Micro Inverter Question

Discussion in 'General Electronics Chat' started by ShockBoy, Jan 19, 2010.

  1. ShockBoy

    Thread Starter Senior Member

    Oct 27, 2009
    I've been researching micro inverters for my solar panels and love the idea of converting the dc to ac at the module itself, but the prices are outrageous:eek:
    What would be the difference in purchasing a 20 dollar cigarette lighter type inverter rated at or above my panels watt rating as opposed to shelling out 200-300 bucks each? Solar is SO overpriced.
    Most I've seen rated at 100 Watts (compatable with my panel @84 Watts). My panel produces (like someone said; On one day in the middle of summer, between 12 and 1:30 pm.) 3.5 Amps.
    I'm not planning on running any load, will convert it back to dc at the controller. Long distance location (100 ft. or so) for the modules.

    I've posted generic pictures of one I found along with the info.
  2. SgtWookie


    Jul 17, 2007
    That inverter requires 10A minimum current to be available. If you have 3.5A @14v available, you're about 1/3 of the way there.

    I wouldn't expect micro inverters like that one to be very efficient. Does it make sense to spend $1,000 or so building a solar array, and then throwing a third of that investment away due to the inefficiency of a cheap inverter?
  3. ShockBoy

    Thread Starter Senior Member

    Oct 27, 2009
    Nooooo Sgt.
    You're right.
    But not everyone can afford the 'good' stuff. BTW, what makes this small inverter cheap?
    Someone remind me every now and then NOT to ask stupid questions.
    Last edited: Jan 19, 2010
  4. Audioguru


    Dec 20, 2007
    The small inverter might be rated for a short duration surge of 100W or 50W continuously.
    It probably has a square-wave output so many electronic products will not work properly when powered by it.
    It probably does not have voltage regulation so its voltage will be too high when the battery is freshly charged and/or the load is light. Then its voltage will be too low when the battery charge is running down and/or the load is near its max.
  5. ShockBoy

    Thread Starter Senior Member

    Oct 27, 2009
    It's rated for 100 continuous. More than likely square wave. I would think that there is voltage regulation since it was constructed to be used in the auto, and the voltage in the auto varies quite a bit from 12V. I'm assuming (I know I should'nt) that this device is being sold for those who need to recharge batteries while they are driving. So this device is playing into the hopes that whatever is plugged into it will have it's own VR?
    Hey, member when things were made to work, and last?
    This is why discussion forums rock. I never would have thought of all of this information.
  6. SgtWookie


    Jul 17, 2007
    You're faced with a difficult problem, particularly if your solar array is located at any significant distance from where the power is to be consumed.

    The more you learn about power conversion, the more you will understand how difficult it is to achieve high efficiency.

    I don't pretend to know everything about power conversion.

    However, there is no "free lunch"; you will incur losses by converting low voltage DC to high voltage AC, and more losses converting that high voltage AC back to DC.

    The flip side to this is, that if the conversion is done efficiently, you can use smaller gauge wiring between the power source and the point of consumption, and lose less than you would if you used heavy-gauge wires.

    Your power company uses 11kv to 22kv in residential neighborhoods in the overhead or underground lines; they have transformers every so often to "tap off" for the residences. They use the high voltage because that allows them to use smaller size wire than would otherwise be required. With AC, it's easy - just put a properly-sized transformer wherever you need it. But if you're starting off with DC, you have to convert the power using a DC-DC converter, or an AC inverter.

    You have a lot more research ahead of you. Thankfully, there are plenty of resources online nowadays.
  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    Run your panels in series, then use a 48v->12v converter etc at the battery end.
  8. 3ldon

    Active Member

    Jan 9, 2010
    The ENPHASE M210-84-208-S12 makes a claim at 95.5% efficiency, and it may be worth the price in the long run if you could get it at half off, (i think retail is $199).

    I would say do not convert it to ac at all, and how you would go about doing that depends on the voltage your panel outputs.

    The difference between a cheap MSW inverter and a real inverter is a few orders of magnitude
    The solar inverter has a battery management algorithm, or uses the grid as the battery. It calculates the correct amount of current to draw from the panel as to extract the most power. It accepts a wide range in input voltage and the efficiency curve is fairly flat and rather high (typically 93-98%) It also has reverse polarity protection, at least a 2 year warranty, is UL rated, and will not burn your house down.