Running small inverter without batteries

GabeGabe Registered Users Posts: 1
Has anyone attempted running a small load (400watts) off a small 120v inverter directly connected to pv panels? 
Will the inverter "wake up" at sun up without problems? 
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  • BB.BB. Super Moderators, Administrators Posts: 29,511 admin
    Yes. There is a guy that sells a box the will reset the dc power (as I understand). Some k many? Most?) AC inverters will shut down on low input voltage and need the dc voltage to turn off/on to start ac conversion again.

    You have to be careful. Many solar panels can output higher voltage than the inverter is rated for. Can damage/ruin your inverter.

    Cheap inverter, try it. Expensive inverter.... Your choice.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • kaipo_boykaipo_boy Solar Expert Posts: 143 ✭✭

    400w load isn't what I'd call small... I'm only running 2 chest freezers off my system, combined probably around 200w if both compressors are on, but they pull a whole helluva lot more watts on startup; and its got 4 golf cart batteries wired into my inverter. I don't see how your panels will put up with any sort of major inductive startup load... what is your load like? lightbulbs or motors?

  • mike95490mike95490 Solar Expert Posts: 8,377 ✭✭✭✭✭
    a solar panel cannot handle ANY surge - unless it has a surge of light (photons) hitting it.  A battery is generally needed to average out the DC power so the inverter can be fed properly.
    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: 29,511 admin
    edited January 2017 #5
    Here is the "magic box" that Missouri Wind and Sun sells to direct connect solar panels to DC inverters (I have no idea how well it works):

    http://mwands.com/store/12-volt-suntaqe-pwb-inverter-controller (link fixed 1/9/2017. -Bill)

    -Bill


    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • kaipo_boykaipo_boy Solar Expert Posts: 143 ✭✭
    Wow! ok then, I probably want around 3kw worth, so I have to order about 30 of these and wire them in series? but still have to light candles at night... and burn wood for coffee if having it before 10am or after 3pm... and no TV at 5pm when the news guys like to come on :(  Still, if it works as advertised during the day, that's something although even rudimentary batteries wouldn't cost much in a setup like that.

    These guys are Missour Wind and Sun... I just got a DC heating element from these guys (around $85), although I don't think they manufactured it themselves.  It is a short (about 6") nickle plated hoop on a standard screw in base with a built in thermostat, that takes up to 48v of DC current up to 700w and the idea is to just screw this heating element into your otherwise normal electric water heater, but tie the new heating element directly to your PV panel so it constantly heats water during the day... no more water heater bills.  I just got it and am building the PV panel mounts (2x trina 285w panels) and waiting for the parallel connectors to come in from amazon and figuring how thick a wire I need to run to it, my water heater is clear across the other side of the property :(
  • bill von novakbill von novak Solar Expert Posts: 850 ✭✭✭✭
    Has anyone attempted running a small load (400watts) off a small 120v inverter directly connected to pv panels? 
    Will the inverter "wake up" at sun up without problems? 
    It's possible but you will have problems doing it directly.  Most inverters can't handle the 18-20 volts the panel puts out open circuit so you either have to dissipate the power or buck the voltage.  There will be no startup surge allowed.  You can add capacitors to give you startup surge capability (for example a Maxwell BMOD0058, which is a 58 farad capacitor) but that's not much different than adding batteries.


  • PhotowhitPhotowhit Solar Expert Posts: 4,996 ✭✭✭✭
    edited March 2016 #9
     

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • cow_ranchercow_rancher Solar Expert Posts: 116 ✭✭✭✭
    Yes I have 35 enphase microinverters, you need to be grid tied or have the right inverter/charger to wake them up.
  • JohannJohann Solar Expert Posts: 240 ✭✭✭
    kaipo_boy said:
    Wow! ok then, I probably want around 3kw worth, so I have to order about 30 of these and wire them in series? but still have to light candles at night... and burn wood for coffee if having it before 10am or after 3pm... and no TV at 5pm when the news guys like to come on :(  Still, if it works as advertised during the day, that's something although even rudimentary batteries wouldn't cost much in a setup like that.

    These guys are Missour Wind and Sun... I just got a DC heating element from these guys (around $85), although I don't think they manufactured it themselves.  It is a short (about 6") nickle plated hoop on a standard screw in base with a built in thermostat, that takes up to 48v of DC current up to 700w and the idea is to just screw this heating element into your otherwise normal electric water heater, but tie the new heating element directly to your PV panel so it constantly heats water during the day... no more water heater bills.  I just got it and am building the PV panel mounts (2x trina 285w panels) and waiting for the parallel connectors to come in from amazon and figuring how thick a wire I need to run to it, my water heater is clear across the other side of the property :(
    2 of your panels will not give you enough power to power that heat element all the way. Looks like you need about 3 or even 4 panels just to power that heat element 100%. $85 is steep for such an heat element, looks like I seen them for half the price at other places on the net.

    Looks like they use a buck converter to bring the panel voltage down so the inverter can be used without damage. Also they may use a low voltage / high voltage  electronic disconnect/reconnect that will turn the power off and on automatically at the on-off switch at the inverter, this way the inverter can be turned on again automatically if the voltage is high enough again.

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