Starting to get really frustrated with an RV solar setup.

I'm a single pops that has some health issues going on so I'm desperately needing to get out of my house (and State) and get on the road for some time to recoup, bond with my son and heal a little.

I have MCS (multiple chemical sensitivity) so normal motorhomes and RVs won't work for me, neither will running a generator for that matter or most RV facilities.

With this means I'm building and designing everything myself and to call it exhausting is an understatement. There is little to no info around on adding 1.7kw of solar to a 21 foot motorhome roof (:

My struggle comes in everybody telling me I need something different, it's starting to drive me mad, I just want to buy some stuff, minimize mistakes and get on the road. Here are my knowns:

6 solar panels (which I'll be running as three 48v banks)
4 AGM batteries (which I will be running at 24v)
Midnite Classic 150
1500 watt sine wave inverter
Shunt to use the Classic 150 as a battery monitor

I just need to know what else is a "must have" to make this system safe and workable. I've been told that between the panels and cc I need a combiner box only, combiner box and another breaker box and still others have said I can do my series/parallel connections on the roof and just run a breaker in a baby box between the panels and cc. All connections (combiner box included) will be made inside as I can't have much (other than the panels) mounted outside.

I would really like to place an order in the next 24 hours so if you could tell (as simply as possible for my brain to understand, like, even parts list style would be great) me what else is "needed" to get this rocket off the ground I would be eternally grateful. I get by on $721 a month so while I'm on a serious budget, I've been saving for this and what's needed to do things right but I can't be excessive either.

Thank you all for the input on my other posts, I hope to contribute more as I learn I just don't have enough real world experience yet to do so.

Comments

  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Re: Starting to get really frustrated with an RV solar setup.
    TucsonAZ wrote: »
    With this means I'm building and designing everything myself and to call it exhausting is an understatement. There is little to no info around on adding 1.7kw of solar to a 21 foot motorhome roof (:

    Thats a good amount of pv for a RV. So you will want to get this right in order to be done safely. If you arent confident, wait until you are. Theres plenty of folk here who can guide you, but only you can be the judge on the safety of your install. And its you who will sleep better at night.
    Here are my knowns:

    6 solar panels (which I'll be running as three 48v banks)
    4 AGM batteries (which I will be running at 24v)
    Midnite Classic 150
    1500 watt sine wave inverter
    Shunt to use the Classic 150 as a battery monitor

    When you say knowns, that means decided, or bought? It will help us if you can fill in the gaps:
    pv vmp, isc
    agm ah and config

    Depending on how much space you have for the disconnect, the distance from the array to the disco, that info will help too. For the disco take a look at the midnite epanel/MNDC disco line, especially their manuals. They show in detail the components you need to safely fuse the controller and the inverter. Even if you decide to build something yourself its educational. However the MNDc is good value and will save you some hassle.

    You can do the array combiner eitehr near the array or at the disco. Distance is the factor there. For three strings of modules, string fusing is almost always required, and string breakers makes serving the array much easier. These breakers are in addition to the main pv breaker in the disco. Personally i would want the combiner inside, on an rv, driving wet etc.
    I just need to know what else is a "must have" to make this system safe and workable. I've been told that between the panels and cc I need a combiner box only, combiner box and another breaker box and still others have said I can do my series/parallel connections on the roof and just run a breaker in a baby box between the panels and cc. All connections (combiner box included) will be made inside as I can't have much (other than the panels) mounted outside.

    I would really like to place an order in the next 24 hours so if you could tell (as simply as possible for my brain to understand, like, even parts list style would be great) me what else is "needed" to get this rocket off the ground I would be eternally grateful.

    It doenst really work like that. If you are going to do the install, you MUST understand the system first. Would you wire up a house for the grid from scratch? A PV system is no less complicated, and in many ways more dangerous.

    Patience i think, take your time and do it right. Fill in the gaps, and the others will chip in with more specfics.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • TucsonAZTucsonAZ Solar Expert Posts: 136 ✭✭
    Re: Starting to get really frustrated with an RV solar setup.

    Thank you zoneblue! I actually checked out your site last night and found it super informative, the most helpful I've seen yet honestly so thank you for having it out there to share with the world.

    The funny thing is, I have wired up 3 houses, complete installs from the ground up and it's about 1/10th as complicated, truly. There is also code involved there so you don't have people telling you 30 different things, with solar (even worse in an rv) you have people running from super simple using all automotive components to extremely complex.

    When I say knows, I mean either bought or decided, the solars (I'm getting today) are 230w panels, vpm is 29.8, isc is 8.25, voc 36.9, the batteries I have, they were free and will get me by for a few months, they're 125ah agm, 12v each.

    I have spent a ton of time on this, researching, reading, the issue is hearing so many people tell me different things for fact, some being "authorities" on the topic. Each time I start a thread to narrow it down, the thread gets derailed or the salient points get lost.

    Running the panels at 48v makes total sense to me and seems very logical.

    Running the 3 positives and 3 negatives from the three strings on the roof into the combiner box with three 15a fuses makes sense to me, I can take a string offline, I can shut down all to service the system.

    Being told in addition to the combiner I need another box with another breaker to protect the 18 inches of wire from the combiner to the cc makes no sense to me and seems like an unneeded complication but I'm told by other "authorities" it's "mandatory".

    Being told the combiner box should be mounted outside on an RV seems completely insane to me, the roof is 21x8 feet, the longest run I will have from panel to combiner will be 20 feet so it seems wise to have that all be inside and easy to access.

    Being told to do all of the connections on the roof also seems crazy, while I would like to only run two wires in from outside I would also like to be able to take each strong off line both for servicing and testing the system.

    It seems I've answered a lot of my own questions here, that only leaves the connections between the Classic 150, the batteries and the inverter as well as how to manage the 24v loads.
  • TucsonAZTucsonAZ Solar Expert Posts: 136 ✭✭
    Re: Starting to get really frustrated with an RV solar setup.

    In fact, as I look things over, I can't even see why I need the combiner box at all, I should just be able to use three of the five breaker slots in the Mini DC Disconnect for that, out to the CC, back in to the Mini DC break, off to my batteries to my inverter via the 175a breaker and that would leave me with two breakers for all of my 24v loads. That seems like going at this with Occam's razor, trimming all of the fat and leaving me with a clean, simple install.
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: Starting to get really frustrated with an RV solar setup.
    TucsonAZ wrote: »
    Being told in addition to the combiner I need another box with another breaker to protect the 18 inches of wire from the combiner to the cc makes no sense to me and seems like an unneeded complication but I'm told by other "authorities" it's "mandatory".

    Being told the combiner box should be mounted outside on an RV seems completely insane to me, the roof is 21x8 feet, the longest run I will have from panel to combiner will be 20 feet so it seems wise to have that all be inside and easy to access.

    Being told to do all of the connections on the roof also seems crazy, while I would like to only run two wires in from outside I would also like to be able to take each strong off line both for servicing and testing the system.

    I suspect that some of the conflicting advice is because the code is for fixed permanent installations in homes. The advice to put the combiner box (with lightning arrester) outside is because if lightning strikes you can divert it to ground OUTSIDE your home. In a motorhome you don't even have a ground rod to divert lightning to ground, so putting the combiner outside doesn't help.

    Your frustration may be because you need to understand the code, not just follow the code. When you understand the code you can make rational decisions about whether to follow the code.

    Stick around... it takes awhile to figure it all out. I think you are doing pretty good... your objections to putting the combiner outside make sense to me.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: Starting to get really frustrated with an RV solar setup.
    TucsonAZ wrote: »
    In fact, as I look things over, I can't even see why I need the combiner box at all, I should just be able to use three of the five breaker slots in the Mini DC Disconnect for that, out to the CC, back in to the Mini DC break, off to my batteries to my inverter via the 175a breaker and that would leave me with two breakers for all of my 24v loads. That seems like going at this with Occam's razor, trimming all of the fat and leaving me with a clean, simple install.

    You posted this while I was writing my previous response. I don't see anything wrong with your reasoning. Midnite makes the Mini DC Disconnect in two (physical) sizes. Get the wider one. Much easier to customize.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • unyalliunyalli Solar Expert Posts: 120 ✭✭
    Re: Starting to get really frustrated with an RV solar setup.

    Just a thought.

    This is a Midnite Big Baby box modified to be a combiner. The strings will come down off the roof through the fridge vent.

    Attachment not found.Attachment not found.Attachment not found.Attachment not found.Attachment not found.

    The bus bar connecting the breakers is a cut down Midnite MNPV6 breaker busbar.

    Attachment not found.

    I will have around 19 feet of 4 gauge from the two busses to the classic 150 in my forward compartment.

    -Jeff
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Re: Starting to get really frustrated with an RV solar setup.

    Fully agreed on off grid being 10 times more complicated!

    Unyallis idea is pretty cost effective. Your idea of putting the string breakers in the mndc, that will work fine too. The one occassional hassle ive had is having to be careful around the pv hot wires when working on the disco. But if you do it right the first time, you shouldnt have to work on it again...i suppose. Learn from my mistakes.

    The great thing about the mndc is it herds you into good components and a safe setup. Im not big on battery switches and stuff bolted all over the show. Most the dangerous stuff is then inside the mndc. Good conduit from there to the bank, and something to protect the bank itself from shorts, and you have 99% of the safety bases covered.

    No worries on the documentation. Its kind of habitual.

    Just remember that the battery is the biggest hazzard. The deliverable current dwarfs anything the grid will ever do. Second to that is the PV which while inherently current limited, its higher voltage DC can produce and sustain plasma arcs like nothing youve ever seen, which is your second main fire hazzard. PV arcs start at about 30V+, and get worse as the string voltage climbs. Your strings are 60V-80V. On a moving vehicle, abrasion, and whatnot to consider. Lots of flexible conduit, good grades of cable, well tied down cables, particular care on the roofing penetrations / anywhere else cables pass though sharp bulkheads etc.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • mike95490mike95490 Solar Expert Posts: 9,274 ✭✭✭✭✭
    Re: Starting to get really frustrated with an RV solar setup.

    What sort of wind speeds to you expect the rooftop panels to be able to survive? Headwinds, going over a bridge seam in the road, can give a pretty nasty shock to a sheet of glass solar panel.

    If you can rig up your PV array to just 2 strings, you can drop a combiner channel, to just 2 breakers, if your Classic will handle the voltage.

    2, 24V agm strings in parallel. That's going to require a lot of care to do it right, without cooking a battery early. You could put all 4 of them in SERIES, build up a 48V system and not worry about parallel batteries. have you already bought a 24v inverter ? would 48v break anything (24v fridge you already have ?)
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • TucsonAZTucsonAZ Solar Expert Posts: 136 ✭✭
    Re: Starting to get really frustrated with an RV solar setup.

    I'm making some progress! I scored 8 brand new US made Solar World 230w panels today at $0.69 per watt, it took some doing to get that good of a deal locally and on less than a pallet but I'm excited to have that off my list!

    What I'm learning is the following:

    1) The only places a compromise free solar system exists is in Bigfoot's house.

    2) You really need to make some educated choices and go into this knowing your goals of the end system and what it will take to get you there. Asking people creates confusion as they're all willing to do different compromises.
    mike95490 wrote: »
    What sort of wind speeds to you expect the rooftop panels to be able to survive? Headwinds, going over a bridge seam in the road, can give a pretty nasty shock to a sheet of glass solar panel.

    If you can rig up your PV array to just 2 strings, you can drop a combiner channel, to just 2 breakers, if your Classic will handle the voltage.

    2, 24V agm strings in parallel. That's going to require a lot of care to do it right, without cooking a battery early. You could put all 4 of them in SERIES, build up a 48V system and not worry about parallel batteries. have you already bought a 24v inverter ? would 48v break anything (24v fridge you already have ?)

    This is two examples of compromise for me, I'm in an RV, I can't always account for power poles, trees and so on as they will change every single day. As such, series strings are a HUGE liability and running to versus three strings could put me in situations often where I'm without 1/2 my power versus 1/3 of it.

    The 24v versus the 48v is another, I can't run a 48v bank with my solar panels configured as 3 banks of 2 so I would have to run them 2 banks of 3 and that creates the aforementioned issue. As I mentioned above, these are experimental batteries, if I can get 12-24 months out of them I would be more than happy. Parallel can't always be avoided in the real world and this is one situation where this is my only option, running a 48v system in an RV with under 2kw of panels offers no major gains for all of the troubles in creates.

    Thank you for the input, this would all really apply in a stationary application for sure and I would do it this exact way.
    zoneblue wrote: »
    Fully agreed on off grid being 10 times more complicated!

    Unyallis idea is pretty cost effective. Your idea of putting the string breakers in the mndc, that will work fine too. The one occassional hassle ive had is having to be careful around the pv hot wires when working on the disco. But if you do it right the first time, you shouldnt have to work on it again...i suppose. Learn from my mistakes.

    The great thing about the mndc is it herds you into good components and a safe setup. Im not big on battery switches and stuff bolted all over the show. Most the dangerous stuff is then inside the mndc. Good conduit from there to the bank, and something to protect the bank itself from shorts, and you have 99% of the safety bases covered.

    No worries on the documentation. Its kind of habitual.

    Just remember that the battery is the biggest hazzard. The deliverable current dwarfs anything the grid will ever do. Second to that is the PV which while inherently current limited, its higher voltage DC can produce and sustain plasma arcs like nothing youve ever seen, which is your second main fire hazzard. PV arcs start at about 30V+, and get worse as the string voltage climbs. Your strings are 60V-80V. On a moving vehicle, abrasion, and whatnot to consider. Lots of flexible conduit, good grades of cable, well tied down cables, particular care on the roofing penetrations / anywhere else cables pass though sharp bulkheads etc.

    Thank you for mentioning some of this. I have arc welded with three 12v batteries, I used to actually keep some rod with me on trails as you never know when an axle may need welding in the field. I guess the question for me is just how much risk is there of shock on the DC side in a system like this? I can touch live 24v wire no issue right? What about 48v? Or as you mentioned the 60v-80v going on to the cc?

    In terms of a short, I'm in an aluminum box, seriously, 2,600 pounds of it, even the floors! So I will really take what you're saying to heart to make sure I'm on the extreme safe end of things. I'm making a box for the batteries to go under the seats, I will be fabricating this and may see if I can even find something plastic to put inside of that box to be on the really cautious side of safe.


    PS To make matters even worse, I'm adding a 7th panel to a cheap mppt controller for a small 12v battery bank to run my 12v items, give me some additional experience with a system that isn't my main system and well, because I already have the solar panel and batteries. This will be a fun system though, low use, something I don't have much invested in, won't use with an inverter and keeps me from having to use a step down on the main system for the 12v things.

    Thank you all!! I'm feeling a lot better about this build now, excited even!
  • BB.BB. Super Moderators, Administrators Posts: 31,684 admin
    Re: Starting to get really frustrated with an RV solar setup.

    24 volts can give you a bite and may be hazardous in some situations. 48 volt battery banks can give you a bad shock or worse (sweaty hands, maximum charging voltage is ~60 VDC--Which is "hazardous/no touch" in any safety specification).

    And, there is the wedding ring/jewelry/hand tools around any goodsize lead acid battery bank--I.e., don't short anything out--It will ruin your day.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
Sign In or Register to comment.