pv voltage for 48v inverter

robocop
robocop Registered Users Posts: 118 ✭✭
edited August 2017 in Solar Beginners Corner #1

Hi wvweybody


Back again after a while.

For a 48v inverter if the panels are 36 v how many should I use?

Or how can I match panels to a 48v inverter?

I see big 315w panel giving about 36v , should I look for  panel of 48v .?

How does that work?

Regards for everybody

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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,113 ✭✭✭✭✭
    edited August 2017 #2
    A panel with a Vmp of Approx. 36 volts Would usually be a 72 cell panel. This is considered a 24 volt nominal panel. The 60 cell panels you see are typically around 30 Vmp. Some people will sell these as 24 volt panels but the thing is, once a 60 cell panel heats up in the sun the voltage will drop to a level that isn't high enough to charge or equalize a 24 volt battery. Power ratings on solar panels are created in carefully controlled conditions to assure all rating is done on a level playing field. In your case, to get a 48 volt NOMINAL output you would just series wire two 72 cell panels together. NOMINAL in this context  basically refers to battery based systems. What type of inverter are you trying to connect to?

    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.

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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #3
    Normally the panels would be connected to a charge controller, which charges a battery, which powers the inverter. The charge controller specifications would dictate what panels can be used. 
    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.
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  • robocop
    robocop Registered Users Posts: 118 ✭✭
    #4

    would like to use rec 315w  solar panels  with a 5000w hybrid solar inverter low/high frequency??

    my total energy will be around 4000w .

    How many panels if only pv use for energy and if a combination of pv-batteries and grid use?

    Hope to have been clear


    thx

    Bob


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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #5
    Ned more information on your loads,  location of install,  and what you are trying to do.

    400 watt  load x 10 hours per day = 4,000  watt *hours per day. But a 1,000 watt inverter would run that load.

    What do you mean with a hybrid inverter?  Grid Tied with off grid+battery bank?

    Emergency backup power? Have net meter utility agreement?

    GT Inverter + generator would be cheaper if you rarely have power failures,
    .

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • robocop
    robocop Registered Users Posts: 118 ✭✭
    #6
    hi Bill  the load is 4000w  for 4 hours a day . it is grid tie . In the future net meter agreement  .Thinking of 8pcs  250ah batt  to form  500ah in 48v. Location is netherlands antilles
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #7
    Why not install a 3Kw grid tie system, with no battery ?  Do you really need backup batteries ?
    A 3 or 4Kw grid tie system would balance out your 4Kw load, and give you close to zero usage from grid.  (only on sunny days, clouds will deprive the panels of bright sun and power will be drastically reduced
    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 ,

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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    edited August 2017 #8
    Hi robocop,
     So the MPK 1800 hybrid inverter/charger that you were considering in a previous post, is the one you bought?. If that's the case, I have attached the spec sheet so the guys can take a look at it.
    Previous post:
    http://forum.solar-electric.com/discussion/351788/solar-system#latest

    Rick
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #9
    • 4,000 Watts * 4 hours per day = 16,000 WH per day
    Normally, for full time off grid, I would suggest 2 days of storage and 50% maximum discharge, or:
    • 16,000 WH per day * 1/0.85 AC inverter eff * 2 days storage * 1/0.50 max discharge * 1/48 volt battery bank = 1,569 AH @ 48 volt battery bank nominal
    I am assuming that this is way more than you really plan on buying (that is a relatively big battery bank for 16 kWH per day).

    The "minimum" flooded cell lead acid battery bank I would suggest for a 5,000 Watt AC inverter and/or 5,000 Watt PV Array would be ~500 AH @ 48 volt battery bank (if you want to charge/discharge the battery bank at a maximum/reliable rate of 1,000 Watts per 100 AH @ 48 volts).

    The size of a solar array that can supply 16,000 kWH per day for Willemstad N.A. with a fixed array would give you hours of sun per day of:
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Willemstad
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 78° angle from vertical:
    (For best year-round performance)
    Jan Feb Mar Apr May Jun
    6.65
              		6.95
              		6.92
              		6.23
              		6.58
              		6.78
     
    Jul Aug Sep Oct Nov Dec
    6.74
              		6.61
              		6.42
              		6.41
              		6.28
              		6.32
     
    For an off grid power system, assuming a minimum of 6 hours per day (minimal AC backup genset usage):
    • 16,000 WH per day * 1/0.52 off grid AC system eff * 1/6.0 hours of sun per day minimum = 5,128 Watt array minimum
    However, if you are, mostly, running Grid Tied mode, then to make 16 kWH per day:
    • 16,000 WH per day * 1/0.77 grid tied AC system eff * 1/6.0 hours of sun per day = 3,463 Watt array minimum
    Then there is sizing the solar array for your battery bank. Normally, suggest 5% to 13% rate of charge for solar... 5% is good for weekend/seasonal usage (and with nominally grid tied system and afternoon brownouts?). 10%+ is suggested for full time off grid usage. Just to give you a range of ideas.
    • 500 AH * 59 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 1,916 Watt array minimum (small battery bank with just "backup" charging)
    • 1,569 AH * 59 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 12,022 Watt array nominal (large battery bank with full time off grid optimal charging)
    Just some discussion points.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • robocop
    robocop Registered Users Posts: 118 ✭✭
    #10

    Hi Mike

    SO you think a 5000kva hybrid inverter is enough? Will use batteries when there is no sun.

    for instance about 4 hpurs in the evening if Not will use grid. So acombination

    How many pcs of panels of 300w?How tocombine panels for 48v inverter?

    Thx in advance   Bob


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  • robocop
    robocop Registered Users Posts: 118 ✭✭
    #11
    Bil let me read and understand your explanation first
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  • robocop
    robocop Registered Users Posts: 118 ✭✭
    #12

    Hi Rick

    No MUST  reveiver I have read their quality is not good and their service is bad


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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    edited August 2017 #13
    Hi Bob,
    Possibly 12 or 14 of this type panel could be used, however it would require the use of a battery that does not need to be equalized. Likely an AGM battery, although some AGM's do require EQ, it's not at so high a voltage as FLAs. For a more accurate assessment, we need the specifications on the battery, charge controller and solar panels. Brand name and model numbers if possible.

    Rick  
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • robocop
    robocop Registered Users Posts: 118 ✭✭
    #14

    good morning people

    Just thinking for a 4600 load 220v 50hz how many rec 315w panels ? inverter is 48v vdc input .

    Just a roughly calculation . Are the pv going up in price?

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #15
    4,600 Watt load for how many hours per day (you said 4,000 watts * 4 hours per day = 16,000 Watt*Hours per day). And I gave you a wide range of battery bank/solar array sizes.

    Off grid solar is expensive--Is there any way that you can reduce the loads (such as, if this is for air conditioning, can you replace the unit with a new mini-split system--more energy efficient--and insulate the home/room)?

    Is this for full time off grid, or just afternoon backups, or what?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • robocop
    robocop Registered Users Posts: 118 ✭✭
    #16

    Hi Rick

    If I use the rec 315w panels and a MPP hybrid v series 5048, 500ah on battery pack for the 4600  load .


    How many panels do you think now. planning using a combination pf both PV-BATT-GRID.

    During the day pv and a couple of hours in the evening the batt pack 

    I think this is the info you needed also for others people you are welcome to help me 

    thnx Bob


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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #17
    Hi Bob,
    The MPP 5048 has an MPPT charge controller capable of 120 amps, will also support a 6000 watt array. Most AGM batteries will handle a 20 to 25% charge rate, however it would be helpful if you could provide the brand and model number of the battery. The last thing you want to do is lose a new set of batteries by charging them with too much amperage. 

    Rick

    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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