I own a newer 18-volt cordless combo (drill and flashlight). I also have an older 16.8-volt drill with two expired batteries. (We all know the high price of replacement batteries.)

I had to ask myself a couple of questions:

1. Do I really want to do the "non-green thing" and send this good tool to a landfill?

2. Would it not be a great idea if the older cordless drill could join my working cordless combo family?

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Step 1: The New Member of My Working Cordless Family

I then searched extensively online for a way to do this, but I never found one. After careful consideration, I FINALLY FOUND MY OWN WAY MAKE THIS HAPPEN!

Step 2: Items Required for the Modification

Cordless device with bad battery – drill, saw, light, etc.

A good battery handle from the working cordless group.

Masking tape and Sharpie marker

Camera – to take pictures for reference

Hacksaw with fine blade and a bench vise

Flat File

Shop rag or old wash cloth

Dremel tool with cutting blade

Solder iron, solder and flux

2” long pieces of 14 gauge wire (1- red & 1- black)

Shrink tubing or electrical tape

A 3” x 6 1/2” piece of 16 gauge galvanized sheet metal

Four - 2” diameter screw-type radiator clamps

Flat screwdriver or nut driver that fits the screws on radiator clamps

Phillips screwdriver to take apart the cordless cases

Safety Glasses and leather gloves

Step 3: Good Battery Handle From the Working Cordless Group

I had another 18 volt battery handle with the flashlight head broken off.

The handle uses that same battery as my cordless combo.

For some reason I had kept the flashlight handle. I am so glad I did!

Step 4: Opening the Plastic Cases

With the batteries removed, use the phillips screwdriver to unscrew and carefully remove one side of each case. Use masking tape to mark the positive lead on the drill battery wire and the broken flashlight handle battery clip.

Step 5: Know How They Go Back Together

Take pictures of the inner parts as they lay in their open cases.

The pictures will be used as a visual reference during re-assembly.

Now, carefully remove the inner parts from both plastic cases.

Step 6: Old Drill Case

Screw the empty drill case pieces back together.
Use masking tape and the Sharpie to draw a horizontal line around the
outer circumference -about 1-3/4” below the trigger opening in the handle.

Step 7: New Battery Holder

Use the Sharpie to mark the outer edges of the flashlight battery handle, just above the internal battery clip holder. Screw the empty battery handle pieces back together. Use the Sharpie to make a complete horizontal line around the outer circumference of the handle.

Step 8: Cutting the Handles

Begin with the old drill case. Wrap a cloth around the case body to protect it from scratches and slipping, then clamp it between the jaws of the bench vise On the line, use the hacksaw to cut the case into two pieces. Repeat the above procedure with the flashlight battery handle. *Use safety glasses to protect the eyes.

Step 9: Cleaning Up the Cuts

Reposition each case in the vise to file smooth newly cut edges. Use the Dremel tool to cut away some of the plastic inside the drill handle so that the new battery clip will recess into that handle when the tool is re-assembled. *Use safety glasses to protect the eyes

Step 10: Preparing the New Battery Holder Clip

I ran into a little problem. The existing wires that went to the old drill battery clip were too short to reach the new battery holder and the wires on the new battery clip were too small to handle higher current. On the new battery clip, use the soldering iron to unsolder the existing small wires. Use flux and solder to install two new 2” long -14 gauge wire pigtails onto the clip. *Use safety glasses to protect the eyes

Step 11: Attaching the New Battery Clip Onto the Drill Wiring

Unsolder the drill wires on the end that went to the old battery clip. Use soldering iron, flux and solder to connect the new battery clip pigtails to the two old drill wires. Be sure to observe the correct polarity (+ to + and - to -). Use shrink tubing or electrical tape to insulate your connections. *Use safety glasses to protect the eyes

Step 12: Re-install the Internal Parts

Using your previously taken photographs as a guide, re-assemble the internal components in one half of the two outer shells. Carefully tuck the wiring in and screw the other side cover back on both pieces.

Step 13: Get the Connecting Pieces Ready

On the piece of sheet metal, use a flat file to round the corners and remove any burrs or sharp edges. Use flat screwdriver or nut driver to fully open up the screw-clamps. *Use safety glasses to protect the eyes and leather gloves to protect hands.

Step 14: Forming the Sheet Metal

Open the bench vise jaws to about 1/8”. Use the top edge of the vise to form or roll the sheet metal into a half circle. (The handle on cordless devices is 6” in circumference; hence the sheet metal is 6-1/2’ long for a good overlap when complete.) *Use leather gloves to protect hands.

Step 15: Applying the Sheet Metal

Close the sheet metal around both handle pieces. Overlap the sheet metal and tighten one screw-clamp around the circumference to hold the metal tightly against the plastic handles. *Use leather gloves to protect hands.

Step 16: Initial Adjustments

Install and tighten the other three clamps. Now you will need to remove the excess banding that extends through each screw-clamp body. Use the Sharpie to mark the excess banding that sticks out past the screw-clamp. Take the clamps off one-at-a-time. Use the Dremel tool to trim off the band at the mark. Use flat file or Dremel tool to round-off and smooth the new edges, then loosely re-install the screw-clamp back onto the handles. Repeat this process on the other three screw-clamp bands. *Wear safety glasses and leather gloves when performing this function to prevent any personal injury.

Step 17: Making the Final Adjustments

Equally space the clamps from the top to the bottom on the sheet metal band. Two should be over the drill handle and two over the battery handle. Install a battery in the new lower handle and set the unit on a flat surface. Have a helper physically push down on the top of the drill body and then tighten all the screw-clamps so the cut handles butt-up tightly inside the wrapped sheet metal.

Step 18: Tightening It All Down

I have big hands and even I cannot get my fingers completely around any cordless tool handle. Individually loosen each band and rotate the screw-clamp heads around the handle and re-tighten to align them in the open space between where the hand palm and fingertips are positioned when gripping the handle.

Step 19: The Finished Product

Insert a battery and test the finished product! Although, the new drill does stand a little taller than the other units, it still serves the purpose. With the screw-clamps tightened securely, the sheet metal wrap makes for a very durable handle If accidentally dropped, the new handle will not break or fall apart. Another advantage to this type of modification is that it can again be disassembled for future drill trigger or motor brush repairs!

Please vote for my entry, if you like it.

(Note: I am so very sorry about the quality of my pictures. I currently cannot
afford a real good camera, so I had to make this Instructable with the only camera I have.)

ONE FINAL THOUGHT: If searching for additional battery handles compatible with your cordless tool group which might be retrofitted this way to orphan tools, consider looking in garage sales, Craigslist or even E-Bay. There are many inexpensive non-operational power tools out there that still have a great battery handle.

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    22 Discussions


    Reply 5 years ago

    Hi, TT13 and thank you for your great question. I have not encountered any problems in performance with my retrofit drill. With direct current (DC) - straying a couple of volts either way from the original device voltage only affects speed. A 12 vdc drill operating on 10 volts will turn just a few rpm's slower and the same drill on 14 volts will turn a few rpm's faster. A variation of ten volts or more from the original voltage might present performance and safety problems. Great observation on your part and hope you might try doing your own retrofit! This "upgrade" has already been a great conversation piece at the local diner coffee hour. (Some called the retrofit ingenious while others shook their head, but it works for me!) ;)


    Reply 5 years ago on Introduction

    For motors the work done requires watts, more work more watts. If the supply voltage varies so does the current draw (P=I*E). Having slightly higher voltage is much better than lower voltage as higher current through the motor winding causes heat and that is what smokes motors when the insulation breaks down from heat.

    I rewire old cordless drills (6, 7.2, 9 and 12 volt models) to run off a length (~1.5 m) of lamp cord with spade lugs to a 12 volt gel cell battery. 7 or so amp hours lasts a long time with a drill. You can rig a belt pouch to hold the gel cell if you need real portability and the drill is lighter in your hand.


    Reply 5 years ago on Introduction

    Thank you for a more indepth explanation of consequences in mating up battery/tool combinations!


    4 years ago on Step 19

    nice guide, I wondered about plastic soldering instead of sheet metal & clamps tho...


    5 years ago on Step 15

    You might try Fiberfix for the handle. I've seen it at Lowes. I've never used it. It's a resin embedded tape you dip it in water and apply it. I've seen used tape on the display and it does get extremely hard. Very interesting stuff and if it works as advertised it would be better than hose clamps.

    1 reply

    Thank you for your response. Yes, the Fiber Fix might work on the two handles. I was concerned if a product like Fiber Fix, tape or epoxy might come loose or separate if pressing hard on the handle or if the tool is accidentally dropped. I already had the hose clamps and scrap of sheet metal, so it did not cost me anything.

    Other great advantages to the “wrap and clamp” method:

    1. The clamps can re-tightened or re-adjusted for the other hand.
    2. The wrap can be dis-assembled for repairs to the tool (trigger replacement, brushes, lubrication).
    3. You might want to make an upgrade. (The original tool wore out or you want to switch to a completely different battery family.)

    Like any other idea, it usually requires 98% thought and 2% action. Thank you again for your comment and please provide a picture of a cordless battery retrofit you have tried! ~energysaver


    5 years ago on Introduction

    When I first thought of this modification, I considered publishing my own instructional DVD and selling it online. I also know many local people own "battery dead" cordless tools. Like me, they are always looking for ways to save their hard-earned money. Since the INSTRUCTABLES website is my favorite place to visit and learn about innovative ways of building things, I knew it was the right place to share my idea with everyone. ~energysaver


    5 years ago on Introduction

    There IS a semi-commercial product on the web - just go to , where they sell various plans and kits. The particularly good thing about the Rambo system is that you can parallel batteries for more runtime and relatively-easily use nimh, li-on or li-po (careful with your charging!) instead of nicd - DON'T actually mix chemistries, of course.

    1 reply

    Reply 5 years ago on Introduction

    I remember the battery adapter now that you bring it up. I think us end users need to stop all of the rechargeable battery madness ourselves. I see loads of cordless tools going begging at yard sales because they have dead batteries that are not worth replacing.


    5 years ago on Introduction

    I like your battery grafting idea for cordless tools. I am thinking about using it to add to my cordless tool collection. I did not go with the best line when I built up my cordless tool set. I am fairly heavily invested in it now though. I would like to upgrade my tools, but do not want to start using a new battery system.

    Your battery grafting method offers me a solution out of my present predicament. I just need to find donor tools to pull the battery holders off of. Which with the kind of tools I use is not hard to do. The company used to have an outlet here, so the area is flooded with their tools. I can usually pick them up cheap used.

    Sometimes I see some other cordless tools cheap though that take different batteries than what I have. With your idea I can keep my batteries and upgrade my collection.

    It might be fun to mod cordless tools too. Cordless tool modification is something I have not really explored. Maybe I can make myself a close quarters drill, or something?

    2 replies

    Reply 5 years ago on Introduction

    Don't you just love instructables? I believe their motto should be - “A SEARCHABLE COLLECTION OF WORLDLY INNOVATIONS.”


    Reply 5 years ago on Introduction

    I browse. I just check out the latest regularly. It is rare for me to use the search function on this site. Usually just to find my articles from my old account that I lost.


    5 years ago on Introduction

    You can get tabbed sub-C sized NiCd cells on eBay and elsewhere for about $2 to $2.50 each in volume then solder them together observing how the original cells were positioned. "Most" battery packs are screwed together and not hard to open.

    1 reply

    Reply 5 years ago on Introduction

    Thank you for input. The idea was to have a universal battery for multiple tools. I have not had much success in solding cells together. :( The heat thing. Thanks again!


    5 years ago on Introduction

    this is awesome. very cool...... one thought... just for knowing how much those metal hose-clamps can scuff up fingers n' hands (I've used em' on handles before too) ... maybe you could get some of that "plumber's epoxy putty", the stuff that is the consistency of play-dough till you kneed it together and it then hardens like strong plastic.... and mold it like a grip around the metal.

    Screen Shot 2014-06-15 at 9.52.17 PM.png
    2 replies

    There is even easier than that. You can now buy tape that is designed to cure extra hard. Look up "Fiber Fix". It is perfect for this 'ible.

    This reply is for all those who would have liked the tool handle to be finished in a different way. During assembly of the retrofit, I had considered applying epoxy or wrapping the handle with some form of tape. I decided to leave the sheet metal wrap bare due to increased size of the handle might feel uncomfortable for someone with smaller hands. I wear a tight
    fitting, rubber faced glove and the screw-clamps present no problem,
    if they are positioned properly. Also, a permanent coating on the handle would make it difficult to re-access and repair the internal tool workings. If you perform this tool retrofit and add your own finish to the handle, please include a picture with your comment so we all can enjoy your efforts. Thank-you again for sharing your thoughts.