Lithium battery question on "new old stock" product

[Bicurico]

Hello,

I am having this "problem". I always fancied the Casio WSD-F10/F20/F21/F30 range of watches. Yes, I know they are big, the battery barely lasts one day, etc. But somehow I would love to have one, perhaps because since I was a kid, I always liked Casio watches and this is kind the ultimate Casio watch with the cool feature being the dual screen: colour TFT and regular LCD watch-style screen for low power consumption.

I happen to have come across one model at sale. It is new and at the current reduced price, I would gladly buy the dream watch of mine, despite there being no objective or reasonable justification to do so (I already own smartwatches and a sport watch with GPS).

What is holding me back, though, is this question: the watch is at least 3 or 4 years old and I mean the one for sale (like sitting in a display or it's box). It is brand new in the sense that it was probably never even switched on. So I wonder what state the built-in Lithium battery is. Will it still have the original charge from factory and since it was never actually use, will it have full capacity when used or is it more likely that this battery is degraded and probably only featuring half or less the original capacity?

I ask myself this question, as I read that Lithium batteries will degrade about 20% per year, no matter if used or not. On the other hand, I own a Fossil smartwatch that I purchased about 4 years ago at the battery is still pretty much OK, despite the more or less regular use. I have an even older smartwatch (>6 years and its battery is fine).

I know that the battery is exchangeable and I could perform the exchange myself, but a new battery would make this an uninteresting purchase, as the replacement batteries are quite expensive. Plus, I wonder how old those are...

Any thoughts on this?

To sum up: is there any consideration to buying new old stock items that rely on included lithium batteries, considering these age? Will they age if never used, apart from the initial factory charge?

Thanks,
Vitor

[tunk]

If you want, get it.
Impossible to tell anything about the cell, some cells are high quality
holding their capacity well (like your devices), others are not. A rule
of thumb is to store cells at ~50% charge, so if the watch hasn't been
charged at all, then it should be better off. For comparison, I just got
a very little used ~10 year old laptop which still holds charge.

[thm_w]

I ask myself this question, as I read that Lithium batteries will degrade about 20% per year, no matter if used or not. On the other hand, I own a Fossil smartwatch that I purchased about 4 years ago at the battery is still pretty much OK, despite the more or less regular use. I have an even older smartwatch (>6 years and its battery is fine).

No that is not a general rule you can apply to all batteries. Highly variable.
Most likely the included battery is fine, but no way to know for sure.

https://www.sciencedirect.com/science/article/pii/B9781782420903000092

[BrokenYugo]

Worst case it isn't like small lipos for these sorts of applications have gotten less common the last few years.