Repairing My Label Maker
2026-04-10 21:43 - Making
I'm not totally sure where and when I first got it, but I know I've got a DYMO LabelManager Plug N Play Label Maker. A nifty device; unlike your typical label maker with a low quality built in keyboard and tiny display, this is a small and sleek unit with neither. But it does have a USB port (original USB A, i.e. "printer USB") for plugging into the computer. Do so and it presents as a USB drive with the simple and portable software to control it.
For some reason however, just like a more typical/portable label maker it uses batteries. A built in, rechargeable, lithium battery. And they go bad
. I know in the past, I had problems with mine. Plug it in and it would say the battery was too low to use, but charging. It never charged, though, almost. If I tried several times I could get it to work. Now however, it never worked. I had the realization that I could do something about that though!
Not only do I have a 3D printer, I've got a collection of "street lithium". Even disposable "e-cigs" have rechargeable lithium batteries in them, plus they end up littering the streets just like cigarette butts. People like me will gather and harvest these battery cells. The original pack I'm replacing says it's "4.81Wh" on the side (and 7.4V which means it's made up of two cells internally), and I found a pair of 2.4Wh cells of appropriate size. First, I crudely connected these bare cells to the label maker with alligator clips. And it worked!
So I designed, more quickly than I expected, a compatible shell to fit in the same space. It's the same overall shape, plus critically two things: it's got notches to mate with a tab in the device (for polarity protection), and it's exactly the right length to snap in against the spring terminals. It doesn't look great; I've been tuning and tweaking the 3D printer and finding the edges of how fast I can drive it. Not quite this fast, for a high quality result. And that was mostly it! But once I got this far I decided to go a smidge further.
I manually hooked the original battery pack up to both charge and discharge it. Via experimentation I noticed that the pack would cut itself off under most charging conditions; this really seemed to be triggering over voltage protection. If I charged very gently I could get it to a sort-of reasonable voltage, but discharging it from this point gave roughly 7mAh &emdash; far less than the 650mAh advertised on the side. I decided I had nothing to lose and started cutting the pack open. Inside as expected I found two cells (though of different dimensions than I expected) and, under their outer wrapper layer, a BMS (battery management system) board, which is of course meant for a two cell pack like this. I harvested it for my replacement. After installing this, which fit in the slight spare space I had already left, I wrapped the replacement in just enough polyimide tape to keep things tucked in neatly.
When I put this replacement pack in, the software says not charging. But that's because, as the display shows, it knows this pack is already fully charged! It fully works as a replacement. With the added layer of tape at least, it's a smidge big, and takes some effort to remove. I'm not going to store this replacement inside the unit. I don't know what kills the batteries, but that might contribute.
So why the battery at all? Well, your more typical label maker will run off of six alkaline cells: nine volts nominal, closer to six and a half as they're nearly empty. This lithium cell will provide around nine to six and a half volts or so, nearly the same range. So it will work. But of course, the thing is designed to plug in via USB, and can't work otherwise. And to charge this battery via the USB connection! I think the hint is the full size USB A style plug. I this device seems to be from 2010, i.e. before the "smart" "phone" market really changed USB. Back when you might only get half a watt, possibly 2.5 watts, from a USB port. Potentially not enough to drive the motors and thermal printer head? So a very low powered boost circuit will slowly charge the battery, and the battery will definitely have the power to run the printer when that's needed. And the software will monitor the battery, refusing to print when it's low. That's my theory.
