Any tips on my setup?

[Sunking]

Sunking, maybe you missed the math showing that the temp corrected Voc is less than 50 V. Two panels in series, in this location, is safe for a 100 Voc controller.

The Controller VOC is 92 volts. His panel Voc is 46 volts @ 25C. Personally I do not care if he wires them in parallel or series. He does not know what he is doing and you know it.

At 40 degree F he goes above 100 volts.

[Wrybread]

I think many people who are involved in solar have something similar - a system that's not quite complete, used for either testing or occasional use.

Mind boggling.

(As is Sensij's patience.)

[sensij]

Sunking, maybe you missed the math showing that the temp corrected Voc is less than 50 V. Two panels in series, in this location, is safe for a 100 Voc controller.

Voc varies with temperature. You'll see a temperature coefficient on the panel's datasheet... typically around -0.3%/K, or -0.14 V/K. If the panels are 46 Voc at STC (25 deg C), it needs to be adjusted for the minimum temperature they'll see. Minimum design temp for Stockton is -3 deg C (see link below), so that would be a 3.92 V increase, raising the 46 Voc panel to 49.92 V. Two panels in series just barely clears the 100 Voc limit for the Tracer charge controller.

http://www.solarabcs.org/about/publi...map/index.html

[Sunking]

You absolutely use Vmp when evaluating operating efficiency and transmission loss. Voc only matters relative to the charge controller's specification, and as we've already established, two 24 V panels in series is fine on this controller in locations that don't get too cold. Surely you are familiar with 2014 NEC 690.7(A).

Stop the nonsense Sensi I do not give a crap about Vmp and has nothing to do with what I am talking about. With his two 300 watt panels in series Voc exceeds his controllers Voc limit period end of discussion. That is exactly what the NEC is telling you and has nothing to do with Vmp. If you do not know the difference between Vmp and Voc, get out of the biz.

[jflorey2]

Incidentally, I think you might be a good illustration of my theory that over complicating solar scares people away from doing it. You're the moderator on a forum dedicated to solar, and yet your RV doesn't have a permanent solar installation. That's kind of amazing.

Not that amazing to me.

I have two solar power systems on my home. The first is a 10kW system that I don't mess with much. The second is a ~1kW experimental system that feeds into either a Kid (and then to a 48V bank + an Outback GVFX) or to several Enphase inverters. It's an experimental system that I run tests on for my work. The longest it has remained the same is about 18 months.

When I had an RV I had an assortment of thin film panels that totaled about 300 watts. They stored under the bed. When we stopped we'd lay them out wherever got the best sun. It would run the fridge and a few lights and that was about it.

I think many people who are involved in solar have something similar - a system that's not quite complete, used for either testing or occasional use.

[Wrybread]

Incidentally, I think you might be a good illustration of my theory that over complicating solar scares people away from using it. You're the moderator on a forum dedicated to solar, and yet your RV doesn't have a permanent solar installation. That's completely amazing.

I obviously could be wrong, but I suspect its because you think its a big undertaking. I'm not talking to you here, but to people who are considering solar for their RVs in general: The beauty of solar is that it absolutely isn't complicated. Get a couple of 300 watt panels (or even just one). If you want to save some money and are somewhat handy with a multimeter, don't be afraid of Craigslist. Personally I think the Tracer 40A MPPT charge controller is just fine for most installs, but obviously that's debatable. Get an Outback if you want to be sure and want room to grow, but in my opinion that's overkill. And no, you don't need to comprehend the minutia of how an MPPT charge controller works to use one, but you should wrap your head around the gist. Get 2 or 4 Trojan T105 batteries (I'm a big fan of 4 of them), and unless you're powering a small village wire them for 12 volts. If you want to go nuts read a few of Sunking's rants, but I have a feeling they've led to more systems never being built than built. And the ones that were built were over-built and over-priced. For a much more reasoned source of information you might hit Arizona Wind & Sun (or similar high end solar dealer), and buy your parts from them if you have more money than knowledge of electricity and time to research.

And it bears repeating that a lot of the info spouted by Sunking isn't there to help people with their solar installs. This is his assessment of solar on RVs:

Solar is just for show and tell or for extending long stays. You still need a generator or Isolator to get charged up dry camping for extended periods.

That is, simply put, completely wrong, and a shocking statement coming from someone who should know better.

In another thread he called the solar industry a scam.

He's not here to advocate for solar, or even to empower people using it. He's here to grind his bag of axes and try to scare people into taking him seriously. And of course I'm not saying that every one of his rants are misinformation (though many are, as sensij awesomely demonstrated in this thread), but they sure are above and beyond what's necessary for an RV solar install. And they sure do ignore the fundamental fact of how well solar installations on RVs in the real world work.

[Wrybread]

> it has a lot of space below to store my portable solar panel system if we decide to go off grid during our long trips

Oof, portable solar systems in RVs are a massive pet peeve of mine. It seems to me that the roof is the best place to store panels anyway.... With the added benefit of not having to do anything once you arrive where you're camping.

But yeah, with a smaller RV I've found the secret is maximum space efficiency. And I'm lucky in that my girlfriend has the same taste in this stuff as I do. We try to take lessons from the RVs in Europe and Japan, and not the usual American behemouths. With garbage disposals! Gotta love American ingenuity sometimes. And, incidentally, only in America is a 24 foot RV considered "small".

That said, if winding roads aren't an issue, and storage isn't an issue, then yeah big RVs are awesome.

Personally I'm not a fan of generators, unless you need a mission critical backup like TX's office. Or unless you need air conditioning (which, granted, covers a lot of people, but I've been living on the Pacific coast for so long I forgot what AC feels like). I think that what most campers are using their generator for could easily be done with solar. It drives me nuts when someone is parked under full sun in cool temperatures with their generator running. We take roadtrips almost every weekend, with frequent long (over 7 days, often longer) stays in one place without moving, and I've never even come close to running out of power with my single 300 watt panel. And the compartment where the generator used to live makes an awesome battery bank and tool shed. The purpose of this expansion is to power my fridge, since we leave it on 24/7/365 (even when we're not using the camper, since we leave food in it) and the propane costs add up, and it sure does suck when it runs out unexpectedly and you arrive to a camper stinking of rotten food.

[SunEagle]

@Suneagle: Ha good point. That's a pretty bad picture of it though. Its perfect for my girlfriend and I: 2 offices (one in the back with awesome panorama views of the beach usually) and another table in the middle, and we sleep in the roomy bed above the cab. Its a 24 foot Class C. For my girlfriend and I I'd call it just right. My previous camper was a Hitchhiker III 5th Wheel very much like TX's, and personally I'm glad for the downsize, but those are because of personal factors like driving on winding Route 1 in California all the time, and slideouts when parked on the beach become a maintenance hassle. My trailer after that was a 45 foot 1956 Spartan. Now *that* was an awesome trailer!

As far as Sunking's new misinterpretations of my needs and statements, I'll just say that I certainly wasn't suggesting that 250 watts would be enough for TX's trailer. Personally I'd go 600 watts of solar (or 900 if you want to go nuts) and a 2000 watt Honda EU for emergencies and call it a day, but I know that diverges from the Platonic ideal of solar systems. But if you don't realize that the way I'm suggesting is the standard high-end way of outfitting RVs, and furthermore that it works awesomely (and is in fact overkill), then you don't have enough experience with the topic at hand (solar for RVs). Ok fine, the Honda EU is cutting corners, but personally I think its an improvement over most RV gennies.

And it's absolutely mind boggling that he still doesn't understand that I'm adding panels to an existing system, so keeping my existing controller, especially when it will very likely work just fine, is, at a minimum, the best way to start. It's also mind boggling that he really feels the need to rant about my controller in like 20 posts. This is also pretty mind boggling.



It's hard to believe that that's a serious statement. Just to name a few reasons to compromise in an RV solar install:

- price (usually the biggie)

- space (also a massive factor)

- simplicity (for example, wiring batteries for 24 volts is usually more efficient, but that doesn't mean its worth the expense, labor and added complexity)

And there's a bunch of miscellany like using your equipment at hand when possible.



Unless, as I explained a bunch of times, you have shade issues! And unless you already have a controller that will probably work just fine with the panels in parallel, so you don't see the need to spend an additional $600 just because some internet blowhard is oddly desperate to get his point across.

I'm seriously questioning his motivations at this point.

Well like I said my wife prefers a little more room in ours and it has a lot of space below to store my portable solar panel system if we decide to go off grid during our long trips. But it also has a 5000 watt genny and the alternator does a real good job keeping the batteries up to snuff. The solar is just a fun (but expensive) project I built for the home because I did not listen to the experts here before I opened my pocket book. Live and learn.

[Wrybread]

@Suneagle: Ha good point. That's a pretty bad picture of it though. Its perfect for my girlfriend and I: 2 offices (one in the back with awesome panorama views of the beach usually) and another table in the middle, and we sleep in the roomy bed above the cab. Its a 24 foot Class C. For my girlfriend and I I'd call it just right. My previous camper was a Hitchhiker III 5th Wheel very much like TX's, and personally I'm glad for the downsize, but those are because of personal factors like driving on winding Route 1 in California from time to time (not fun in a 5th Wheel!), and slideouts when parked on the beach become a maintenance hassle. My trailer after that was a 45 foot 1956 Spartan. Now *that* was an awesome trailer!

As far as Sunking's new misinterpretations of my needs and statements, I'll just say that I certainly wasn't suggesting that 250 watts would be enough for TX's trailer. Personally I'd go 600 watts of solar (or 900 if you want to go nuts) and a 2000 watt Honda EU for emergencies and call it a day (and try to keep some headroom so you can expand in the unlikely event you find you need to), but I know that diverges from the Platonic ideal of solar systems. But if you don't realize that the way I'm suggesting is the standard high-end way of outfitting RVs, and furthermore that it works awesomely (and is in fact overkill), then you don't have enough experience with the topic at hand (solar for RVs). Ok fine, the Honda EU is cutting corners, but personally I think its an improvement over most RV gennies.

And it's absolutely mind boggling that he still doesn't understand that I'm adding panels to an existing system, so keeping my existing controller, especially when it will very likely work just fine, is, at a minimum, the best way to start. It's also mind boggling that he really feels the need to rant about my controller in like 20 posts. This statement is also pretty amazing for its sheer lack of understanding:

Today there is absolutely no reason you have to make any compromises in RV application.

It's hard to believe that that's a serious statement. Just to name a few reasons to compromise in an RV solar install:

- price! (usually the biggie) I don't know what parallel universe Sunking is living in where price isn't a factor, but most people don't spend $600 (or $10,000) lightly. Cost/benefit analysis.

- space (also a massive factor with RVs)

- and the number one reason: the fact that with modern panels and controllers you can get all the power you need without getting the absolute best (and most expensive) of everything. That's not to say we shouldn't, in my opinion, aim for maximum efficiency, but as with everything you have to assess the costs and benefits.

And there's a bunch of miscellany like using your equipment at hand when possible, simplicity (within reason) and shade issues.

There is no need to wire panels and batteries in parallel,

Unless, as I explained a bunch of times, you have shade issues! And unless you already have a controller that will probably work just fine with the panels in parallel, so you don't see the need to spend an additional $600 just because some internet blowhard is oddly desperate to get his point across.

I'm seriously questioning his motivations at this point.

[sensij]

You do not use VMP voltages, you use Voc. A 34 Vmp panel Voc is 48 volts on a 92 VOC or even a 100 Voc New Zealand model controller will not work. Not hard to comprehend.

You are also arguing a 1% loss difference. The saving in cost on wiring and material is worth 1% loss difference.

Your argument is a moot point and not valid.

You absolutely use Vmp when evaluating operating efficiency and transmission loss. Voc only matters relative to the charge controller's specification, and as we've already established, two 24 V panels in series is fine on this controller in locations that don't get too cold. Surely you are familiar with 2014 NEC 690.7(A).

NEC.JPG

[Sunking]

One factor to consider when evaluating whether or not to put panels in series, which isn't directly applicable to the OP's situation but may still be worth discussing here, is the impact on the charge controller's efficiency as panel voltage gets further away from battery voltage. For example, the Tracer's manual provides the following chart, showing how panels in series would perform in a 12 V system (despite Sunking's insistence that this configuration is not possible on this controller). You can see that putting two 34 Vmp panels in series would drop the efficiency at full load from 95% to just under 94%,

You do not use VMP voltages, you use Voc. A 34 Vmp panel Voc is 48 volts on a 92 VOC or even a 100 Voc New Zealand model controller will not work. Not hard to comprehend.

You are also arguing a 1% loss difference. The saving in cost on wiring and material is worth 1% loss difference.

Your argument is a moot point and not valid.

[sensij]

One factor to consider when evaluating whether or not to put panels in series, which isn't directly applicable to the OP's situation but may still be worth discussing here, is the impact on the charge controller's efficiency as panel voltage gets further away from battery voltage. For example, the Tracer's manual provides the following chart, showing how panels in series would perform in a 12 V system (despite Sunking's insistence that this configuration is not possible on this controller). You can see that putting two 34 Vmp panels in series would drop the efficiency at full load from 95% to just under 94%, according to this chart. Depending on the length of the run from the panels to the CC, and the size and cost of wire and terminations selected, the system could in fact be more cost-effective / efficient with the panels in parallel. The extra cost from fusing when exceeding two panels in parallel is another difference to be aware of, though.
TracerEfficiency.JPG

[Sunking]

Beats $100/night hotels every day and twice on Sundays!

20170309_090039_001.jpg

Yes looks nice. But you are going to need a lot more than a 250 watt solar system.

[SunEagle]

Beats $100/night hotels every day and twice on Sundays!

20170309_090039_001.jpg

Nice. Looks comfortable to me.

[Sunking]

2k, awesome! What are you doing for a battery bank?

That indeed is a massive system and I'd go 24 volt for that too.

I agree with some things Sunking said about MPPT. Don't get me wrong, I'm not advocating PWM. Where I disagree with him is a) that the Tracer 4210A controller is a POS (I don't think he's updated his thinking since the early Chinese "MPPT" controllers on ebay that were fakes; these are very well reviewed), and b) that its inadequate for my setup to the point that it justifies spending another $600+..

You are hard headed and not listening.

While at 2000 watts, 24 volts is a poor choice and too expensive. That would require an 80 amp controller and no room to grow. Not having room to grow is not a deal breaker, but a simple change to 48 volts only requires a much less expensive 40 amp controller. Not only a lot os savings in controller cost, but also trickles down to lower wiring cost.

The Tracer is a fair entry level controller if it is matched and made to work with your equipment. That is where you went off track as the Tracer is not compatible with your panels. It will not allow you to wire your panels in series so you can take full advantage of MPPT and utilize all the power available. Why is that so hard for you to understand?

I believe you have 20 years of experience, not from your knowledge as it is severely lacking and way out of date. Your approach is that of 20 years ago when you had to make compromises and you are stuck in antiquated methods. 20 years ago there were no high voltage solar panels, MPPT Controllers or near the amount of batteries available today tailored to RE use. If I had to guess you are a mechanic and work on RV's and have not kept up. Today there is absolutely no reason you have to make any compromises in RV application. There is no need to wire panels and batteries in parallel, or over power a controller to gain a few more AH. That is a waste of money and resources. You could have achieved the same thing for less money by simply matching th equipment up to work with each other. 20 years ago when you started you had to make compromises, not today. You are stuck in the past.

Anyway I really do not care what you do, it is your money and life you are wasting away. But I nor the management of this forum are going to allow you to give bad advice. You will not get away with it here. It is not personal, just facts. If you want to quit learning fine with me. Just do not be giving anyone any advice.