inverters/batteries to use?

We have been given several boxes of stuff that included a 12 volt 3000/6000 watt OSP Tiger Claw modified sinewave inverter wired to a Generac 6 circut 30 amp manual transfer switch that looks easy enough to install to the in house breaker box. Manuals included too.

Along with that we received 4-125 amp hour(1000 amp rated?) 12 volt deep cycle marine batteries. 2-100 amp hour rv/marine 405 cca, 525 mca batteries. All the batteries are connected positive to positive and negative to negative. We also have a small 350 watt honda xl 350 honda generator that has a 12 volt charging system built in, is supposed to be super efficient and was used to keep the battery bank charged. Also in this is some sort of charging controller rated at 25 amps / 12 volts. There is no other writing on front or back of it.

In our mobile (900 sq ft) we use 23 watt flourescent bulbs (incandescent style) a full size refridgerator, coffee pot, computer with monitor and a 50" big screen tv, a 110 volt 1/3 hp surface well pump and 2 outdoor security lights with 75 watt bulbs in them.

Just wondering if what we have available to us is enough to keep us ok during a power outage for a couple days. Is there something in all of this that we are missing and is needed to complete it? We are now contemplating going solar and wind power with all of these items if applicable. Can someone actually help us out with this?

Thank you.


  • BB.BB. Super Moderators, Administrators Posts: 29,717 admin
    Re: inverters/batteries to use?

    For round numbers--lets start with 1,000 watts of solar panels (1 kW) using the PV Watts Program for Kalispell Montana. Assume that this is an off grid system with derating of 0.52 (off grid inverter and battery bank).
    "Station Identification"
    "Lat (deg N):", 48.30
    "Long (deg W):", 114.27
    "Elev (m): ", 904
    "PV System Specifications"
    "DC Rating:"," 1.0 kW"
    "DC to AC Derate Factor:"," 0.520"
    "AC Rating:"," 0.5 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 48.3"
    "Array Azimuth:","180.0"

    "Energy Specifications"
    "Cost of Electricity:"," 7.9 cents/kWh"

    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 2.14, 34, 2.69
    2, 2.96, 42, 3.32
    3, 4.02, 63, 4.98
    4, 4.70, 69, 5.45
    5, 5.42, 81, 6.40
    6, 5.77, 80, 6.32
    7, 6.24, 87, 6.87
    8, 6.19, 88, 6.95
    9, 5.23, 72, 5.69
    10, 4.08, 61, 4.82
    11, 2.16, 31, 2.45
    12, 1.46, 21, 1.66
    "Year", 4.21, 730, 57.67

    Assume that you would like to run 8 months out of year without using a genset... 61 kW per month or 61/30=2kWhours of 120 VAC 60Hz power per day per 1,000 watts of solar panels.

    Size the batteries for 5%-13% of C/20 capacity (for optimum charging rule of thumb). Lets start with 12 volts system:
    • Battery max AH rating = 1,000 watts * 1/12 volt batt * 1/0.05 = 1,667 AH @ 12 volts
    • Battery min AH rating = 1,000 watts * 1/12 volt batt * 1/0.13 = 641 AH @ 12 volts
    So--you need next look at how many Watt*hours or Amp*Hours (at what voltage) to run your home per day (by season)...

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,355 ✭✭✭✭
    Re: inverters/batteries to use?

    As has been said, ever so often. Do your homework, avoid the ready, fire, aim. First define the loads (and their likely duration) to see how big they are. Then you can work backward to see what you can power with the hardware you have.

    As Bill suggests so often as well. Most people will find it is much cheaper to provide power during grid outages via a well designed generator installation.

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