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There have been some instructables published on how to rebuild your portable drill batteries with the goal of resurrecting an old drill, and perhaps doing it for less than an standard replacement battery.  Usually this involves buying cells and wiring them into the old case.  I have done this, but with a twist, I harvested the cells from a new Harbor Freight drill and did the job for under 20 dollars ( plus labor ).  I was going to write this up, but then decided an easier way was to modify the drill and use the batteries as is.  I will show you how I did it in this instructable.

Step 1: Tool and Supplies

Step 2: Test the Old Drill

If the old drill is dead there is no point in continuing, so test it.  One way to do this is to power it up with your new battery using jumper wires.  You can skip this step if you are sure your old drill is good,  in the worst case you will just wreck you new drill.  You may need to take apart the old drill ( as in the next step ) or not.

Step 3: Dissect the Old Drill

You just need to take apart the old drill enough to get at the leads for the old battery contacts, perhaps you can do this without any disassembly. In my case I removed the the screws that are transverse to the drill bit and the two sides came apart. Add wire extensions, ideally red for positive and black for negative. Solder. You can then put the drill back together. ( in my case a bit too much of the drill came apart, but I just put the parts back ) You may want to test again through the new leads.

Step 4: Dissect the Harbor Freight Drill

All you need from the drill is the power connector at the base of the handle. I put the drill in a vise and used a hack saw. The handle is pretty much empty here but you may cut the wires which is ok. Cut above the screws holding the two sides of the bottom of the handle together. I wanted to get as close to these screws as possible so I used a power sander to get closer and smooth the cut. You could use a different sander, a file, or whatever for this step. Try to think of a use for the rest of the drill, it has a nice motor, charger, gear reduction train, chuck.  Post it as another instructable? Some have used drill motors for low powered vehicles. 

Step 5: Attach the Battery Connector

I planned to just use some countersunk bolts, you need countersunk to keep the connector smooth where the battery slides in. A fly in the ointment was the bolt at the rear of the drill. It would not come through the top of the handle. To fix this I fastened ( a bit of glue and some screws ) a block of wood inside the hollow part of the handle. Then I put a countersunk screw from the connector into the block. Also connect up the leads. The pictures should make it pretty clear. It is a bit hard to remove the battery as the release is under the flange of the original handle, you may want to cut this away.

Step 6: Start Drilling

You can buy more batteries for the drill from Harbor Freight, but often buying the whole drill is just as cheap. As always with Harbor Freight watch out for sales and coupons.

Remember if you Drink don't Drill see: http://home.earthlink.net/~foghornj/drinkand.html

<p>That's a pretty good idea if your drill isn't quite worth the cost of a new battery and it saves all the soldering/welding batteries.</p><p>Heads up I noticed a couple of errors you might want to change. (&quot;ideally red for positive and black for red.&quot; &amp; &quot;vise&quot;)</p>
<p>Thanks, a few things now cleaned up[ in the text.</p>
<p>why not just use the harbor freight drill? its under $20 bucks</p>
<p>The drill being restored is a much better drill, 2 geared speeds, better chuck....</p><p>Sometimes I get the new harbor freight battery as part of a drill kit. Actually can usually do this for 15 bucks, get charger and drill. Or 2 hf batteries for 20. Suit yourself.</p>
<p>This was a pretty clever Instructable. I have pondered for a long time about how to make an adaptor to fit one brand of battery onto another brand of drill, and this is about the best way I have seen so far.</p>
<p>Thanks, it has worked well for me this is now one of my favorite drills.</p>
Thanks Russ: <br>Great idea, especially about testing the old drill with the new battery first ! <br>I usually assume it's just the battery that's bad . <br> <br>I've got an old Sears that needs this upgrade.
Now you can use the drill chuck from the new drill that you just gutted on one side of your bench mounted grinder, the new drill motor in an auger fed automatic pet feeder, and all the other leftover parts can be put in the parts bin for future use. <br> <br>Query: Why didn't you just gut the old battery case and drop the new battery (case and all ) inside the old one? It looked like it would have fit and you wouldn't have had to mess with aesthetics.
I actually have not seen one that would fit case and all, I have always had to significantly rearrange the cells to get a fit. Additionally this way I can use more replacement batteries with no work at all. But it is an interesting idea for cases where it would work. <br>Good ideas on the parts.

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Bio: For now see me at: http://www.opencircuits.com/User:Russ_hensel
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