1st time post - ? about higher voltages 72.9v

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KD0CAC
KD0CAC Registered Users Posts: 3 ✭
in Advanced Solar Electric Technical Forum #1
I have been around alternative energy almost 40 yrs. , and was for older systems [ not as old as 40yrs ] but have been using the limit of 48v as a high .
And found a craigslist add with some 425w 72.9v panels .
I was under the impression that generally 48v was where the limit was - not counting panels with mini-inverters mounted on panels .
Have not noticed any gear for higher voltage , maybe because what I have used in the past , hole house RV systems running airconditioning and everything , with 3500watt surge , 2000watt continuous , 600-1000watt total solar .
A little bragging - but to also make the point of correct system design - makes for long battery life - the proof is with the above system mostly no grid , the Trojan L16's lasted over 12 1/2 yrs. 
So how much use and how rare of gear to build with 72.9 volt panels .

Thanks John  
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,134 ✭✭✭✭✭
    edited September 2018 #2
    Grid tied systems are now running up to 1000 VDC in some areas. Completely different creature than Off Grid battery based systems.  While there are higher voltage battery backup systems they are generally only commercial systems and are under a whole different set of regulations than residential off grid.  There are high voltage MPPT charge controllers that allow you to run up to 600 Vdc but you still will be charging a lower voltage battery bank which will be powering a lower voltage inverter.

     There are many high voltage solar panels around. Either they will be series wired to high voltage and sent to a string inverter or to a MPPT charge controller and stepped down to charge a lower voltage battery bank. 

    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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  • KD0CAC
    KD0CAC Registered Users Posts: 3 ✭
    #3
    It's hard to walk away from $00.32 per watt panels , just trying to figure if I could incorporate with my next system .
    Not sure what or when , had a fire and lost a lot of panels , charge controller etc.
    I did repair the inverter , but would like to upgrade that anyway from the Freedom 458 2512 .
    Get into pure sine-wave .
    Also into ham radio , so to complicate things , trying to get RFI quite .
    Also may build a 18650 lithium power wall .
    Thanks    
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  • Estragon
    Estragon Registered Users Posts: 4,498 ✭✭✭✭✭
    #4
    You might be able to use the panels on something like a Midnite Classic controller.  Two in series might be too high VOC depending on your local record low temps for a 150v controller, but a Classic200 should work.  Three in series might work on a Classic 250.
    Off-grid.  
    Main 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
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #5
    73Vmp  panels  on a real MPPT controller would charge a 48V bank fine.  But you barely get the real benefit of MPPT unless you series the panels to save on wire size.  As was stated before, you need a 200V controller to be able to use those in series.
    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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