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  • Powering cordless drill with wall wart.

    I have Dewalt and B&D 9.6V cordless drills that I would like to power with a wall wart for use on a bench. I have no idea what amperage they require. Tried to get an ohm reading across the terminals but got nothing.

    I have read that they can run 12 volts, have a 12V 1.3 amp supply from a printer or something. Will I burn up the supply or the drill and how do I get the polarity right?
    North Central Arkansas

  • #2
    I doubt that any wall wart that you have will power the drill. They need heavy currents and the batteries will supply it. A charger with less current capability can charge the batteries over a long time so greater currents are never needed.

    I don't think you will burn up anything trying for a short time (seconds). The drill will just have very little torque. If you try to run it for a longer time then you may burn up the wall wart.
    Paul A.
    SE Texas

    And if you look REAL close at an analog signal,
    You will find that it has discrete steps.

    Comment


    • #3
      A reasonable drill will be about 1/5 HP, which is about 150 watts and thus at 12V it will be about 12 amps. You can get a 12V 200 watt switching supply for about $20, but some of them have a fast-acting overcurrent shutdown that might kick in when you start the drill or need a quick burst of torque. You could add a large capacitor to provide this surge current, although it may also trigger the overcurrent limit due to the capacitor charging.
      http://pauleschoen.com/pix/PM08_P76_P54.png
      Paul , P S Technology, Inc. and MrTibbs
      USA Maryland 21030

      Comment


      • #4
        If you really want to ise mains power, why dont you use a pc power supply. They give 12volts at some serious amperage. Othewise a small 12v 7ah lead acid or gel battery also works very well. Just make sure the wiring is thick enough to handle the current

        Comment


        • #5
          The small battery is the best idea. But you probably want to avoid the battery altogether, or you'd use the one that came with it.

          I'd probably measure the current from the battery that runs it and see just what it really DOES draw. The number is surely more than your wall wart, but may be less than some other estimates.

          The wires in the device itself are not usually that big, BTW.
          CNC machines only go through the motions.

          Ideas expressed may be mine, or from anyone else in the universe.
          Not responsible for clerical errors. Or those made by lay people either.
          Number formats and units may be chosen at random depending on what day it is.
          I reserve the right to use a number system with any integer base without prior notice.
          Generalizations are understood to be "often" true, but not true in every case.

          Comment


          • #6
            RE: The Wire Size

            Yes, the wires in the drill are not that big, but they also are not that long so they do not have much resistance. If you are going to do it from the outside with some length of cord, then you will need at least a 14 gauge. Zip cord comes to mind. 12 gauge or heavier would probably be better.



            Originally posted by J Tiers View Post
            The small battery is the best idea. But you probably want to avoid the battery altogether, or you'd use the one that came with it.

            I'd probably measure the current from the battery that runs it and see just what it really DOES draw. The number is surely more than your wall wart, but may be less than some other estimates.

            The wires in the device itself are not usually that big, BTW.
            Paul A.
            SE Texas

            And if you look REAL close at an analog signal,
            You will find that it has discrete steps.

            Comment


            • #7
              You can consider many types of power supply, but the battery with a wall wart smart charger is hard to beat. Probably cheapest too, when you consider that you'll need 25 amps available for the drill motor- expensive capacity for a purchased power supply. Consider also that getting that current to the drill motor without significant losses means large gauge wiring. The size wire coming from a wall wart would guarantee a 12 volt loss in the wire, with nothing left for the drill. From my experience, 12 gauge is not too large- but hard to find in a parallel pair with enough flexibility to be comfortable.

              I've hard-wired a few cordless drills and the best 'cord' was a home-made. I started with some air line tubing found at a pet shop, the blue stuff that's the most flexible- not vinyl. I found some large gauge stranded wire with a high strand count and systematically pulled as thick of a cluster of strands as would fit into sections of the urethane tubing, aided by talc and a pull wire. Comes to about 12 ga, maybe 10 ga. Anyway, two resulting insulated wires are now twisted and intertwined into a pair, heat shrink placed to secure the ends, and suitable connectors attached to connect to the battery. Because of the way most cordless drills are made, it seems to be best to make a solid connection inside the drill by attaching directly to the old battery contacts, rather than pulling that out and trying to make connections further inside. The old battery contact terminal inside the drill acts as a strain relief for the wire. I've soldered the cord to those terminals, but I've found that the best connection is made using the sections out of a terminal block. This is the two screw terminal type thing where you poke a wire in one side, tighten the screw, then insert wire from the other side, tighten screw. If you pull the screws out completely, you will have the connection piece fall out in your hand, or at least easy to push out. Slip that piece over the wire end, then insert over the terminal inside the drill, tighten screws. This makes about the best connection you can get, mechanically and electrically. Use some heat shrink over that if you have the need to.
              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

              Comment


              • #8
                Hmm, now what type of battery? I think the easy answer is a gel cell or similar, but consider buying a li-po pack from a hobby shop along with an appropriate charger. I've seen the chargers at a pretty good price, and the battery pack is well capable of supplying a cordless drill- even the high torque, higher voltage ones. The package size is minimal compared to any lead acid battery, and the charger is ready-made to manage the battery appropriately. Keep in mind that you would need a smart-enough charger to properly maintain a lead acid battery anyway, so the basic wall wart probably won't cut it.

                If you choose to stay with lead acid, it could make sense to use a solar charge controller as the brain. Feed it from a power supply capable of about 20 volts dc output- and maybe even wire in a solar panel if you want to get fancy.
                I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

                Comment


                • #9
                  I've resurrected a few 12v cordless drills by soldering a lamp cord line on them with a cigarette lighter plug on the end for use near car/truck. wire size did not seem an issue --- the motors aren't all that big. I think 12v to a 9v drill might not last, but who knows?

                  Comment


                  • #10
                    If you are going to use a 12V source to power a 9V drill, I would put it to you that the wire is not going to matter much unless you try to use something crazy-small.

                    You have 3V of headroom, so obsessing over wire resistance is going to buy you nothing much. Ten feet of 18 ga wire is 0.07 ohms, so if the thing draws 15A, you are still well over 9V. You could go up to 25 feet (12 feet of cord) of 18 ga wire and a 12V battery will still give you 15A at 9V.
                    CNC machines only go through the motions.

                    Ideas expressed may be mine, or from anyone else in the universe.
                    Not responsible for clerical errors. Or those made by lay people either.
                    Number formats and units may be chosen at random depending on what day it is.
                    I reserve the right to use a number system with any integer base without prior notice.
                    Generalizations are understood to be "often" true, but not true in every case.

                    Comment


                    • #11
                      Thanks everyone. I have 4 or 5 batteries for these drills but they won't hold a charge for more than a few minutes or few seconds. I have upgraded to 18V lithium drills and an impact driver.

                      I think I still have a PC power supply but it is in storage. I will be able to hunt for it in a few months. At least I now know the wall wart is not suitable.
                      North Central Arkansas

                      Comment


                      • #12
                        I've set them up with battery charger cords and clamps. Easiest way to connect them to the drill is to disassemble a dead battery and solder the leads to the inside of the contacts, running the cord out the back of the battery. That way it keeps the drill usable as a cordless when you want or need it.

                        If looking for a bench tool, instead of a wall wart look into a low cost automotive battery charger, may want to pick up or make a full wave rectifier as many of chargers (wall warts as well) are only half wave. Or look for someone with a discarded satellite dish or cable modem, most come with very hefty power supplies, but some are 30v, so check them.

                        Comment


                        • #13
                          Lamp cord, Zip cord IS large compared to the wires inside most electric drills. This illustrates my point.



                          Originally posted by Juiceclone View Post
                          I've resurrected a few 12v cordless drills by soldering a lamp cord line on them with a cigarette lighter plug on the end for use near car/truck. wire size did not seem an issue --- the motors aren't all that big. I think 12v to a 9v drill might not last, but who knows?
                          Paul A.
                          SE Texas

                          And if you look REAL close at an analog signal,
                          You will find that it has discrete steps.

                          Comment


                          • #14
                            You can use speaker cables, which are polarized and are available in ridiculously heavy wire gauge and yet are very flexible.

                            Also some USB cables have pretty good size wires for the 5V lines, and you could wire all 4 inner wires in parallel and use the shield for return.
                            http://pauleschoen.com/pix/PM08_P76_P54.png
                            Paul , P S Technology, Inc. and MrTibbs
                            USA Maryland 21030

                            Comment


                            • #15
                              I have often wondered in a corded add on would work with cordless when you need it, ie plug it in the mains, transformer where the battery normally lives.
                              High strand count cables are very flexible, I suppose that's what good test leads are made of
                              Mark

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