A Few Basic Questions

Dagwood_55
Dagwood_55 Registered Users, Users Awaiting Email Confirmation Posts: 2
Hello all, Newbe and my first post here.

I have a new 5th wheel RV.  I recently added 4-6 v AGM batteries and a Magnum 2012 inverter with the Magnum battery moniter., so now  I want add 2 160 w solar panels to the roof with the ability to add another later if needed.  I've called several vendors asking them to quote complete systems and I've got so many different answers that I've become confused.  I'd like to keep my cost under $1000 but can spend 1500 if I need to.  So here are a couple of questions.  

1)  With 2 or 3 160 panels wired in parallel should I go 12 or 24 volt??

2)  MPPt or PWM???  I've read about he differences, but still get different answers....

3)  Combiner box or connectors??  On the roof.

4)  And lastly, since I already have a battery moniter, temp sensor that is tied into my Magnum control panel, will I still 
need a battery moniter for the solar charge controller??

Thanks in advance,

Comments

  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,039 ✭✭✭✭✭
    Welcome Dagwood_55,
     Assuming you haven't purchased the panels yet I would ask why are you thinking of 160 watt panels?  Granted, they are 12 volt and you can use an inexpensive PWM controller. Have you considered larger panels and a MPPT controller? Large 60 or 72 cell panels are considerably cheaper and, being larger you can use only two series wired panels and not need a combiner box. You can add two 250 to 300  watt panels without needing to fuse them, into a 30 to 40 amp MPPT controller and get the most bang for your hard earned bucks. This method will keep your wiring simple, with fewer connections ie; potential failure points.

     The only Magnum charge controller I find is their 100 amp MPPT controller. This would be too large and expensive for your needs so whatever charge controller you go with would need it's own temp. sensor.

    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,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • Dagwood_55
    Dagwood_55 Registered Users, Users Awaiting Email Confirmation Posts: 2
    At first I was looking at 265 w panels, 2 of them.  But mostly changed my mind because of the size.  I might just squeeze 2 on my RV roof but it would be close, possibly too close so I decided to go smaller and have more options on placement.
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,039 ✭✭✭✭✭
    edited July 2017 #4
    At first I was looking at 265 w panels, 2 of them.  But mostly changed my mind because of the size.  I might just squeeze 2 on my RV roof but it would be close, possibly too close so I decided to go smaller and have more options on placement.

    Understood. Whatever way you go an MPPT controller would be a better bet. There are some "Imported" ones that are OK in the $150.00 to $250.00 dollar range. You cant go wrong buying one of the better brands like Morningstar, or Midnite solar. I'd add Outback to that list except their smallest controller is 60 amps and just under $600.00.
     You can series wire 3 or 4 of the 160 watt , 12 volt panels using a 150 Voc. limit controllers and, being only one string you wont need any combiner or fusing.

    When placing your panels be sure to avoid any areas that will cast a shadow on your panels. Especially series wired panels don't play well with shadows. AC units, crank up vents and plumbing vents are things to steer clear of.

    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,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    Hello all, Newbe and my first post here.

    I have a new 5th wheel RV.  I recently added 4-6 v AGM batteries and a Magnum 2012 inverter with the Magnum battery moniter., so now  I want add 2 160 w solar panels to the roof with the ability to add another later if needed.  I've called several vendors asking them to quote complete systems and I've got so many different answers that I've become confused.  I'd like to keep my cost under $1000 but can spend 1500 if I need to.  So here are a couple of questions.  

    1)  With 2 or 3 160 panels wired in parallel should I go 12 or 24 volt??

    2)  MPPt or PWM???  I've read about he differences, but still get different answers....

    3)  Combiner box or connectors??  On the roof.

    4)  And lastly, since I already have a battery moniter, temp sensor that is tied into my Magnum control panel, will I still 
    need a battery moniter for the solar charge controller??

    Thanks in advance,

    Since stated, you already purchased a 12V inverter, the system nominal voltage would  be 12V, the first question is fundementaly answered by the second question, which in turn answers the third.

    If using a PWM charge controller , you would be committed to using 12V nominal panels in parallel, with a combiner , if however a MPPT CC  were used cheaper 60 cell panels could be utilized, so using 2 × 250W in series, an option with MPPT, there would be no need for a combiner.

    Have you done a load calculation to determine the size of the battery and the array needed to charge it, that is the best starting point. 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    As lh2 says, it may be worth considering larger panels in series and mppt controller. Cost-wise, it comes down to what your local panel pricing is. Shipping a couple of big panels is generally prohibitively expensive as they need to go at truck freight rates. Shipping smaller panels is usually more reasonable. If you can get big panels locally at under $1/watt, that may make more sense. Small panels tend to run ~$2/watt. With about a 500w system, saving ~$500 on panels should more than make up the added cost of mppt. Also, if you have more than two panels in parallel you'll need a combiner box with fuses or breakers for each.

    One downside to the big panels in series route is shading. If you have anything on the roof (eg drain vent stack) that could shade any part of the panels, output will be drastically cut.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,039 ✭✭✭✭✭
    edited July 2017 #7
     Here in the Los Angeles area New 72 cell panels are selling for 35 cents a watt. Applied to a 160 watt panel that would be $56.00.

    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,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    In my part of Canada they run from ~.70/watt to well over $1 (USD). Installer/dealers tend to be at the high end of the range, though I bought 3 left over from a part pallet installation at around .75CAD (~.60USD) a few months ago.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter