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Thread: Portable Emergency Power - Inverter

  1. #11
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    Quote Originally Posted by FionaZuppa View Post
    hence why you do not use 12v
    use 48v

    but it would be a large batt bank.

    solar panels for daytime running of equip, small batt setup for night time lights. ez, cheap.
    With an off grid PV system with batteries, you are always running off the batteries, even in the daytime. The only purpose of the solar array is to recharge the batteries. Load analysis and desired autonomy time (the sun does not shine every day) dictates the battery bank size and battery bank size determines the PV array size.

  2. #12
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    ggunn: Does the battery set up make it uneconomical?

  3. #13
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    Quote Originally Posted by Sahib View Post
    ggunn: Does the battery set up make it uneconomical?
    It depends. If it's totally off grid, then to size your batteries you must consider how much it would cost to get the grid to your location as an alternative, how many days of autonomy (no significant sunlight) your system can take without running the batteries down too far to use, and what your loads look like and how many hours a day each one runs.

    If you are wanting batteries for backup in case of a grid outage, you need to consider your loads (which ones you'll need to run during an outage and which ones you can do without), autonomy, and how often and for how long the grid goes down.

    If you want them for storing energy from solar and using it later, you have to look at the specific tariff structure under which you operate to see whether there is any economic benefit to doing that.

  4. #14
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    if the pv's dont have enough sunlight during the day then you simply do not run the equip, but maybe a few lights. if you run a freezer full of ice jugs you can use them as needed to keep fridge items cold enough w/o spoiling. the starting point is poco + cold fridge + freezer full of ice jugs. the use of fat jugs, like 2lb coffee can size, makes the ice last longer.

    w/o poco and when sunlight is good enough you charge batts AND run the fridge & freezer. the goal is to run batts only at night, and only as needed.

    if you build it right your batt bank size will not be too big.

    you can likely get by for a few days w/o any sunlight and w/o running batts for freezer/fridge.

    and its FL, no sunlight is like pizza w/o cheese

  5. #15
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    Quote Originally Posted by indcontrols View Post
    I live in Florida, where in the summer, power can go out for days. I am investigating the use of sealed lead acid batteries and a 12VDC to 120VAC inverter for temporary, portable, emergency power to keep the refrigerator going and microwave, phone charger, lamp(s) as needed.
    The 2000 watt continuous (4000 watt surge) inverter I purchased has 3 prong receptacles on it. I opened the cover and found that the ground terminal of the receptacle is connected to the case of the inverter. There is no ground lug on the inverter and no mention of connecting the inverter to ground. The pictures on the inverter show it used in vehicles, tent camping and home use.
    The ground issue prompted me to investigate the NEC. There are code related to photo voltaic inverts wired into the house wiring, but I do not see anything related to a free standing inverter, not wired into the house wiring. My search on the web did not produce anything.
    Questions:
    1. Are there electric code(s) related to Temporary Emergency Power systems that are not wired into the house wiring?
    2. Should I ground the inverter to a copper water pipe with a ground clamp and a wire to the chassis of the inverter?
    3. Other means of grounding like using a plug with only the ground wire connected. Plug into local outlet and other end wired to inverter chasis?
    4. The wire provided for connection from battery to inverter is #4AWG, 600V, 105 degree C, VW-1. 2000W/10VDC(minimum inverter source voltage)=200Amps. This seems a little small for the ampacity.
    5. The wire is also not marked as being UL., nor is the inverter. Is this a problem?


    Thank you!
    As others had noted, your battery bank will not provide enough power for your mentioned load. The microwave is definitely a no no. Most microwave units are rated 1500 watts. Good enough to start the microwave and run for less than 20 seconds if it will even start at all.
    As for other loads like the fridge, phone chargers and maybe a couple of led lamps, your battery will work with a single full charge for three hours (tops) before it needs another recharge.
    The most efficient fridge model draws 500 watts which conservatively at 120v is ~4 amps and ~40 amp draw from a regular 12V deep cycle battery.
    Most regular sized car batteries are rated 100 Amp Hour. So you hook up a fridge that draws 40 Amps will enable you run it for two hours on an ideal setting (temperature, age of battery etc.)
    Peukert's Law will tell you how batteries behave with different loads.
    I have three of these inverters in my RV (Motor Home) that I spend time on long weekends. Along with these inverters I have solar panel and generator to recharge the four battery bank. I haven't experienced shortage of energy probably because we have sufficient sunshine in CA. I hardly ran my 2KW Honda generator.
    With regard to house hookup, I don't think you have to be concerned whether house grounding should tie in to inverter since this is only temporary. The key here is not to connect any house circuit. . . just connect the load that you absolutely need.
    A minimum of four 12 volt deep cycle lead acid batteries, along with a 200W solar cells (for recharging) will last you the whole night running your fridge until the next daylight.

  6. #16
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    Quote Originally Posted by FionaZuppa View Post
    if the pv's dont have enough sunlight during the day then you simply do not run the equip, but maybe a few lights. if you run a freezer full of ice jugs you can use them as needed to keep fridge items cold enough w/o spoiling. the starting point is poco + cold fridge + freezer full of ice jugs. the use of fat jugs, like 2lb coffee can size, makes the ice last longer.

    w/o poco and when sunlight is good enough you charge batts AND run the fridge & freezer. the goal is to run batts only at night, and only as needed.

    if you build it right your batt bank size will not be too big.

    you can likely get by for a few days w/o any sunlight and w/o running batts for freezer/fridge.

    and its FL, no sunlight is like pizza w/o cheese
    Not accurate. You cannot simply run your loads off solar during the day. PV modules are current sources; they cannot deliver current on demand. When a PV array is producing energy you have to have someplace to store it or the system will shut down.

    The way to design an off grid PV system is to start with a load analysis, which will determine the size of the battery bank you need to service the loads. THEN you design the PV part of the system to keep the batteries charged and healthy. You are always (day or night) running off the batteries because you need batteries to regulate the voltage and supply current on demand.

    Telling someone that they can just run their loads off the PV system during the day and keep a small battery bank to run minimal loads at night is incorrect. It doesn't work that way.

  7. #17
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    Quote Originally Posted by ggunn View Post
    Not accurate. You cannot simply run your loads off solar during the day. PV modules are current sources; they cannot deliver current on demand. When a PV array is producing energy you have to have someplace to store it or the system will shut down.

    The way to design an off grid PV system is to start with a load analysis, which will determine the size of the battery bank you need to service the loads. THEN you design the PV part of the system to keep the batteries charged and healthy. You are always (day or night) running off the batteries because you need batteries to regulate the voltage and supply current on demand.

    Telling someone that they can just run their loads off the PV system during the day and keep a small battery bank to run minimal loads at night is incorrect. It doesn't work that way.
    what?
    i worked on US govt contract where we had pv's out in remote fields (off grid remote shelters), during the day the solar panels charged the batts AND ran the electric (+ hvac) during the day, a transfer switch went to batt when pv voltage dropped below a threshold. a propane backup gen was there if batts died down too low. batts and panels powered an array of inverters.

    what do you mean solar panels cannot power a load?
    Last edited by FionaZuppa; 10-04-17 at 07:50 PM.

  8. #18
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    Quote Originally Posted by FionaZuppa View Post
    what?
    i worked on US govt contract where we had pv's out in remote fields (off grid remote shelters), during the day the solar panels charged the batts AND ran the electric (+ hvac) during the day, a transfer switch went to batt when pv voltage dropped below a threshold. a propane backup gen was there if batts died down too low. batts and panels powered an array of inverters.

    what do you mean solar panels cannot power a load?
    Perhaps a better statement would have been that PV without energy storage cannot sustain a full rated load through clouds or other disturbances, nor can it supply any starting load current beyond the panel capability at any given moment.

    Such PV systems work best with motor loads far enough below their nominal rating, or with a built in VFD or soft start capability.

    Sent from my XT1585 using Tapatalk

  9. #19
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    Quote Originally Posted by indcontrols View Post
    I live in Florida, where in the summer, power can go out for days. I am investigating the use of sealed lead acid batteries and a 12VDC to 120VAC inverter for temporary, portable, emergency power to keep the refrigerator going and microwave, phone charger, lamp(s) as needed...
    Generac has an informative Q&A on the limits of battery backup systems
    http://www.generac.com/service-suppo...battery-backup

    NEC ARTICLE 480 Storage Batteries - describes requirements for ventilation & safety.

    480v Sterling Biopower engines are very efficient backup power systems using natural gas.
    http://www.stirlingsupercoolers.com/energy.asp

    50hz Sterling Systems in the European residential market
    http://www.qalovis.com/en/flexgen-st...er-generation/
    Roger Ramjet NoFixNoPay

  10. #20
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    Quote Originally Posted by petersonra View Post
    I think you will find that the battery stack you need to do any good will make some kind of gas or diesel generator a lot more attractive.
    Sure, attractive enough but you have to turn your stereo full volume to drown out the noise of either engine.

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