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Re: [Electronics_101] Re: using welder to zap new life into dead ni-cad batteries

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  • Donald H Locker
    I suspect the fixit-er doesn t understand the flash circuit in the disposable cameras. There is a capacitor that is charged to a few hundred volts connected
    Message 1 of 15 , Nov 30, 2011
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      I suspect the fixit-er doesn't understand the flash circuit in the disposable cameras.

      There is a capacitor that is charged to a few hundred volts connected directly across the flash tube. To initiate the flash, a pulse of voltage (switch on the shutter grounds one side of a pulse transformer to generate the voltage) is applied to an electrode attached to the flash tube, ionising some of the Xenon in the tube. The voltage on the main flash capacitor finishes the ionisation and the energy in the cap is dumped through the flash tube.

      Connecting a NiCd cell or battery across the flash tube won't cause the flash to happen in the cell or battery, it will just divert the charging current. That _might_ be enough to clear the cell, but I wouldn't count on it. (quick calculation - i = C*dV/dT = 50uF*300V/15sec = 1mA = not nearly enough to clear a NiCd cell whisker, no matter how many times you click the shutter.)

      On the other hand, if you wait until the cap is charged, then connect the cell across the tube (watch those fingers - I've been bitten!) you will dump a few amps through the cell and that may work. I prefer a larger cap at lower voltage - less spectacular failures and fewer chances for owies.

      Donald.
      --
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      ----- Original Message -----
      > From: "(;harles" <charlessenf@...>
      > To: "Electronics 101" <Electronics_101@yahoogroups.com>
      > Sent: Wednesday, November 30, 2011 6:55:20 PM
      > Subject: [Electronics_101] Re: using welder to zap new life into dead ni-cad batteries
      > There is a safer approach using an old toss away flash camera circuit.
      > Connect the cell to the output to the old flash tube and click once
      > for "fixit."
      >
      > Its on Instructables somewhere. will look it it up later if you need.
      >
      >
      > [Non-text portions of this message have been removed]
      >
      >
      >
      > ------------------------------------
      >
      > Please trim excess when replyingYahoo! Groups Links
      >
      >
      >
    • Reese
      ... Don t top post, it disrupts the natural reading order, as the next paragraph demonstrates: that eyes can be laid upon the individual cells inside. blow up
      Message 2 of 15 , Dec 1, 2011
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        At 06:57 AM 12/1/2011, bb cc wrote:

        > Batteries will blow up doing that by a new one
        >
        >________________________________
        > From: Reese <reeza@...>
        >
        >I've had both Milwaukee and Ridgid cordless tool batteries go dead. When
        >I removed the screws (tamper-resistant in one case), I could clearly see
        >that one or more cells had failed insulation on the side and was shorting
        >to ground. Attempting to jumpstart such a battery (with a bad cell like
        >that) can only end badly. I suggest you do some disassembly yourself and
        >see if you still think a jumpstart is advisable, after you've seen what
        >the problem is.
        >
        >Reese

        Don't top post, it disrupts the natural reading order, as the next
        paragraph demonstrates:

        that eyes can be laid upon the individual cells inside.
        blow up if you remove the screws holding the plastic case together, so
        A Ridgid or Milwaukee cordless tool battery most emphatically WILL NOT

        Individual cells can be swapped out or the entire battery should indeed
        be replaced.
      • Stefan Trethan
        There is no group rule to that regard. Nobody cares about your preference, and you are free to delete any posts that don t comply with your requirements. I
        Message 3 of 15 , Dec 1, 2011
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          There is no group rule to that regard.
          Nobody cares about your preference, and you are free to delete any
          posts that don't comply with your requirements.

          I really hope we will not have that silly discussion again.

          ST

          On Thu, Dec 1, 2011 at 1:14 PM, Reese <reeza@...> wrote:

          > Don't top post, it disrupts the natural reading order, as the next
          > paragraph demonstrates:
          >
        • AlienRelics
          Don t do that. We ve been through this many times before. If you don t like top posting, don t do so. This has been hashed to death and is a dead topic. It is
          Message 4 of 15 , Dec 1, 2011
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            Don't do that. We've been through this many times before. If you don't like top posting, don't do so. This has been hashed to death and is a dead topic. It is kind of ridiculous to give an example where you've reversed the order of every line.

            In addition, you are hijacking a thread.

            And he wasn't saying cells would blow up if you took the screws out, he was saying that he had taken some batteries apart and found cells externally shorted, and that such a condition could calls cells to explode if the welder/car battery zap were performed.

            I would not replace individual cells unless this were a brand new pack that had a cell externally short from failed insulation. Otherwise, you are putting a brand new strong cell with a bunch of weak cells, almost certainly resulting in reverse charging as the pack runs down.

            Steve Greenfield AE7HD
            Your friendly neighborhood moderator

            --- In Electronics_101@yahoogroups.com, Reese <reeza@...> wrote:

            > Don't top post, it disrupts the natural reading order, as the next
            > paragraph demonstrates:
            >
            > that eyes can be laid upon the individual cells inside.
            > blow up if you remove the screws holding the plastic case together, so
            > A Ridgid or Milwaukee cordless tool battery most emphatically WILL NOT
            >
            > Individual cells can be swapped out or the entire battery should indeed
            > be replaced.
            >
          • Reese
            ... My earlier post contained on-topic material. If anyone hijacked the thread, it was he who isolated one line and responded only to that. ... Are you a mind
            Message 5 of 15 , Dec 1, 2011
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              At 07:56 AM 12/1/2011, AlienRelics wrote:

              >In addition, you are hijacking a thread.

              My earlier post contained on-topic material. If anyone hijacked the
              thread, it was he who isolated one line and responded only to that.

              >And he wasn't saying cells would blow up if you took the screws out,
              >he was saying that he had taken some batteries apart and found cells
              >externally shorted, and that such a condition could calls cells to
              >explode if the welder/car battery zap were performed.

              Are you a mind reader? bb cc needs to clarify what was meant. We can
              argue possible versus probable some other time.


              >I would not replace individual cells unless this were a brand new
              >pack that had a cell externally short from failed insulation.
              >Otherwise, you are putting a brand new strong cell with a bunch of
              >weak cells, almost certainly resulting in reverse charging as the
              >pack runs down.

              Good point, I should not have suggested replacing cells without that
              qualifier. Incidentally, Harbor Freight has some inexpensive security
              driver bits should any be needed for battery pack disassembly:

              http://www.harborfreight.com/33-piece-security-bit-set-93388.html

              Those go on sale periodically and can be had for about 1/2 of that
              sticker price.

              Man, I wish September would end.

              Reese
            • AlienRelics
              ... The point remains, top, bottom, interleave, don t like one, delete. ... I guess I am a mind reader. I read what he wrote and deciphered what he meant. ...
              Message 6 of 15 , Dec 1, 2011
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                --- In Electronics_101@yahoogroups.com, Reese <reeza@...> wrote:
                >
                > At 07:56 AM 12/1/2011, AlienRelics wrote:
                >
                > >In addition, you are hijacking a thread.
                >
                > My earlier post contained on-topic material. If anyone hijacked the
                > thread, it was he who isolated one line and responded only to that.

                The point remains, top, bottom, interleave, don't like one, delete.

                > >And he wasn't saying cells would blow up if you took the screws out,
                > >he was saying that he had taken some batteries apart and found cells
                > >externally shorted, and that such a condition could calls cells to
                > >explode if the welder/car battery zap were performed.
                >
                > Are you a mind reader? bb cc needs to clarify what was meant. We can
                > argue possible versus probable some other time.

                I guess I am a mind reader. I read what he wrote and deciphered what he meant.

                > I've had both Milwaukee and Ridgid cordless tool batteries go dead. When
                > I removed the screws (tamper-resistant in one case), I could clearly see
                > that one or more cells had failed insulation on the side and was shorting
                > to ground. Attempting to jumpstart such a battery (with a bad cell like
                > that) can only end badly. I suggest you do some disassembly yourself and
                > see if you still think a jumpstart is advisable, after you've seen what
                > the problem is.
                >
                > Reese

                That seems pretty clear. I don't see where he said anything like removing screws blows up cells.


                > >I would not replace individual cells unless this were a brand new
                > >pack that had a cell externally short from failed insulation.
                > >Otherwise, you are putting a brand new strong cell with a bunch of
                > >weak cells, almost certainly resulting in reverse charging as the
                > >pack runs down.
                >
                > Good point, I should not have suggested replacing cells without that
                > qualifier.

                Old hands will know that, I often speak to the masses reading along.

                > Incidentally, Harbor Freight has some inexpensive security
                > driver bits should any be needed for battery pack disassembly:
                >
                > http://www.harborfreight.com/33-piece-security-bit-set-93388.html
                >
                > Those go on sale periodically and can be had for about 1/2 of that
                > sticker price.

                Good tip.

                > Man, I wish September would end.
                >
                > Reese
                >
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