Solar Panel Choice for RV Application

babyrocketbabyrocket Registered Users Posts: 4
edited July 12 in Solar Beginners Corner #1
I have a Lance travel trailer with 2 190 watt Go Power solar panels (specs here) wired in series on top.  I have recently upgraded my solar/electric system with Victron components and expanded my lithium battery bank to 400Ah.  I would now like to expand my solar capacity as well.  I have a Victron MPPT 150/70 solar controller, and using their calculator I have determined that the my controller can handle the addition of two Rec Alpha 365 watt panels (specs here).

I'm planning to run each of the two 365 watt panels, as well as the pair of 190 watt panels (in series), all three in parallel to the controller.    I plan to upgrade the wiring from panels to controller to handle the additional current.  I have the specs for all panels.  Can someone tell me what I need to find out with both the Go Power and Rec panels to determine if this proposed setup will work? 

Thanks for any help you can provide!

Comments

  • mike95490mike95490 Solar Expert Posts: 9,363 ✭✭✭✭✭
    More than 2 strings of panels in parallel, you need to use fuses/breakers in your combiner box.

    Panels in parallel should be within 10% of Vmp voltage.  The array will be pulled to the lowest voltage panels', voltage
    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 ,

  • BB.BB. Super Moderators, Administrators Posts: 32,019 admin
    For Mike's comments:

    Your 190 Watt panels have Vmp=20 volts (voltage maximum power)

    The 360 Watt panels have Vmp=37 volts

    2x 20 volt panels in series = 40 Volts Vmp

    40 Vs 37 volts is "close enough" (within 10%)

    The 190 Watt panels have a max series fuse of 15 amps

    The 365 Watt panels have a max series fuse of 25 amps

    So--Each string will need its own/different fusing. 15 amps for the 2x190 Watt panels. And 25 (or 20-25 amps) for the 365 Watt panels.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • babyrocketbabyrocket Registered Users Posts: 4
    Thanks much guys, very helpful.  Any suggestions on a good combiner box with fuses/breakers built in?
  • mike95490mike95490 Solar Expert Posts: 9,363 ✭✭✭✭✭
    I like the MidnightSolar 3 or 6 position, with breakers.

     https://www.solar-electric.com/mnpv6.html
    breakers: https://www.solar-electric.com/mnepv.html

    Breakers provide a very easy way to test a PV array against all the strings in the array.
    Fuses & fuse holders are often not rated to break a live circuit.


    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 ,

  • babyrocketbabyrocket Registered Users Posts: 4
    Looks like that is for a home solar installation, whereas mine is going on the roof of my RV.  Any good sources for a mobile installation?
  • mike95490mike95490 Solar Expert Posts: 9,363 ✭✭✭✭✭
    electricity at 40V is the same, on a home or a RV or a boat.  Don't cheap out and get automotive stereo parts, they are not rated beyond 30V and seldom are able to handle a solid 20A for hours, that solar generates while charging.
    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 ,

  • babyrocketbabyrocket Registered Users Posts: 4
    It's not a cost issue, but rather finding a box that can handle the abuse and waterproofing required for installation on an RV roof.  One that has been recommended is here on Amazon.  I'd need to upgrade the breakers.
  • mike95490mike95490 Solar Expert Posts: 9,363 ✭✭✭✭✭
    I'd use a good weather head and put all that stuff inside.  Gotta get the power inside somehow .
    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 ,

  • BB.BB. Super Moderators, Administrators Posts: 32,019 admin
    edited July 13 #10
    I posted this to the wrong thread... Repost here:

    You might also think about bringing the separate cables from the panels down into the van and installing (for example) DIN Rail breakers:

    https://www.solar-electric.com/search/?q=din+rail+breaker
    https://www.solar-electric.com/dinrail-6-inches.html

    And you can get some bus bars (as needed) to combine wires (nice for mixed AWG wires instead of using wire nuts):

    https://www.solar-electric.com/search/?q=bus+bars

    Breakers are nice because they are also on/off switches. Fuses and fuse holders--Cannot usually be switched under loads. There have been issues with "touch safe" fuse holder--Push to open and they start arcing/catching fires.

    As you have found, the NEC (national electric code for North America homes/businesses/buildings) require easy access to any connections (covered box--No installations behind drywall--for example).

    Also, check that all sharp edges are rounded and/or protected with grommets/etc. so that there is no chance for shorts/cuts in insulation.

    Another reason to bring wiring from panels down (beside rain proof interior, no wasted space on roof for electrical boxes/access), is you can use an AC/DC current clamp type meter to measure the current for each panel (if you have breakers, easy to turn breaker off/on to check current flow--If fuses and for other current measurements a clamp meter is really nice).

    For example one mid-priced AC+DC Current Clamp DMM:

    https://www.amazon.com/gp/product/B019CY4FB4

    Current Clamp meters are very easy and safe to use--Just clip and insulated current clamp over the wire you want to measure current in. Very nice for Van/Boat/Car debugging (and the AC setting for AC inverter output/home checking/monitoring).

    One suggestion if you have "sealed" boxes on the exterior of the van (boat/etc.)... Even sealed boxes need to have a small weep hole drilled in the low point of the box. Any condensation is expelled out the hole as it warms up (sun/ambient air).

    -Bill

    PS: I should add... Cables should come up from "bottom" of box, have drip loops from horizontal runs and such... Keep water from being directed into the seals, glands, and boxes.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
Sign In or Register to comment.