Skoolie Solar Help

samroonsamroon Registered Users Posts: 8 ✭✭
Hello All! I am in the process of converting a retired ski shuttle into a home for myself and my fiance. I'm in the process of a solar installation and wanted to see if I good get some help wrapping my head around the installation and how things should be set up. Here is what I am working with: 
- Renogy 400 Watt Kit 
- Rover 40a MPPT
- 5 MC4 Male/Female Connectors
- AIMS Pure Sin Inverter/Charger 2000w with 6000w surge
- 50ft 10AWG Solar Cable
- 60 amp fuse
- TriMetric TM-2030 Battery Monitor 
-4 Vmax SLR155 AGM 12v Deep Cycle 155ah (620ah) 

With this setup the biggest thing I will be charging is a 110v fridge. I have not decided on the fridge yet but it should be a 4ish cubic ft. energy efficient fridge. For the 12v system I will have LED light strips, small water pump, and a suburban water heater (propane with electric spark). For the 110v system I will just be needing to charge two phones and two laptops occasionally, sometimes we will use a small 900 watt Nutribullet blender. For the most part our energy consumption is fairly low, our biggest appliance will definetly be the 110v fridge. 

From what I have read, it sounds like parallel makes more sense for rv/skoolie applications because there will be times where there may be shade on a panel or two thus making the others not work if they were mounted in series. As far as installing the panels in parallel do I need to buy the special branch connectors or is there a way to make it work with the MC4 male/female connectors? Is the provided 10AWG wire sufficient for mounting in parallel? Would the MPPT controller benefit more from series or parallel in a skoolie application? I still haven't worked out the separate 12v and 110v systems but I'm trying to sort out the solar installation and charge controller first. 

Thanks for all the help! Apologizes if I left anything out or didn't include all the right information, trying to teach myself the ins and outs of my system. Any help appreciated. 

Comments

  • mike95490mike95490 Solar Expert Posts: 7,249 ✭✭✭✭
    For joining more than 2 PV panels in parallel, you need a Overcurrent Protection Combiner system

    After you combine the currents of the 4 panels, you will experience losses if you wire with 10ga wire.   I would suggest at least 8ga

    Another suggestion, would be ignore the little 100w panels, and look at normal grid tie panels, they run 30-60V, and cost less per watt then 12V panels.  If your bus has the space on the roof for the panels, I'd not limit myself to just 4 panels.
    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 ,

  • samroonsamroon Registered Users Posts: 8 ✭✭
    Thanks for the help. I've already purchased and installed the renogy panels, they fit best on the bus because there is limited space due to a roof rack.

    So the mc4 branch connectors will not suffice for joint the panels in parallel? Renogy claims the 10awg wire is what should be used when installing the panels, you think I should get 8awg? Thanks for the help!
  • mcgivormcgivor Registered Users Posts: 1,190 ✭✭✭✭
    edited October 8 #4
    Your array wattage is  undersized for the battery capacity, typically ~ 10% of the battery Ah capacity in charging current is required, or 62A in the case of 620Ah for full time use, weekend use can be less, say 5%, with 400w derated to 75% you are under 5%. Moblie application is not perfect so this figure could be substantially less, if lying flat, for example, just something to keep in mind, everything may appear to work for a week, then voltage begins to drop and capacity is lost due to sulfation, which manifests as time goes by resulting in battery failure. The reason I caution you is because a refrigerator is involved, even small ones consume a supprising amount of energy, additionally the inverter must remain on at all times, which in some cases, can consume as much as the refrigerator itself, all other loads are small or intermittent. Would hate to see you destroy your first set of batteries, it's so easy to do, to get a clear picture use a logging device such as a kill-a-watt meter, run on grid for a week and find out exactly what it consumes. From the inverter specs find out the self consumption and efficiency use these figures to estimate, along with the load, the total daily energy required just to run the refrigerator, you will be supprised, albeit  unpleasantly supprised.

    Not trying to be a fear monger, just giving the heads up, to hopefully avert dissapointment.
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • littleharbor2littleharbor2 Solar Expert Posts: 635 ✭✭✭✭
     Your MPPT controller needs higher voltage than your 12 volt panels put out to operate efficiently. You should series wire your panels 2 at a time, giving you 2 strings which can be ran through a branch connector without the need for fusing. This is for a 12 volt system. If you go 24 volt you would need to series wire 3 or more panels. Can you fit 6 panels on the roof?

     You should do some serious homework regarding your refer selection. Small refers can use as much or more than a mid sized energy efficient model.  BTW 400 watts of solar isn't going to run a refer, time to redesign your roof layout to accept more solar.

     Since you are building from scratch you should consider selling your 12 volt inverter and getting a 24 volt version. lots of LED lighting can run on 24 volts Water pumps come in 24 volt versions. Check on the water heater as to whether it can run on 24 volt.  You will be able to run twice the watts through your CC @ 24 volts. You will need it if you are going to run a refer successfully. 

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • samroonsamroon Registered Users Posts: 8 ✭✭
    Thanks for the info guys. I already have the inverter, water pump and water heater and I'm not going to sell them at this point to change to 24v. I understand the wattage not being quite enough to always keep the batteries topped up. For now, this solar setup is for me to get all my electrical sorted out and a start on solar. This winter I'll be parked with shore power for the whole time, maybe tinkering with the solar some but not solely relying on it. I want to have this system ready to go off the grid and be self sufficient and planned on upgrading to 600w sometime soon (with two more renogy panels). As far as this system being bad for my batteries, is it bad because It won't fully charge them? Or because the batteries will die all the way? Im still get some mixed messages on how I should wire the panels, in series parallel? Only generating 12v but two panels in series with the two sets in parallel? Thanks for the help guys!
  • kamchukakamchuka Registered Users Posts: 51 ✭✭
    Ima chime in but I'm not as good as these other guys, I just know what I have done. the wiring of your panels will be dictated by your charge controller. I had four 12v panels in parallel going to a 12v only charge controller. I upgraded and added panels so my new controller was a multi volt IE: 12,24,etc. so my panels are now wired in series/parallel giving me higher voltage in order to use smaller wire for the run from the pole to battery room. Goes in 70v and charges my 12v bank.
    your CC should have the info on it. I would reckon the thing is designed to run in parallel though as it is a kit. 
    700 watts pv (building on) on poles, off grid 60a mppt, magnum 2k 12v msw, 1400 ah forklift battery (rewired to 12v), 8k diesel gen for house. honda eu6500, 2x 8D, coleman 800w inv for shop, honda 5k for well (pumps to 1000g cistern), ryobi 2k suitcase for mobile ops. 
  • littleharbor2littleharbor2 Solar Expert Posts: 635 ✭✭✭✭
    edited October 8 #8
    samroon said:
    As far as this system being bad for my batteries, is it bad because It won't fully charge them? Or because the batteries will die all the way? Im still get some mixed messages on how I should wire the panels, in series parallel? Only generating 12v but two panels in series with the two sets in parallel? Thanks for the help guys!
    Your 400 watts of panels won't be able to keep up with your refer. Once your battery bank becomes depleted you need to charge it AND try to keep up with the demands of the refer. The only meaningful charging you will get will be, say from 10 00 to 2 00in the afternoon. the rest of the time you will be relying on battery power to keep that refer cold.  

     The reason I recommended series/parallel wiring your panels is that your MPPT controller want's higher input voltage for your 12 volt battery bank. Also while being incorrect to parallel wire all 4 of your panels you would need a fused combiner or , at minimum fusing on all 4 of your panels. You need to be diligent in parking your bus where you get unobstructed sun, regardless how you wire your array.




    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • samroonsamroon Registered Users Posts: 8 ✭✭
    My charge controller can take either 12v or 24v according to the manual. The max solar input at 12v is 520w and the max at 24v is 1040w. I'm thinking about mounting in series-parallel. Just kind of concerned about shading and knocking out the usefulness of the panels. Parallel looks like it could work as well, on the renogy website and in the installation guide not looks like they just use the branch connectors and 8awg wire to mount in parallel. I don't see where it says I need an overcurrent protection combiner, but I will definetly get one if that is something that is needed. Again, thanks so much for being patient with me haha still trying to sort all this out
  • samroonsamroon Registered Users Posts: 8 ✭✭
    > @littleharbor2 said:
    > samroon said:
    >
    >
    > As far as this system being bad for my batteries, is it bad because It won't fully charge them? Or because the batteries will die all the way? Im still get some mixed messages on how I should wire the panels, in series parallel? Only generating 12v but two panels in series with the two sets in parallel? Thanks for the help guys!
    >
    >
    >
    >
    > Your 400 watts of panels won't be able to keep up with your refer. Once your battery bank becomes depleted you need to charge it AND try to keep up with the demands of the refer. The only meaningful charging you will get will be, say from 10 00 to 2 00in the afternoon. the rest of the time you will be relying on battery power to keep that refer cold.  
    >
    >  The reason I recommended series/parallel wiring your panels is that your MPPT controller want's higher input voltage for your 12 volt battery bank. You need to be diligent in parking your bus where you get unobstructed sun, regardless how you wire your array.


    Okay that makes sense. Ya I've been debating between 2 way fridge or just an energy efficient model. I hate using propane but it could be the way to go. Just pricey at $1000+ for a 2 way fridge. One of my buddies thought rather than put $1000 into a propane fridge just take the money you would've spent on the fridge and beef up the solar more. So in theory, if I were to buy an energy efficient fridge for $200 I could spend the rest of the money on two or three more panels.

    That makes sense wiring in series parallel. Combining two 12v panels going into the charge controller would be 24v correct? Would that mean that I must set my battery bank up to 24v or would the charge controller still charge the bank at 12v?
  • littleharbor2littleharbor2 Solar Expert Posts: 635 ✭✭✭✭
    You are misunderstanding the info on your CC. It can CHARGE 12 or 24 volt. It can TAKE, as you say,  higher input voltage. 

    Sounds like you are going to do this your way regardless what you are told. Good luck.


    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • samroonsamroon Registered Users Posts: 8 ✭✭
    Sorry if I misunderstood the info. I am completely open to suggestions and really appreciate the help. I was trying to make that clear and I'm not sure where I gave the impression that I am doing it my way regardless of what I am told. Littleharbor2, you suggested wiring in series parallel and that is what I am looking into and honestly what I will probably end up doing. I really do appreciate the help and I apologize if I get confused and give the wrong impression. 

    Thank you for the help with the charge controller, just trying to wrap my head around it. I understand my CC can take 12v or 24v and I understand that the MPPT works more efficiently at higher input voltage. I guess my (maybe stupid) question is that if the 12v panels wired in series going to the CC as 24v will charge my 12v batteries at 24v. Again I apologize if this is a stupid question. I was under the impression that the Solar Beginners Corner was a place for solar novices like myself to get help from the solar experts. 
  • kamchukakamchuka Registered Users Posts: 51 ✭✭
    your charge controller should default 12 or 24. you hook it up to the batteries first so it can think. check your voltage as well (from the panels), prior to pluggin em in.  
    700 watts pv (building on) on poles, off grid 60a mppt, magnum 2k 12v msw, 1400 ah forklift battery (rewired to 12v), 8k diesel gen for house. honda eu6500, 2x 8D, coleman 800w inv for shop, honda 5k for well (pumps to 1000g cistern), ryobi 2k suitcase for mobile ops. 
  • samroonsamroon Registered Users Posts: 8 ✭✭
    Okay that makes a lot more sense now. Thanks for helping me. I've been talking on the phone with one of my buddies who is familiar with this kind of setup. I checked the volts for each panel and they all appeared to be working good in full sun. Apologies if I made it seem as though I wasn't taking the advice you guys have been giving me. I guess my confusion came off as me not taking advice? Tough crowd around here lol
  • kamchukakamchuka Registered Users Posts: 51 ✭✭
    edited October 8 #15
    No worries. I didnt feel that way. Geet r dun! theres a hundred ways to skin this cat, I relied on this forum for info and had a local "guy" but mostly (at the risk of expense) i played with it. thick gloves and a positive can do attitude...lol One thing I've found is everybody does it differently and people go off grid for a reason so its not likely your gonna just head down driveways to touch peoples stuff...that was the hardest for me. you can read all you want but hands on is my way and you just wont find people willing to let you look around and ask questions. I have folks near me that rely on the generator for all there needs, 6-8 hours a day on a 1200 watt 200$ amazon genny. whatever works i reckon.
    700 watts pv (building on) on poles, off grid 60a mppt, magnum 2k 12v msw, 1400 ah forklift battery (rewired to 12v), 8k diesel gen for house. honda eu6500, 2x 8D, coleman 800w inv for shop, honda 5k for well (pumps to 1000g cistern), ryobi 2k suitcase for mobile ops. 
  • mcgivormcgivor Registered Users Posts: 1,190 ✭✭✭✭
    edited October 9 #16
    samroon said:
    Sorry if I misunderstood the info. I am completely open to suggestions and really appreciate the help. I was trying to make that clear and I'm not sure where I gave the impression that I am doing it my way regardless of what I am told. Littleharbor2, you suggested wiring in series parallel and that is what I am looking into and honestly what I will probably end up doing. I really do appreciate the help and I apologize if I get confused and give the wrong impression. 

    Thank you for the help with the charge controller, just trying to wrap my head around it. I understand my CC can take 12v or 24v and I understand that the MPPT works more efficiently at higher input voltage. I guess my (maybe stupid) question is that if the 12v panels wired in series going to the CC as 24v will charge my 12v batteries at 24v. Again I apologize if this is a stupid question. I was under the impression that the Solar Beginners Corner was a place for solar novices like myself to get help from the solar experts. 
    The charge controller is 12 or 24V nominal, which means it can charge either voltage battery, this has nothing to do with the array voltage.

    The maximum  array voltage will be determined by the CC, 100V in your case, the voltage to take advantage of MPPT, generally speaking it should be around double the battery or "nominal " voltage to work efficiently, so for 12V nominal you would need around 24V or higher, but always less than the maximum. So 2 of your 12V nominal panels in series will be ~45V Voc, for arguments sake , which is safe for the CC 100V maximum and 36.5 Vmp so  above double but not excessively high.

    Using parrallel panels with MPPT as you suggested, will mean the voltage to the controller will be less than what is required to allow the MPPT to function efficiently, 18.8V gives only ~5V headroom, as the controller attempts to draw current from to array the voltage will drop, it will recalculate to a higher voltage whereupon the whole process will repeat itself, causing the CC to hunt, during each hunting cycle there is lost production, this particularly important in partly cloudy conditions. The more expensive the CC, the more rapidly it will search for the maximum power point.
    Read this and other information in the learning center, it is a useful resource.  https://www.solar-electric.com/learning-center/batteries-and-charging/mppt-solar-charge-controllers.html
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • bsolarbsolar Solar Expert Posts: 98 ✭✭
    dont know where your at with it but i can give you some 'real world' feel for what youre trying to do .. the fridge is a problem with the size system youre talking about unless its really small and efficient... i have a normal size 'efficient' type late model fridge, run a fan, and a couple of led lights which are nothing really, and run a laptop maybe an hour .. (4) 210AH batts will go to ~55% overnight, which starts basically around 6-7pm and goes until the sun hits the panels around 9am .. so thats not a large enough bank for batt longevity you really need (8) 210AH batts ... draw will be the same as far as what you need to recharge plus keep things going in the day ... you need about 900W of panel to keep things going and that doesnt leave much room for a dark and rainy crap day .. 1800W of panel would be better ... how you wire it imho is of no consequence .. its not going to change the game that much, if your panels fall way off at low or angled light then mppt and higher voltage will keep the system operational at least alittle longer , thats how i look at it ..
  • samroonsamroon Registered Users Posts: 8 ✭✭
    Thanks for the help, all of your information is really helping me get all this. Added to my thread over in the skokie forum and there is quite a few guys over there that recommend a residential fridge over the absorption fridges. I'll probably end up adding two more panels making 600w and I would love to eventually get up to 900w. 

    From what you guys have been saying about parallel v. series I think my best option is to wire two panels in series and then combine in parallel. From the info I've been reading and what has been said in the thread seems as though the MPPT needs the higher voltage that wiring in series provides to function efficiently.
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