Need a check setting up my first PV system

nigelknoynigelknoy Posts: 2Registered Users
Hello everyone,

My name is Nigel, and this is my first post here.

I'm looking to build a small solar electric system for my off-grid cabin.  I've read a lot of pages and posts all over the internet, and have put together a list of components, but this is still new to me and would greatly appreciate some feedback.

Some background first.  I've calculated my average daily watt-hours at 3,845.  My battery bank capacity will only be 7,690Wh, but I plan to supplement with the generator I'm currently using for house power on extended cloudy days; I live near Prescott, AZ, so I don't expect too many low-production days. 

I understand a 48V system is best as a rule of thumb, so I've selected 8 12V, 110AH AGM batteries (2 strings of 4):
https://www.altestore.com/store/deep-cycle-batteries/sealed-agm-batteries/universal-ub121100-12v-110ah-20hr-sealed-agm-p1995/

I calculated my minimum array wattage at 967, looking at 4 24V, 360W solar panels (2 strings of 2):
https://www.altestore.com/store/solar-panels/seraphim-solar-panels-p40805/#SEP360SRP3606MA

MPPT controllers seem to be most recommended, and I calculated 30A minimum.  This 40A from Morningstar was the closest I could get:
https://www.altestore.com/store/charge-controllers/solar-charge-controllers/mppt-solar-charge-controllers/morningstar-mppt-solar-controllers/morningstar-prostar-mppt-40a-solar-charge-controller-with-display-p11991/
I found that Morningstar is recommended by most people that took the time to write anything on the topic, but I found this AIMS Power 40A for nearly $175 less:
https://theinverterstore.com/product/6000-watt-pure-sine-inverter-charger-48-vdc-to-120-vac/

I had the hardest time with the inverter.  The best fit I think is this Schneider Electric 48V, 4000W:
https://www.altestore.com/store/inverters/off-grid-inverters/schneider-electric-conext-sw-inverterchargers-p40463/#SCNCONSW4048
This is a cheaper alternative, also 48V, but rated at 6000W:
https://theinverterstore.com/product/6000-watt-pure-sine-inverter-charger-48-vdc-to-120-vac/

Any thoughts are appreciated.  I know I have plenty yet to learn, so I have an open mind. Thank you in advance!

Comments

  • mcgivormcgivor Posts: 2,164Solar Expert ✭✭✭✭✭
    Welcome aboard.

    Batteries, my recommendation is go with flooded at least for your first set, they allow the opportunity to learn and are forgiving to some degree, golf cart 6V T105 225Ah are common hense cheaper. Voltage wise 48v allows smaller conductors and a wise choice.

    Array,  this should be determined by the battery capacity, which in turn are determined by loads, if frequent generator use is proposed, then being under sized is not such an issue.

    Morningstar are excellent, they are, in my opinion worth the extra  $$, excellent support, not to exclude any of the other offerings, Midnight, Outback, SMC, Schneider etcetera.

    Inverter wise, buy to suit loads, the SW Conext series are nice professional units, for the price they offer features the cheaper variety don't and are of superior quality for  ~$200 more are well worth it   https://www.solar-electric.com/schneider-electric-sw-conext-inverter-4048-120.html
    If you choose to go the SW route I would recommend the charge controller be Schneider because it can communicate with the inverter thereby making it an integrated system, rather than a mix of parts. A Combox or System  Control Panel would also be needed to program, the Combox is the more versatile with graphics, remote monitoring and so forth used with a PC. Yes it dose drive the price up but it's worth it, in my opinion.
    https://www.solar-electric.com/xaxwmp60amps.html
    https://www.solar-electric.com/schneider-electric-conext-combox.html
    https://www.solar-electric.com/schneider-electric-xw-plus-sw-system-control-panel.html

    Currently I have both Morningstar and Schneider controllers both have been excellent, my choice was because of passive cooling, some others rely on fans, which I'm not a fan of. Do it right the first time if finance permits you won't regret spending the extra money, at least that's what I discovered by going cheap first, lessons learned.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • mike95490mike95490 Posts: 7,871Solar Expert ✭✭✭✭
    edited March 17 #3
    if you are at all fluent with networking and can connect a Router and ethernet cables, i'd strongly suggest the Morningstar MPPT-60 and skip the $100 meter panel, and simply use the web interface to monitor the Controller

    And +1 on the 8 golf cart batteries, half the cells to check and add water, and parallel banks are less reliable than a series string
    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 ,

  • EstragonEstragon Posts: 2,760Registered Users ✭✭✭✭
    Also +1 on the flooded golf cart batteries.

    The panels in a string of 2 don't have a ton of voltage headroom. In Arizona, I assume it can get pretty hot, and hot panels will have lower voltage - maybe too low for an mppt controller. You may want to consider 2 strings of 3 (pv charging capacity a bit light anyway IMHO), or use a pwm controller that doesn't need as much vpltage headroom?

    Like McGivor, I'd be inclined to stick with Morningstart et al. for domestic service etc., but people do use the cheaper stuff sucessfully.

    The 2 inverters are somewhat diifferent beasts. Do you have a split phase generator and/or 240v loads? The 4048 appears to be 120/240v. If you have 120v only, it may not be the best choice. The cheaper one appears to be120v only, so you'd need to add an autotransformer to run any 240v loads (eg. pumps, HVAC). The 6kw inverter also has an idle load of ~80w. Left on all day, that's 80x24=1920w - a significant load in the context of a 3800w daily budget. Didn't look at idle loss on the 4048, which is likely lower but still material.
    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
  • nigelknoynigelknoy Posts: 2Registered Users
    Thanks for the feedback everyone! It's much appreciated.
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