Converting a cordless tool battery to use a cord – chapter 1

Some time ago my father gave me several cordless tools that he had retired. They where pretty much on their last legs and he was moving over to the then, new lithium ion type batteries.

I appreciate cordless tools for their handiness, but overall my experience with them is that they don’t run long enough and the batteries stop taking a full charge way before I feel like they’ve paid for themselves. My understanding is the lithium batteries are better about holding a charge and can be recharged many more times than the Ni-Cd battery used for this project.

Why the Cordless to Corded Conversion?

I have several AC corded drills, so I don’t really “need” to build a corded, cordless drill. What I didn’t have was a 1/4 impact driver. This is a tool that I didn’t have a use for until I used one, now I don’t know how I got by without it. The cordless tools my dad gave me included a 1/4 impact driver, two 14.4v batteries. One battery was a Dewalt that works enough for quick tasks, the other was after market copy of the Dewalt, and it’s dead as a door nail.

Frankly the impact driver isn’t worth buying a new $60+ battery for, it makes more since to replace the driver and battery with a new one, but since I have the dead battery, Converting it over to use a cord looks like a fun project.

I’ve seen other people do projects like this, but for the most part they’ve converted drills to run off a remote power supply. That’s what this project is, except I want to convert the 1/4 impact driver. From what I can tell 1/4 impact drivers are always cordless, unlike drills that are easy to find in both formats.


Disassembly and evaluation of the battery components

This is the before photo of the after market, Dewalt® style, 14.4v battery. The internal cells are dead, but the shell, wiring and posts are in pretty good condition. It’s Marked “Premium Gold” brand, 14.4V-1500mAh, Ni-Cd. When I put it on the charger it looks like it’s charging, but it says it’s full after a few minutes and it’s pretty darn warm. If you try and run it after charging, the tool will run very slowly,and only for a short time.


I removed the 5 screws. One is hidden under the sticker in the center top of the battery case. I’ll need to put a drop of glue in each of the screw holes, I get the feeling I wasn’t the first person who opened the battery pack shell. That said, the shell fits pretty snugly, for a knock off the fitment isn’t bad. I should also mention that since it was given to me used, I don’t know how long these cells lasted. I can’t speak to the quality of the battery calls.


This is a look at the inside of the empty battery pack, showing the 5 screw posts. The battery pack cells are held into the shell bottom by a piece of double sided foam tape.they are also snugly fit into the shell so they don’t rattle around. If you take your time you can work them out of the shell without resorting to a screw driver or hammer. You want to keep in intact so you can measure, and salvage all of the parts.


This is where the magic happens. Well kinda. My goal is to recreate this terminal without the battery cells. I would like to end up with the unit close to the same weight as it was with the cells inside. It isn’t too complicated, but I don’t want it to feel Jerry rigged, or to be a fire hazard when it’s done. Hell, I don’t even want to get shocked if it can be helped.



Making Rough Measurements

You get a good look at the cells that make up the battery pack, along with the rough footprint measurements. The footprint of the internal cell pack is roughly 2.5in(63mm) x 4in(102mm). Make sure that you make your own measurements since it’s unlikely that your battery pack is identical to this one. Also note the location of the battery support, battery cell (replacement object), and contact points that all need to line up inside the handle of the cordless tool.


This is a side view of the battery pack with a rough measurement diagram. The next part of the process is getting the components separated and cleaned up.


Project Notes:

  • Just for fun I put a small socket on my 1/2 inch pneumatic impact gun and tried using it as a driver. It worked, but it’s definitely too powerful, heavy and large to use for long in that roll. I didn’t test to failure, but my guess is that it would shear the .25″ conversion parts pretty quickly.

Index – Converting a 14.4v Battery to Corded DC Power Supply

Harbor Freight 18v .25in Impact Driver

Harbor Freight Impact Driver, A fathers day gift

For fathers day 2017 my sons gave me some money to spend on some tools I’ve been wanting. Thanks to you both.

recipt with discountFirst on the long list of tools I’ve been wanting was a 1/4 inch impact driver with a battery that actually works. So with that in mind I swung by my local Harbor Freight and bought one of their 18v 1/4 impact driver packages. It’s the driver, charger, and single battery in a fitted plastic box. Normal price is $99.00, but it was on close out at $39.97. I’ve seen it priced at ~$99.00 in store before, but I think that it’s usually right at ~$40.00. I also purchased a magnetic bit holder for $2.00.

I gave the cashier a 20% coupon figuring .40 off of the $2.00 bit holder was something. The other cashier was desperately tying to get me to buy the warranty so I didn’t really look at my change. I noticed later that they had applied the 20% coupon to the impact driver, saving me about $8.00. I swore you couldn’t use a coupon on close out items, so either I was wrong or I just got hold of a nice cashier. I’m happy either way.

Right out of the box

The battery had at least some charge out of the box, I made sure it went forward and reverse and then put the battery on the charger. The charger, driver, and battery seem of reasonable quality. The driver is roughly the size and weight of my Dewalt 14.4v impact driver. The Harbor Freight 18v charger seems a fair bit lighter than the Dewalt 14.4v charger. The Harbor Freight 18v battery is larger, but about the same weight as the Dewalt 14.4v battery.

The new battery with a full charge shows 20.5v on my meter. I’m no electrician, but based on experience that’s about what I would expect.

I ran a few deck screws into some treated lumber, and it runs quite well. This is the first run on it, so I expect it to be strong, it will be interesting to see how it runs in a year.


Harbor Freight Impact Driver and Dewalt Impact Driver

Why not use the Dewalt?

The Dewalt driver I’ve mentioned, was a hand me down. If I remember right, my father bought it second hand, and it was well used. It looks pretty rough, but to it’s credit, it runs like a champ. The issue is that the Dewalt branded battery is out juice after 3 or 4 deck screws. I’m not knocking Dewalt, that battery didn’t owe anybody anything.

To replace the Dewalt 14.4v battery it would cost nearly $70.00, and at that price I may as well buy the DEWALT DCF885C1 20V Max 1/4″ Impact Driver Kit. At the time of this article it was about $100.00. That’s a pretty good deal, but I’m SUPER CHEAP.

I’ll continue using the Dewalt impact driver, but the battery is an exercise in frustration. I’m going to convert it to run off of a ~15v power supply. This means it will have a cord attached to it, but it will have full power all the time.

Why buy the Harbor Freight impact driver?

Simply put, I want an impact driver that I can throw in my tool bag when I’m away from my shop. The Harbor Freight impact driver and an extra battery will cost me less than just one new battery for the Dewalt.

If I can buy 2 tools for about the same price as a name brand tool, I usually buy the cheap one. When the cheap one craps out on you, you’ll know how long the cheap tool will last and also if you depend on the tool enough to make quality of the name brand worth the cost. Then you either replace the low cost tool, or upgrade to he name brand.

impact driver gallery – click to enlarge


The Harbor Freight 18v battery is substantially larger than the Dewalt 14.4 battery, but the drivers and their chargers are roughly the same size.

As I use the new driver I’ll add notes and photos to this post.