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  • nimh aa loading capacity

    Having become intrigued by the 'power belt' idea, I'm wondering what is reasonable to expect from a double A nimh cell as far as peak currents. Have not had much luck finding anything on the net as a guideline. My own tests are showing that you can easily draw 5 amps from that size of cell, as long as you can live with a voltage drop down to about a volt or so. At some point with increasing current draw, the cell is not going to like it- so far this is just an idea to make a belt to carry lots of these cells, and with a few loops to drop the (semi) cordless tools into. I would probably wire a series/parallel arrangement of cells, so what I'd be getting is a 4.2 AH pack at some reasonable voltage between 12 and 18, depending on how many cells I design the belt to hold.

    For now, I'd use a few of the cordless drills which I have wired to run from a 'portable' battery box. Eventually, the plan would be to build some very compact drivers using brushless motors, and there would be room on the belt to hold these. There might be three- each would be loaded with a commonly used driver- one would have my most commonly used size of drill bit.

    I can get a small quantity of these nimh cells for a decent price, so I'm just trying to figure out if they would be useful in this application, or if perhaps they simply aren't suitable. Any thoughts?
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    Id recommend finding sub-c cells insted. Much better capacity, and a better match for drills (thats the size they use anyway)
    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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    • #3
      I have some of those sub C cells which I could use, and they're tabbed as well. They are only 1.3 AH though, but being nicad they are probably capable of much larger currents without as much voltage drop. For the equivalent output, they are bulkier and heavier than the nimh cells and you could not build the belt as flat. Don't really want to talk about lipos at this point, though I could get an 18v pack of 4.5 AH cells for only about $180 wholesale-

      Maybe I should start small and do a proof of concept test- use these nicads up and see how I like having a cord attached.
      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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      • #4
        I think the low discharge variants like the sanyo eneloop also have extra low internal resistance. This should translate into better peak performance.

        http://www.eneloop.info/home/perform...e-current.html

        Or here:


        From
        http://www.candlepowerforums.com/vb/...ad.php?t=79302

        Igor
        Last edited by ikdor; 02-06-2011, 09:50 AM.

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        • #5
          Sheesh, are you skeert? Why not go for it and use LiPo's like the r/c airplane guys use for max power/weight? Just a minor problem with uncontrollable fires and explosions if overcharged!

          More seriously, check around over at http://www.rcgroups.com/batteries-and-chargers-129/ Those guys are in the know about NiCad, NiMH and all the other stuff. I think 5 amps is a walk in the park for a decent NiMH if I remember correctly from back in my r/c days.
          Milton

          "Accuracy is the sum total of your compensating mistakes."

          "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

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