Modified drill battery pack

[Bobhdus]

Been thinking about modifying one of my old dead dewalt 18V drill batteries to allow me to use a cord to operate my dewalt cordless drill if the batteries went dead on a job. Anyone ever do this or know how?

I figured if it was easy, these cordless power tool companies would offer this feature to go along with the batteries they sell. I know that I would need to step down the 120v to 18v, but I don't know what I'm going to do to figure out amperage as most drills do not include this info or it varies.. Any ideas besides to keep buying batteries?

 

[7thDimension]

Just order some high capacity nicad sub-c cells and tabs from eBay. They're easy enough to solder into the battery case. They're cheap and the batteries will work like new...

Or you can get the 18v lithium batteries, they seem to last a couple years longer than the nicad batteries.

I make sure to keep my batteries charged all the time, and most of mine are around 5 years old so far and still work fine... My dad has some 14.4v dewalt batteries that are around 20 years old and will still hold a charge.

 

[bareass172]

The problem you're going to run into is having the power "on demand" to give you good torque. You can easily buy a DC supply to put out 18V, but getting an 18V supply that puts out good current is going to be expensive and bulky. I'm not saying it can't be done, but you really would be better off rebuilding your packs as mentioned above.

Conversely, if you can scrounge the cash, just buy Ridgid at Home Depot. Lifetime warranty on their electronic tools that includes batteries. That's what I did, when I have a problem I walk in the store and they swap me out.

 

[volleyball]

How about buying a corded drill to carry with you?
Extra battery packs area no brainer but they can get stolen at some sites.

 

[Farmall450]

I know you can convert 12 volt ones to run off a car/truck battery but Idk about stepping 120 down to 18v.

Edit:
I agree w/ above, just get a corded drill.

 

[pepi]

I know you can convert 12 volt ones to run off a car/truck battery but Idk about stepping 120 down to 18v.

Edit:
I agree w/ above, just get a corded drill.

Yes, car batteries are easy to carry around and portable, put a strap on it, hang it from the ladder, hmm maybe velcro strap make a sling for your shoulder, goes dead take it to auto zombie get it tested for free.

 

[Bobhdus]

I have corded drills, and cordless drills blah blah blah... Just looking to create a "hybrid". Many times I go to get my cordless drill and others have run it down and it has enough juice to start then craps out. Be nice to just "plug" it in and finish the job. Won't be long and some big tool company will come out with this "hybrid" and I'm going to say yep, should have patented this. Had the idea for a cordless tig foot pedals years ago and people on the welder forums thought that was the dumbest idea and would never work. Now it's the greatest thing since sliced bread.

 

[mrvm]

Been thinking about modifying one of my old dead dewalt 18V drill batteries to allow me to use a cord to operate my dewalt cordless drill if the batteries went dead on a job. Anyone ever do this or know how? I figured if it was easy, these cordless power tool companies would offer this feature to go along with the batteries they sell. I know that I would need to step down the 120v to 18v, but I don't know what I'm going to do to figure out amperage as most drills do not include this info or it varies.. Any ideas besides to keep buying batteries?

Black+Decker marketed a cordless drill several years ago that had a corded option that was really neat even though the drill was not heavy-duty. Technically what you propose can be done but it will probably be impractical and not too cheap. If the Dewalt is still in good shape you may consider having the battery rebuilt. Several to choose from and not necessarily this one:
http://www.toolbatteryrebuilders.com/

 

[GSteg]

Dewalt rates their power tool in UWO (Unit Watt Output). Their smaller 18V drill has a rating of 380 UWO so that makes it a bit over 21 Amps. Of course, that's assuming the system is 100% efficient but in reality, it could very well be over 30A.

 

[Bobhdus]

Great! Thanks guys!!!

 

[pauls_workshop]

Hi there, I've done this to an older Ryobi 14.4 drill I had. You need to use a big laptop DC power supply, at or a little higher than your drill's voltage was cordless. You need amps. 5 amps is pretty good for most any drill. I like LIte-On brand laptop power supplies for this purpose. Running tools that take major amps like reciprocating or circular saws, or grinders, etc., you will find you need alot more than 5 amps. But drills should be fine with 5 amps. Mine was. - Paul

 

[Packard V8]

Interestingly, the Samsung laptop on which I'm writing this uses a Lite-on 19.2 volt power supply.

I'm going to scrounge up another power supply and try it on the old Black&Decker Industrial 14.2V for which there are no new batteries or rebuilding available. (Yes, I've asked three different rebuilders. For whatever reason, they don't want to get these sealed 14.2V batteries.)

jack vines

 

[djb2]

Interestingly, the Samsung laptop on which I'm writing this uses a Lite-on 19.2 volt power supply.

The power supply likely puts out 3 to 5 amps maximum, and will shut down within milliseconds if you try to draw more current.

A NiCad battery pack can briefly put out 50 amps, and can sustain 20 or 30 amps for tens of seconds. Building a power supply to do that isn't especially difficult, but it does require specialized experience. There isn't a market and you are unlikely to see hobby projects.

Typically a NiCad battery pack is designed for a 10C or lower usage, meaning that the battery would nominally last six minutes at maximum load. Maximum load is usually when the motor stalls or is moving very slowly. With a 1.6 Amp-hour pack that would be 16 amps.

NiMH cells have much higher capacity, but generally can't deliver the same peak power as NiCad cells of the same size. The battery packs are typically the same size as the tool's NiCad pack, with greatly extended run time.

 

[JasonTX]

About 10 years ago, Skil offered such a saw. 12V, definitely homeowner grade. When the already undersized battery went flat, the charger had a connector for a battery surrogate cord. Acceleration was definitely slower on the cord. The current spike required to spin up a modern drill is quite high, and a power supply that can deliver this costs more than most drills.

 

[pauls_workshop]

Well, all I can say is my little Ryobi that was 14.4 has no problem drilling through just about anything on the 5 amp lite on laptop dc power pack. I'd be pretty shocked to find any normal drill really needing 10 amps to turn. If it does, it needs to be upgraded to a more modern design or you need to not try to use that in concrete. Also, if that drill needed those 10 or 20 amps to turn, people would not be too happy with their battery pack lasting only 6 minutes. That is silly. Most battery packs last a good hour on most drills. Mine do. They don't use that amperage is the reason why.

For comparison, I also have a cheap harbor freight hammer drill, corded, that was I think $30 or less after coupon. That has more power than my Ryobi for sure and can do more with the hammer drill option it has. I think it is rated at 7 amps at the most for comparison but is one massive drill. So it isn't about what the battery CAN do, it is about what the tool actually requires from the power source. 5 amps is quite a bit actually for many tools like normal drills.

Having said all that, I wouldn't try this on a recip saw or circular saw or grinder, as those tools DO need more amperage than 5 amps typically. Then you would need the more expensive proper DC power supply that can put out the amps. But it could still be done well then.

Here's a different take on some things you can do here, with some interesting links to other sites that may be of some interest. Check out Instructibles website for sure:

http://www.garagejournal.com/forum/showthread.php?t=229042

- Paul

 

[volleyball]

Corded drills are cheap, probably cheaper than the power pack you will need. If you stop and go back to get the power pack and extension cord, you can just as easily grab the corded drill.