12 volt system upgrade

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garynappi
garynappi Registered Users Posts: 120 ✭✭
Sorry to be so vague on system details, I'm still fleshing out much of the power needs. 

My 12v system upgrade is still in process but now that I've committed to it I have a few questions.

The new controller is a Renogy 60A which by the specs the max PV wattage is 800w @ 12 volts and four new 200w panels are en route. 

Since solar panels do not provide their max power output (The panels will lose a bit extra since I may use the year round tilt angle of 24 1/2 deg. for my south Florida location) what is the feasibility of adding two more 135w panels having a total of 1070 watts instead of the max listed 800 watts in the specs??   

Or should I just add another CC for the extra 270 watts? 









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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,076 ✭✭✭✭✭
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    What is the Voc. and Isc. of both the 200 and 135 watt panels? Adding the 135's could  cost you considerable power when mixed with the 200 watt panels.

    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.

  • garynappi
    garynappi Registered Users Posts: 120 ✭✭
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    Thanks for the reply.

    135W has VOC 22.1v ISC 8.37A 
    200W has VOC 24.6v ISC 10.14A


  • BB.
    BB. Super Moderators, Administrators Posts: 33,522 admin
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    Placing the two panels in series or in parallel is less than optimum, but should work OK. We try to aim for 5% to 10% (max) difference in Vmp (parallel connected panels) and 5% to 10% (max) for Imp (series connected panels). The "closer the match", the better overall harvest.

    You will not "break" anything by paralleling or series connecting these panels.

    Nominally, the typical "optimum" for Vmp-array is roughly 2x your battery charging voltage (i.e., charging at 15 volts, then Vmp-array~30 volts or more).

    There are a lot of Renogy 60 Amp MPPT controllers (I think)... Here is an example of one:

    https://www.renogy.com/rover-60-amp-mppt-solar-charge-controller/

    Notice:

    Max. PV Input Voltage: 140VDC

    That usually works out to around Vmp-array maximum of 100 (plus a bit) volts Or 3 (to possibly 4) panels in series if it does not get too cold at your place (Voc-array-cold needs to be less than 140 VDC).

    If you have a longer cable run from the array to the "battery shed/MPPT controller", higher array voltage lets you use much smaller diameter cable (save $$$, longer cable runs if needed).

    Don't know your loads, but what type of batteries (FLA, AGM, Lithium Ion, or what) type of batteries and what is the AH rating (XXX AH @ 12 VDC or whatever). Typically like to see 5%/10%/13%/20% rate of charge for solar battery systems, and at least 10%+ for off grid daily use systems. That will give us a better idea of what size solar array is "better" for your needs. At this time, solar panels tend to be cheap, and batteries tend to be expensive. "Over paneling" your system (with a good charge controller) usually gives you much better battery life--Plus extra power for loads during cloudy/poor weather.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,076 ✭✭✭✭✭
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    garynappi said:
    Thanks for the reply.

    135W has VOC 22.1v ISC 8.37A 
    200W has VOC 24.6v ISC 10.14A


    The lower Voc and Isc of the 135 watt panels are slightly more than 10% LOWER. I wouldn't try to mix them in as thy will cause a negative effect on the higher output panels. If either of the stats were higher you could take advantage of that in your wiring scheme

    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.