Rail (750Wh) Battery doesnt charge back to 100%

[Bam104]

Why doesnt battery charge back to a 100% stops charging at 96%? If I unplug and replug it then will go to 100%

 

[Stihldog]

Mine does something similar. (625wh). Sometimes it changes to 100%, other times 96-98%, after an overnight change. I don’t worry about it too much because it changes each time.

I usually try not to discharge below 5%, and try to store at 60% for any length of time (2+ weeks). I believe the condition of the battery is still good after 4+ years.
Btw; I use a Kiox.