I thought the difference was the form factor: button cells are thick with smaller diameter; coin cells thin with larger diameter.
Stacking them up to ~12 to 15V would approximate 'rectified' power from the DCC voltage.
Anyone knowledgeable about computer tech knows how to implement a charging controller/float charger for a battery of 3V cells.
It does seem like there's overlap in the namings, in recent months I've bought LR44-size batteries (would I would consider a button cell) and CR2032 batteries (what I would consider a coin cell). Five 20mm batteries (wired in series to get 15V; 4 @ 12V might not be quite enough) take up a lot of space.
Huh. I didn't know that button cells and coin cells were different things.
Most of those rechargeable cells are 20mm in diameter, which I guess are considered 'coin' cells. But I have found some that are 12.5mm in diameter. Would they qualify as 'button' cells? Dunno. But here is a link.
https://www.ebay.com/itm/324545601466?hash=item4b906cdfba:g:AfwAAOSw1btgYkDP&amdata=enc%3AAQAIAAAAwCJAoO3d0e4O7jCix6YCsCmAsAszgIU8KriFO1lhzxeut8AB0edWqg6rIwtr6BYJXdq2eSlW%2BS8NI6Rbw4y1zidZNerQKHM9wZpC7cnM6%2B9w%2BZ9OThGDjEIjTi89WQj2Tg3aeaN%2FdNnGDu9aXG7xPbQXob2v6LlTj40tbE5U20eeUTxc79gaE%2Bi2ygpdHIscrVrAQsq5CEDiatTLwv6mrITXTBn1tuP5nhMdJsBHXVs7BuinnGFSNS%2BPAJWCZVcPLw%3D%3D%7Ctkp%3ABk9SR9Ca5qDWYg
Almost all of the 3-volt rechargeable cells are the tempermental lithium-ions. Probably the only safe way to use them are in a true dead rail system. Charge them with a proper designed-for-lithium charging unit. Maybe hooked up to dedicated sections of track so the locos can be recharged without removing the batteries.
Can you please provide a link to rechargeable 3V button cell batteries? I can find rechargeable coin cell, but not button cell.
A short stack of 3-volt button cells should be able to run a loco for a while. If those are rechargeable cells, in theory, they could be juiced from the rails.
Compared to what a off-the-shellf 'Keep Alive' costs, and the spece it takes up, a few button cells looks like an economical alternative and attractive fit.
The fact I've seen no discussion about button cells, rechargeable or otherwise, makes me feel there are good reasons they are not used. Lithium cells don't take well to overcharging. They are known to catch fire. Metal hydride cells are less potent, but safer. Once-and-done batteries may need to be replaced fairly often, but you'd buy a lot of them for what a 'Keep Alive' costs.
If the idea is to simply maintain power despite dirty track a few rechargeable button cells might be a very practical solution, even if their performance is degraded by sub-optimal charging.
Commercial 'Keep Alive' units typically use capacitors to store the power. Capacitors are not ideal. They don't maintain a set voltage, and supercapacitors have been known to explode.
I'm sure someone has tried using button cells. I'd like to know what their experience was.