Strange battery behaviour/readings at low and full charge



I'm getting some very strange behaviour (or readings?) from my Ascend P6 battery at low (<15%) and full charge.

Let's say I charge up to the phone to 100% and, for some reason, leave it plugged in for a few minutes after it has reached 100% (acording to the battery indicator). If I then unplugg the charger, the battery will remain at 100% for a while before dropping to 99%, depending on how much I use it, it can be 15-20 minutes with intense use, to several hours in deep sleep.

At low charge, after it has dropped below 15%, it will drain to 0% in less than a minute. If don't let the battery drain to 0% in that process and plugg the charger say at 7%, the indicator would change to 0% right after and start charging from there. This behaviour repeats in the other direction: it charges up to 20% in less than 5 minutes.

Aditionally, voltages level seem very strange (see screenshots).

I've tried calibrating the battery several times using different methods with no results. This has happened everytime I let the phone get below 15% (except once, no idea why).

Can this be a calibration issue? The battery appears to be fine, it lasts all day and it behaves normally between 99% and 15%.

I'm attaching screenshots from the battery monitoring app I'm using with 30 seconds intervals (I know this drains the battery, but it happens without it)

Thanks in advance_


Huawei Ascend P6
International official ROM (B512)
Android 4.4.2




EDIT: Added screenshots at full charge. Remained at 100% for 15 minutes (intense use).