One issue we keeping getting is when someone emails us and says his or her battery level readings are way off, or the full battery alarm never goes off even when it reads 100%. Since the typical charger applies less and less charge to the device as it approaches 100% (sometimes down to a trickle) so as to not overcharge the battery, it may sometimes take a bit longer (20 minutes or more) after the battery level reads 100% until the device reads the battery as being full and the full battery alarm finally goes off. This is why it is generally safe to leave the device on the charger overnight. However, there are sometimes when the full battery alarm NEVER goes off. Or the battery level reads that you have a significant amount of charge left, right before your device turns itself off because in reality it is completely drained. I am going to address those issues in this post.
The problems mentioned above usually occur with two types of batteries. One that is either very old, in which case it can no longer reach the 100% threshold it recognizes in its current batterystats.bin file it has been saving over the years during the battery's life, or in the case of a new battery and a new device, in which case not enough information has been collected yet in the batterystats.bin file for the device to determine exactly what percentage it thinks the battery is at.
Batteries these days come in various different sizes, so without charging the battery to 100% and then completely draining the battery to zero until the device turns itself off, there is no way for the batterystats.bin file to have enough information to accurately tell you what exactly the remaining battery level percentage is. This is called calibrating the battery. This should be done at least once when getting a new device, and when you have an older battery and you suspect the information in the batterystats.bin file has been corrupted because you are getting wildly inaccurate readings.
The following link gives an excellent guide on how to recalibrate the battery in case of a new or old battery that is giving you inaccurate battery level readings, or where the full battery alarm won't go off.
https://www.nextpit.com/how-to-calibrate-the-battery-on-your-android-device#without-root
The rest of the page is also worth a read, but the link above takes you directly to the method you should use to recalibrate the battery.
The very first smartphone I ever had was a Samsung with a replaceable battery, where after a few years the battery would never reach 100%, and would get to maybe 96% or 97% at most, and the full battery alarm would never go off. The simple solution at the time was to just replace the battery. However, if this is not an option, recalibrating the battery may be a solution.
Recently, I bought a refurbished Onn Android 10 tablet from Walmart which was considerably cheaper than a new one. After charging the battery to 100%, the full battery alarm did not go off. When going into the general Android battery settings, it said "100% charging" and not "100% full" which is what it should say, and which is probably why the full battery alarm never went off. Both in the battery settings and in the Battery Notifier dashboard it should eventually say "Full" and not "Charging" when showing 100%. Even more odd, when I unplugged the charger, it said "Last full charge 0 minutes ago" so I guess the device was confused. That's what I get for buying a "refurbished" device I guess.
After carefully following the instructions for recalibrating the battery, my "refurbished" device still didn't read the battery as being full when reading 100%. Fortunately, if you are stuck with a device like mine, there is a workaround if you have the Pro version of the app, either Battery Notifier Pro BT or Battery Notifier Pro BT 2020. In the Pro version of the app there is a feature called "Custom full charge %". Simply check that box and leave it set to 100%, and you will now get the battery alarm when it reaches 100%. This is because the "Custom full charge %" option looks for the battery percentage to trigger the alarm and not to get a proper signal from the device that the battery is full.
Tips when recalibrating the battery...
If you have to drain the battery from 100% to zero multiple times, it can sometimes take forever to drain the battery to zero. Here's what I do to speed up the process...
1) Make sure you are connected to the Internet.
2) Turn the brightness on the screen up as high as it will go.
3) Play a 10 hour long video on YouTube or watch a live streaming broadcast.
Suggested if you will be away from the device: LUCASTA live 24/7 rain video or Danny Louis 10 hour long videos of rain
Another method I found which also works really well to run the battery down faster is to use a live wallpaper. One I found that is totally free and has no ads and no extra permissions is Blox Free: Live Wallpaper" by Fabmax.
https://play.google.com/store/apps/details?id=de.fabmax.blox.free
To speed up the process to drain the battery even faster, go into the settings for the Blox live wallpaper. Under "Appearance" for "Animation speed" turn it up from 2.0 to 10.0. Under "Effects" check the box for "Dynamic shadows". Under "Performance" for "Performance presets" change from "Medium quality" to "High quality".
