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From: VanguardLH <V@nguard.LH>
Newsgroups: uk.telecom.mobile,comp.mobile.android
Subject: Re: Calibrating a battery without Android launched
Date: Fri, 18 Jul 2025 19:26:18 -0500
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Pamela <pamela.private.mailbox@gmail.com> wrote:

> Is it necessary to have launched Android while charging a battery to 100% 
> as part of the re-calibration process?
> 
> (Android would be launched for the re-calibration step when running the 
> battery down).

Without using a 3rd-party app, battery recalibration for Android entails
charging to 100%, leave it charging for 2 hours more even though the
phone says 100%, discharge the phone until it turns itself off (when
Android or the battery turns off the phone, not some battery management
app), and recharge while not using the phone to 100% again.

If the phone has a battery protection mode (e.g., Samsung), disable it
when cycling the battery.

The only reliable means on knowing how much maximum capacity a battery
can hold is not via voltage, but by charging to full, and counting
Coulombs on discharge (until the protection circuitry within the battery
halts current output).  That is highly impractible for mobile devices as
the testing equipment is very expensive.  So, phones and laptops rely on
measuring voltage, but voltage is a measure of potential, or electrical
pressure, not on capacity.  Battery capacity is very inaccurately
measured in portable devices.  All calibration does is measure voltage
difference between fully charged to fully (or near fully) discharged;
however, capacity is not linerally consumed.  Mobile devices detect
voltage at "full" charge, voltage at full discharge, and plot a linear
interpolation between the two.  But capacity is not linear.  Batteries
are chemical, not mechanical.  For example, you could have a phone that
says there is 30% capacity left for its battery, and it stays powered up
for hours thereafter.  Another phone will say it has 30% capacity, but
shuts down in 15 minutes.  The battery's voltage does not indicate a
weak battery that doesn't have the same capacity at the same voltage as
another battery.  The older the battery, the more worn its chemistry,
the faster a battery will drop in capacity, because an old battery
cannot hold as many Coulombs of energy as a new battery.

With a new battery, my phone can stay up even when the phone says
capacity is down to 5%.  With the old battery, when the phone got to 15%
capacity, poof, off went the phone.  No amount of charge cycling could
make the old battery perform like a new one.  Batteries die.  

You can't pour as much beer back into a can that gets crushed over time,
so you can't get as much beer out of a smaller can.  The beer may taste
the same, but the can has less capacity.  We don't know hold old is your
beer can to know how much it has been crushed over time.  You can try
the recalibration procedure, but you won't get more capacity.