SwissMicros Calculator Forum

Dumb first post: I would like a replacement battery on hand. What is the battery spec.?

I scanned the online manual and didn't see it there. (That doesn't mean that it is not there, just that I didn't see it there.)

CR2032

CR2032 lithium battery.

Your DM42 probably shipped with a Panasonic but any well-known brand will do. Just avoid the cheap no-name variety, they're more trouble than they're worth: viewtopic.php?f=3&t=239&p=3218#p3218

There is only one CR2032 battery.

Memory will very likely be lost, however simply plug in a USB cable, with the other end plugged into a PC or charger, and you will be ok.

Yesterday my DM42 was blocked, the bottom half of the screen was not completely drawn and...nothing happens with the keyboard.
Maybe the battery...? Displayed voltage was around 2.9 V though.

I connected the USB cable, DM42 was alive again.
This gave my the opportunity to save a "state", oh thanks ! Just a date as the filename.

I changed the battery, one CR2032 as Robert told above. Next, remounting the cover and loading the saved state.
Hello world, with a 3.24 V voltage.

What a nice machine !

If it comes to a push, a CR2025 will work too. The differenes are:

Battery Thickness mAh
CR2016 1.6mm 90
CR2025 2.5mm 160
CR2032 3.2mm 225

(I Google'd the mAh figures)

CR2025 still fits quite well, but won't last as long as a CR2032 - presumed by the figures.

(I get packs of CR2016/CR2025/CR2032 batteries for about £1.50, 4 x 2032, 2 x 2025, 2 x 2016 - the 2016 I use in Casio watches)

That being said, I've got 2.66666yrs out of the CR2032s that came with my DM42 and DM41. Not used heavily, nor daily, but perhaps a couple hours each week. We'll see how long the CR2025s last.

edit: CR2032 == Chromium/20mm/3.2mm

Note that the 2025 is not able to provide as much current as the 2032, which could be a problem if your use includes extended run-time programs (e.g. more than 20-30 seconds) as this draws far more current than interactive use. In this case, the voltage will drop too low and the device will RESET,and possibly lose the current program, but likely then turn-on again and seem fine for a while. But for short programs and interactive use, the 2025 should work, with obviously shorter life.

Apologies but I don't get it why anybody would ever replace a small coin cell battery by an even smaller one. If I had to decide, I'd run the DM42 on two AAA cells - standard and good for many more mAh.

rprosperi wrote: ↑

Sun Jan 07, 2024 2:29 pm

Note that the 2025 is not able to provide as much current as the 2032, which could be a problem if your use includes extended run-time programs (e.g. more than 20-30 seconds) as this draws far more current than interactive use. In this case, the voltage will drop too low and the device will RESET,and possibly lose the current program, but likely then turn-on again and seem fine for a while. But for short programs and interactive use, the 2025 should work, with obviously shorter life.

I did state "If it comes to a push...", not that it would be a substitute... and "CR2025 still fits quite well, but won't last as long as a CR2032"

so perhaps a few "test" programs could be created to quantify the differences???? A challenge to write a cpu intensive routine to quantify battery difference? Just for sh!ts and giggles?

Panasonic and Renata make pretty solid CR2032 cells.

the internal resistance of these small cells is high enough that going smaller seems like recipe for unhappiness.