Converting a cordless tool battery to use a cord – chapter 3

Figuring out how to best replace the internal battery structure

battery cell widthThe individual battery cells in my battery pack are roughly 7/8 of an inch wide. I looked through my scrap bin and found I had a wooden dowel that was close if not exactly the same size. Don’t depend on my measurements, there’s a good chance that if you do this type of conversion, the battery cells in your battery will be a different size.


battery replacement dowelSince I’m removing the internal components of the battery pack I need to replace the contents with something to hold the electrodes in the correct position for use. The stem of the battery is roughly twice the height of the main battery pack so I will be running the dowel from the top of this down to the bottom of the shell.


battery replacement dowelA bottom up view of the dowel placement and how the dowel will go into the stem of the battery pack. The electrodes will sit on top of this dowel.



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Converting a cordless tool battery to use a cord – chapter 2

Dissecting the internals of the battery pack

battery pack cellsI started by snipping the leads on the bottom of the battery pack, leaving as many cells grouped together as possible. This, in case I needed to measure anything as I work through the project. I then pried the positive lead from the cell below the stem.


closeup of terminalsThe “-” terminal is soldered to the top of the stem. Later in the project I’ll solder the “-” lead to this tab.



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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.

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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.

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