I’m experiencing similar issues as reported elsewhere in this article. Since I upgraded the Fairphone OS from 1.8 to 1.8.5 (end May–begin June), the battery level indication seems to be faulty. The battery discharges pretty linearly for 1-2 days—I didn’t use my phone intensively since I was studying for finals–until it reaches about 30%, then drops to 0% in a matter of minutes, even if the phone is inactive. However, the sudden drop in battery level does not always occur, as shown in the screenshot below
Let’s dig a little deeper. In the past month, I tried to figure out a pattern about the circumstances in which this problem occurs. Unfortunately, I didn’t find a consistent cause. However, I did notice that the problem is most likely (yet not exclusive) to occur when wifi or data connection is turned on. The sudden drop also occurs when the phone (display) is inactive, so whether the screen is on or not does not seem to correlate with whether the problem occurs or not. I included a screenshot illustrating the battery drop problem below. (I’ve taken several similar screenshots, but new users are allowed to upload no more than 3 images, so I only included the most illustrative one).
I’m sure it’s not a problem with the battery itself. My battery is not bloated. It rather seems to be a problem with the calculation of the battery energy level. I noticed another anomaly that supports this hypothesis: once, after turning off and on the phone, the battery level suddenly jumped from ~50% to ~15%. This proves that the problem is software-related, i.e. a wrong computation of the battery drain, rather than the battery itself.
In addition to the battery level drop issue, I noticed a third anomaly: the battery charging does not always follow the pattern I suspect it to do. As shown in the screenshot below, the battery level sticks to a single percentage (1% in this case) for longer than normal, and the increase from 60% to 100% is abnormally fast. I haven’t tested if this is always the case though.
Although the 1.8.5 upgrade was supposed to fix the 14% bug, it only appears to have made the situation worse, and judging from this article I am by far not the only one experiencing issues with the battery calibration. This article proves that it is a serious problem, and it deserves to be flagged as a known issue, and looked into as soon as possible. For me, especially the sudden battery level drop is highly annoying since I’ve lost all trust in the battery level indication. Sometimes a level of 30% means I can still go on for half a day, other times it means that my phone will die in a few minutes (see the first screenshot again).
Until the issue is patched: is there any way that allows me to reset/recalibrate the battery level indication? Anything that relieves the problem even slightly until a definitive solution is distributed is highly appreciated. I don’t mind doing pretty technical stuff to achieve this if necessary (e.g. editing system files).