Rechargeable Button Cells (LR44 or CR2032) and OPUS BT-C3100.

I’ve got a few small devices that use button cells.

I’ve got a OPUS BT-C3100 Smart Charger.

I’ve got some wire, soldering iron, and magnets.

Can I charge some rechargeable button cells with Opus charger? Or does someone make some sort of 18650>Button Cell charging adapter?

Can you set the Opus to 10mA or whatever low current that is needed for a rechargeable CR2032?

Lowest current setting on my OPUS BT-C3100 is 200mA.
That is a bit steep for a 10440, and even more so for a ML2032 or a LIR2032.

I wouldn’t charge those past 5 or 10 mA. I only have one charger that I might trust with them, and it’s a custom-made board from CRX that he shipped with a pair of 10250 cells. Even that is probably too high.

If I’m remembering right, there’s a couple of Micro-USB charging circuits that you can configure the charging current (I think that’s what CRX did) with resistor choice or something. Someone more knowledgeable than me will have to chime in, though.

Such button cells are made? Capacity must be very small. Are they worth it?
Seems if they do make them, there should be an appropriate charging device for them.

Addendum - there are.

Honestly speaking, coin cells can be bought for affordable money if ordering in packs from China, or even from my own country or some nearby one. This is what I do. Buying them at local shops usually is noticeably more expensive.

If you have coin cell devices with high power consumption (?), rechargeables may be the way to go. Chargers for coin cells and other small batteries can be found. Can't comment about their overall quality, but in my experience they at least usually work fine enough.

For example, let's take a look at this search: LIR2032 charger @ AliExpress.

Overall the reviews seem so-so. If the internal construction in those is too bad, the electronics inside their frames could be replaced with something better. TP4056 modules resistor modified for sufficiently low charging currents would be a very good choice.

you can get cr2032 etc for under 15c/cell from china
you may have to buy 50 but still

The tough bit with coin cells is the marked difference between Panasonic’s coin cells and everybody else’s. At a previous job, I dealt with very high numbers of coin cells, of all varieties of quality. “Made in Japan” stood out from the rest.

Now, if you can find them cheap enough, $/Wh may be better from China. But for a lot of coin cell devices, changing them is a bother.

I”ve bought coin cells from China several times and on checking found most of them about 80 percent of rated voltage, with sporadic dead ones.

I suspect we get QC rejects.

There are many other japanese manufacturers who make high quality cells, like Murata/Sony or Maxell. Last time I bought a 10-pack of Maxell branded CR2032s, the usual brand I get, on a small sale for less than $4 including shipping. I doubt there's much of a quality difference between any of the big brands.

On the other hand, I once dared to pay less than $0.75 for 5-packs of TianQiu branded cells on eBay. Ugh! I must admit those cells worked, but a lot less than expected. :facepalm: