Comment # 10 on bug 1095451 from Ralf Czekalla

Hello Kacpar,

these devices usually have a very low battery power consumption and you are
true: I also recognized on my devices that it stays on 90% for a long time and
then after 1-2 years goes down rapidly in about some days. 

The reason for this behavior is in the battery characteristics curve. You see
this behavior especially with devices which have a very low power consumption
and the interior of the battery can keep a very stable equilibrium state of
chemical and electrical power. During my chemistry studies I looked deeper into
it. Let's see if I can find a wiki page for these batteries characteristics
curves. Found one here https://www.mpoweruk.com/performance.htm. The curve
falls at the beginning to something like 90% and then stays there for quite
some time. 
The weaker the power consumption, the later the next fall comes and is then
much steeper. 

At least with Solaar I could get a heads-up some days ahead when the battery
died finally. This I had in several of my devices. Yes, Solaar is also working
on our living room entertainment PC and I use it mostly every day for these
Logitech K400* living room keyboard with mouse.

Best Regards
Ralf