t provide the monthly data that a Victron displays.

Again, production is dependent on usage. I haven’t been able to use more than around 100AH in a day with my old Airstream so that limits my production to under 1.5kWH. But if a system is capable of maxing out the 30A controller, it is capable of equaling your production given similar circumstances.

My 600W system has only put up a 1.54kWh because it’s only been used for thirty days with overcast and significant tree canopy. I haven’t had the opportunity to run the DC refrigerator on a sunny day which will get my consumption higher than 100Ah.

You are doing your best to spin the argument against series-parallel but everyone can look at the hundreds of days of data and see that it keeps my Airstream powered without ever needing to be connected to shore power. That is the bottom line. 400W of solar in any configuration can power the stock Airstream, basically offering perpetual battery power, without ever connecting to shore power.

[pteck]

Originally Posted by AirMiles

Pteck, no I didn’t remember your post on the Solar Show and Tell thread. Thanks for the link. But again you keep trying to cut down my system rather than showing why yours is better. I understand now that your controller can’t provide the monthly data that a Victron displays.

Again, production is dependent on usage. I haven’t been able to use more than around 100AH in a day with my old Airstream so that limits my production to under 1.5kWH. But if a system is capable of maxing out the 30A controller, it is capable of equaling your production given similar circumstances.

My 600W system has only put up a 1.54kWh because it’s only been used for thirty days with overcast and significant tree canopy. I haven’t had the opportunity to run the DC refrigerator on a sunny day which will get my consumption higher than 100Ah.

You are doing your best to spin the argument against series-parallel but everyone can look at the hundreds of days of data and see that it keeps my Airstream powered without ever needing to be connected to shore power. That is the bottom line. 400W of solar in any configuration can power the stock Airstream, basically offering perpetual battery power, without ever connecting to shore power.

Hi AirMiles. You misinterpret and misunderstand my intent.

I'm an engineer. A rather accomplished one at that. As any engineer, I've been wrong enough times and will willingly concede when logic and data is shown to the contrary. That's what good engineers do. Design a starting point, pick, poke, and test. Rinse repeat until the final answer stands up to a measure of rigor and truth, and the design meets requirements.

It's not about the amount of data. It's about what it tells you.

Your lots of data tells me something you are misinterpreting. Worse still, you're the individual that is spinning here, changing your premise (overcome factory pre-wire) as you see fit to suit your argument of why you want to enlighten others to follow your wrong path. I've patiently point for point discussed the how's and why's with you in the other thread.

Question should be, what is your intent?

My intent is for truth and best practice. Best practice here is all parallel because that has always been the configuration least impacted by dynamic environments and shade. Serial configurations, even partially, are greatly susceptible to shade with each shaded panel impacting other panels potential production.

It's why you feel the need to upgrade to 600W even when your data suggests your consumption needs don't warrant that. Your system is poor performing under compromised shade scenarios, moreso than an all parallel system.

[pcskier]

Originally Posted by FC7039

Why? I am thinking (watch out) that if the panels are not getting much sun then in series may provide enough voltage. Won’t the mppt controller handle the high voltage of in series full sun?

If your concern is that series parallel will double the voltage and therefore switch the controller on sooner, don't be concerned. My Victron controller (fed by 400 watts of parallel panels) switches on before the sun is even up over the horizon. (Trojan T105 6v Batteries). Victron says the panel voltage needs to be 5V higher than the battery voltage to switch on. Running the water pump briefly might trigger this, though I haven't tested that theory. I just know mine turns on very early in the morning. In this pic I was in a forest clearing in the mountains of Montana. Sun was nowhere in sight due to mountains to the east as well as high tree canopy adjacent. Zero direct sunlight. But the controller was on and providing amps already, and ready to really go to work when direct sun hit the panels. 20 minutes later it was 19.8 volts, still with the sun well below the mountain and tree-line. I'm not saying series/parallel would not also show this result. I'm just making the point to NOT worry about increasing the voltage to make sure the controller fires up sooner. Mine fires up literally at dawn without direct sunlight.

[pteck]

Originally Posted by CarterKraft

I have posted 1.69kwh from 4x100w HQST panels over 8ga series/parallel wire. I just don't see any of these TOP numbers being useful for determining a configuration. These numbers are very useful for determining what is possible for a given solar array size but that is about the end of it as far as I can tell.

The premise for evaluating top numbers is because of the assumption that series-parallel configurations decrease transmission losses, especially over limited gauge factory pre-wire, such that the system can eek out more efficiency to support more overall production.

My all parallel setup with 4x 100W system has demonstrated on multiple occasions production upwards of 1.8kWH. Which I wished I would have captured. On 10gauge factory prewire no less. I computed it in the other thread but transmission losses even on the sunniest days when overall production is not that much of a concern is less than 1%. Or maybe something like 18Wh.

Then the premise is that serial-parallel starts earlier in the day. My system regularly starts production before sunrise in twilight which I have a picture of in the other thread. pcskiers data also suggests the same. Yet if you insist, those minor watts are still not something to optimize for as again, it's something like a few watt hours. Which parallels pulls in just fine. Actually better, because each panel can contribute on it's own and not wait for other panels to wake up due to alignment. Twilight is a form of extreme shade if you will. Something that parallel handles far better.

Which is why the data speaks for itself. It shows all parallel peak production numbers are surely not suffering from factory wiring or starting later in the day.

First order principles would say that we should optimize for the greatest impact: shade. Because as we all know, shade is the greatest barrier to solar production. Why choose a configuration that is known to be highly impacted by shade. In series setups, shadows cast partially over a single panel, will impact production of other panels in the system. The larger the system the more opportunity lost. In a 6x 100W panel setup, a little shade cast by a cloud, tree, A/C shroud, or vent pipe even, can and will impact production to something like half of the interconnected system. Or 300W of opportunity lost at a time. Not something an MPPT controller can work around. Yet some are insisting that we should optimize for the 18W or 3W tertiary factors?

[CarterKraft]

Originally Posted by pteck

The premise for evaluating top numbers is because of the assumption that series-parallel configurations decrease transmission losses, especially over limited gauge factory pre-wire, such that the system can eek out more efficiency to support more overall production.

My all parallel setup with 4x 100W system has demonstrated on multiple occasions production upwards of 1.8kWH. Which I wished I would have captured. On 10gauge factory prewire no less. I computed it in the other thread but transmission losses even on the sunniest days when overall production is not that much of a concern is less than 1%. Or maybe something like 18Wh.

Then the premise is that serial-parallel starts earlier in the day. My system regularly starts production before sunrise in twilight which I have a picture of in the other thread. pcskiers data also suggests the same. Yet if you insist, those minor watts are still not something to optimize for as again, it's something like a few watt hours. Which parallels pulls in just fine. Actually better, because each panel can contribute on it's own and not wait for other panels to wake up due to alignment. Twilight is a form of extreme shade if you will. Something that parallel handles far better.

Which is why the data speaks for itself. It shows all parallel peak production numbers are surely not suffering from factory wiring or starting later in the day.

First order principles would say that we should optimize for the greatest impact: shade. Because as we all know, shade is the greatest barrier to solar production. Why choose a configuration that is known to be highly impacted by shade. In series setups, shadows cast partially over a single panel, will impact production of other panels in the system. The larger the system the more opportunity lost. In a 6x 100W panel setup, a little shade cast by a cloud, tree, A/C shroud, or vent pipe even, can and will impact production to something like half of the interconnected system. Or 300W of opportunity lost at a time. Not something an MPPT controller can work around. Yet some are insisting that we should optimize for the 18W or 3W tertiary factors?

Slow down, I didn't proclaim either method superior.

But as near as I can tell all your data is you telling me(us) which way is better. You have not posted any "data" that shows why/how it is true only the claim that it is.
Again peak production numbers are a joke, I could leave my inverter powering fans all day while I am gone and have no doubt add 30% to my highest daily production but what would that show? Would it show my system was superior to yours and AirMiles, nope. It would only show I consumed more.
I am not too proud that I won't move my system to all parralel at some point to see how it does but I don't really see how I will know, or how I will accurately test the system.
Here is a log of the output at a recent music festival with 12v only powering lights and bathroom vent fan. Does that log show my system performs poorly due to measly 480wh production with only 172 max watts? No it shows with my battery only drawn down to a low of 12.56v that's all that was needed to recharge. Using heavy loads during peak solar has the same effect on the Victron logs, it skews the production higher. Neither high or low output is a reflection on wire method. I honestly have no idea at this point which way is better or how to prove it. My data shows I'm doing fine as does yours, Wire it as you see fit and try to keep the voltage drop as low as possible for budget and labor costs. I hope on that we can all agree.

[FC7039]

Well, hmmmm, I don’t know what to say. Thanks?
I was thinking in low light like evening or morning that series would do more. I was not thinking about shade. My panel are not attached even if place in a good place. The earth move and the sun’s angle changes. Trees get in the way. Most times I set them and leave for most of the day.

I would think a simple “because of shade parallel is better” or a simple argument/ make that “reason” for series would also be a good post. Again thanks.

I will read the other thread.

[GMFL]

Originally Posted by FC7039

Well, hmmmm, I don’t know what to say. Thanks?
I was thinking in low light like evening or morning that series would do more. I was not thinking about shade. My panel are not attached even if place in a good place. The earth move and the sun’s angle changes. Trees get in the way. Most times I set them and leave for most of the day.

I would think a simple “because of shade parallel is better” or a simple argument/ make that “reason” for series would also be a good post. Again thanks.

I will read the other thread.

Good luck

[waninae39]

if one panel in series gets shade, the whole output drops
if one panel in parallel gets shade, the current output drops

[SandKSmith]

For the past couple of months, i’ve been updating our Safari to enable more varied stays with out worrying too much about power & commications. I’ve added a Weboost, a Yeti1400 and transfer switch, an EMS, LED lighting, and finally, four 100 watt Renogy solar panels and a Victron MPPT charge controller. The solar was finished in a bit of a rush because we were to leave last Saturday for Half Moon Bay, Ca. In the rush, I wired the solar in the series parallel configuration using the factory prewire. It was two less cables and I had little time. The panels are set up like this: the front of the Airstream has one on each side, set in 5 inches from the roof rail for work/foot clearance. The other two are on the street side as far back as I could go, but one is next to the A/C unit. The TV / Weboost antenna is on the street side on our 25’ Safari so a panel won’t fit there. In retrospect I probably should have put the 4th panel in front of the A/C unit.

You’ve probably read about the PG&E power shut down in California. That included us in Half Moon Bay. We ran the heat too high last night.... (they should put makings on that old mechanical thermostat.... ) and we woke up with more than 50 AH consumed on our 100 AH marine deep cycle batteries. ( to be replaced soon). The good news is that this was a potentially a great test of our solar capabilities. The batteries were depleted as I care to go.

We are parked facing mostly south so the morning sun would hit really only 1 panel first, the front left. And it took a good two hours after sunrise before I saw any meaningful power from the solar. The angles are all wrong for morning sun on the curb side of the Airstream. The series - parallel wiring isn’t helping us here. Later in the morning, the A/C unit was probably shading one of the two rear panels. Again, the series/parallel isn’t working to our benefit.

During the mid day, all seemed okay. It recharged the house batteries and topped off the 3% used on the Yeti, but just barely. The batteries were at 99% at 3:30pm. In total, the system put in 1.1 KW on a cloudless day. Much less than other 400 watt installations I’ve read about here using the factory 10 ga prewire.

What do you think about my conclusions? Do you more experienced guys/gals see this the same way? I think I’ll rewire these in parallel when we get home.

[uncle_bob]

Originally Posted by waninae39

if one panel in series gets shade, the whole output drops
if one panel in parallel gets shade, the current output drops

Hi

If they are in series *and* we are talking about two 12V panels ( so up above 24V) the voltage drops but the controller keeps right on going.

If you have two 6V panels (from where???) in series and the voltage drops below 13V or so, yes the controller drops out. You see a lot of YouTube videos showing this happening. Shade a 12V panel and you can do the same thing.

Either way, the power goes down when one is in the shade.

Since there are no "standard" accessories to wire in series, you will have a hard time getting an installer to do it that way. They very much want to use stock parts and hook them up in the way the manufacturer told them to. Their insurance agent is *much* happier if they do it that way.

Bob

[cru-in]

I ran two panels, in series and on one side of the roof, to one Morningstar MPPT Controller and a second set of panels, in series and on the other side of the roof, to a 2nd Morning star MPPT controller.

It worked great. Each MPPT maximizing for each set of panels and sun conditions. It was interesting to watch, throughout the day, the different production from the left and right side panels as the sun moved across the sky.

With MPPT controller prices coming down, I am surprised more folks do not do this.

[GMFL]

Originally Posted by cru-in

I ran two panels, in series and on one side of the roof, to one Morningstar MPPT Controller and a second set of panels, in series and on the other side of the roof, to a 2nd Morning star MPPT controller.

It worked great. Each MPPT maximizing for each set of panels and sun conditions. It was interesting to watch, throughout the day, the different production from the left and right side panels as the sun moved across the sky.

With MPPT controller prices coming down, I am surprised more folks do not do this.

Neat idea!