Phone loses 20% of charge when restarted?

Factual Questions
1

Droid Turbo 2 running Android 7.0. Yesterday I noticed some odd behavior on the phone so before I went to bed last night I powered the phone off then turned it back on to reset it. The phone had been charging for the last couple hours and the battery was nearly full – it showed 97% when I powered it off.

When I turned the phone back on, the “Motorola” splash screen that first displays stayed on for several minutes, and never completed the startup. (Normally the Motorola logo will change from a white to black background after a few seconds, then a Droid logo is displayed, then finally the desktop displays). So I powered it off and on again, and this time it restarted normally, but then I noticed that the battery was down to 78%.

This doesn’t happen every time I restart the phone, but it’s something I’ve noticed more than once. What could be draining the battery that fast during a restart? Even during my most resource-intensive phone usage, I don’t think I’ve ever seen the battery drain that fast (20% in about five minutes).

2

It sounds like you have a bad battery. You’d better address the issue because a bad battery can wreck your whole phone.

3

That’s not a bad idea. The phone is about four years old with the original battery, so it wouldn’t surprise me if the battery needs replacing. Another thing I’ve noticed lately, which may be related, is that if I plug the phone in to charge while I’m still using it, it gets very sluggish and unresponsive.

(I miss my old phone where I could pop the back off and take the battery out. That doesn’t seem to be an option with the newer phones. You pretty much have to take them into the shop to have them opened up.)

4

I am not a phone expert but there are two things that determine the % charge you see:

  1. How much charge the battery has
  2. How much charge your phone *thinks *your battery has

Your battery might not really be draining 20% instantaneously. Maybe your phone is confused.

At one time, the advice was to occasionally let the battery run down until the phone shuts off, which recalibrates the sensor that determines the % charge. I do not know if this is still true.

However, this does not mean you can’t have a bad battery.

5

I have a strong suspicion that all cell phone companies slowly drained the batteries on purpose overtime. They really want us buying a new cell phone every two years. Right around the 18 month mark on every phone I’ve ever had it literally get significantly worse in terms of the performance.