why my phone battery after it's fully charged goes to 89%

[AC Question]

I have cubot cheetahphone and i have it 5 months but never had this problem. In the last 3 times i charged my phone when it's fully charged it goes to 89% in less than an hour without using it at all. Is it a problem? Why is it happening??

 

[belodion]

Do your battery stats indicate anything after the discharge?

I have a phone that loses charge without use, though not as quickly as yours. It does so even if powered off. It also does so with the battery removed, proving that the fault is in the battery rather than the phone.
Does your battery lose charge with the phone powered off, or when removed from the phone?

https://forums.androidcentral.com/showthread.php?t=409154

 

[Panagiotis Pate]

Here are the screenshots about the battery dropping of. In the red circle it's from 100% to 89%. I can't remove the battery from cubot cheetahphone. It's a non removable