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Thread: Inverter question

  1. #1
    New member reuben_j_cogburn's Avatar
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    Default Inverter question

    I am presently running batteries and an inverter that is 400 watts. My question is this: Does this inverter draw 400 watts regardless is whether I'm only running a few watts in lights?
    If I switch to a 75watt inverter when I'm only running a laptop or a light (got only one light in my shack anyhow), will my batteries last longer until I need to fire up the generater and recharge them?

    Thanks ya'll......

    reuben...

  2. #2
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    Your 400w inverter is limited to 400w output. The power loss from the inverter isn't enough to worry about, like 1/4 amp from your battery. That 1/4 amp will drain even with no load, so turn the inverter off when you're leaving for the day to keep your battery at max.

  3. #3
    New member reuben_j_cogburn's Avatar
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    Default reply

    Thanks for the reply. Let me try and clarify a bit though as I may have been a bit confusing in my first question.
    I always turn things off when I'm not there including shutting the inverter off and or unplugging it.
    My question is more like: is the actual drain on my battery 400Watts when actually using it? Or is the drain only what the wattage of the computer/appliances demand?
    IE if I am only using a 24watt bulb through my inverter does my 400watt inverter drain more power from my battery than the 24watt bulb requires?
    I have a lower power inverter (in storage) and if it wold give me more hours before recharging (no panels yet), I'd use it instead.

    Thanks again!!


    reuben..

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    Your battery usage is equal to your demand plus the small loss from the inverter. If you turn 3 light bulbs on, your battery is being used at three times the rate as if you turned on one light. Even with your 400w inverter, a 50 watt device is only sucking 50 watts equivalent out of the battery. The only advantage you'd see in using a smaller inverter is the inverter consumption may go down, but probably not enough that you'd notice a difference in battery duration.

  5. #5
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    For the fun of it I tested my 300 watt inverter.
    Idle current = ? did not check.
    150 watt light plug into inverter = 14 amp @ 13v from battery = 182 watts dc
    The inverter is using, 32 watts or 2.46 amp @ 13v to produce 150 watts @ 120v ac.

    Efficiency = 82%

    Letís assume we are now using a 23w fluorescent light.
    23w ac @ 82% = 28 watts @ 13v.
    28 watts = 2.15 amps @ 13v
    Youíre wasting 3 watts or .23 amps.

    For minimum battery drain, I would turn off the inverter when not in use.
    I would also use a 12v led light (hard to read by) or a 12v car/marine cabin light. I think they use about 2.5 amps. and I would run everything directly off the battery, if possible.

    Another problem you may have is under charging or over charging your battery. Wasting gasoline on a battery that is fully charged.

  6. #6
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    Where is the best place to buy a complete package(inverter, batteries, panels)?

  7. #7
    New member reuben_j_cogburn's Avatar
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    Thanks for the inverter answers. That answered my question perfectly.
    Susitna energy systems in Anchorage is a full service solar/alternative energy store. They seem to really know their stuff. rices don't seem to bad for what they are but I haven't done any comparison shopping yet. There is another place in anchorage but I haven't checked them out yet.
    I did look online but shiping cancels out any savings as far as I can see.

    ciao...


    reuben..

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