I have a small battery-operated Dremel tool, but the original battery is old and only runs it for a short time. Instead of rebuilding the battery pack, I made a simple AC adapter so the tool can run from a USB power source (Photo 1-3). Now the tool can run forever without losing power.
The original battery pack (Photo 4) is rated at 4.8 V, which makes it a good candidate for USB power.
To make the adapter, I found a pill container that fits closely into the battery compartment (Photos 5 & 6). Inside the container, I made terminals that match the battery pack contacts. These terminals are made from long bolts, and the cable is secured in place with Green Stuff epoxy putty.
Because the pill container is slightly undersized, the fit is loose. To fix this, I glued small tabs (Photo 6 black circles)—cut from the same pill container—around the outside to increase the diameter. There’s no need to glue all the way around; adding tabs in just two locations is enough to make the fit snug.
Photo 7 shows how I made a retaining tab that engages with the hole inside the battery compartment to keep the adapter from pulling out. I cut two grooves in the tab so it has a bit of spring and can flex during insertion.
Photo 8 shows some additional details. A small notch was cut to clear an internal fin in the Dremel housing (green circle), and the tab fits into the square hole in the tool body to lock the adapter in place (red circle).
This isn’t meant to be a step-by-step guide—just a demonstration of one approach if you want to convert a DC-only, battery-powered Dremel to run from an external power source.
Pretty neat but that's not an AC adapter.
USB is normally 0,5A or 2,1A. And will cut power if more is drawn.
A dremel-like tool will use more like 5A - 10A.
So he can use a Laptop USB-C charger, a PD-decoy and a DC-DC stepdown for 10A.
No argument there. Just pointing out that this doesn't adapt AC to DC, which is what an AC adapter does.
You can call it whatever you want. I just need it to run on AC power.
Sure but this doesn't make it run on AC power. It runs on USB power, which is DC.
OK! I just want my dremel to run in a USB block plugged into the wall. So I don't depends on battery power. Now I can run it for a long time. AC, DC, call it whatever you want.
How well does it work?
I have the same Dremel, but the battery is 30 years old and, like you said, doesn’t work for very long.
Extremely well. I encourage you to make the same thing.
Resourceful, but can it supply enough current?
I have been using this dremel for years. I have been running it for up to 20min at a time for my grinding. Never have a problem.
I just got my account on Reddit so I thought I'd post it.
From a USB type A you can draw 2.2 amps at 5 volts. That battery is only .7 amp hours and 4.8 volts. There should be more than enough juice from the type A.
Youre talking about capacity, not about momentary current draw, which in power tools can be quite high, USB cant handle those peaks. This contraption will result in a damaged USB power supply, "magic smoke" if you will.
Dremels are not a high current draw tool. Even the AC versions.
the moment there is physical resistance there are peaks that might exceed what a USB supply can provide, even a small battery tool can jump to a momentary 5 Amps or more while in use. The reason battery operated power tools are even possible in the first place is because Lithium and NiCad batteries can handle those peaks.
A 12V cordless drill for example can draw close to 20A under load, lets roughly assume this dremel will draw a quarter of that, its still 5A, most USB power supplies cant provide that.
You are assuming a lot. You are not talking about a Dremel in any of what you said, you mention other tools, not Dremel's. You load a Dremel heavily, they just stop. They don't ramp up the current to keep running. They don't pull 5A. That Dremel pulls .7A. max.
Once again you are not talking about the Dremel, and a USB type A can provide more than enough to power that tool.
You are wrong. OP is going to be fine. No blue smoke. If you are going to reply tell me about the Dremel in question.
"A typical 4.8 V cordless rotary tool can momentarily draw between 15 W and 25 W under heavy load, which translates to about 3–5 A of current at 4.8 V. This is the peak draw when the motor is stalled or cutting through dense material, not the average operating power."
The average draw is not that high, the problem is the peaks while you are working with resistance (which of course you are, its a rotary tool), a USB power supply is not built for handling these peaks, and can supply 3A at the very most (unless you are using a PD charger with a trigger PCB, then your max is 5A at 5V, assuming you have the right PD charger that uses the suitable power profiles for 5A@5V). Additionally, OP is using a type-A cable, that actually can never exceed 3A.
When you load the dremel and they stop, is a behavior when connected to a battery, not to a USB power supply, batteries can handle this kind of abuse, USB power supplies cant.
It might work temporarily while OP is doing very light work, but its bound to fail.
Op could have mentioned this in the title, but he didn't.
I think you underestimate the power of the
darksideusb charger.To be honest we don't know what USB power supply they use, basic ones are [5V@2.4A](mailto:5V@2.4A), but i wouldn't trust a setup like that, good for them that it works, they must probably doing very light work. Also, 0.7Ah is not current draw, its battery capacity, these are not the same thing.
I use a 1A USB block. If I use anything less the dremel will stall out when I work. I use it for light work only. This dremel is light duty in the first place.
Going further, Max peak load able to be supplied by the USB A would be 10.1w. Battery at .7 ah @ 4.8v = 3.36wh. This means that if it did consume that, it would run for 18.3 minutes continuous. That seems reasonable for a brand new battery, so it may be close to being restricted.
Fuckin nice job buddy. Love the magnet.