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Dumb Teacher with Simple Question

  1. Jul 4, 2008 #1
    I can do some things.
    I CAN NOT get a simple answer to this.
    I would like to go off-grid in the mountains of Honduras. I am taking a set of 18volt power tools (SKIL) with me to help build and would like to charge/ power them with solar. I have looked at many sources of power, but am always faced with...Is this product going to be enough to run the tools. PLEASE, don't just give me the formula for watts/ amps/ etc (That's where the dumb teacher part comes in) :confused:I would be charging (AGM) deep cycle batteries to recharge the tool battery packs.
    My problem/ question is this...
    I know(think) I need an inverter to run the tools. How MUCH power do I need to do this?
    Remember: KISS, for me.
    Thanks in advance to all that try to help.:smile:
  2. jcsd
  3. Jul 4, 2008 #2


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    Welcome to PF, Doggie. You shouldn't need any kind of inverter. Those tools are DC. You didn't state what voltage your batteries are, but I'm assuming 12. You can series connect 2 of them and regulate the output down to 18, or simply series wire a 12 with a 6 to get your 18 directly. (Unless I'm missing something about the situation.)
  4. Jul 4, 2008 #3
    Good to be here, Danger, and thanks.
    The 12 and a 6 to equal the 18 volts almost sounds too easy to be true. And that's a good thing.:approve:
    I would, however, prefer two 12 v batteries. So what' s involved in "regulating the power down" to 18?:uhh:

    And as long as I have you here, I believe I would need an inverter to run anything household-like.
    (Blender, radio) ? Yes?:redface:
  5. Jul 4, 2008 #4
    I would get an inverter if I were you. They are quite reasonable as far as price is concerned. I have one I use to charge batteries. As for the draw from the Skil it will be less than an amp – mine is 400mA.

    For the benefit of other readers the tool he is referring to is at this site. It comes with a charger that you plug into 100 volts
  6. Jul 4, 2008 #5
    Last edited by a moderator: Apr 23, 2017
  7. Jul 8, 2008 #6
    Simple answer, use a solar panel directly. AllElectronics.com has a 12V and 6V solar panel that can safely charge your batteries, albeit slowly. Solar cells have an intrinsic series resistance that will limit the current. You will also want to add a 1N4007 diode.

    Another option would be to use a car battery that is charged with the solar cell and then use an inverter and the original charger.

  8. Jul 8, 2008 #7


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    Homework Helper

    You want to build a house with battery powered tools?
    Generally, these are fairly light duty items.
    Great for small quick jobs, but leave a lot to be desired for serious construction, like building an entire house.

    They don't list power consumption (that I know of) for these battery tools, but I think it would be reasonable to assume that they will use the same amount of power to do a task equivalent to what an AC line operated power tool will use to do the same task.

    Say a line operated skill saw uses 7A while cutting 2x4s or sheathing plywood.
    An hours use will be 840 watt hours.
    Two fully charged 12v deep cycle batteries hooked to an inverter can probably run the saw for about 2 hours.
    Two large 180w solar panels (about $800 each) will recharge the two batteries in about 6 hours, assuming they make rated power.

    If the house is going to stay off grid then you can use the panels and batteries in the final configuration, so the cost may be worthwhile.
    Ordering the building materials precut to the needed sizes, as much as possible, could help a lot.
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