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Behold, The Semi-Cordless Drill! - Home Effinomics, or Effin' Around the House [entries|archive|friends|userinfo]
Home Effinomics, or Effin' Around the House

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Behold, The Semi-Cordless Drill! [Jul. 28th, 2014|09:33 pm]
Home Effinomics, or Effin' Around the House

home_effinomic

[peristaltor]
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Several years ago, I had a quite adequate cordless drill set I got for Xmas one year. That was, I must repeat, several years ago. Then, I bought a heavily discounted cordless drill set with a removable head that could convert from drill to jig saw to sander, and all with the same battery pack that my first one used! This gave extra life to my first, now fading battery pack.

Then, with none of the battery packs working, I picked up another drill and battery pack in a pawn shop for ten bucks. The pack it came attached to was working better than the others in my collection, and my charger kept it running for a few more years.

Then, I had a drawer filled with three dead drills and a collection of potential toxic nickle cadmium batteries just waiting to poison a landfill. Dope that I am, I was determined to prevent that from happening. I bought a mediocre corded drill and resigned myself to packing extension cords for the rest of my drilling days.

Then, a glimmer of hope. solarbird posted a small lead acid gel cell from a UPS unit for sale, cheap. Soon thereafter, I inherited a cordless string trimmer from my sister that needed nothing but a new battery.

After I disassembled the string trimmer battery holder, I noticed how darned small the thing was. Why, it was almost as small as the little batteries that used to power my drills. And it put out the same voltage.

With this revelation, it was time to unscrew the drill battery pack and see what lurked within. Behold the tiny ni-cads, spot welded into a little base and tower.


Em-big-en-nay-shun.


That tower cell, by the way, was the reason I didn't simply march into my local tool purveyor and purchase new packs when they started going bad. Here's the deal: a battery pack is only as strong as its weakest cell. When a cell goes bad, it can refuse to process any current beyond a certain voltage. So the charger keeps pushing amps through the pack, hoping the darn thing will eventually drink up. The weak cell, though, lacking the ability to draw as much power as the rest of the battery's cells and store it chemically simply starts to convert the juice running through it into heat. This starts cooking the cell, which can have some bad, bad effects once the cell's innards swell and, in some cases, explode.

When the tower cell of this particular cordless affair failed on the charger, it would swell, right? Of course. When this happened—which, if the cell were bad would be inevitable, since the manufacturer opted for the cheapest charging outfit possible, one that trickle charged up to a certain voltage, but didn't have anything in the way of over-current protection or excess heat detection—the pack would be stuck permanently in the charger. Oh, sure, lots of people buy extra battery packs; but who has extra charging bases?!? Recall time! Nowadays, cordless batteries lack the single-cell storage in the handle idea for a horizontally sliding pack case that holds all of its cells in one level grouping. All those handle-mounted packs disappeared from the gizmo aisle just about the time I needed them.

Instead of new packs, we needed to rethink the whole cordless drill thing-a-majig. "Cordless" meant "cords to plug into the wall," right? Meaning one could wander about and screw things randomly as people are wont to do? No cordy commitments tying one to a particular house or, dare it be so, room? Which brings me to the slightly larger lead-acid gel cell from solarbird. Why not carry that slightly larger thing around, connecting its power to the drill through a small but not stultifyingly limiting cord?

The biggest problem was the connectors.


Em-big-en-nay-ay-ay-shun.


Those two cords connect the pack to the gizmo that mates its power to both drill and charger. It had to be removed intact. That proved simple. What proved a bit more challenging was the retrofit. The tower cell was tack welded to one leg of two; that white cord did not go to the terminal as one would suspect, not at all. With the terminal tack welded to the tower cell, it would need to be soldered to a wire that made the new battery connection. It was an ugly soldering job, to say the least; solid bits of sheet metal don't like to solder to strands of copper wire without some, er, persuasion.

Once re-wired, there was the matter of solidity. It was no use just shoving the whole assembly back up the case that held the tower cell; it would fall down with nothing to hold it. A dowel the size of the cell did the trick.


It makens it big.


A small hole, some raw 16-gauge extension cord I bought from a hardware store going out of business 20 years ago, some crimp connections within (with a bit of carving along the dowel to allow for the wire to squeeze in, crimp connector and all), and we have the final product.


It makens it bih-ih-ih-ih-ih-higger.


Final cost? The dowel was scrap; the gel cell $15 (IIRC), the crimp connectors frickin' dime a dozen (okay, maybe buck a dozen), the cord, as I said, too old to value. I think I paid twenty bucks for two hundred feet on a spool, and here I only used eight feet. Oh, and ten bucks stupid charge for once again misplacing my solder.

I took it for an inaugural screw just tonight. The battery was small enough to fit in one pocket of my tool belt, though the weight was a bit much, kinda like packing both the framing and the finishing hammer with plenty of nails. It might be time to invest, as I have been mulling, in some suspender styled tool wearing kit, especially if I intend to get some use out of this thing. I'll also have to make a case for the battery, something fabric, probably, just enough so I can strap the wires down and prevent them from ripping from the crimp connectors.

I'm just shocked that I waited 5 years before putting the whole thing together. Ah, well.
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Comments:
[User Picture]From: solarbird
2014-07-29 04:40 am (UTC)
Well I'll be damned. This is definitely in the "did not think of that" category. Well done, and I hope the battery lasts a while. It's pretty old at this point! XD
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From: maineshark
2014-07-29 02:16 pm (UTC)
I've often thought of doing something like that with the 24V set I have with dead batteries. The drill isn't in the best of shape (many years of use), but there's a circular saw that's gotten almost no use at all. And the circular saws eat batteries faster than drills, so even when the set was new, that thing did not last long on a charge. A larger battery would be an excellent way to get more work done (and I don't exactly use a circular saw on a ladder, so a heavier, separate battery is not a big deal - but being able to use it in a building that does not have power yet is helpful, since I'm often the one installing the power equipment for the building).
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[User Picture]From: peristaltor
2014-07-29 07:40 pm (UTC)
Good point!

I thought about buying a cordless circ saw when they came out, but the battery life issue loomed large. I didn't have enough jobs needing portable sawing to make the battery pack purchases worth it.

But hey, two li'l' 12 volters lashed together in series, and yours will saw again!
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