Auto-Based 12 Volt Expeditionary Rotary Hole-Maker

Introduction: Auto-Based 12 Volt Expeditionary Rotary Hole-Maker

If you're anything like me, you spend a good portion of your time living out of your truck, DOWN BY THE RIVER! Well then, I don't need to tell you how many times I wish I had a drill for one reason or another. Sure, you could get a cordless drill, battery charger, and converter. But that's stupid! Wouldn't it be better to have a straight 12 volt drill that doesn't need recharging? Of course it would! And that's where I come in. There are a couple similar approaches here on Instructables, but nothing that addressed my needs exactly or, frankly, as elegantly as this little jewel. The project turned out much better than I hoped, so I see it as the first in a series. Eventually, I'd like to have a direct 12v circular saw and reciprocating saw. Okay, then, let's kick this mule!

Step 1: Bring Out Your Dead (Drill)!

You see these at thrift shops by the boatload: poor, lifeless, cordless, batteryless drills. Skil, Ryobi, DeWalt, Makita, Milwaukee. Piles and piles of them. They come in all shapes, sizes, and colors. 9.5 volt, 12 volt, 18 volt, 19.2 volt, 28 volt lithium ion cadmium isotropic Cadbury bunny eggs. Their said story is written across their hollow bases: their crappy, proprietary, obsolete-inside-of-a-week batteries gave up the ghost and it was easier -- nay, necessary! -- to toss them aside and buy a new drill. So they end up at your Goodwill; your Savers; your St. Vincent de Paul's. Maybe some bloke's got a fully-functioning, Makita brand, model MK56729L-08, 9.5-volt CI battery, with charger, but no drill for it. Uh, yeah, right. So these lost children sit on the shelf, gathering dust until the thrift shop manager finally shovels them into the dumpster. What we need is a 12-volt model. Who cares about the rest of that crap? Here's the one I got for $3.00. I could have waited for half-off day, but what the hell.

Step 2: De-Exoskeletonization

Start by removing the obvious (and less than obvious) screws that hold the drill body together. The screws in mine were Torx T10s and odds are yours will be something just as annoyingly obscure. They came out pretty easily, for the most part. A couple were recessed deeply and my Torx bit wouldn't fit down far enough so I "enhanced" the approach hole a bit with another cordless drill that I have yet to drop off at Goodwill.

Step 3: Check Out Them Guts!

Once all the screws were out, I could lift off the one side of the casing, revealing the drill's innards. I'm not very mechanically oriented and have trouble differentiating between electronics and electrolytes. Nevertheless, this seemed pretty straightforward. There were two metal prongs jutting downward, into the battery well. One was marked "B+" and the other "B-". I assume the "B" stands for battery and the +/- signs indicate positive and negative. I've been wrong before. These prongs go into a black thing, that is connected by some wires to a round thing. There's a gear on the end of that, which fits up to another black thing that goes out and holds your drill bit. See? Like I said, pretty straightforward.

Step 4: From "Competition" Grips to "Combat" Grips

I got to thinking that the case looked kind of stupid, what with the big battery flanges at the bottom. So I cut them off. Problem solved.

Step 5: Wiring

I broke down and got a pair of $10 jumper cables from Harbor Freight. I cut these in half, so I'll be able to use the other half down the road. After cutting the cables, I stripped 1-1/2" of insulation off each of the wires.

Step 6: Making Connections

The "B+" and "B-" prongs were oddly shaped, as you can see in the picture. I don't really know how to describe them and I don't particularly want to try. Yours will probably be different anyway. To make mine work best, I folded the stripped cable wires in half. They then slid into the weird prong end thingies. For consistency, I attached the red wire to the "B+" terminal and the black wire to the "B-" terminal. I suppose a "professional" would have soldered the wires to the prongs, but I don't happen to have some fancy soldering machine. What I did have, though, was a couple zip-ties, which seemed to do the trick. Then I used about 3/4 of a roll of electrical tape, making sure to cover all metal parts, keeping the two terminals apart. Once the two terminal/wire connections were adequately insulated, I taped around everything to prevent movement.

Step 7: Reassembly

Things are pretty anticlimactic from here on out. I shoved all those parts back into the modified case and screwed it shut. The jumper cables exit through the old battery compartment. I thought that looked a little unprofessional, so I used the rest of my electrical tape to create a seamless transition from handle to cord. Now it looks pretty much like a sci-fi death ray laser gun or something. But don't let the looks fool you, it's really just a drill. Not, not just a drill, a bad-ass, off-road, adventure-seeking, alpha drill! Now when some un-holey nightmare threatens to derail your camping trip, you just pop the hood, clamp the cables onto your old Optima yellow-top, and get to perforating! You're welcome.

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59 Discussions

Anyone who has ever seen the after effects of a direct short circuit of an automotive battery would never attempt this. The power outlet or cig lighter is a much better idea. The outlet is fused, and most adapters are also fused. I know it is only 12 volts, but the available current is extremely high which can cause arcs, sparks and worst case battery explosion. Zip ties for any electrical connection is beyond ridiculous.

2 replies

I totally agree that however you use this mod, you should protect the circuit with a fuse or breaker. Your car's cig. outlet and/or accessory port is fused as are many after market 12v adaptors you can add to a back up battery or your car's main battery.

Just to agree with em1jamo. You really do need a fuse in the circuit to protect the car battery and any connecting wires. A car battery can supply several hundred amps if shorted, enough to vapourise a small screw driver (seen this!) or worse still cause the batery to explode (not seen this thankfully but heard of it happening!)!

Ask yourself why do so many cars burst into fire? Look out for the tell tail signs of black patches of scorched road from vehical fires. Once you start looking you will be amazed at how many there are!

I like this idea. I have a nearly-dead 12V DeWalt in a drawer that I'll probably resurrect for this. I specifically want to complement you on your clear, and somewhat humorous writing style. As others have said, it would be a good idea to solder those connections. And, an in-line fuse, like you can get at any car parts store, wouldn't be a bad idea, either.

somente uma ideia coloquem em português por favor obrigado a e quanta i ideia da furadeira genial vol fazer sim colocarem em português bele

I pulled the batteries out to use the empty case as storage for drills and bits. Also although some have overstated the danger of shorting the battery terminals with your idea, I used normal dc cable with a inline blade fuse holder at the clip. I toyed with including a low voltage disconnect, but decided it would only a be a low duty tool.

nice instructable! thanks


Very cool idea, only my dead drills are 14.4 volt. Three suggestions: first, use very lightweight jumper cables, they will carry the current, are cheaper, and will make it more maneuverable. I would use the full length of the cables for flexibility. Second, I would use grounding cable clamps to attach the wires together if you are not going to solder them. Finally, I would use silicone tape instead of electrical for wrapping the bottom. I have had very good luck with it for repairing where power cords come out of a tool handle. Enjoyed your sense of humor.

4 replies

A Car Battery should give your 14.4 volt drill enough umph to get many jobs done. A car battery may have a few volts less then your dead drills old battery pack, But its got significantly more pushing power in terms of current. And a car battery will very likely have less voltage drop under load then your drills old battery pack . At worst your dead drill is a little more dead and you had a fun Friday afternoon tinkering.

You might look into power bricks for printers and the like from thrift stores . I know some of them source a very strong 14-15 volts. I use one as a battery charger for car batteries.

Are you sure joseph? I recall power supplies failing under a load that's too big for them too handle, then again i've learnt that from microcontrollers and led strips,which are more sensitive circuits.

It should serve well enough as long as it can source a few amps, But I Would not invest much in this,
Micro-controllers and the like are fairly light duty only needing a few milliamps to function. For something like this. I would try to find something that could source at least 5 amps If i could. A scrap pc powersupply would work decent. Older power bricks should work alright as well. For pushing something like a motor in this sort of hack fashion you want to find something close to its target voltage and that is ratted for at least a few amps. Not milliamps. Amps.
Just keep in mind this is something that will burn up one day and you should do alright.

If your drill is 14.4 volt, jus use the cigarette lighter plug with the engine running. The alternator puts out a bit over 14 volts, making it a close match for a 14.4 volt drill.

Been there, done that, in my experience, a 9V drill works even better on a 12V battery, however it will heat up if used for hours on end. Nice 'ible non-the-less!

4 replies

Not really. With a 9V you generally have a smaller motor capable of less torque so you might initially get a little higher RPM but it would more easily bog down under load and be very easy to damage the motor.

Even using a 12.0V drill is not a good idea. People have done this hack before and found that a 12V drill will also overheat fairly easily, that it sort of depends on it's battery voltage drop and non-infinite capacity to keep the motor from overheating. The best candidate drill would be a contractor grade 14V, BUT I suppose if you have to spend more time or money then the worry of frying a drill is offset by that.

I understand the concern with using a 12 v or even a 9.5 v drill on a 12 v vehicle battery; however we must keep in mind that these are so-called DC series motors, and as such their behavior differs from other motors. Getting hold of a copy of 'Design and Performance of DC Motors' by Mr Clayton (most probably out of print by now) would clear this up. Basically they (like the self-starter motor on your car) develop max torque at very low revs, and having very low resistance windings draw much current. The torque diminishes with speed, and top speed is reached when the torque (very low at high speed) equals the friction and gearbox load. (Theoretically they have no max. top speed if the friction etc. could be eliminated.)

(Recall -ye older gentlemen - some 30 - 40 years ago, you removed several windings from your Scalectrix car's motor-windings to make them go a bit faster. The penalty was that the motor ran somewhat hotter.)

A 9.5 v motor would do fine on a 12 v battery, given a reasonable load, an resting the drill when it overheats. (The insulation on the winding can usually handle 120ºC or more.)

The 'ible's author did make it clear that the purpose is not to have a drill to utilize 24hrs/day at max load, but purely for "emergency" use.

Personally I have been using a 4.5v Bosch on a 6 v battery for more than 5 years in my electronics workshop,and I cannot recall ever needing to let it cool down.

Reasonable use and some care and maintenance makes a huge difference, and besides these motors were made to take some punishment!

I have never seen a series dc motor in a battery drill. They have always used a permanent magnet instead of a winding to provide the field across the armature. That is how they get them small and light enough to be used in hand held equipment.

A 12 volt drill is fine unless you want to run it continuously for extended periods of time.

I made it with an old Black & Decker drill. A piece of cake. Thank you.


I liked your comments and image inserts even better than the 12-volt idea - and that idea is superb!

Keep 'em coming.

I would probably add a set of 2 wire trailer light connectors, and a fuse box then you can easily switch the devices and only need the one cable. I would put the fuse on the battery side. the boxes only cost 3 bucks, but then you only need one.

An old extension cord or a vacuum cleaner cord would probably work well too. I would snip the plugs and use different connectors so someone doesn't actually use AC though.