Make a Power Tool Battery Multipurpose





Introduction: Make a Power Tool Battery Multipurpose

My goal was to add an external power connector that would allow me to plug my battery up to whatever I wanted to while still being able to use it in my tools and the standard charger without any extra effort. This has been achieved.

Step 1: Gather Your Battery and Take It Apart.

For my project I used a Ryobi P108 battery. I was able to get several of them for a cheap price and I know these batteries are built using high quality Samsung INR18650-20Q cells. Also I have a large collection of Ryobi One+ tools so it was a win win.

So first, gather your battery. Figure out how it needs to come apart. My Ryobi is pretty simple. Has 4 Torx 10 security screws. One has a plastic cover that you have to remove by prying it out with a small screw driver or knife.

Step 2: Figure Out the Best Place to Add Your New Wires.

For the Ryobi and probably all batteries, I think the best place to add your new wires is to the battery contacts where the current wires are soldered on.

Step 3: Solder on Your New Wires.

The Ryobi battery has 18awg wires coming from the circuit board to the contacts. I added 16awg wire for my modification. I figure that if 18awg is safe for the stock length, using 16awg for my short extension should be adequate. I also added a piece of electrical tape to help protect the wires from the connections stick out of the board. I also added a ziptie to each wire remove strain from the soldered connections.

Step 4: Modify the Case So the Wires Can Get Out, Cut Wires to Length, Add Your Favorite Connectors, and Put Back Together.

At first I was going to make one large hole for both wires to share, but then I realized the wires would fit better if they each had thier own hole. So I driled two matching small holes for the wires.

Once that was done I put the battery back together with the wires coming through their holes.

Next was to cut the wires to length, do them one at a time so you don't short the battery.

Then add your favorite connectors, again doing the wires one at a time. My favorite is Anderson Powerpoles.

Step 5: Testing and Proof of Concept.

In the first photo I have the battery connected to my power meter then that is connected to my hobby battery charger. The Ryobi battery is powering everything.

You can see that the power meter shows 20.63v which is around what a fully charged 5S lithium battery pack should be. Not the 18v it is advertised to be. (18v comes from the NiCD battery days and Ryobi has not changed that nomenclature).

You can also see the battery installed in my Ryobi vacuum. You can see that the extra connector does not cause any obstructions. The battery will still fit into any Ryobi One+ tool as well as all their chargers.

Step 6: Multiple Uses - Only Limited to Your Imagination.

This can pretty much power anything. I have a ton of projects that I've done in the past years that this can be used with.

  • RC Wheelchair
  • RC lawn mower
  • Power Wheel battey (other mods may be needed to handle the extra voltage)
  • Wire 2 or more in series for even more voltage (A 40V Ryobi battery is not very different from 2 of these in series)
  • Portable FPV ground station (most need 12v so add a DC to DC converter)
  • Mobile device charger
  • Emergency power supply



    • Water Contest

      Water Contest
    • Oil Contest

      Oil Contest
    • Creative Misuse Contest

      Creative Misuse Contest

    25 Discussions

    I am glad I found this. I will buy Porter Cable flashlight to modify. I want to power some dc outside lights.Thanks!

    I've been trying to work out how to turn the Ryobi 40v battery into 12v using the original charger base as the 'box'. Any suggestions or ideas? If you steal this idea and make one I will not mind at all.

    1 reply

    You could use a DC-DC converter for that. Search for B01ARRA56Y on Amazon for an example capable of 40V input and up to 10A at 12V. There are also adjustable converters available.

    Thanks! I'm totally modding a few of mine today. Another option would be to buy the $13 Ryobi flashlight that takes the same battery and drill that, if you didn't want to break open the more expensive battery. It would allow you swap out batteries when one was low.

    1 reply

    That's another good option if you can fit the flashlight where you plan on using the battery or don't mind chopping the flashlight up just to use the base. I use this battery in my daughter's power wheel. It was originally meant for a 6v battery under the seat so space is tight. The ryobi battery fits perfect though.

    Cool stuff, I knew I could find link minded tinkerers here. I'm in an off-grid situation and it occurred to me that I could use the leftovers on my 18v tool batteries to power my led light strips. I recently was given a couple of 40v snowblower batteries that I'm dying to repurpose to run lights or even some usb charging. I also have 2 40watt solar panels that could maybe charge them. Anyhow, I'm wondering about the process of going from 18v or 40v down to 12v applications without frying your device? Is that something the power meter handles?

    1 reply

    You just need to know the amp requirement of your device. There are dc to dc adjustable voltage converters on ebay for very cheap. Most can handle about 3 amps.

    i wonder if i can do this with dewalt?


    3 years ago

    I thought about taking one of the Ryobi battery testers(I believe they call it the Fuel Gauge) and adding some Anderson power pole connectors like you did. That way I don't have to tear each battery open and I can swap with any good battery.

    15, 6:29 PM.jpg
    2 replies

    Actually what I was looking for was a 3D printed connector that could be placed on top of the ryobi one battery. There are a few projects on thingiverse that may work.

    I actually bought one for the same purpose. Got it home and didn't like how loose it felt on the battery so I took it back.

    i really enjoyed this instructable- thanks!
    you may know the answer to this - is it possible to use the housing of a cordless tool battery and convert it to 110v (so you can plug your tools directly into the wall outlet instead of using batteries)? or are the tools not strong enough to handle that power input?


    4 replies

    Yes, but its not that simple. You will need to also use an AC to DC converter (DC power suppply) with the proper voltage and sufficient amperage. Just plugging a DC cordless tool into a wall outlet will cause a lot of damage to the tool and possibly you.

    There are a few instructables made that have done exactly what you want. In my opinion its only feasible with tools that don't need a lot of amps. If your power tool is amp hungry, you'll need a large (expensive) power supply for it to work properly. At that point it would be cheaper to just buy a corded version of the tool.

    yeah i saw some forum that suggested the same thing. i was just thinking in terms of reducing the size of my tool kit on a job site. thanks again, this is a great instructable!

    I want to do this for a bicycle light I have. I want to use it for my dirt bike so I can ride at night.


    3 years ago

    Good to know. I'll cross that off the list. Perhaps I'll cannibalize an old non-working flashlight that I have...