STOF-FORD

22 minutes ago, Chad Heiser said:

The open circuit voltage (Voc) on my panels is 36.9 volts.  That puts me up over 70 volts with my series pairs.  I have seen around 70 volts plus or minus in good sun conditions.  I discussed my install with Magnum before I installed it.  They gave me there blessing with my proposed set up and said it would function fine, which it has.  I could easily go to two series strings of three with my system, but I haven’t seen the need to do so.  It has been functioning fine as it is.  Even in full cloud cover, I get right around 60 volts to the controller (although the wattage drops considerably).

Thanks for that Chad and good to know.  That is what I was seeing in the system performance statistics you had published previously.  The posting from ewacobay (thanks for that also) caused me to go read the entire chapter in the PT100 owners manual dealing with system sizing calculations.  I now know that this is not nearly as simple as I had hoped.  In the manual, Magnum stresses that it is not open circuit voltage, but rather the maximum performance voltage (Vmp) that should be used in these calculations.  That voltage seems to run anywhere from 15% to 30% lower than open circuit voltage on most of the panels I've looked at.  However, as you say, your system is working fine.

This information does throw a bit of a wrench into what I was planning however, because the smaller output panels I was looking at have significantly lower open circuit voltage ratings as well as Vmp.  Back to the drawing board as they say.  Better to know now, than after it's all installed.

Thanks again to everyone for their input.

47 minutes ago, Chad Heiser said:

The PT-100 does require high voltage to work properly.  In an RV install, that simply means running a series/parallel set up with the panels to get the appropriate voltage.  There are some drawbacks to series installs on RV roofs, but having integrated components is very nice and is worth the trade off in my opinion.  

If starting from scratch and wanting an integrated component system, Victron would edge out Magnum in my opinion because they have more options for solar controllers and some other nice components.  When starting with a factory Magnum inverter, then a Magnum system makes sense rather than spend extra money to change out the inverter.

I'm getting a significant education in a very short period of time here tonight.  Chad, looking at the CS6P - 235 panels you went with I see that there Vmp rating is 29.8 V at an ambient of 25 deg C.  AS you have wired them into 3 parallel banks of 2 series panels, it would only produce 59.6 V.  Any derate for increasing temperatures would bring them down from there.  The PT-100 owners manual calls our a minimum Vmppt of 60 V for a 12 V system.  So, in theory, unless you are somewhere cold, your array would never get to the PT-100's minimum Vmppt.  However, from the statistics you have posted, it is clearly providing a respectable charge rate for your storage banks.  What am I missing here?

Did you ever consider reconfiguring your array to two parallel banks of three series panels?  That would get your Vmp up closer into the 90 V range before temperature derating.  In theory, that should improve the overall performance of the PT-100.

I don't mean to sound like I'm trying to redesign your system, which I am still quite impressed by.  I'm just learning on the fly and thinking out loud.

14 minutes ago, Yarome said:

In an RV application I think the biggest drawback with flexibles is the durability factor. They are quite easily scratched. Road grit can deteriorate the surfaces rather quickly, you can forget about even a light tree branch scrape or fine hail and even washings can produce fine line scratches in the surface material that will affect production.

The other major factor is heat build-up. As panel temperatures increase production decreases. Having a flexible mounted directly onto a white roof... you can imagine... heat convection itself will be greater and heat dissipation only has one route away from the panel. With a rigid raised an inch and 1/2 or so you reduce heat convection from the roof itself and allow for air passage and heat dissipation from all sides of the panel.

It may or may not be an issue, but something that should be considered is shading. Shading might be more of an issue with flexibles. Ie., a rigid raised 1-1/2" above the roof will receive less shading from other roof mounted appliances/fixtures than a panel of the same size, occupying the exact same position, but sitting 1-1/2" lower.

Not that fexibles don't a have a place. Some RV's may have "extremely" slim cargo capacities. Flexible panels weigh dramatically less than rigids and can be a viable choice. Curved top RV's might also benefit. Flexibles can be curved to around... IIRC... about 30 degrees so what may be an exceptionally challenging and awkward install with rigids might be greatly simplified by using flexibles... and likely give you a greater number of watts to boot.

Personally, for RV use I see the greatest useability of flexibles as portable stand alone arrays. They are lightweight, easy to store, easy to manipulate, can be "strung" with cordage between any two points and at any angle you desire. That also leaves you the option to only put them out when weather permits.

Yarome,

Really great points about flexible.  I had actually thought a great deal about the exact thermal issues you identify.  I was actually concerned about the possibility of damage to the white rubber roof material as well as panel performance degradation.  I've searched for actual test data on this point but have not really found any.

I think you've convinced me.  Thanks!  It's just not worth the risk.

29 minutes ago, DesertMiner said:

Do your research on flexible panels and their "pros & cons" before you think about flexible panels.  You might want to  also consider before the purchase of the solar panels is the physical size vrs rated output vrs available  "roof space"!  Lots of roof protrusions can make it a challenge to arrange panels depending on size of the panel.  Hopefully you persuaded DRV to "increase" the wire size of the "solar option" to help out in the panel placement and the total size of your solar array.  I believe DRV uses Magnum products for inverters and such.  Do some research on some of the other products lines that are available.

 

Good thoughts all here.  Yes, I absolutely will not be ordering any panels until I actually have the new rig in my grasp.  As you say, there are just too many variables on the roof to be able to order panels without first being able to do some careful dimensioning. However, I will have everything else on hand to complete all the rest of the project except for panel install which really can happen at the very end as an isolated project.

Also, yes, I did upsize the solar prep feed.  I actually would have been quite happy with 6 ga. as that would more than comfortably support the installation I am planning, but my dealer persuaded me to go to 4 ga.  If I end up at 600 watts and series gang panels in two-panel arrays, I should be looking at no more than about 25 amps max and 6 ga should comfortably support 70 amps over this short run, with minimal loss.  However, as we all know, bigger is almost always better.

I did also evaluate other brands of equipment, and I have used others in previous installs.  However, I ended up settling on Magnum for three reasons.  First, I really like how the broad range of both solar and inverter/charger and accessories are all designed to play together and communicate over their network.  Second, I figure Chad has already tested the system for me and he sure seems pretty happy so I don't have to do that myself.  Third, I like that DRV will have already installed the primary inverter and it's remote in the house systems panel for me.  I will likely rearrange stuff in the basement to suit my overall design, but I won't need to deal with the remote or its wiring.

On 2/25/2018 at 9:00 AM, Chad Heiser said:

I’m happy to help and I would be happy to discuss my build out and why I did what I did.

I added the small inverter in my system for several reasons.  Primarily, I wanted to be able to isolate the refrigerator for travel.  I did not want to power the whole house while rolling down the road, just the refrigerator.  The second inverter is also a redundant system in case I ever have an issue with the main inverter.  When boondocking, the small inverter running just the refrigerator will also draw less power from the batteries than the large inverter powering the whole house (as you mentioned above).  There are some other reasons, but these are the main ones.

My main battery disconnect does completely isolate the batteries from everything.  This disconnect has never been turned off since I installed it.  It is really just there in case I need to service/replace the batteries or in case I am working on an electrical component in the 12 volt system.  With this switch, I can completely remove power from the 12 volt system in one place.  For a full timer, the batteries would only be isolated for servicing the system.  

I am not full time, but I do not need to isolate my batteries for storage.  I am fortunate to have indoor storage with shore power.  Because my storage is indoors, I actually isolate the solar system when in storage and leave the inverter/charger on to maintain the batteries.  If the PT-100 goes more than 24 hours without sensing solar generation, it errors out and has to be reset.  By isolating the PT-100 on both sides (input and output) when stored indoors, I don’t have to deal with the error and resetting it.  If I were storing my trailer outside with no shore power available, I wouldn’t have run the PT-100 output through the main power disconnect.  I would have connected it directly to the battery bank.  This way I could disconnect all power draws from the batteries and allow the solar and PT-100 to keep them charged up.

Feel free to PM me with contact information if you would like to actually talk about my system and what you plan to do to yours.

Chad,

Thanks much for taking the time.  Right now, I'm just doing some preliminary planning.  As I mentioned, Alicia tells us we won't see our Houston before early to mid June.  However, this is one project I want to be all ready to go with when we do take delivery as I want to start using our new rig as quickly as possible.  When we bought our current toy hauler, it was stock right off the dealer's lot and I then proceeded to spend the next year on upgrades and projects, instead of enjoying it and using it for the intended purpose.  I don't want to make that mistake again.

I'm actually stuck in Europe right now until the end of March on a consulting project.  However, the good news is that I have lots of evening and weekend hotel time to plan and do research, and place orders for stuff.  Just for grins, I've attached the bill of materials I've assembled so far.  On projects like these, the planning is half the fun for me.  I'll be interested in your thoughts on it as it looks pretty much like yours.

The big open question for me is what to do for solar panels.  As I mentioned in my previous post, my objective for solar and storage is not nearly as ambitious as yours.  My goal is around 600 watts of solar collection capacity.  Maybe 800 if the right opportunity comes along.  I'm really intrigued by the flexible panels and I'm frankly surprised that more RV installs don't seem to use them.  Is there something I'm missing?  I like the idea of the low weight and low wind profile.  It looks like collection efficiency is now on a par with rigid panels, and cost is comparable.  There must be a reason why more folks don't go that route.

I look forward to starting a dialog with you on this project and sharing the results when it's finished.  I'll reach out by PM when back in Colorado in April.  In the mean time, these forums are my touch with the real world back home.

Solar and Battery BOM.PDF

On 2/25/2018 at 6:18 AM, TheLongWayHome said:

Try to PM him directly. Will never find this needle in the massive daily haystack.

Find one of his postings, click on his Profile name or icon (can also hove over it) then click on Message.

He is usually fast and with great responses. Very helpful.

Good luck.

Thanks for the tip.  It seems every forum has a slightly different approach for reaching someone.

Chad,

I realize this is now a bit of an old thread, but I'm hoping you are still visiting it from time to time.  We have recently ordered a Mobile Suites Houston from Rolling Retreats, and I discovered from Alicia that I was requesting a number of the same "specials" that you had on your rig.  That caused me to go find your post on SOITC forum, and that led me here so I could see the pics of your install and the schematic you posted.

And all of that has caused me to have about a hundred questions for you, since you've already installed and tested much of what I'm hoping to accomplish with our installation.  For now though, let me start with just a couple:

Was the reason you installed both the MSH3012 and the CSW1012 that the smaller unit would have a lower "idle" current draw when the fridge is cycled off?  From spec sheets on the two, it looks to me like it's the difference between 1.2 and about 2.4 amps at idle.  Is that what you see?

I notice from your wiring diagram that your main battery disconnect also interrupts the feed from the solar charge controller.  I was intending to switch that separately, as I'm hoping to leave the charge controller maintaining the batteries when the rig is in storage.  Does that make sense to you?

I will not have anywhere nearly as much storage or solar collection as you have.  I am shooting for approximately 600 W. of collection and 640 Ah of storage in four 12v AGMs.  I think our objectives on this issue are different.    For the inverter I just want to be able to reliably manage entertainment devices, fridge and water-pic in the evening when we are dry camping.  For solar, I just want to be able to bring the storage back up with minimal or, hopefully, no generator use when we're camped in an idyllic and pristine spot and I don't want to disrupt it with the gen-set noise.

I had already ordered the MSH3012, PT100, Onan 6.5 commercial and associated wiring and system monitoring hardware as part of our DRV order, but I'm really interested in a dialog with you, if you have time, to learn how I might improve on the design I have in mind.  We don't expect delivery of our rig before early June, given DRV's current expected lead time, so I have plenty of time to get this right.

Thanks in advance for any insights you are able to share.